Updated GNS Central New Zealand Earthquake Forecast

Paul Somerville, Risk Frontiers

Until now, GNS Science earthquake forecasts have been mainly focused on aftershocks occurring within the region affected by mainshock events.  This has been the case for the 2010 Mw 7.1 Darfield and 2011 Mw 6.2 Christchurch earthquakes as well as the 2016 Mw 7.8 Kaikoura earthquake. However, these events have the potential to trigger large earthquakes in adjacent regions (as described in Briefing Note 332). Now, GNS Science and an international group of earthquake scientists have developed a forecast, excerpts of which are reproduced below, that accounts in part for such large events. 

The probability of an earthquake with magnitude 7.8 and higher has doubled compared with that in the National Seismic Hazard Model, while that for an earthquake of magnitude 7.0 and higher has only increased by 20%.  Although the information released by GNS does not indicate which earthquake sources are contributing to these increases, we can deduce, with reference to Briefing Note 332, that the Hikurangi subduction zone is making the largest contribution, because the Wairarapa fault is the only crustal fault that is thought to be capable of producing an earthquake with Mw larger than 7.8.  The Hikurangi subduction zone may be capable of generating earthquakes as large as Mw 9.0.

GNS Science have taken considerable care to lucidly explain the forecast to the general public, but as in previous forecasts this new one is characterized by sanguine verbal descriptions of probabilities, such as “We estimate that there is a 2% to 14% chance – in verbal likelihood terms this is a very unlikely chance – of a magnitude 7 or above earthquake occurring within the next year in central New Zealand.”


GeoNet – Geological hazard information for New Zealand

Published: Tue Dec 19 2017 11:45 AM

https://www.geonet.org.nz/news/5JBSbLk9qw8OU4uWeI86KG

Updated Forecasts

We estimate that there is a 2% to 14% chance – in verbal likelihood terms this is a very unlikely chance – of a magnitude 7 or above earthquake occurring within the next year in central New Zealand.

The area inside the yellow box in the map below indicates the area of the earthquake forecasts that we refer to in this story. Our best estimate is a 6% (very unlikely) chance, which is about a 1 in 16 chance. This has decreased over the last year (in December 2016 it was greater than 20% within the next year), but it is still a higher chance than before the 2016 Kaikōura earthquake.

The table below shows the estimated chance of large earthquakes within the next year, and within the next 10 years. For example, within the next 10 years, there is a 10% to 60% chance (best estimate is 30%, unlikely) of a magnitude 7 or higher earthquake occurring in the area shown on the map (the map below shows what we mean by central New Zealand).

Updated probabilities table for central New Zealand.

The magnitude ranges are for a magnitude 7.8 or greater and magnitude 7 or greater within the next year and within the next 10 years.

How did we come up with these numbers?

Scientists from Japan, Taiwan, and USA met with our scientists to estimate the chance of a large earthquake occurring in central New Zealand. Together they assessed all the earthquake models, plus newly developed models of how slow slip events impact the probability of future earthquakes.

The results of these models were then combined with other information, including observations of how the numbers of earthquakes change during slow slip events, and evidence of earthquake clustering over the past few thousand years to estimate revised probabilities for large events in central New Zealand.

How does this forecast compare to before the Kaikoura earthquake?

The best estimate over the next year for a magnitude 7.0 or higher earthquake is 6%. This is an increase of 20% over the long-term estimates from the National Seismic Hazard Model (i.e., it is 1.2 times higher).

The best estimate for a magnitude 7.8 and higher earthquake is 1% within the next year. This is double the long-term estimates (i.e. it is twice as likely to happen now as it was before November 2016). The upper bounds for both magnitude range estimates are much higher than the long-term estimates.

That being said, the chance of a very big earthquake has been going down over the past year, since we first estimated the numbers following the Kaikoura earthquake.

Back in December 2016, there was a 5% chance of a M7.8+ earthquake within the coming year (December 2016 to November 2017), now the best estimate is 1% within the next year (December 2017 to November 2018).

This exercise has been focused on earthquake forecasts for larger magnitude earthquakes over central New Zealand rather than the Kaikōura aftershock sequence- (those will still be regularly updated here).

Science contact: Matt Gerstenberger m.gerstenberger@gns.cri.nz.

Science input received from Matt Gerstenberger and Sally Potter (GNS Science) as well as valuable contributions from our colleagues at MCDEM and USGS This research was funded by the Natural Hazards Research Platform Kaikoura Earthquake short term research projects.

 

Newsletter Volume 17, Issue 2

Weather-related natural disasters 2017: was this a reversion to the mean?

Professor Roger Pielke Jr (University of Colorado, Boulder)

Last July, I observed here that the world had recently experienced an era of unusually low disasters and that streak of good luck was going to end sometime. Little could I know that less than one month later the United States would be hit by Hurricane Harvey, which was soon followed by Hurricanes Irma and Maria. Not only did these three major hurricanes emphatically break the more than decade-long drought in major hurricane landfalls in the US but, according to Aon Benfield (PDF), together they resulted in > $220 billion in total losses and >$80 billion in insured losses.

In this column I take a look back at 2017 and put its catastrophes into longer-term historical perspective. Media reports have sent mixed messages about the catastrophes of 2017. On the one hand, there have been headlines about the record insured catastrophe losses of 2017. On the other hand, the impact of record losses on pricing in insurance and reinsurance has been less than many had expected or hoped for. How might we reconcile these two perspectives?

The short answer is that 2017 did indeed result in record weather-related catastrophe losses, but understanding the significance of losses requires understanding the inexorable growth in global wealth in addition to patterns in weather extremes. Total global losses in 2017 were $344 billion worldwide according to Aon Benfield. In terms of total catastrophe losses, 2017 trails only 2011 which had $486 billion in losses. Insured losses followed a similar pattern, with $134 billion in total losses (almost all of which were weather-related), just below that of 2011 and just above 2005.

The figure below places total weather-related catastrophe losses into the context of increasing global GDP. The graph presents data on losses from Munich Re (1990-2017) and Aon Benfield (2000-2017) in relation to global GDP (World Bank) all expressed in constant 2017 dollars (US Office of Management and Budget) (OMB). The data show clearly that 2017 was indeed an extreme year, with losses exceeding 0.4% of global GDP.

 

 

 

 

 

 

 

Yet, at the same time, since 1990 total global catastrophe losses are down by about one third, based on a simple linear trend. Over the past decade, reinsurance capacity, according to Aon Benfield, has increased by almost 80% (to $605 billion in 2017), whereas global GDP increased by about 24%. Simple math here helps to explain why reinsurance market pricing did not respond as much as some thought despite the 2017 record losses: (1) global GDP has increased, (2) reinsurance capacity has increased much faster than global GDP and (3) catastrophe losses have decreased as a proportion of global GDP. The consequence of these dynamics explain why it is that, even with losses in 2017 at a record levels, the market is nonplussed.

The majority of 2017 catastrophe losses and vast majority of insured losses resulted from the three major Atlantic hurricanes. How should we understand the 2017 Atlantic hurricane season?

According to Phil Klotzbach of Colorado State University, 2017 saw the most active North Atlantic hurricane season since 2005. (This assessment uses a metric called ACE, accumulated cyclone energy.) Three of the previous four years were well below average. These data reinforce what I wrote last July: “A simple regression to the mean would imply disasters of a scale not seen worldwide in more than a decade.” The active 2017 hurricane season reminds us that catastrophe luck cuts both ways.

Interestingly, in addition to the three major hurricanes that made landfall in the North Atlantic, there was only one other intense landfall worldwide (tropical cyclone Enawo struck Mozambique, killing 81 and causing >$20 million in damage). The figure below (based on updated data provided by Ryan Maue http://(tropical cyclone Enawo struck Mozambique, killing 81 and causing >$20 million in damage- @ryanmaue –http://(tropical cyclone Enawo struck Mozambique, killing 81 and causing >$20 million in damage based on our 2012 study) shows global tropical cyclone landfalls since 1970.

In 2017 there were 18 total landfalls at hurricane strength, above the long-term average of 15.3 (median = 15, record = 30 in 1971), but the four major landfalls were below the long-term average of 4.8 (median = 4; record = 9 (five times)). Overall, 2009 to 2016 were all below average for global landfalls, which helps to explain the good fortune experienced with respect to global weather catastrophe losses.

Despite the record catastrophe losses in 2017, according to Aon Benfield, the year continued a streak of well-below average (and below median) loss of life, according to longer-term data provided by Max Roser and Hannah Ritchie at Oxford University. However, large loss of life in 2004, 2008 and 2010 (>200,000 in each year) reminds us that the challenge of protecting lives in the face of disasters remains a crucial priority.

2017 saw a range of other catastrophes, including notable severe weather and wildfire events, together totaling more than $50 billion in losses, whereas flood losses were well below a longer-term average. However, despite these various catastrophes and associated losses, 2017 was notable primarily due to the three major hurricanes in the North Atlantic.

What does 2017 portend for 2018?

My advice has not changed: Even with the record losses of 2017, over more than a decade the world has had a run of good luck when it comes to weather disasters. The hurricanes of 2017 show how quickly good luck can come to an end.
Understanding loss potential in the context of inexorable global development and long term climate patterns is hard enough. It is made even more difficult with the politicized overlay that often accompanies the climate issue. Fortunately, there is good science and solid data available to help cut through the noise. 2017 was far from the worst we will see: even bigger disasters are coming – will you be ready?

The Hawaii nuclear alert: how did people respond?

Andrew Gissing & Ashley Avci

Nuclear tensions between the United States and North Korea have been extensively reported as both sides continue to posture via threats and propaganda and North Korea continues its missile tests. North Korea’s leader Kim Jong-Un has promised to decimate the US and has referred to President Trump as mentally ‘deranged’. A story in the New York Times based upon consultations with leading security experts recently suggested that the chance of war breaking out was between 15 and 50 percent (Kristof, 29/11/2017). Given the threat of an attack, U.S. government officials have encouraged residents to be prepared and have commenced monthly drills to test warning systems.

Within this environment of heightened geopolitical tensions, a single text message was sent in error to people in Hawaii on the 13th of January at 8.07am, warning of an imminent ballistic missile strike. The message read:

Emergency Alert. BALLISTIC MISSLE THREAT INBOUND TO HAWAII. SEEK IMMEDIATE SHELTER. THIS IS NOT A DRILL.

Officials alerted the public to the error via social media 13 minutes later, but it took 38 minutes to send a follow-up text message. In the meantime, the community was left to react as if a real missile was to strike Hawaii within twelve to fifteen minutes. It has been revealed that the delays were the result of local officials believing they required federal approval to cancel the alert.

The alert presents an opportunity to improve the understanding of how people react to warnings of extreme events. Risk Frontiers researchers conducted an analysis of media interviews with 207 individuals (respondents) who received the warnings to identify people’s attitudes and responses after the alert was received. The media interviews were sourced from a search of global online media outlets that had reported on the false alarm. Interview responses were coded, analysed and are reported in this article.

Results

Respondents commonly spoke of where they were when they received the alert. Locations varied, highlighting the importance of considering the many likely locations of people when an alert is issued. Most frequently respondents were in a hotel (n=39) or awake at home (n=38). Others were at home, but in bed (n=11); at work (n=10), in a car (n=10), at the beach (n=7) or in the ocean (n=3).

Most respondents received the alert via the official text message issued by the State (n=89), but a minority were informed by someone else: for example, a family member (n=17). Some respondents, however, spoke of being spared the stress of the false alarm as they did not receive the initial warning (Hawaii News Now, 16/1/2018).

Respondents often spoke about how they had trusted the alert because they had interpreted it in the context of existing North Korea and United States tensions (n=36) and therefore believed the alert to be plausible.

Those that chose to validate the warning did so through a multitude of different channels including social media (n=26), making contact with others (n=15), searching websites (n=16), listening for sirens (n=16), watching TV (n=11) or calling authorities (n=3). Based on interview statements in which residents stated how they had immediately responded to the warning, we estimate that a large number of residents may not have attempted to validate the warning (n=64).

Respondents often spoke about how they felt when they received the alert. Most often people described their emotions as fearful (n=51), concerned (n=23), panicked (n=21), upset (n=13) or calm (n=13).

Most respondents undertook protective actions in response to the warning (n=136), most often stating that they attempted to seek shelter within the building they were located in (n=43); called or texted others to alert them (n=23) or called or texted others to express their emotions (n=22). Other actions included packing emergency items (n=17); gathering family members (n=16); attempting to leave a building to seek shelter elsewhere (n=15) and leaving an open space to seek shelter (n=12). Eighteen respondents stated that they did not know what to do when they received the alert.

Respondents also commented on what they observed other people doing. Most commonly others were observed attempting to seek shelter (n=50), crying (n=26), running (n=25) or calling or messaging others (n=13).

When seeking shelter, respondents most often stated that they had attempted to seek shelter within their home (n=34), frequently within the bathroom (n=18). In addition nineteen respondents spoke about sheltering within their hotel. Some commented that they did not know where to seek shelter (n=18).

A small number of respondents stated that they did not take any action (n=16). Reasons for not responding were that respondents thought that there was nothing that could be done (n=7); the warning was false as sirens did not sound (n=4); the missile would be shot down or would miss (n=2); or the warning was a joke or hoax (n=2).

Those that mentioned how they had discovered the alert was false found this information through social media (n=21) or via a text message from authorities (n=12). On discovering that the alert was a false alarm, respondents described their emotions as relieved (n=23), concerned (n=7) or upset (n=7).

Respondents commented on how the situation was handled or how warnings could be improved in the future. Most often, respondents were concerned about the lack of safeguards to avoid such a false alarm and that it took too long for authorities to notify the public that the alert was false. In some cases, respondents reflected on their own personal disaster preparedness, noting specific actions that they had not undertaken to be prepared.

Discussion and Conclusion

The Hawaii missile false alarm provides numerous insights into how people behave when warned of an extreme event. Practitioners should note the importance of social media as a communications mechanism, particularly for people to validate warnings and share with others.

The case study demonstrates the role of informal networks in both communicating and validating warnings. Hotels were clearly an important node of communication with their guests, and should always be considered an important network in communicating warnings in at-risk areas with large tourist populations.

Interestingly, it would appear that the population had been primed to respond to such an alert by their knowledge or concerns regarding tensions between North Korea and the United States. This demonstrates the importance of communicating long range forecasts to build the community’s awareness of a risk so that individuals will recognise and respond to a warning when it occurs.

Given that the official advice as to what to do in the event of a real alert is for “all residents and visitors to immediately seek shelter in a building or other substantial structure”, it appears that most respondents reacted appropriately. However, consistent with previous Risk Frontiers briefings on community responses to warnings, not everyone responded or knew how to respond. This is a further demonstration that even in extreme circumstances, emergency warnings cannot be relied on to achieve full compliance by communities. This finding should be considered when relying on warning systems to justify the permitting of development in high risk locations.

As for improving warning technologies, the Hawaiian Emergency Management Agency has suspended all future drills until a review of the event has been completed; instituted a two-person activation/verification rule for all tests and actual alarms and instigated a cancellation command that can be activated within seconds of a false alarm.

References

HAWAII NEWS NOW. 16/1/2018. If you didn’t get the false alert about an inbound missile, this might be why. Available: http://www.hawaiinewsnow.com/story/37269695/if-you-didnt-get-the-false-missile-alert-this-might-be-why [Accessed 27/1/2018].

KRISTOF, N. 29/11/2017. Are we headed toward a new Korean war. New York Times.

Risk Frontiers’ Multi-Peril Workbench 2.4 has now been released!

Workbench 2.4:

  • features a major update to our HailAUS hail loss model to national coverage
  • includes our Demand Surge model that can be applied to all Australian Perils
  • contains updates to FloodAUS, FireAUS, CyclAUS as well as many enhancements to the Workbench itself

Changes are coming to QuakeAUS … have you heard?

Prof. Paul Somerville of Risk Frontiers has been participating in the Geoscience Australia update of the seismic hazard model for Australia through the National Seismic Hazard Assessment (NSHA18) project. We have commenced preparations to update our Australian earthquake loss model, QuakeAUS, and expect to have preliminary results in the first quarter of this year!

Flood Deaths in the Northern Territory

Alice Carney1, Lucinda Coates1,2,3 and Katharine Haynes1,3

1 Macquarie University
2 Risk Frontiers
3 Bushfire and Natural Hazards Cooperative Research Centre

Risk Frontiers recently examined the circumstances surrounding deaths from flood events in Australia as part of a wider Bushfire and Natural Hazards CRC (BNHCRC)-funded project, An analysis of human fatalities and building losses from natural disasters. One of the results found was a heightened level of risk in the Northern Territory. We decided to investigate this a little more closely.

Introduction

In the previous Risk Frontiers research project, 1859 individually identified flood-related deaths were recorded in Australia from 1900 to 2015 and, of these, 79% were males (Haynes et al., 2016). Death rates showed a steep statistically significant decline up to 1960, with a lesser, steadier decline over the most recent 55 years (Haynes et al., 2016).

Queensland and New South Wales accounted for 75% of the total fatalities across Australia (Haynes et al., 2016). However, when deaths were examined in relation to population size, a heightened level of risk in the Northern Territory (NT) was revealed, with a death rate almost double that of the jurisdiction with the next highest fatality rate (Haynes et al., 2016). When fatalities in the various jurisdictions were examined longitudinally, an expected downward trend in deaths over time was observed, apart from in the NT – particularly in more recent years, where an increasing proportion of flood deaths were seen (Haynes et al., 2016).

This warranted further investigation. This briefing note summarises the results obtained when the demographic characteristics of flood-related deaths occurring in the NT from 1960-2015 were examined.

Fatality totals and trends

From 1960 to 2015 there have been at least 27 fatal floods in the NT, claiming 38 lives. Annual flood fatalities are increasing with time, while death rates have remained constant (figure 1. Note: zero deaths 1960-1964). Males accounted for 74% of the fatalities. The numbers of both male and female flood fatalities are increasing and, although Australia’s male:female ratio is decreasing, the gap between male and female flood deaths in the Northern Territory is growing, showing no sign of equity in the near future.

 

Figure 1: Flood fatalities in the Northern Territory, 1960-2015

Males tend to be more at risk in flood events due to their risk-taking behaviour: for example, males are over-represented in attempting to cross floodwaters (67%), and undertaking an activity near (100%) or in (80%) floodwaters. In all these activities, males are aware of the flood and undertake the activity nonetheless. On the other hand, females are less likely to take these risks and are over-represented only in carrying out activities not near usual watercourses such as staying at home (71%). These statistics suggest gender-specific approaches must be developed to address the clear differences in causes of death.

In regards to age, males are over-represented in most age brackets. Most (98%) decedents were aged 0-59 years, the age group most at risk being those aged 30-39 years.

The Daly River Drainage Basin has claimed the most lives, accounting for 34% of flood fatalities in NT (figure 2). There have been five fatal floods there since 1960, three of which were high fatality (≥ 3 deaths) events. The Todd River Drainage Basin is the second most dangerous, accounting for 21% of fatalities, and having also experienced five fatal flood events.

Figure 2: Location of flood fatalities in NT by drainage basin, 1960-2015

Indigeneity was investigated from 2000 onwards. A clear inequity is presented, as the indigenous account for 65% of fatalities from 2000-2015. Indigenous males account for over half (52%) of all flood fatalities in NT. This is alarmingly high in comparison to the group least at risk – non-indigenous females, who account for only 4% of fatalities. In terms of age, those most at risk are the 0-9 year-old non-indigenous and 10-19 year-old indigenous groups. It is clear that, similar to the case of the male population, indigenous persons are more prone to risk-taking activities: the majority (71%) of those crossing a flooded watercourse and 67% of those engaged in an activity in a flooded watercourse were indigenous. Research suggests indigenous persons are more likely to present risk-taking behaviours due to poor education on the risks (Atkinson, 2012). A key to reducing flood fatalities in NT is, therefore, training in flood-safe behaviours targeted to the indigenous population.

The riskiest “activity prior to death” was found to be crossing flooded watercourses, which accounts for over a third (35%) of fatalities in NT: 67% of these were male. A total of 57% of female decedents were attempting to cross floodwaters. The second most risky activity (21%) was being engaged in an activity near floodwaters: males were over-represented (100%). [The results for those engaged in an activity not near a usual watercourse – e.g, being at home – are skewed due to one large event in 1977, in which five people were drowned at a cattle station.]

The familiarity of the decedent with the death location was investigated. The term “familiar” as used in this research refers to being within 10km of one’s house. Locals accounted for 87% of flood fatalities. In relation to activity prior to death, locals were most likely to be crossing floodwaters (29%), engaged in an activity in or near floodwaters (21%) or at home (21%). An analysis of those decedents who died at home clearly showed that they chose not to evacuate when warnings were received. This suggests that behavioural changes must be made through education of the risks of ignoring flood warnings. [Note: a relatively small dataset means these results should be treated with some caution.]

Some 25% of the decedents from 2000-2015 were intoxicated and, of those, 80% were attempting to cross a flooded river and 20% were engaged in activities in flood waters. 80% were male; 80% were indigenous. [Note: a relatively small dataset means these results should be treated with some caution.]

There are a few take-home messages around mitigation and education strategies for the Northern Territory. Appropriate strategies must be developed targeting, especially, indigenous males. The aim should be to educate on the risks floods present and the measures that should be taken to avoid them, such as not attempting to cross, or engaging in activities in or near, floodwaters. Haynes et al (2016) gives insight into potential mitigation strategies which should be modified to best suit the target population. The three key strategies should be to educate, pose consequences and apply structural interventions.

Acknowledgements

Risk Frontiers employed Macquarie University climate science PACE student Alice Carney to investigate the circumstances surrounding flood deaths in the Northern Territory (NT). PACE is Macquarie University’s Professional and Community Engagement program, which gives students a chance to explore key economic, social and ethical challenges by seeing at first-hand how contemporary organizations (such as Risk Frontiers) address them, allowing them to develop new knowledge and skills and explore future career opportunities.

The work utilised Risk Frontiers’ database PerilAUS and the National Coronial Information System (NCIS) database of coronial data, sourced from the Department of Justice and Regulation, Victoria: a resource of coronial records across Australia from July 2000 onwards.

References

Atkinson, J. 2012. Anthropometric correlates of reproductive success, facial configuration, risk taking and sexual behaviors among indigenous and Western populations: the role of hand-grip strength and wrist width. In: GALLUP, G. G. & SVARE, B. (eds.). ProQuest Dissertations Publishing.

Haynes, K., Coates, L., Van Den Honert, R., Gissing, A., Bird, D., Dimer De Oliveira, F., D’Arcy, R., Smith, C. & Radford, D. 2016. Exploring the circumstances surrounding flood fatalities in Australia—1900–2015 and the implications for policy and practice. Environmental Science & Policy, 76, 165-176.

National Coronial Information System. (2017). Home – National Coronial Information System.   [online] Available at: http://www.ncis.org.au/ [Accessed 4 Oct. 2017].

Hawaii False Alarm Hints at Thin Line Between Mishap and Nuclear War

The following article, by Max Fisher, appeared in The Interpreter, New York Times, on January 14, 2018, the day after state emergency officials in Hawaii made a false warning to take shelter from an inbound missile threat.   Three days later, Japan’s public broadcaster accidentally sent news alerts that North Korea had launched a missile and that citizens should take shelter. The Japanese broadcaster, NHK, corrected itself five minutes later and apologized for the error on its evening news, initially blaming the J-Alert system but later conceding it was not to blame.  NHK’s swift rectification of its error stands in contrast to the 38-minute delay by officials in Hawaii on Saturday in cancelling warnings of an incoming ballistic missile threat. Notwithstanding common misperceptions to the contrary, there is no legal means to prevent launch once the President of the U.S. has made an order to launch, which can be done without consultation and whose timing follows “launch on launch (by the enemy)” to pre-empt the destruction of ground-based missiles by the enemy. Today’s issue of The Independent has an interesting take on how the Hawaii alarm may have been interpreted in Pyongyang on the following website:

http://www.independent.co.uk/voices/hawaii-missile-alert-nuclear-war-text-stop-north-korea-us-norad-defence-pacific-a8161501.html

and a very close call is described by former U.S. Secretary of Defence William Perry on this website:

https://www.npr.org/2018/01/16/578247161/ex-defense-chief-william-perry-on-false-missile-warnings


Nuclear experts are warning, using some of their most urgent language since President Trump took office, that Hawaii’s false alarm [on January 13, 2018], in which state agencies alerted locals to a nonexistent missile attack, underscores a growing risk of unintended nuclear war with North Korea. To understand the connection, which might not be obvious, you need to go back to the tragedy of Korean Air Lines Flight 007.

In 1983, a Korean airliner bound from Anchorage to Seoul, South Korea, strayed into Soviet airspace. Air defense officers, mistaking it for an American spy plane that had been loitering nearby, tried to establish contact. They fired warning shots. When no response came, they shot it down, killing all 269 people on board.

But the graver lesson may be what happened next. Though it was quickly evident that the downing had been a mistake, mutual distrust and the logic of nuclear deterrence — more so than the deaths themselves — set Washington and Moscow heading toward a conflict neither wanted. The story illustrated how imperfect information, aggressive defense postures and minutes-long response times brought both sides hurtling toward possible nuclear war — a set of dynamics that can feel disconcertingly familiar today.

Ronald Reagan had taken office in 1981 pledging to confront the Soviet Union. Though he intended to deter Soviet aggression, Moscow read his threats and condemnations — he had declared its government an “evil empire” that must be brought to an end — as preludes to war. Mr. Trump’s White House has issued its own threats against North Korea, suggesting that it might pursue war to halt the country’s nuclear weapons development.

The 1983 shooting down, on its own, might have passed as a terrible mistake. But the superpowers had only fragmentary understanding of something that had happened on the far fringes of Soviet territory. In an atmosphere of distrust, technical and bureaucratic snafus drove each to suspect the other of deception.  Moscow received contradictory reports as to whether its pilots had shot down an airliner or a spy plane, and Soviet leaders were biased toward trusting their own. So when they declared it a legal interception of an American military incursion, American leaders, who knew this to be false, assumed Soviet leaders were lying. Moscow had downed the airliner deliberately, some concluded, in an act of undeclared war.

At the same time, Washington made a nearly perfect mirror-image set of mistakes — suggesting that such misreadings are not just possible, but dangerously likely.  Mr. Reagan, furious at the loss of life, accused Moscow of deliberately targeting the civilian airliner. He denounced Soviet society itself as rotten and in pursuit of world domination.  In fact, a C.I.A. assessment, included in the president’s daily briefing that morning, had concluded the incident was likely an error. Mr. Reagan appeared to have simply missed it.

But Soviet leaders had never considered this; they assumed Mr. Reagan was lying about their intentions. Some concluded he had somehow lured the Soviet Union into downing the aircraft as cover for a massive pre-emptive attack, which they feared might come at any moment.  Each read the other’s blundering and dissembling as intentional, deepening suspicions among hard-liners that the other side was laying the groundwork for war. And if war was coming, the logic of nuclear deterrence all but required firing first.

Nuclear-armed missiles had recently achieved a level of speed and capability so that one power could completely disarm another in a matter of minutes. This created something called first-strike instability, in which firing first — even if you think you might be firing in error — is the only way to be sure of preventing your own obliteration.  The result was that the United States and the Soviet Union repeatedly went to the brink of war over provocations or even technical misreadings. Often, officials had mere minutes to decide whether to retaliate against seemingly real or impending attacks without being able to fully verify whether an attack was actually underway. In the logic of nuclear deterrence, firing would have been the rational choice.

That dynamic is heightened with North Korea, which is thought to have only a few dozen warheads and so must fire them immediately to prevent their destruction in the event of war.  “Today’s false alarm in Hawaii a reminder of the big risks we continue to run by relying on nuclear deterrence/prompt launch nuclear posture,” Kingston Reif, an analyst with the Arms Control Association, wrote on Twitter, referring to the strategy of firing quickly in a war. “And while deterring/containing North Korea is far preferable to preventive war, it’s not risk free. And it could fail.”

If similar misunderstandings seem implausible today, consider that an initial White House statement called Hawaii’s alert an exercise — though state officials say it was operator error. Consider that 38 minutes elapsed before emergency systems sent a second message announcing the mistake. If even Washington was misreading events, the confusion in Pyongyang must have been far greater. Had the turmoil unfolded during a major crisis or period of heightened threats, North Korean leaders could have misread the Hawaiian warning as cover for an attack, much as the Soviets had done in 1983. American officials have been warning for weeks that they might attack North Korea. Though some analysts consider this a likely bluff, officials in Pyongyang have little room for error.

Vipin Narang, a nuclear scholar at the Massachusetts Institute of Technology, suggested another possible scenario, using shorthand terms to refer to the president and his nuclear command systems, which Mr. Trump has nearby at all times. “POTUS sees alert on his phone about an incoming toward Hawaii, pulls out the biscuit, turns to his military aide with the football and issues a valid and authentic order to launch nuclear weapons at North Korea,” Mr. Narang wrote on Twitter, adding, “Think it can’t happen?”

Unlike in 1983, no one died in Hawaii’s false alarm. But deaths are not necessary for a mistake to lead to war. Just three months after the airliner was shot down, a Soviet early warning system falsely registered a massive American launch. Nuclear war may have only been averted because the Soviet officer in charge, operating purely on a hunch, reported it as an error.

North Korea is far more vulnerable than the Soviet Union was to a nuclear strike, giving its officers an even narrower window to judge events and even greater incentive to fire first. And, unlike the Soviets, who maintained global watch systems and spy networks, North Korea operates in relative blindness. For all the power of nuclear weapons, scholars say their gravest dangers come from the uncertainty they create and the fallibility of human operators, who must read every signal perfectly for mutual deterrence to hold.

In 1983, Washington and Moscow took steps that heightened the uncertainty, darkly hinting at each other’s illegitimacy and threats of massive retaliation, in a contest for nuclear supremacy, and survival. Each was gambling they could go to the brink without human error pushing them over. William J. Perry, a defense secretary under President Bill Clinton, called the false alarm in Hawaii a reminder that “the risk of accidental nuclear war is not hypothetical — accidents have happened in the past, and humans will err again.”

Mr. Reagan concluded the same, writing in his memoirs, “The KAL incident demonstrated how close the world had come to the nuclear precipice and how much we needed nuclear arms control.” Mikhail Gorbachev, who soon after took over the Soviet Union, had the same response, later telling the journalist David Hoffman, “A war could start not because of a political decision, but just because of some technical failure.”  Mr. Gorbachev and Mr. Reagan reduced their country’s stockpiles and repeatedly sought, though never quite reached, an agreement to banish nuclear weapons from the world. But Mr. Trump and North Korea’s leader, Kim Jong-un, remain locked in 1983, issuing provocations and threats of nuclear strikes on push-button alert, gambling that their luck, and ours, will continue to hold.

6 ways you can prepare for the on-coming heatwave

Australian Geographic spoke with heatwave risk management experts to determine what you can do to beat the heat over the next week.

Most of south-east Australia is gearing up for what’s predicted to be a sweltering five day heatwave, according to the Bureau of Meteorology, and fire-fighters are on high alert.

Weather risk management experts Andrew Gissing and Lucinda Coates from Risk Frontiers say that when the heatwave hits, it’s important to avoid complacency and have a well thought out plan.

Read more.

 

Australia’s ‘deadliest natural hazard’: what’s your heatwave plan?

This article by Andrew Gissing and Lucinda Coates has appeared in today’s The Conversation.

“Heatwaves are Australia’s deadliest natural hazard, but a recent survey has found that many vulnerable people do not have plans to cope with extreme heat.

Working with the Bushfire and Natural Hazards Cooperative Research Centre and the Bureau of Meteorology, my colleagues and I surveyed 250 residents and 60 business managers in Western Sydney and the NSW North Coast.

We found that 45% of those at risk – including the elderly, ill and very young – did not proactively respond to heatwave warnings as they did not think it necessary or did not know what to do.”

Follow the link below to read more:

https://theconversation.com/australias-deadliest-natural-hazard-whats-your-heatwave-plan-90165

The heat is on: but we’ve been there before

By Lucinda Coates, Risk Frontiers

Sydney was the hottest city on earth on Sunday 7 January 2018 (and no, I’m not talking about its nightlife) when Penrith, in the outer west, reached 47.30C, pipping its previous record set on 11 February 2017 (News Limited, 2018).

But if you want really hot, then travel back in time to 1939, when the Old Richmond Station set Sydney’s official heat record at 47.80C.  Yes, we’ve had heatwaves before.  Way before.

The table below shows numbers of deaths and death rates per 100,000 population from episodes of extreme heat in Australia by decade between 1844 and 2010, as recorded in Risk Frontiers’ PerilAUS database (after Coates et al. (2013)). PerilAUS is a resource of natural hazard event impacts reaching back to the early days of Australia’s European settlement.  The death rate is the number of deaths per head of population in the country at that time, and was consistently significantly higher between 1890 and 1939 than for any period before or since.

Of all of the entrIes in the Table, the January 1939 event was notable for its longevity and record daily temperature maxima. Victoria and South Australia, as well as country NSW, were affected with Melbourne reaching a high of 45.60C and Adelaide 46.10C.  In NSW, Bourke suffered through 37 consecutive days over 380C.

PerilAUS records show that at least 420 people died in the 1939 event across Australia, most (77%) in NSW. The series of heatwaves were accompanied by strong northerly winds, and followed a very dry six months. This led to the disastrous Black Friday bushfires in Victoria, which killed 71 people.

Most will remember the catastrophic bushfires that destroyed several towns in Victoria in 2009 but not many will remember that these fires also followed two heatwave events across Victoria and SA, where at least 432 people died.

This figure comprises mainly a measure of excess deaths rather than recorded individual deaths. An excess death is a premature death and, in this context, a measure of the number of deaths occurring over and above that expected for that location and time of year.

In 2009, new records of three consecutive days over 430C in Melbourne and eight over 400C in Adelaide were set.  A feature of these heatwaves was the very hot minimum temperatures, with Melbourne’s temperature falling to between 20-250C overnight and Adelaide to just 300C.

A similar death toll resulted from the heatwave that occurred from October 1895 to January 1896 that impacted nearly the entire continent but especially the interior. PerilAUS records 435 deaths, 89% of them within NSW.  Deaths also occurred in SA, WA, Victoria and Queensland. Bourke, in NSW, lost 1.6% of its population to the heat: temperatures of 400C in the shade were already being recorded in October, mid-Spring.

Heatwaves in Australia, including catastrophic ones, are not new. Risk Frontiers first noted the fact that they are Australia’s number one natural hazard killer more than two decades ago (Coates, 1996). For further reading on this important natural hazard, the reader is referred to Coates et al. (2013).

References

Coates L, 1996, An Overview of Fatalities from Some Natural Hazards, Proceedings, NDR96 Conference on Natural Disaster Reduction, 29 September-2 October 1996, Gold Coast, ed. R L Heathcote, C Cuttler and J Koetz. 49-54 http://search.informit.com.au/documentSummary;dn=547566533577889;res=IELENG

Coates L, Haynes, K, O’Brien, J, McAneney, J and Dimer de Oliveira, F, 2014, Exploring 167 years of vulnerability: An examination of extreme heat events in Australia 1844-2010, Environmental Science & Policy, 42:33-44. http://www.sciencedirect.com/science/article/pii/S1462901114000999

News Limited, 2018 – news.com.au [Daily Telegraph, 8 January 2018, originally published as Sydney: The hottest place on Earth], NSW heatwave: Sydney the hottest place on Earth, http://www.news.com.au/technology/environment/nsw-heatwave-sydney-the-hottest-place-on-earth/news-story/0486ad5df9b5025ac24a4507aa1b8a17, accessed 8/1/2018

Scars left by Australia’s undersea landslides reveal future tsunami potential

Paul Somerville, Risk Frontiers

 The following article, written by Tom Hubble and Samantha Clarke (U. Sydney) and Hannah Power and Kaya Wilson (U. Newcastle), appeared on The Conversation on December 10, 2017. The authors have modelled tsunamis that would be generated by these slides and conclude that “we suspect that such tsunamis pose little to no immediate threat to the coastal communities of eastern Australia” although it seems that very localised effects could be significant. Notably the article does not mention onshore geological evidence for the occurrence of large tsunamis in Australia (e.g. Bryant and Nott, 2001, attributed to cosmogenic sources by Bryant et al. 2007), perhaps because this evidence is highly controversial. There are few data on the speed with which these submarine landslides move; if they move slowly they may not be tsunamigenic.

One recent example of a destructive tsunami that may have been caused by an undersea landslide triggered by an earthquake is the 1998 Sissano Lagoon, New Guinea tsunami associated with an Mw 7.0 earthquake (Tappin et al., 2008; 2014). There is evidence that a delayed, earthquake-triggered, submarine slump caused 2200 deaths from a tsunami with maximum coastal flow depths of 16 m, and a focused runup along a limited length of coast. (I was a high school teacher for two years in Wewak, just down the coast from this event, and was motivated to study seismology after experiencing, some years earlier, a neighbouring earthquake that did not generate a tsunami).


It is often said that we know more about the surface of other planets than we do about our own deep ocean. To overcome this problem, we embarked on a voyage on CSIRO’s research vessel, the Southern Surveyor, to help map Australia’s continental slope – the region of seafloor connecting the shallow continental shelf to the deep oceanic abyssal plain.

The majority of our seafloor maps depict most of the ocean as blank and featureless (and the majority still do!). These maps are derived from wide-scale satellite data, which produce images showing only very large features such as sub-oceanic mountain ranges (like those seen on Google Earth). Compare that with the resolution of land-based imagery, which allows you to zoom in on individual trees in your own neighbourhood if you want to. But using a state-of-the art sonar system attached to the Southern Surveyor, we have now studied sections of the seafloor in more detail. In the process, we found evidence of huge underwater landslides close to shore over the past 25,000 years.  Generally triggered by earthquakes, landslides like these can cause tsunamis.

Into the void

For 90% of the ocean, we still struggle to identify any feature the size of, say, Canberra. For this reason, we know more about the surface of Venus than we do about our own ocean’s depths. As we sailed the Southern Surveyor in 2013, a multibeam sonar system attached to the vessel revealed images of the ocean floor in unprecedented detail. Only 40-60km offshore from major cities including Sydney, Wollongong, Byron Bay and Brisbane, we found huge scars where sediment had collapsed, forming submarine landslides up to several tens of kilometres across.

A portion of the continental slope looking onshore towards Brisbane, showing the ‘eaten away’ appearance of the slope in the northern two-thirds of the image, the result of previous submarine landslides. Samantha Clarke.

What are submarine landslides?

Submarine landslides, as the name suggests, are underwater landslides where seafloor sediments or rocks move down a slope towards the deep seafloor. They are caused by a variety of different triggers, including earthquakes and volcanic activity.

The typical evolution of a submarine landslide after failure. Geological Digressions.

As we processed the incoming data to our vessel, images of the seafloor started to become clear. What we discovered was that an extensive region of the seafloor offshore New South Wales and Southern Queensland had experienced intense submarine landsliding over the past 15 million years. From these new, high-resolution images, we were able to identify over 250 individual historic submarine landslide scars, a number of which had the potential to generate a tsunami. The Byron Slide in the image below is a good example of one of the “smaller” submarine landslides we found – at 5.6km long, 3.5km wide, 220m thick and 1.5 cubic km in volume. This is equivalent to almost 1,000 Melbourne Cricket Grounds.

This image shows the Byron Slide scar, located offshore Byron Bay. Samantha Clarke.

The historic slides we found range in size from less than 0.5 cubic km to more than 20 cubic km – the same as roughly 300 to 12,000 Melbourne Cricket Grounds. The slides travelled down slopes that were less than 6° on average (a 10% gradient), which is low in comparison to slides on land, which usually fail on slopes steeper than 11°.

We found several sites with cracks in the seafloor slope, suggesting that these regions may be unstable and ready to slide in the future. However, it is likely that these submarine landslides occur sporadically over geological timescales, which are much longer than a human lifetime. At a given site, landslides might happen once every 10,000 years, or even less frequently than this.

A collection of submarine landslide scars off Moreton Island. Samantha Clarke

Since returning home, our investigations have focused on how, when, and why these submarine landslides occur. We found that east Australia’s submarine landslides are unexpectedly recent, at less than 25,000 years old, and relatively frequent in geological terms. We also found that for a submarine landslide to generate along east Australia today, it is highly likely that an external trigger is needed, such as an earthquake of magnitude 7 or greater. The generation of submarine landslides is associated with earthquakes from other places in the world.

Submarine landslides can lead to tsunamis ranging from small to catastrophic. For example, the 2011 Tohoku tsunami resulted in more than 16,000 individuals dead or missing, and is suggested to be caused by the combination of an earthquake and a submarine landslide that was triggered by an earthquake. Luckily, Australia experiences few large earthquakes, compared with places such as New Zealand and Peru.

Why should we care about submarine landslides?

We are concerned about the hazard we would face if a submarine landslide were to occur in the future, so we model what would happen in likely locations. Modelling is our best prediction method and requires combining seafloor maps and sediment data in computer models to work out how likely and dangerous a landslide threat is.

Our current models of tsunamis generated by submarine landslides suggest that some sites could represent a future tsunami risk for Australia’s east coast. We are currently investigating exactly what this threat might be, but we suspect that such tsunamis pose little to no immediate threat to the coastal communities of eastern Australia. That said, submarine landslides are an ongoing, widespread process on the east Australian continental slope, so the risk cannot be ignored (by scientists, at least).  Of course it is hard to predict exactly when, where and how these submarine landslides will happen in future. Understanding past and potential slides, as well as improving the hazard and risk evaluation posed by any resulting tsunamis, is an important and ongoing task. In Australia, more than 85% of us live within 50km of the coast. Knowing what is happening far beneath the waves is a logical next step in the journey of scientific discovery.

References

Bryant, E.A. and J. Nott (2001). Geological indicators of large tsunami in Australia. Natural Hazards, 24, 231–249.

Bryant, E.A., G. Walsh and D. Abbott (2007). Cosmogenic mega-tsunami in the Australia region: are they supported by Aboriginal and Maori legends? University of Wollongong, Research Online

Tappin, D., P. Watts, and S.T,  Grilli, (2008). The Papua New Guinea tsunami of 1998: anatomy of a catastrophic event. Natural Hazards and Earth System Sciences 8, 243–266.

Tappin, D. et al. (2014). Did a submarine landslide contribute to the 2011 Tohoku tsunami? Marine Geology 357 (2014) 344-361.

You should never drive into floodwater – some roads are more deadly than others

This article by Andrew Gissing appeared on The Conversation.

The floods that deluged parts of Victoria over the weekend are the latest in the state’s long history of flooding, following on from major floods in 2010, 2011, 2012 and 2016. In all such events, emergency services are on standby to rescue motorists who drive into floodwaters and get stuck or washed away – with potentially fatal consequences.

Most of the 178 flood-related deaths since 2000 have been a consequence of motorists driving into floodwaters.

Although there is a growing body of research on the decision-making of people who choose to enter floodwater, little research has been done before now on the factors that make some stretches of road more dangerous than others.

Read more:

https://theconversation.com/you-should-never-drive-into-floodwater-some-roads-are-more-deadly-than-others-88551

Forecast of Increased Earthquakes due to Slowing of Earth’s Rotation

Paul Somerville, Risk Frontiers.


In the past few weeks there have been sensational reports about a forecast accelerated rate of occurrence of large earthquakes in 2018.  Fortunately, one of the authors of the work that lies behind these reports has explained her calm view of the situation.  The following article, written by Sarah Kaplan, appeared in the Washington Post, last updated 22 November 2017.


Rebecca Bendick would like you to not panic. The University of Montana geophysicist knows you may have read the articles warning about “swarms of devastating earthquakes” that will allegedly rock the planet next year thanks to a slowdown of the Earth’s rotation. And she feels “very awful” if you’ve been alarmed. Those dire threats are based on Bendick’s research into patterns that might predict earthquakes – but claims of an impending “earthquake boom” are mostly sensationalism.

There is no way to predict an individual earthquake. Earthquakes occur when potential energy stored along cracks in the planet’s crust gets released, sending seismic waves through the Earth.  Since scientists know where those cracks exist, and how they are likely to convulse, they can develop forecasts of the general threat for an area. But the forces that contribute to this energy buildup and trigger its release are global and complex, and we still cannot sort out exactly how it might unfold.

In a paper published in August in the journal Geophysical Research Letters, Bendick and colleague Roger Bilham, a geophysicist at the University of Colorado, Boulder, did find a curious correlation between clusters of certain earthquakes and periodic fluctuations in the Earth’s rotation. By examining the historic earthquake record and monitoring those fluctuations, scientists might be able to forecast years when earthquakes are more likely to occur, they suggest.

“Something that people have always hoped to find . . . is some kind of a leading indicator for seismicity, because that gives us a warning about these events,” Bendick said. But that conclusion is by no means set in stone. It hasn’t been demonstrated in the lab or confirmed by follow-up studies. Several scientists have said they’re not yet convinced by Bendick’s and Bilham’s research. “The main thing I came away thinking was real old-fashioned scientific ‘let’s check this’ kind of thoughts,” research geophysicist Ken Hudnut told Popular Science. Hudnut, who works on earthquake-risk programs at the US Geological Survey, was not involved in the paper. And that reaction is okay with Bendick. That’s how these things are supposed to go: “Someone says something kind of marginally outlandish, and everyone checks their work and that’s how science progresses,” she said.

Historically, the field of earthquake forecasting has seen some particularly outlandish claims. People have tried to predict temblors based on the behaviour of animals, gas emissions from rocks, low-frequency electric signals rippling through the Earth – all without much success.  For that reason, Bendick said, “it’s a little bit scary to get into the game.” But getting a prediction right can mean the difference between life and death for countless people. The stakes are too high not to try.

For their recent paper, she and Bilham looked through the century-long global earthquake record to see if they could spot any signs that temblors around the world are linked. Initially, the data appeared completely random. But then Bendick and Bilham added a new number to their analysis: the “renewal interval,” or the amount of time a given earthquake zone requires to build up potential energy for a really big quake. “Basically you can think of earthquakes as something like a battery or a neuron; they have a certain amount of time they need to be charged up,” Bendick said.

A certain class of earthquakes – those with a magnitude of 7.0 or more, and a short renewal interval between 20 and 70 years – seemed to cluster in the historic record. Every three decades or so, the planet seemed to experience a bunch of them – as many as 20 per year, instead of the typical 8 to 10. It was as if something was causing the earthquakes to synchronise, even though they were happening in spots scattered around the globe. Contrary to some reports on the study, “it’s not exactly the case that every 32 years we have a bad patch,” Bendick said. “If it were that, people would have found [the pattern] ages ago. That would be super obvious in the record.” Instead, she explained, “events with that renewal interval happen together more often than they happen at random, and that pattern is statistically significant.” Sure, it’s a less flashy finding than, “we know when earthquakes will happen,” she acknowledged. But that’s geophysics for you. “We’re scientists, not magicians,” she said.

Next, Bendick and Bilham tried to figure out what mechanism might explain these earthquake clusters. They studied a wide range of global phenomena that unfold over the same time scales: sloshing of the molten rock in the mantle, ocean circulation changes, momentum transfer between the Earth’s core and the lithosphere (the planet’s solid, outermost shell).

The best fit were tiny, cyclical changes in the speed of the Earth’s rotation. The planet slows down infinitesimally every 30 years or so, and roughly five years later, a cluster of these severe, short-interval earthquakes appears. Russian geophysicists Boris Levin and Elena Sasorova have pointed out this correlation before, Bendick noted. So she and Bilham tried to take it a step further: They found a mechanism that might link the Earth’s rotation and clusters of quakes.

See, when the Earth’s rotation rate changes, its shape shifts. As the planet speeds up, mass moves toward the equator, much the way a dancer’s skirt flares out when she spins. When it slows, that mass shifts back toward the poles. The cumulative effect is tiny – a millimetre difference in the width of the globe. But if potential energy has already built up at a number of faults – “if they’re locked and loaded, as we’d say in Montana,” Bendick noted – “that tiny change is enough to kick some proportion of the faults over into their failure mode, which is earthquakes.”

Earth is currently at the end of a slowing period, Bendick pointed out, and the historic record would indicate another “cluster” may be on its way. She and Bilham hope the pattern might help scientists and public officials make some sense of the Earth’s unpredictable shaking. If disaster planners can say with some assurance that the planet is entering a period in which quakes are more likely, they might have an easier time making the case for preparedness measures.

But that doesn’t necessarily mean 2018 will be a particularly devastating year. For one thing, the kinds of temblors Bendick and Bilham analysed happen in areas that are already earthquake-prone – Japan, New Zealand, the west coast of the United States. For people who live in those regions, there is always a risk of a quake, and it is always good to be prepared.

Their study is about probabilities, not predictions, Bendick cautioned. Earth’s slowing does not mean that a quake will happen in the next year or so, just that the likelihood may have gone up. Moreover, this pattern of earthquake occurrence is definitely not the only factor influencing the Earth’s behaviour – if it were, scientists would have noticed the pattern a long time ago. There are doubtless other earthquake cycles on the planet, driven by phenomena not considered in the paper.

The research got a lot of attention after Bilham presented it at the October meeting of the Geological Society of America. Several critics noted that correlation is not causation – earthquake clusters and fluctuations of Earth’s rotation might happen on the same time scales, but that does not mean they are linked. Bendick acknowledged that there is less evidence for the proposed mechanism than for the pattern itself. But she’s confident the pattern is there. “I think this is likely to inspire many people to look at this pattern, and it’s possibly someone will come up with an even better explanation,” she said.

Notes by Paul Somerville

The following is excerpted from the abstract of Bilham and Bendick (2017).

On five occasions in the past century a 25-30% increase in annual numbers of Mw≥7 earthquakes has coincided with a slowing in the mean rotation velocity of the Earth, with a corresponding decrease at times when the length-of-day (LoD) is short. The correlation between Earth’s angular deceleration (d[LoD]/dt) and global seismic productivity is yet more striking, and can be shown to precede seismicity by 5-6 years, permitting societies at risk from earthquakes an unexpected glimpse of future seismic hazard.

The cause of Earth’s variable rotation is the exchange of angular momentum between the solid and fluid Earth (atmospheres, oceans and outer core). Maximum LoD is preceded by an angular deceleration of the Earth by 6-8 years. We show delayed (increase in) global seismic productivity is most pronounced at equatorial latitudes 10°N-30°S.

The observed relationship is unable to indicate precisely when and where these future earthquakes will occur, although we note that most of the additional Mw>7 earthquakes have historically occurred near the equator in the West and East Indies. A striking example is that since 1900 more than 80% of all M≥7 earthquakes on the eastern Caribbean plate boundary have occurred 5 years following a maximum deceleration (including the 2010 Haiti earthquake).

The 5-6 year advanced warning of increased seismic hazards afforded by the first derivative of the LoD is fortuitous, and has utility in disaster planning. The year 2017 marks six years following a deceleration episode that commenced in 2011, suggesting that the world has now entered a period of enhanced global seismic productivity with a duration of at least five years.

The correlation between the change in Earth’s rotation rate and the frequency of Mw>7 earthquakes from Bendick and Bilham (2017) is shown in Figure 1.  I have not seen the Bilham and Bendick (2017) presentation.

Figure 1. Changes in the length of the day correlate with decadal fluctuations in annual M ≥ 7 earthquakes, smoothed with 10 year running mean. Peak seismic activity and rotational acceleration occur at 15, 33, 60, and 88 year intervals. Source: Bendick and Bilham, 2017.

References

Bendick, R., and R. Bilham (2017), Do weak global stresses synchronize earthquakes?.  Geophys. Res. Lett., 44, 8320–8327, doi:10.1002/2017GL074934

Bilham, R. and R. Bendick (2017). A five year forecast for increased global seismic hazard.  Invited presentation, Geological Society of America Meeting, Seattle, Washington.