California Fire and Power

Paul Somerville, Risk Frontiers

Once again, wildfires have caused catastrophic property losses in the late Californian summer, but loss of life is much lower than last year, possibly because of radical mitigation measures including the widespread use of deliberate blackouts to avoid ignition by power lines and related equipment.

Causes of Fire Ignition

In the United States, about 84% of wildfires are caused by human activity or equipment, with the remaining 16% caused by lightning. 95% of the fires that the California Department of Forestry and Fire Protection (Cal Fire) responds to are caused by human activity.

The largest cause of wildfires is electric power lines and related equipment. Pacific Gas & Electric (PG&E) transmission lines caused the 2018 Camp fire in Northern California, which razed 90% of the town of Paradise, killed 86 people and destroyed more than 13,900 houses. This loss was the reason PG&E declared bankruptcy based on an estimated liability of $30 billion for fires in 2017 and 2018 (RF Briefing Note 372; see also Briefing Note 375). Sceptics have pointed out that, with stable revenue from electricity and gas subscribers, bankruptcy was declared to shield the company from its liabilities. California Governor Newsom implied on 1 November 2019 that the State may become involved in the restructuring of PG&E. Some of the largest fires in Southern California’s history were also caused by power lines: Southern California Edison (SCE) and San Diego Gas & Electric (SDG&E).

Other causes of fires are sparks from vehicles and other equipment.  The Carr fire in Trinity and Shasta counties, which killed 8 and destroyed more than 1,600 structures, was caused by sparks from a wheel rim exposed by a flat tyre. Failure to fully extinguish the Berkeley–Oakland  Hills fire in 1991 resulted in it blowing out of control, killing 25 people and destroying over 2,200 structures. Camp fires are another cause, and two small fires lit by a lost deer-hunting hiker in southern San Diego County resulted in 15 deaths and the loss of over 2,300 structures. Arson is a rare cause of large fires in California.

Changes in the Frequency and Size of Fires

All ten of the largest fires in California have occurred since 1991.  This is attributable, in part, to the increased numbers of houses located in regions of high fire hazard.  However, in the past few years the winter rains (from storms originating in the Gulf of Alaska), that used to begin in late September (Figure 1), have been delayed by a month or more, which may be attributable to climate change. This has extended the fire season into October and, this year, into early November. The headline in an opinion article in the New York Times (2019) warned that “It’s the end of California as we know it” and declared that “at the heart of California’s rot” is the “failure to live sustainably.” The Atlantic (2019) wrote that “California is becoming unliveable.”

Fires burning on 3rd November 2019 in California (Channel 4 TV) Temperature and rainfall for Sonoma County, California.  Source: LA Times and ChartFX.

Mobile Phone Outages

According to the San Francisco Examiner on 4 November 2019, “As the lights flickered out and wildfires flared, PG&E’s blackouts also cut off thousands of Californians from cell phone service, leaving them unable to get emergency alerts or call 911. It exposed a troubling gap in the state’s readiness for mass outages that could, according to PG&E, keep happening for a decade. And it’s left regulators scrambling to find a fix — though it will be difficult. Neither California nor the federal government requires cell phone towers to have backup power, even though network service is a critical part of modern life. Instead, maintaining service is left up to cell phone companies, which have generators lasting days at some sites but batteries which can survive just a few hours at others. When those run out, they must send trucks to refuel or install generators, at times when fires may cut off roads, blackouts darken traffic lights and their own outages hamper communication. Companies said their personnel worked around the clock to put in place hundreds of generators during PG&E’s unprecedented and fast-changing power outages, but in some cases they couldn’t access sites because of the location — on top of buildings or in fire evacuation zones. They’re pledging to prevent future problems. But regulators, politicians and emergency response agencies are pushing for stricter rules to protect public safety.”

Fire Mitigation by Electric Power Companies

Responding to the declaration of bankruptcy by PG&E in 2019 following the fires in 2018, the major public utilities have engaged in intentional blackouts, to varying degrees, as a means to reduce fire ignition.  These measures range from:

  • no blackouts (Los Angeles Department of Water and Power, which admits that a branch blown from a eucalyptus tree onto its power lines ignited the Getty Fire beside the iconic Getty Museum)
  • tightly targeted blackouts (in San Diego by SDG&E)
  • less targeted blackouts (in Los Angeles by SCE) and
  • large scale blackouts (in Northern California by PG&E instigating power outages for days and risked the health of people requiring power for medical support equipment)

The question of when to turn the power back on was highlighted by the outbreak of the Maria Fire 13 minutes after SCE turned the power back on in Ventura County on November 1.  SCE is not yet conceding its fault but has announced that its electrical equipment will probably be found to be associated with the Woolsey fire of 8 November 2018, which burned more than 1,500 structures in Los Angeles and Ventura Counties and killed 3 people.

Financial Management of Fire Losses

In its quarterly earnings report, SCE disclosed that various fire and mudslide events could result in a liability of $4.7 billion, of which $1.8 billion will be borne by shareholders after insurance and other offsets. But in the company’s third-quarter earnings call last week, Edison International President and Chief Executive Pedro J. Pizarro said it was adequately prepared for the blow, saying on 1st November 2019 that the company “understands this is a difficult time for the many people who are being impacted. The company’s top priority is the safety of customers, employees and communities, which is why we continue to enhance our wildfire mitigation efforts through grid hardening, situational awareness and enhanced operational practices.”

The protocols for shutting down power are outlined in SCE’s 2019 Wildfire Management Plan. Incident management teams, that include meteorologists, base the decision on wind speeds, humidity and temperature, fuel moisture and fuel loading. Other less prescriptive considerations may include the potential effect on customers and communities, alternative ways to reroute power, the progress of the customer notification process and situational awareness from weather stations. The length of time customers are without power is one factor that may be considered in the decision to restore power. The plan states that, “The order in which circuits are re-energized will depend on many factors including, but not limited to, customer safety and well-being, consideration of affected essential services, damage to electrical and other infrastructure, and circuit design/topology.” Before power is restored, field crews inspect the lines for “any condition that could potentially present a public safety hazard when re-energizing circuits.”

The duration of a power outage can matter in small and large ways. Food may last only four hours in a closed refrigerator, while frozen food could last a day or two (depending on how full the freezer is) as long as the door stays shut most of the time. For those dependent on medical equipment requiring rechargeable batteries, time can be critical. SCE’s plan says it maintains a list of those customers and contacts them individually before a shutdown. If unable to confirm the notification, field representatives go to the customer’s house.


The Atlantic (30 October 2019). California Is Becoming Unlivable

New York Times (30 October 2019). It’s the end of California as we know it.

Newsletter Volume 18, Issue 4 – October 2019

What areas of Australia are most at risk from natural perils?

by Andrew Gissing and Foster Langbein

The Commonwealth Government recently released a National Disaster Risk Reduction Framework. A key priority of the framework is accountable decision making which includes a strategy to identify highest priority disaster risks and mitigation opportunities. The strategy is based on the principle that it is not possible to reduce all identified risks and that investments must be targeted to minimise risks with the greatest potential impacts. The Australian Prudential Regulation Authority has also recently outlined the importance of mitigation investment in increasing insurance affordability across Northern Australia. The Commonwealth Government in October announced an additional $50 million dollars annually in mitigation funding.

Catastrophe loss models can be used to develop an understanding of the relative risk profile of Australia. Catastrophe loss models are decision support systems used extensively in the (re)insurance industry to assist in pricing risk and aggregate exposure management. Risk Frontiers has developed a suite of Australian probabilistic catastrophe loss models to quantify the impacts of flood, bushfire, hail, tropical cyclones and earthquake. These hazards contribute the majority of disaster losses in Australia as shown in Table 1. Risk Frontier’s catastrophe loss models have national coverage and are comprised of hazard, exposure and vulnerability modules (read more in Briefing Note 399). The models provide scientifically based damage estimates that can be used to rank the risk profiles of different communities nationally.

Table 1: Breakdown of normalised losses by peril based on ICA disaster list (1966-2017). (Source: (McAneney et al., 2019))

To identify what areas of Australia pose the greatest risk of financial loss to insurable assets such as residential and commercial property we have used the full suite of Risk Frontiers catastrophe models (hail, flood, tropical cyclone, earthquake and bushfire) to calculate average annual losses (AAL) for each Australian postcode based on exposure information derived from the NEXSIS database. The results of this analysis are illustrated in Figure 1 from which we can identify the top 20 priority postcodes nationwide as listed in Table 2.

Figure 1: National natural hazards relative risk profile.
Table 2: Postcodes ranked based on total average annual loss including damages from flood, bushfire, cyclone, earthquake and hail.

All the highest rated postcodes are in WA, QLD or NSW, with flood and cyclone being the most significant perils. Bundaberg (4670) is rated as the postcode with the highest AAL relative to other post codes, with its total AAL contributing 0.02% of the nation’s overall total AAL. The total AAL for Bundaberg is over twice that of the estimated AAL for 10th placed Townsville (4814) and over two hundred times greater than the lowest ranked postcode of Cooladdi (QLD) (4479). Such information about relative disaster risks is useful in determining national mitigation investment priorities.

Results can also be dissected by peril. Table 3 provides the highest rated postcode for each of the five modelled perils nationally.

Table 3: Top postcode for each peril.

Postcodes were chosen to best represent Australian towns and suburbs. Results will vary depending upon the loss metric utilised, for example a return period, AAL or probable maximum loss. They will also vary depending upon the geographic boundaries used for example post code, statistical area, local government area or electoral boundary. Using post codes ignores potential losses attributable to wider regional scenarios. For example, potential losses due to flooding in the Hawkesbury-Nepean Valley are greater than just the post code of Windsor and are said to be the greatest nationally by the insurance industry. Such comparison of wider scenarios could be considered in a future analysis.

Understanding Future Risk

Risks are likely to change into the future due to climate change and urban development and future mitigation investment decisions should consider this. Risk Frontiers’ catastrophe loss modelling framework is ideally suited to consider influences on future risk such as climate change, mitigation investment, increased development and changes to building codes. The Geneva Association, a peak insurance industry think tank, concluded that by combining catastrophe models with latest climate science an enhanced understanding of future weather-related risk impacts could be developed. Such use provides greater insights into the impacts of climate change on natural hazards not currently possible using Global Climate Models.

More information on Risk Frontiers catastrophe loss models can be found at


AUSTRALIAN PRUDENTIAL REGULATION AUTHORITY. 2019. Submission – Northern Australia Insurance Inquiry Second Update Report. Available: [Accessed 8/10/2019].

DEPARTMENT OF HOME AFFAIRS. 2018. National Disaster Risk Reduction Framework. Available:

MCANENEY, J., SANDERCOCK, B., CROMPTON, R., MORTLOCK, T., MUSULIN, R., PIELKE, R. & GISSING, A. 2019. Normalised insurance losses from Australian natural disasters: 1966–2017. Environmental Hazards, 1-20.

Bushfire and tropical cyclone activity for 2019/20

By Ryan Crompton

The most recent ENSO Wrap-Up was released by the Bureau of Meteorology (BoM) on 29 October 2019 under the headline ‘Strong positive Indian Ocean Dipole persists’. The wrap-up was summarised as:

The strong positive Indian Ocean Dipole (IOD) event continues while the El Niño–Southern Oscillation (ENSO) remains neutral.

As explained in Crompton et al. 2010 a positive IOD (pIOD) event is when the eastern Indian Ocean is cooler than normal and the western Indian Ocean is anomalously warmer and often associated with a more severe fire season for southeast Australia. Their analysis of building damage due to Australian bushfires concurred with this and interestingly, in terms of the current conditions, they found that the two most damaging combined IOD and ENSO phases were pIOD/neutral and pIOD/El Ninõ in terms of average annual normalised damage for years 1925-2008.

Compounding the bushfire risk for this season is another phenomenon called ‘sudden stratospheric warming’ which is when temperatures in the stratosphere high above the South Pole begin rapidly heating. (The stratosphere is the second layer above the Earth’s surface and is roughly 10-50km above the ground). In a Conversation article published at the beginning of September authors from the BoM discussed how this warming commenced in the last week of August and:

Record warm temperatures above Antarctica over the coming weeks are likely to bring above-average spring temperatures and below-average rainfall across large parts of New South Wales and southern Queensland.

At the time, the BoM was predicting the strongest Antarctic warming on record, likely to exceed the previous record of September 2002, with the impacts reaching the Earth’s surface during October and possibly extend through to January.

The increased risk of fire and heatwaves along eastern Australia has already been borne out with fires, at the time of writing, currently raging throughout the mid-north coast of NSW and northern NSW, including around my hometown of Forster-Tuncurry.

The ENSO phase also impacts tropical cyclone activity in the Australian region as discussed in the recently released BoM Australian Tropical Cyclone Outlook for 2019 to 2020. The outlook is ‘Fewer cyclones than average likely for Australia this season’ with this based on the historical relationships between the status of ENSO over the preceding July to September and the subsequent tropical cyclone season. The Outlook notes that indicators have been ENSO-neutral since April 2019 and the majority of climate models forecast neutral ENSO for the remainder of 2019 and into the first quarter of 2020.

The outlook of fewer cyclones than average not only applies to Australia but all other regions as shown in Figure 1. The Australian region has a 35% chance of more tropical cyclones than average, meaning a 65% chance of fewer tropical cyclones than average. The Outlook states that around four tropical cyclones cross the Australian coast in a season and the accuracy for the Australian region is high. Similar descriptions are presented in the Outlook for other regions.

Figure 1. Long-term average number of tropical cyclones, using data from the 1969–70 season to this (2019) season and the percentage chance of more tropical cyclones than average (Source: BoM).

WeatheX needs you, the citizen scientist, to watch and report severe weather events wherever you are using your smartphone.

Severe weather events are often missed by weather instruments and are difficult to capture. Your reports will vastly improve our ability to capture these events and contribute to better understanding.

WeatheX allows you to report the severity, location and timing of hail size, wind damage, flooding and tornadoes. You can also capture a photo or add a description of the event. This information will be used by weather and climate researchers, including the ARC Centre of Excellence for Climate Extremes, Monash University and Australian Bureau of Meteorology. All reports and photos will remain anonymous and no identifying information is collected.

The app also allows you to view the location and time of recent reports across Australia. Zoom, pan and investigate what’s happening locally or the other side of the country. You will also see your own report on the map immediately after reporting too!

To get started with reporting, download the WeatheX app from Google Play or the App Store.

The WeatheX app is funded by The Centre of Excellence for Climate Extremes (CLEX) and is managed by the School of Earth, Atmosphere and Environment at Monash University and is supported by Risk Frontiers.

Coastal flooding and coral bleaching: what the latest IPCC Special Report means for Australia

Thomas Mortlock, Risk Frontiers

On 24 September, the Intergovernmental Panel on Climate Change (IPCC) published the latest of three Special Reports in the Sixth Assessment Cycle, this time focussing on the Ocean and Cryosphere. Our Briefing Note 377 outlined some of the key points of the previous Special Report on Global Warming.

The focus of the third Special Report is of particular relevance to Australia, given the importance of the ocean in modulating Australia’s climate; the large portion of the population exposed to coastal hazards; and the significance of the Great Barrier Reef to the tourist industry. This briefing note highlights some of the key findings of the report[1] and relevance for Australia.

Sea level rise

Global mean sea level (GMSL) is rising and accelerating due to increased ice loss from the Greenland and Antarctic ice sheets, as well as land-based glacier mass loss and thermal expansion of the ocean. The rate of GMSL rise over the past decade was 3.6 mm/yr, about 2.5 times greater than the average rate over the past century. Mass loss from Antarctica over the past decade has tripled relative to the previous decade and doubled for Greenland over the same period.

Figure 1. Ice sheet melt in Antarctica is a major source of uncertainty for global sea level rise projections. Source: Reuters/Pauline Askin (2019).

While Greenland is currently contributing more to GMSL than Antarctica, Antarctica could become a larger contributor by the end of the 21st century because of ongoing, rapid ice sheet retreat. Beyond 2100, the increasing divergence between Greenland and Antarctica’s relative contribution to sea level rise, if global greenhouse gas (GHG) emissions continue unabated, has important consequences for the pace of relative sea level rise around Australia.

In Australia, the rate of sea level rise is lower than the global average (1.6 mm/yr at Sydney between 1966 and 2009, when ENSO is removed). Similarly, projections are lower: 0.38 m under Representative Concentration Pathway (RCP) 2.6 and 0.66 m under RCP8.5 for Sydney for the end of the 21st century (CSIRO, 2015), compared to 0.39 m and 0.71 m globally. This is because land is still rising from post-glacial rebound and atmospheric pressure is increasing around Australia, suppressing relative sea levels. However, there are large uncertainties attached to these projections, mainly associated with Antarctic contribution to future GMSL but also the longevity of the “suppression effect” around Australia (e.g. Sniderman et al. 2019).

Another component of sea level rise is thermal expansion of the ocean. It is virtually certain that the global ocean has warmed since 1970 and has taken up more than 90 % of the excess heat in the climate system, and up to 30 % of total anthropogenic CO2 emissions since the 1980s. This has several additional consequences, including; acidification of the ocean; higher energy potential for the formation of tropical cyclones (noting other factors also influence formation); and, a higher number, length and severity of marine heatwave events associated with coral bleaching.

Coastal flooding

Sea level rise impacts coastal communities by contributing to an increased frequency of extreme sea level events resulting in coastal flooding. Extreme sea level events that are historically rare (once per century in the recent past) are projected to occur frequently (at least once per year) at many locations by 2050 in all RCPs, especially in the tropics. As a result, annual coastal flood damages are projected to increase by 2-3 orders of magnitude by 2100 compared to today.

In tropical Australia, this effect is compounded by changes to storm surges associated with tropical cyclones. While the sign and magnitude of changes to tropical cyclones in the Australian region remains uncertain, some research indicates they may track further south (Sharmila and Walsh, 2018) with the poleward extension of warmer SSTs, and slow down as tropical circulation changes (Kossin, 2018), although there is only limited evidence to suggest this is occurring at present. Other research suggests a decrease in the number of tropical cyclones forming in the Australian region (Knutson et al., 2015).

Outside the tropics, coastal vulnerability is associated with changes in ocean waves in addition to sea level rise. In the Southern Ocean, a strong trend of increasing wave heights is observed (Young and Ribal, 2019), resulting from a ‘spin-up’ in the mid-latitude westerly winds, with potential consequences for coastal flooding and erosion along Australia’s southern margin. As the tropics expand, it is expected that changes in wave direction will also occur, which can be hugely impactful for sub-tropical coastlines (Goodwin et al., 2016). Erosion caused by the 2016 East Coast Low along Sydney’s Northern Beaches (Figure 2) was an example of the impact of an ‘unusual’ storm wave direction for the coast (Mortlock et al., 2017).

Figure 2. Coastal erosion and flooding on Sydney’s Northern Beaches associated with the June 2016 East Coast Low. Source: UNSW WRL (2016).

Overall, attribution of current coastal impacts on people to sea level rise remains difficult in most locations since impacts are exacerbated by human-induced non-climatic drivers (e.g. groundwater extraction, habitat degradation and sand mining).

Coral bleaching

A major impact of ocean warming and acidification for Australia is the impact of marine heatwave events on coral bleaching and mortality, particularly for the Great Barrier Reef. Marine heatwaves have doubled in frequency and have become longer-lasting, more intense and more extensive.

Climate model-based attribution studies suggest it is very likely that up to 90 % of all marine heatwaves that occurred between 2006 and 2015 are attributable to anthropogenic temperature increases. By 2081-2100, climate models project increases in the frequency of marine heatwaves by approximately 50 times under RCP8.5 and 20 times under RCP2.6 for the tropical oceans.

Because of the sensitivity of tropical corals to sea surface temperatures, marine heatwaves often result in coral bleaching or mortality. When bleaching occurs, recovery is slow (more than 15 years) and may be impeded if the next bleaching event follows too soon.

Figure 3. Extreme coral bleaching on the Great Barrier Reef. Source: Australian Marine Conservation Society (2019).

Tangible impacts on the Great Barrier Reef extend from losses to the tourist and associated industries, and degradation of an important coastal defence. Research suggests the Great Barrier Reef dissipates up to 90 % of all offshore wave energy (Gallop et al., 2014), acting effectively as an underwater breakwater. As this defence reduces, increased wave energy and coastal erosion may be expected for the North Queensland region.

Uncertainties and risk appetite

A particularly important component of sea level rise for Australia is ice sheet instabilities in Antarctica. Acceleration of ice flow and retreat has been observed in both West and East Antarctica and may be the onset of irreversible ice sheet instability. Processes controlling the timing of future ice-shelf loss and the extent of ice sheet instabilities could increase Antarctica’s contribution to sea level rise to values substantially higher than the IPCC’s likely range on century and longer timescales.

Ice sheet instabilities pose a difficult question for coastal planning because there is no time horizon or probability assigned to ice sheet collapse. Uncertainties related to the onset of ice sheet instability arise from limited observations, inadequate modelling and understanding of processes.

Despite the large uncertainties about the magnitude and rate of sea level rise post 2050, many coastal decisions with time horizons of decades to over a century are being made now. The sea level rise range that needs to be considered for planning depends on the stakeholder’s risk tolerance.

Stakeholders with higher risk tolerance (e.g. planning for adaptable investments) may adequately use the likely range of IPCC projections, while it may be prudent for those with a lower risk tolerance (i.e. planning for critical coastal infrastructure) to also consider sea level rise above the upper end of the likely range (i.e. typically > 1 m by 2100). We argued in our recent article in The Conversation that planning for many airports in Australia should include consideration of extreme sea level rise associated with Antarctic ice sheet collapse.


In summary, the IPCC’s latest report highlights that coastal erosion, flooding and coral bleaching are the three main coastal hazards likely to be experienced with either greater frequency or intensity over the coming century. Given that over 80 % of Australia’s population lives within 50 km of the coast, these changes are likely to have a significant financial and economic impact for business and government.

Risk Frontiers has recently launched its ClimateAUS framework to assist business to understand physical climate change risks. For more information contact


CSIRO and BoM (2015). Climate Change in Australia: Projections for Australia’s NRM Regions. Commonwealth Scientific and Industrial Research Organisation and Bureau of Meteorology.

Gallop, S., Young, I., Ranasinghe, R., Durrant, T., Haigh, I. (2014). The large-scale influence of the Great Barrier Reef matrix on wave attenuation. Coral Reefs, 33(4), 1167–1178.

Goodwin, I.D., Mortlock, T.R., Browning, S. (2016). Tropical and extratropical‐origin storm wave types and their influence on the East Australian longshore sand transport system under a changing climate. Journal of Geophysical Research Oceans, 121(7), 4833-4853.

Knutson, T.R., Sirutis, J.J., Zhao, M. (2015). Global Projections of Intense Tropical Cyclone Activity for the Late Twenty-First Century from Dynamical Downscaling of CMIP5/RCP4.5 Scenarios. Journal of Climate, 28, 7203-7224.

Kossin, J. (2018). A global slowdown of tropical-cyclone translation speed. Nature, 558, 104-107.

IPCC, 2019: Summary for Policymakers. In: IPCC Special Report on the Ocean and Cryosphere in a Changing Climate [H.-O. Pörtner, D.C. Roberts, V. Masson-Delmotte, P. Zhai, M. Tignor, E. Poloczanska, K. Mintenbeck, M. Nicolai, A. Okem, J. Petzold, B. Rama, N. Weyer (eds.)].

Mortlock, T., Goodwin, I., McAneney, J., Roche, K. (2017). The June 2016 Australian East Coast Low: importance of wave direction for coastal erosion assessment. Water 9(2), 121, 1-22.

Mortlock, T., Gissing, A., Goodwin, I., Wang, M. (2019). Rising seas threaten Australia’s major airports – and it may be happening faster than we think. The Conversation, 28 May 2019.

Sharmila, S., Walsh, K.J.E. (2018). Recent poleward shift of tropical cyclone formation linked to Hadley cell expansion. Nature Climate Change, 8, 730-736.

Young, I.R., Ribal, A. (2019). Multiplatform evaluation of global trends in wind speed and wave height. Science, eaav9527.

Sniderman, J.M.K., Brown, J.R., Woodhead, J.D., King, A.D., Gillett, N.P. et al. (2019). Southern Hemisphere subtropical drying as a transient response to warming. Nature Climate Change, 9, 232-236.

[1] The Special Report uses CMIP5 climate model projections and mainly RCP2.6 and RCP8.5 (RCP2.6 represents low greenhouse gas (GHG) emission, high mitigation future, which in CMIP5 gives a two in three chance of limiting global warming to below 2 °C by 2100. RCP8.5 is a high GHG, low mitigation scenario).


History of early season bushfires in NSW and Queensland

By Lucinda Coates, Andrew Gissing & Paul Somerville

The ongoing fire emergencies in northeast New South Wales (NSW) and southeast Queensland (QLD) have attracted significant media attention and concern given the resulting damage early in the bushfire season. Nine homes in NSW and some 17 homes in QLD were destroyed last week. The NSW Rural Fire Service stated that fire dangers have not previously been recorded this high early in the fire season (Hannam, 2019a).  The fires may reflect not only high temperatures and strong winds but also a rainfall deficiency.  According to the Bureau of Meteorology, rainfall over much of the fire-hit regions has been the lowest on record for the 20 months starting January 2018, and the 32 months starting January 2017 (Figure 1).

Figure 1. Rainfall deficiency across Australia over the past 17 months, April 1, 2018 – August 31, 2019. Source: BOM; Hannan (2019a).

The severity of the drought in the catchment of Burrendong dam, 40 km west of Mudgee in central NSW, is illustrated in Figure 2. None of four previous droughts dating back to 1906, including one as recent as 2012-2015, has been anywhere near as severe as the current one (Water NSW, Hannan, 2019b).

Figure 2. Cumulative inflows into Burrendong Dam, NSW during droughts. Source: Water NSW, Hannan (2019b).

A search of the Risk Frontiers’ PerilAUS database provides further details about historical early season bushfires in NSW and QLD. Analysis of recorded events supports that the September 2019 bushfires may be the most damaging on record for bushfires occurring in August or September. The fires, however, have caused significantly less damage than those that have occurred later in the fire season.

QLD did, nevertheless, experience a large number of separate fires in its southeast/ southern area in 2000 in the last ten days of August and in 2011 from August to October, and also in the Gulf Savannah in 2012 from July to September. NSW experienced several damaging fires on 10 September 2013 just before the devastating fires of late September/ October 2013. Details of previous bushfires that occured during August and September are provided below.


QLD – Mountain Creek bushfire, 15 August 2013. A bushfire caused the closure of the Sunshine Motorway, having started in bushland beside the east-west slip-lane to the motor way and the Sunshine Coast TAFE. No buildings were damaged, however the fire threatened to engulf the Maroochydore SES headquarters. 1000 people were evacuated from the TAFE campus.

NSW – Ettalong bushfire, 4 August 1936. Burning for 8 hours and accompanied by strong winds this bushfire destroyed houses, fencing and outhouses.

QLD – Toogoolawah bushfire, 25 August 1970. Horses and cattle were lost in the Toogoolawah bushfire, and one injury was sustained.

QLD – Mount Tambourine bushfire, 25 August 1991. One death occurred in the Mount Tambourine bushfire.

QLD – Palmerville bushfire, 25 August 1996. 110,000ha of pasture was destroyed in the Palmerville bushfire.

QLD – South East Qld bushfires, 29 August 2000. Queensland Fire Service had received more than 1,000 reports of fires in southern Queensland in the previous 10 days.  Fires scorched hundreds of hectares of scrub and bushland at Deception Bay, Caboolture, Elimbah, Morayfield, Tarragindi, Wynnum, Mt Crosby, Bribie Island, Woodridge and Redbank.  A house in Deception Bay was destroyed. A total fire ban was extended in the council regions of Ipswich, Boonah, Gatton, Laidley, Esk and Beaudesert.

NSW – Lake Macquarie bushfire, 30 August 1995. A granny flat and a caravan were destroyed in the Lake Macquarie bushfire.

QLD – Southern Queensland bushfire, August, 2011. From August to October 2011, approximately 345 fires occurred in Queensland over 42 local government areas. No homes were lost but there was significant loss of farm infrastructure such as fences, tanks and sheds.


QLD – Gulf Savannah bushfires, September 2012. Many fires throughout the Queensland Gulf Savannah had been burning over a period of three months, affecting more than 20 cattle stations to varying degrees. The historic Croydon-Esmeralda Homestead, dating back to the late 1800s, was lost, along with 90% of the Abingdon Downs Station. More than 500,000ha were burned, leaving no food for more than 60,000 cattle. At least 1500 cattle were lost.

NSW – Marsden Park grassfire, 10 September 2013. A 120 ha grassfire caused the loss of a home and damaged cars and sheds. Winds gusting 70km/h fanned the flames, which were sparked by record temperatures of 32 degrees. The fire is suspected to have been started by arson.

NSW – Windsor grassfire, 10 September 2013. A severe bushfire sparked by powerlines falling on trees caused the evacuation of the University of Western Sydney campus. No property or homes were damaged.

NSW – Castlereagh grassfire, 10 September 2013. Bushfires burnt through more than 63ha of bushland, with more than 1000 firefighters needed across the region. Winds gusting 70km/h fanned the flames, which were sparked by record September temperatures. Only one shed was lost but homes and property were threatened, causing the evacuation of some areas.

NSW – Winmalee bushfire, 10 September 2013. 1370ha of bushland was burnt when hazard reduction burns jumped containment lines after a change in weather conditions. One house was destroyed as a result of the event as well as sheds, cars and caravans.

QLD – Pomona bushfire, 11 September 1970. Some pasture was destroyed (8ha of thickly timbered country was burnt) and one death occurred in the bushfire between Pomona and Cooran, Qld.

NSW – Morisset bushfire, 12 September 2013. A hazard reduction burn turned into a bushfire at Morisset, causing the closure of the F3 motorway (M1). A change in wind direction caused the controlled burn to jump and start a spot fire, causing the bushfire on the western side of the M1. The entire freeway was closed for an hour; a single lane was later opened. Motorists experienced significant delays.

QLD – Woodgate bushfire, 15 September 1969. Outhouses were destroyed and one death occurred in the Woodgate bushfire.  More than 1,013ha were burnt in total. A huge “wallum” bushfire threatened to engulf 200 houses.  Fires had been in the area for one week; no rain for a month: the bush “was like tinder”.

NSW – Sydney outskirts bushfires, 24 September 2006. High temperatures and strong winds of 110km/h saw seven homes lost around south west and north western Sydney. 32 fires were battled across NSW with 2000 ha burning across the state.

NSW – Taree Bushfire, 26 September 2013. A bushfire to the south of Taree burnt over 100ha, threatened 20 homes and caused the closure of the Pacific Highway in both directions. Taree South service centre was also evacuated as a result of the fire.

NSW – Shallow Bay bushfire, 26 September 2013. 50 homes were threatened by an out-of-control bushfire at Shallow Bay. The fire destroyed several sheds and burnt through 70 hectares of bushland. Residents in Shallow Bay were advised to stay in their homes as, for many, it was too late to evacuate.

NSW – Yarrowitch bushfire, 26 September 2013. A bushfire burnt through 300ha and threatened 6 properties near Blomfields Rd and Kangaroo Flat Rd, Yarrowitch. One firefighter was injured after the NSW RFS truck he was driving crashed into a tree due to poor visibility.

NSW – Barrenjoey Headland bushfire, 28 September 2013. A blaze destroyed 60% of the headland surrounding the Barrenjoey lighthouse: the lighthouse was saved but the nearby lighthouse cottage sustained some roof damage. 80 firefighters and three aircraft were needed to contain the fire.

About PerilAUS

Risk Frontiers has, since the early 1980s, built and maintained its PerilAUS database. PerilAUS holds records on natural hazard impacts in Australia from European settlement (1788), but with good confidence from 1900. It includes building damage and fatality information for bushfire, earthquake, flood, gust, hail, heatwave, landslide, lightning, rain, tornado, tropical cyclone and tsunami.

PerilAUS is unique in Australia and is distinguished from other hazard databases by the length of the period covered, the wealth of descriptive detail and the use of a “house equivalent” damage indicator (Blong, 2003; Blong, 2005). PerilAUS is comparable in some respects to well-known international disaster databases such as the Dartmouth Flood Observatory global flood database and the CRED/OFTA International Disaster Database, EM-DAT.

The database contains about 15,700 records from 1900 to 2015. Data has been sourced from news media, government reports, the Insurance Council of Australia (ICA) Disaster List and publicly available coronial records.

The database has been used as a key data source in numerous peer-reviewed research papers and major reports. Its completeness has in part been supported by the Bushfire and Natural Hazards Cooperative Research Centre.

For any further information about PerilAUS please contact Risk Frontiers at

Further information

For further information please contact Andrew Gissing at


Blong, R. J., 2003: A new damage index.  Natural Hazards 30: 1-23.

Blong, R. J., 2005: Natural hazards risk assessment: an Australian perspective. Issues in Risk Science 4. Benfield Hazard Research Centre, London. 29 pp.

Hannam, P (2019a) An ill wind fans the flames. Sydney Morning Herald. [Available Online]

Hannan, P. (2019b). ‘We’ll be bathing in salt water’: At the epicentre of Australia’s big drought. [Available Online]

Death Benefits

In her latter years the author of To Kill a Mocking Bird, Harper Lee, obsessively followed the case of a rural preacher, Reverend Willie Maxwell. The case gripped Alabama. Maxwell was accused of murdering five of his family for insurance money in the 1970s. With the help of a savvy lawyer, Maxwell escaped justice for years until a relative shot him dead at the funeral of his last victim. Despite hundreds of witnesses, Maxwell’s murderer was acquitted – thanks to the same attorney who had previously defended the Reverend.

Lee had the idea of writing a true-crime classic like the one she had helped her friend Truman Capote research (In Cold Blood). Casey Cep’s book, Furious Hours, details this history and that of the book that was never written. This extract provides a short history of insurance.

“Before Lieutenant Henry Farley fired the first ten-inch mortar at Fort Sumter, there was not much of a life insurance industry in the United States. There was property insurance, of course, for ships and warehouses, and, appallingly, for slaves, but even the most entrepreneurial types in an entrepreneurial young nation had not figured out a way to make money from insuring lives. To know how much to charge people until they died, you had to know how  long they were likely to live, which was impossible because companies lacked actuarial data; to maintain consumer confidence, you had to have enough money on hand to cover all death benefits, no matter how early or unexpected someone’s demise, which was difficult because capital was hard to raise. The Civil War solved both of those problems, changing not only the way Americans died but how they prepared for death. By the time that Union soldiers had taken all the souvenirs they could from the house at Appomattox where General Lee surrendered, Americans were insuring their lives at record rates.

Although it took hold in the United States over the course of four short years, the life insurance industry was, by then, thousands of years old. lts earliest incarnation, however, looked less like companies selling policies than like clubs offering memberships. During the Roman Empire, individuals banded together in burial societies, which charged initiation and maintenance fees that they then used to cover funeral expenses when members died. Similarly, religious groups often took up collections for grieving parishioners to cover the costs of burial and to provide aid to widows and orphans. It was centuries before these fraternal organizations came to operate like financial markets, and it took one city burning and another one crumbling for them to do so.

The city that burned was London. One Sunday morning in 1666, at the end of a long, dry summer, a bakery on Pudding Lane went up in flames. The houses around it caught fire one after another, like a row of matches in a book, and strong winds carried the blaze toward the Thames River, where it met warehouses filled with coal, gunpowder, oil, sugar, tallow, turpentine, and other combustibles. By Monday, flames and embers were falling from the sky; by Tuesday, the blaze had melted the lead roof of St. Paul’s Cathedral and the iron locks of the city gates. On Wednesday, the winds shifted, and the breaks made by demolishing buildings at the edges of the disaster finally held. By then, though, the Great Fire of London had destroyed more than thirteen thousand structures and left one hundred thousand people homeless.

One of the men who made a fortune rebuilding the city after the blaze was a medical doctor turned developer with the appropriately fiery name of Nicholas If-Christ-Had-Not-Died-for-Thee-Thou-Hadst-Been-Damned Barebone. (The hortatory name had been given to him by his father, the millenarian preacher Praise God Barebone. With his considerable profits, Dr. Barebone founded an “Insurance Office for Houses” that employed its own team of firefighters to protect the buildings on which it held insurance—five thousand of them, eventually. In an apt abridgment, the doctor became known around London as “Damned Barebone,” not only because of the ruthlessness with which he ignored housing regulations and local opposition to his construction projects, but also because of the soullessness with which his firefighters responded exclusively to fires in homes where a small tin plaque indicated that the owners were clients. Barebone’s “firemarks” soon proliferated in first-floor windows around the city, and the practice of paying a little money now to insure against larger risks later became more popular. Within a decade, Barebone had come up with another innovation in the field, one that paved the way from fire insurance to life insurance: he created a joint-stock company to finance his policies. The first of its kind, it allowed investors to buy and own stock in an insurance company, the way they already could in mills, mineral mines, and spice trades.

Newly able to attract investors, insurance companies could finally raise capital. But the value of any given life was uncertain—far more so, even, than the fluctuating prices of saffron or gold. Say a banker in Dover bought a policy and then lived another four decades; by the time he died, he would have paid premiums for forty years, and his policy would have matured enough for the insurer to provide the full benefit to his widow and still make a profit. But say the same banker went straight from buying his policy to visiting the White Cliffs and promptly drowned in the English Channel. In that case, the banker’s wife would get the full benefit at a fraction of the cost, while the insurer, far from making a profit, would take a substantial loss. The success of insurance companies depended on being able to guess which scenario was more likely, dying of old age or falling off a cliff—in the utter absence of any actual information about aging, falling, or all the other myriad ways that people die.

Part of the reason that information didn’t exist was theological. Devout Christians were not meant to concern themselves with the details of their deaths. Like the timing of the Second Coming, as Christ proclaimed in the Gospel of Matthew: “Of that day and hour knoweth no man, no, not the angels of heaven.” God, who kept watch even over the sparrow, would provide, and to doubt those provisions by making one’s own end-of-life preparations was thought to reveal a lack of faith. Thus was the life insurance industry caught between a math problem and God.

To make matters worse, the overall reputation of the insurance industry had been tarnished by the sale of speculative policies, a practice barely distinguishable from betting. You could buy speculative policies with payouts contingent on everything from whether a given couple got divorced to when a particular person lost his virginity—or, in one infamous case, if a well-known cross-dressing French diplomat was biologically a man or a woman. Such policies could be purchased in secret, and the purchaser did not need to have any connection to the “insured.” These seedy practices, along with the obvious incentive to murder someone whose life you had insurance on, had led France, Germany, and Spain to ban life insurance outright. England, meanwhile, created the insurable interest standard, which mandated that an insurance policy could be sold only to the person being insured or someone who had an “interest” in his life—that is, an interest in his remaining alive. But not even those advances cleaned up the industry. They only encouraged a new kind of speculation, in which elderly, indigent, or ill policyholders auctioned their insurance policies to investors who bid based on how long they thought the seller would live.

Of these various obstacles to establishing a life insurance industry—spiritual, mathematical, reputational—the mathematical one was solved first. Everyone knew that death, while uncertain, was also inevitable, yet before the seventeenth century no one had even tried tracking it, let alone measuring life spans in particular populations or for specific professions. The closest thing to an actuarial table at the time was a Bill of Mortality, a grim British innovation that listed plague victims in various parishes around the country. In 1629, a quarter century after he commissioned a new translation of the Bible, King James I instructed his clergy to start issuing those bills for all deaths, not just the ones caused by plague. Later, around the time of the Great Fire, John Graunt, a London haberdasher who dabbled in demography, organized those bills, arranging twenty years’ worth of death into eighty-one causes and making it possible to see when people were most likely to die and what was most likely to kill them.

Armed with population information for the first time, insurance companies began to get a handle on probability calculations, and soon enough a natural disaster helped ease their difficulties with religion. On the feast of All Saints in 1755, just before ten in the morning, one of the deadliest earthquakes ever recorded struck the city of Lisbon. When the shaking finally stopped—fully six minutes later, some records say—tens of thousands of people had died as homes and churches collapsed, and fissures up to sixteen feet wide gaped open in the earth. Not long after, the waters along the coast of Portugal drew back in a sharp gasp, exposing the bottom of the harbor. Throngs of amazed onlookers had flocked to see old shipwrecks newly revealed on the seabed when, nearly an hour later, the ocean exhaled and a tsunami washed over the city, killing thousands more. The scale of the tragedy was so vast that existing theodicies seemed inadequate, and all of Europe struggled to answer the existential questions raised by the Lisbon catastrophe.

In the course of that struggle, theologians found themselves competing with Enlightenment philosophers, who seized on the earthquake to offer a rival account of the workings of the natural world. If earthquakes were not divine punishments but geological inevitabilities, then perhaps insuring oneself against death was not contrary to God’s plan but a responsible and pious way to provide for one’s family. By the end of the eighteenth century, that idea had gained legitimacy throughout Europe. Once it took hold, religious groups, initially opposed to the entire notion of life insurance, became some of its strongest advocates, in some cases even starting denominational funds to sell policies to their members.

That practice eventually spread to the United States, where even today millions of Americans buy their life insurance through religiously affiliated companies like Catholic Financial Life and Thrivent Financial for Lutherans. But such developments were a long time coming. Unlike Europe, which had decades’ worth of mortality tables by the eighteenth century, colonial America had little reliable information on life expectancy, making it difficult for insurers to set prices and underwrite policies. When companies did try to offer life insurance, there were often too many beneficiaries attempting to make claims at once and rarely enough money to cover them.

In addition, although most states required insurable interest, the American life insurance industry remained exceptionally vulnerable to fraud. Some policyholders lied from the start, fibbing about their age or forging their medical history. Others lied as they went along, violating the terms of their policies by traveling to restricted places (the malarial South, for instance) or by restricted means (by railroad, without the appropriate rider). Still others lied at the end, faking their own deaths or disguising their suicides as accidents. But calling out such lies was tricky. Contesting any claim was expensive, and litigation rarely resulted in denial of coverage, since jury members were far more likely to want to see their own policies honored than care about the profit margins of insurance companies. Moreover, whenever a company preserved its profits by denying a fraudulent claim—say, a father who had failed to disclose an illness, or a husband who had purchased arsenic a few days before he died—it risked damaging its reputation in the eyes of a skeptical public, who worried that their own heirs might be cheated, too.

As companies attempted to grow, they exposed themselves to even more fraud through their own lapses in judgment. Some of their agents approved policies too freely in an effort to earn larger commissions, while some managers invested assets too dangerously in an effort to earn larger returns. Spreading into new territories meant recruiting new agents, not all of whom were scrupulous, and the more geographically diverse a company became, the less it knew about the background, life, and likely death of its would-be customers, making arbitrage of any kind difficult. The expansion of the postal service in the second half of the nineteenth century enabled mail-based sales but also mail-based fraud, on both ends: nonexistent companies could market nonexistent policies by mail, while unscrupulous clients could send away for policies they might never have qualified for in person.

Individual states tried to protect consumers by setting deposit requirements for companies and restricting their investments. But those same protections slowed sales, because they required more due diligence at every stage of the process, and decreased investment returns, because they left firms with less freedom to take the kinds of risks that could make their stocks rise. Unable to sell as many policies, companies had to pool risks across a smaller population, which left them struggling to remain profitable. Eventually, however, an industry shift from stock companies, which were owned by investors, to mutual companies, which were owned by policyholders themselves, allowed insurance companies to free themselves from the capital game; instead of attracting investors, they needed only to recruit customers. That became possible due to the carnage of the Civil War, which did for the United States what earthquakes and fires had done for Europe: spread a sense of both dread and obligation around the country, creating a massive demand for life insurance.

The total value of policies increased from $160 million in 1862 to an incredible $1.3 billion in 1870. Within fifty years there were almost as many life insurance policies as there were Americans.”


Using catastrophe loss models to improve decision making in disaster management

By Andrew Gissing and Ryan Crompton

Catastrophe loss models

Catastrophe loss models are decision support systems used extensively in the (re)insurance industry to assist in pricing risk and aggregate exposure management. They also offer significant benefits in improving disaster risk reduction decision making.

Figure (1): Catastrophe model framework

Risk Frontiers over the last 25 years has developed a sophisticated suite of Australian probabilistic catastrophe loss models to quantify the impacts of flood, bushfire, hail, tropical cyclone and earthquake. These risk models have nationwide coverage and are comprised of the following modules (see Figure 1):

Figure (2): Risk exposure comparison
  • Hazard – estimates the hazard intensity footprint for a specific event. For example, flood extent or ground shaking intensity.
  • Exposure – provides location-based information about relevant assets.
  • Vulnerability – estimates the level of financial loss to different types of property as a function of hazard intensity.

Risk Frontiers’ catastrophe loss models provide scientifically based damage estimates to insurable assets such as residential, commercial and industrial properties and provide users with information about possible financial losses and associated average recurrence intervals (ARIs). Standard outputs from the financial module include exceedance probability (EP) curves (return periods) and average annual losses (AALs).

Using a suite of models enables the comparison of possible losses between hazards at various ARIs for a given geographic area (Figure 2). Loss estimates can also be used to inform benefit cost estimations of different disaster risk reduction investments by varying the vulnerability module1.

In addition to estimating financial losses, model outputs can be combined with vulnerability functions that enable the estimation of loss of life and infrastructure disruption.

Catastrophe loss models can be used to inform disaster planning and capability analysis by enabling the development of ‘what if’ scenarios. For example, to estimate the impact of a magnitude 7 earthquake occurring underneath Melbourne (Figure 3). The models can also be used before or during actual events to forecast possible impacts.

Risk Frontiers combines output from its hazard modules with other data sources to maintain a multi-hazard database for Australia (Figure 4). This database provides national address-based risk ratings for flood, bushfire, earthquake, severe storms, storm tide, tropical cyclones and other hazards. It can be used to assess risk across national asset portfolios, identify community risk profiles and inform property owners of their natural hazard risk profile.

Figure (3): Damage estimate for magnitude 7 earthquake in Melbourne
1 Walker, G. R., M. S. Mason, R. P. Crompton, and R. T. Musulin, 2016. Application of insurance modelling tools to climate change adaptation decision-making relating to the built environment. Struct Infrastruct E., 12, 450-462.

Understanding future risk

The catastrophe loss modelling framework is ideally suited to consider influences on future risk such as climate change, mitigation investment, increased development and changes to building codes. The Geneva Association, a peak insurance industry think tank, concluded that by combining catastrophe models with latest climate science an enhanced understanding of future weather-related risk impacts could be developed. Such use provides greater insights into the impacts of climate change on natural hazards not currently possible using Global Climate Models.

Figure (4): Multi-hazard address-based risk rating

Risk Frontiers’ Australian catastrophe loss models

FloodAUS. FloodAUS is based on the National Flood Information Database. The scope of the model is further extended using Risk Frontiers’ Flood Exclusion Methodology. Correlations between catchments are modelled to provide estimates of total event losses.

FireAUS. The upcoming release uses MODIS Burnt Area Products along with other data sources, machine learning models and fire-tracking algorithms to derive a national synthetic event set from which losses are calculated.

QuakeAUS. QuakeAUS is a national earthquake model for Australia. Starting from a record of historical seismicity, it uses a ground motion prediction model developed specifically for Australia. A major update of the model has been completed to incorporate Geoscience Australia’s recent revision of the National Seismic Hazard Assessment, including a revision of the Australian Earthquake Catalogue. It also includes for the first time an active fault model.

HailAUS. HailAUS is a loss model for hail with nationwide coverage. It includes a catalogue of hailstorms reflecting the frequency and severity of ‘high storm potential days’ derived from reanalysis data and the observed historical record. In addition to calculating damage to property the model includes a motor vehicle damage estimation module.

CyclAUS. CyclAUS is a tropical cyclone wind loss model for Australia. It covers the entire region at-risk of tropical cyclone. Detailed vulnerability functions enable the estimate of loss.


For further information contact Andrew Gissing at


The 14 July 2019 Mw 6.6 Offshore Broome and Mw 7.3 Halmahera Earthquakes

by Paul Somerville

A magnitude Mw 6.6 earthquake occurred about 200 km west of Broome on 14 July 2019 (Figure 1). It is the second largest earthquake to have occurred in or near Western Australia in historical time. This earthquake was followed about 3.5 hours later by a magnitude Mw 7.3 earthquake in Halmahera, Indonesia (Figure 2).  Both earthquakes occurred at shallow depths of about 10 km, and both had strike-slip focal mechanisms, which involve the horizontal movement of one side of the fault past the other side. This is presumably why no tsunami warning was issued (and none was observed) for either event, because tsunami generation requires uplift or subsidence of the sea floor, or some other form of volume change that could be caused by submarine landsliding or volcanic eruption.  As described below, the focal mechanisms indicate that the earthquakes were caused by similarly oriented stress fields, but the large distance separating them suggests that their close time of occurrence was coincidental.

The Offshore Broome earthquake occurred at about 1:30 pm local time and was felt widely in Western Australia, from Esperance to Darwin.  The duration of the shaking was consistently reported to be between 45 seconds and one minute. There are no known reports of structural damage, but there was some non-structural damage to ceilings, and objects fell from supermarket shelves in Broome and other towns. Based on these reports, it is likely that the peak ground accelerations were in the range of 2-10%g. Several people reported that the initial shaking was accompanied by a roaring noise. This may have been caused by the acoustic coupling of the compressional (P) waves, which are sound waves in rock, into the air.  Although no tsunami warning was issued, the Shire of Broome announced just after 4pm that it would be closing Cable Beach, Town Beach, Entrance Point and Reddell Beach for the time being as a temporary precaution against any potential tidal surge.

The Halmahera earthquake occurred at about 4pm local time, and Indonesia’s earthquake monitoring agency, the BMKG, estimated that 4000 people were exposed to “very strong” effects from the earthquake.  It is reported that people were seen fleeing a building on the neighbouring island of Ternate, about 168 kilometres north-west of the epicentre.  Ternate is the largest city in the province of North Maluku, and home to about 200,000 people.  One person is reported to have been killed in southern Halmahera.

Figure 1. Left: The small white star shows the location of the Offshore Broome earthquake, and the beach ball shows a map view of the two possible fault planes, one oriented northeast and the other oriented northwest. Right: Historical earthquakes in northwestern Western Australia, showing the Offshore Broome earthquake as a red star. Source: European-Mediterranean Seismological Centre.
Figure 2. Left: Location map of the Halmahera earthquake. Centre: Detailed location map. Right: Focal mechanism showing possible northeast and northwest oriented fault planes. Source: USGS.

Causes of the earthquakes

As shown in Figure 3, the Indo-Australian Plate is subducting (diving down beneath) the Sunda Plate along the Java Trench (western part of the map), because oceanic crust is thin and dense and easily subducts.  However, the Indo-Australian Plate is colliding with the Sunda Plate in the Timor region (eastern part of the map), because in this region the Indo-Australian plate consists of thick, buoyant continental crust that cannot be subducted.  Consequently, the part of the Indo-Pacific plate that is subducting beneath the Sumatra Plate is moving to the northeast at a higher rate than the part that is colliding with Timor. This causes strike-slip earthquakes, like the Offshore Broome earthquake, to occur along the Western Australia Shear Zone, as shown by the numerous offshore earthquakes with a northeast-southwest alignment on the right side of Figure 1. The focal mechanism of the earthquake, shown on the left side of Figure 1, indicates faulting on either a northeast or northwest oriented fault plane; the northeast plane is consistent with the northeast orientation of the Western Australia Shear Zone in Figure 3. In either case, the earthquake was caused by local crustal shortening in a north-south direction and extension in an east-west direction.

Unlike the Offshore Broome earthquake, which occurred within the Indo-Australian Plate, the Halmahera earthquake occurred within the Sunda Plate, and was caused by the collision of those two plates in Timor.  As for the Offshore Broome earthquake, the focal mechanism of the Halmahera earthquake, shown on the right side of Figure 2, indicates faulting on either a northeast or northwest oriented fault plane. In either case, the earthquake was caused by local crustal shortening in a north-south direction and extension in an east-west direction, due to the plate collision shown in Figure 3.

As shown in Figure 3, the Western Australia Seismic Zone extends onshore in the vicinity of Dampier. The largest earthquake known to have occurred in historical time in Western Australia is the Mw 7.25 Offshore Geraldton earthquake of 11 November 1909. The location of that event is shown in the bottom left corner of Figure 3; the Ms of 7.8 is the surface wave magnitude. The Mw 5.58 1968 Meckering earthquake had a marginally lower magnitude that the Offshore Broome event, and practically destroyed the town of Meckering. The Offshore Broome earthquake is also larger than the 1941 Mw 5.52 Meeberrie earthquake.

Figure 3. Tectonic map of northwestern Western Australia showing the locations of the Western Australia Shear Zone (the zone outlined by white lines; mapped faults shown by red lines). The Offshore Broome earthquake occurred near the eastern edge of the zone, southeast of the letters “RS” (Rowley Shoals). The purple line, which lies just north of Timor, shows the edge of Australian continental basement. The Indonesian islands are located on the Sunda Plate to the north, and Australia is located on the Indo-Australian plate to the south. Source: Hengesh & Whitney, 2016.


Hengesh, J. V., and B. B. Whitney (2016). Transcurrent reactivation of Australia’s western passive margin: An example of intraplate deformation from the central Indo-Australian plate, Tectonics, 35, 1066–1089, doi:10.1002/2015TC004103.


The 4-5 July 2019 M 6.4 and 7.1 Ridgecrest, California Earthquakes

Paul Somerville, Chief Geoscientist, Risk Frontiers

An M 6.4 earthquake occurred near Ridgecrest, Southern California, about 180 km north of Los Angeles,  on July 4th, 2019, preceded by a short series of small foreshocks (including an M 4.0 earthquake 30 minutes prior), and was followed by a strong sequence of aftershocks, whose epicentres aligned with both possible fault planes (NE-SW and NW-SE) of the focal mechanism solution of the M 6.4 event, as shown in Figure 1. On July 6th UTC (July 5th 20:19 locally) an Mw 7.1 earthquake at the northwest extension of the M 6.4 event was preceded by 20 seconds by a magnitude 5.5 earthquake.

Figure 1. Location of the M 6.4 July 4 earthquake and aftershocks (left) and the M 7.1 July 5 earthquake and aftershocks (right), also showing in green the M 6.4 event and its late aftershocks. Source: Temblor.

M 6.4 Earthquake Ruptured Two Orthogonal Faults

The epicenter of the M 6.4 earthquake is located near the intersection of its two possible fault planes, and the distribution of aftershocks on two orthogonal planes, shown on the left of Figure 1, suggests that it ruptured both of them. As shown on the left side of Figure 2, an earthquake is represented by a shear dislocation on a fault, shown by the opposing thick arrows, which has a force representation consisting of two equal but opposing couples, represented by the two pairs of thin arrows shown near the outer edges of the cloverleaf pattern. The opposing couples maintain dynamic equilibrium by yielding no net force and no net torque. This means that, observed from a distance and only using information on the direction of first motion of the seismic waves (up or down), we cannot identify on which of the two possible fault planes the earthquake occurred.

Figure 2. Map views of the double couple representation of a vertical strike-slip earthquake mechanism.

As shown in the centre panel of Figure 2, the same force system – north-south compression and east-west extension, shown by the wide double arrows, can produce strike-slip movement on either the northwest (left) or northeast (right) striking fault plane.  This explains why the M 6.4 event could rupture both of the two possible fault planes in the same earthquake. Seen from afar using first motions of P waves, the two potential fault planes are demarked by up (compressional) and down (rarefactional) quadrants that cover the earth’s surface, as shown on the right of Figure 2.

To resolve which plane or planes hosted the earthquake, we need to look at aftershock locations (Figure 1), look for surface faulting (Figure 3), or analyse the mainshock waveforms to identify where the seismic waves actually came from (Figure 4).  The latter has been done of the M 7.1 event (Figure 4), which shows horizontal rupture of up to 2.5 metres over a length of 60 km of the fault extending from the ground surface to a depth of about 10 km.  The road that was ruptured by both earthquakes is State Highway 178, whose location is shown partially in Figure 5; it extends eastward from Ridgecrest.

Figure 3. A few cm of left-lateral surface rupture of the M 6.4 earthquake (left) and about one metre total of right-lateral surface rupture of the M 7.1 earthquake (right). Here and in Figure 2, left lateral means the other side of the fault from the one on which you are standing has moved to the left; and right-lateral means it has moved to the right.
Figure 4. Slip on the vertical fault plane of the M 7.1 earthquake, right end is southeast. Source: USGS.
Figure 5. Map of earthquake epicentres and roads. Source: USGS.

Relationship to the San Andreas Fault

The San Andreas fault, which runs diagonally from northwest to southeast on the left side of Figure 6, forms the main and long-established boundary between the North American plate to the east and the Pacific plate to the west. It runs through San Francisco and lies close to Los Angeles and other Southern California cities, so news of a large earthquake in California raises alarm among the general public.

Figure 6. Fault map of central and southern California (CGS, left), with Ridgecrest located above the first “M” in “Mojave Desert”(see also Figure 7 for location), and map of the 1872 Owens Valley earthquake showing the location of the Ridgecrest earthquakes in the lower right (Temblor, right).

However, another incipient part of the boundary is forming to the east of it, running in a north-northwesterly direction, and it hosted the M 7.6 Owens Valley earthquake of 1872 and the July 2019 Ridgecrest earthquakes, shown on the right side of Figure 6. The orange lines in Figure 6 indicate faults that have not ruptured in historical time, and the red lines are ones that have. The three big historical earthquakes in California are the M 7.9 1857 Fort Tejon, south-central San Andreas earthquake (roughly from the latitudes of San Luis Obispo to Riverside, Figure 6, left), the 1872 M 7.6 Owens Valley earthquake (Figure 6, right), and the 1906 M 7.8 San Francisco earthquake on the Northern San Andreas fault (roughly from the latitude of San Luis Obispo past San Francisco, off the map in Figure 6, left). Since the 1872 Owens Valley earthquake, other earthquakes that have occurred recently on this incipient eastern plate boundary are the 1992 M 6.3, Joshua Tree, 1992 M 7.2 Landers, 1992 Big Bear, 1995 M 5.8 Ridgecrest, and 1999 Hector Mine earthquakes. The rupture zones of the Landers and Hector Mine earthquakes are shown by red lines east of Victorville on the left side of Figure 6.

Reported Damage and Future Warnings

The MMI Intensity shakemap of the earthquake is shown on the left side of Figure 7.  The main damage to the towns on Ridgecrest (population 29,000) and Trona (population 1,900) appears to have been incurred by older houses and trailer homes (which readily topple from their foundations, right side of Figure 7); some house fires also started but were soon extinguished.  There were no reported deaths or serious injuries.

Figure 7. Shakemap (USGS, left), and damage to a trailer home and a fire (right).

The Governor of California announced that the estimated losses are about $US100 million, but the USGS made a preliminary estimate of at least $1billion. It is possible that this larger estimate may include damage to the Naval Air Weapons Station China Lake, a 1.1 million acre weapons testing facility, the Navy’s largest, whose location is shown in Figure 1 and within which the epicentres of both the M 6.4 and 7.1 earthquakes were located.  The facility’s Facebook page announced that it is “not mission capable until further notice,” but officials said that security protocols “remain in effect.”

According to the current USGS forecast, over the next one week, beginning on July 6, 2019 at 2:20 p.m. Pacific Time (5:20 p.m. ET), there is a 2% chance of one or more aftershocks that are larger than magnitude 7.1. The number of aftershocks will drop off over time, with the largest expected to have a magnitude of about 6, but a large aftershock can increase the numbers again temporarily.

The recently installed early earthquake warning system ShakeAlert, which detects earthquakes and announces that they have occurred in near real time, worked as planned but not as some people would have liked.  The designers of the ShakeAlert LA app decided that most people would not want to be notified of large earthquakes that are too distant to cause damaging shaking near them.  Consequently, the ShakeAlert LA app was designed to only send an alert if the magnitude is above 5 and the MMI intensity is 4 or higher somewhere in Los Angeles County.  The Ridgecrest earthquakes met the magnitude criterion but not the intensity criterion in Los Angeles, and so did not result in alarms.  However, many people were alarmed because they clearly felt the long “rolling” motions (surface waves) of the distant large earthquakes and were concerned that the alarm was not working properly.  The designers of the app may now consider providing alarms, perhaps nuanced, of large distant earthquakes that people may feel but that do not present local damage potential.

Darwin shaken by a deep Mw 7.3 earthquake in the Banda Sea

By Paul Somerville, Chief Geoscientist, Risk Frontiers

Darwin was shaken at around noon today by a deep Mw 7.3 earthquake that occurred in the Banda Sea. Both Geoscience Australia and the United States Geological Survey reported that the earthquake occurred at a depth of about 200 km.  Such deep earthquakes do not generate tsunamis, and no tsunami warning has been issued.

Figure 1. Location of the Mw 7.3 Banda Sea earthquake of 24 June 2019. Source: Geoscience Australia.

There was an alarming level of shaking in Darwin, but the earthquake was far enough away that damage would not be expected, and none has been reported to date. Parts of the Darwin CBD were evacuated, but we are not aware of any evacuation order and surmise that the long duration of the earthquake shaking caused sufficient alarm to prompt voluntary evacuation.

If proper procedures had been followed, the people who evacuated would have followed the “drop, cover and hold on” procedure described here:, and would not have evacuated the building until the shaking was over.

Unlike the sharp (high frequency or short period), short duration ground motion that is experienced near small earthquakes in Australia, the shaking from large distant earthquakes is often described as “rolling” (low frequency or long period) ground motion that can last for a long time.  Some people reported shaking lasting 5 minutes. This long duration may have added to the sense of alarm and prompted people to evacuate.  This shaking is expected to have been most pronounced in the upper floors of the taller buildings in the CBD, because their height causes them to have relatively long natural periods of vibration and they are thus “tuned” to the long period of the incoming seismic waves.  In contrast, low-rise buildings are most vulnerable to the short period ground motions from nearby small earthquakes, and are less vulnerable to long period ground motions.

Unfortunately, it appears that we have missed an opportunity to record the ground motions in these Darwin CBD buildings. Without such recordings, we are left with uncertainty in the level of ground motion that they experienced. We need recordings so that we are better able to estimate the ground shaking levels that should be used in northern Australia to design buildings and infrastructure to withstand large earthquakes to our north. The frequent large earthquakes that occur to the north and east of Australia are illustrated by the earthquake epicenter map for 2019 shown in Figure 2.

Figure 2. Locations of earthquakes that have occurred in 2019. The Mw 7.3 Banda Sea earthquake of 24 June 2019 is shown by the large red circle north of Darwin. The radius of the circle increases with increasing magnitude. Source: Geoscience Australia.

Risk Frontiers Seminar 2019

Wednesday, 11th September 2019

at the Museum of Sydney
cnr Bridge and Phillip Streets, Sydney
2pm until 4.30pm followed by light refreshments in the foyer.

Provisional Programme:

  • Prof Andy Pitman AO – Do climate models tell us about future extremes?
  • A/Prof Lisa Alexander – Using climate observations in actuarial assessments of risk
  • Dr Greg Holland – Projecting changes in tropical cyclone activity in a warmer world
  • Prof Seth Westra – Quantifying the impacts of climate change and variability on floods and drought
  • Dr Ryan Crompton – Assessing future natural catastrophe risk using NAT CAT models

At the conclusion of the presentations, there will be an interactive panel session including all of the above speakers.

To register please email