Category Archives: Tsunami

The Lessons From “Last Year’s” Catastrophes

Catastrophe modeling remains work in progress. With each upgrade we aim to build a better model, employing expanded data sets for hazard calibration, longer simulation runs, more detailed exposure data, and higher resolution digital terrain models (DTMs).

Yet the principal way that the catastrophe model “learns” still comes from the experience of actual disasters. What elements, or impacts, were previously not fully appreciated? What loss pattern is new? How do actual claims relate to the severity of the hazard, or change with time through shifts in the claiming process?

After a particularly catastrophic season we give presentations around ”the lessons from last year’s catastrophes.” We should make it a practice, a few years later, to recount how those lessons became implemented in the models.

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How to Maintain Awareness of Tsunami Risk

Today is World Tsunami Awareness Day — designated by the United Nations General Assembly, and according to the United Nations Office for Disaster Risk Reduction (UNISDR), on average, tsunami events have a higher mortality rate than any other hazard. Over the past 20 years (1998-2017) tsunamis have claimed more than 250,000 lives and are also attributable for US$280 billion of the US$661 billion of total recorded economic losses for earthquakes and tsunamis. Between 1978-1997, tsunamis claimed 998 lives, and US$2.7 billion in losses. Overall, tsunamis are rare, but as the UN points out, when they occur they are deadly and hugely damaging. This infrequency makes building awareness and preparedness more of a challenge.

The UN has promoted World Tsunami Awareness Day since 2015, and the UN Secretary-General’s Special Representative for Disaster Risk Reduction, Mami Mizutori, stated that “…it is an occasion to promote greater understanding of tsunami risk to avoid future loss of life. This year we also want to bring attention to the economic losses tsunamis can inflict as a result of damage to critical infrastructure located along vulnerable, densely populated coastlines.”

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Ultra-liquefaction Changes Everything

It turns out the biggest killer in the Palu earthquake on the island of Sulawesi, Indonesia, may not have been the tsunami after all — but liquefaction. Two thousand victims of the earthquake and tsunami are confirmed but 5,000 people remain missing, many of them presumed swallowed up in extraordinary ground deformation and mudflows, which took off when the underlying solid ground liquefied. Some buildings were transported hundreds of meters, others were ripped apart, many collapsed into fragments that then became absorbed into the mud. Media reports state that in Balaroa, just a few kilometers from Palu City, many of the 1,747 houses in the village appear to have sunk into the earth. In Petobo, a village to the east of Palu, many of the village’s 744 houses have disappeared.

What we have witnessed at Palu merits the term “ultra-liquefaction”, as witnessed in the 2011 Christchurch, New Zealand earthquake when perhaps half the total insurance loss costs were a consequence of liquefaction. For Christchurch, in the eastern suburbs it was single storey houses, ripped apart by the ground movements. In the Central Business District (CBD), many mid-rise buildings had to be demolished because underlying liquefaction had led to one corner of the structure sinking by ten or twenty centimeters (four to eight inches).

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The Tragedy at Palu

A version of this article was originally published in Insurance Day

The Mw7.5 earthquake in Sulawesi, Indonesia on September 28 reminds us that fourteen years after the terrible Indian Ocean tsunami, and despite significant investment in systems intended to provide tsunami warnings, the risk to life and property is not going away. To understand why the destruction and loss of life in the city of Palu, with a population of 350,000, is so great (1,300 and rising) we need to understand why this location has proved such a nexus of vulnerabilities.

First, Palu is located less than one degree south of the equator. That means it is in the “shadow zone” for tropical cyclones. In most of the world’s oceans, no tropical cyclone can exist within ten degrees of the equator, although in the western Pacific the typhoon exclusion zone can narrow down to six to eight degrees from the equator. The lack of Coriolis force at the equator prevents a collection of thunderstorms gaining a structured rotation (and tropical cyclones spin in opposite directions in the northern and southern hemispheres).

The lack of tropical cyclones means there are no significant storm surges, or even much in the way of significant wind-driven waves, and as a result people build their houses right down to sea level. This means, in comparison even with a coastal city in Philippines or China, there were many more seafront buildings exposed to a tsunami that reached no more than three to five meters above sea level.

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Sulawesi Earthquake and Tsunami: The Deadliest Earthquake of 2018

The earthquake and subsequent tsunami that struck the Indonesian island of Sulawesi on Friday, September 28, has already claimed the sinister accolade of being the deadliest earthquake in the world this year.

According to local authorities, there have so far been 1,374 reported fatalities, but this figure is set to rise as rescue efforts spread out from the main cities. At this stage, thousands of people are believed to still be trapped under the rubble of collapsed buildings, and at least 60,000 people are displaced with limited food and water supplies.

The 7.5 magnitude earthquake struck the island of Sulawesi on Friday, September 28, approximately 48 miles (78 kilometers) north of Palu, a coastal city with around 330,000 residents. The earthquake triggered a ten foot (three meter) high tsunami, that impacted the coastal areas of western Central Sulawesi, including Palu City and Donggala, a regency with a population of around 275,000.

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The Ever-present Threat of Tsunami: Are We Prepared?

Last week’s Mw8.3 earthquake offshore the Coquimbo region of central Chile served as a reminder that many coastal regions are exposed to earthquake and subsequent tsunami hazard.

While the extent of damage and loss of life from the recent Chile earthquake and tsunami continues to emerge and is tragic in itself, it is safe to say that things could have been much worse. After all, this is the same subduction zone that produced the 1960 Valdivia earthquake (or “Great Chilean earthquake”) 320 miles further to the south—the most powerful earthquake in recorded history.

The 1960 Valdivia earthquake had a magnitude of Mw9.6 and triggered a localized tsunami that battered the Chilean coast with waves in excess of 20 meters as well as far-field tsunami around the Pacific Ocean. Many events of M8.5+ produce tsunami that are truly global in nature and waves of several meters height can even reach coast lines more than 10,000 kilometers away from the event source, highlighting the need for international tsunami warning systems and awareness of population, city planners, and engineers in coastal areas.

 Coastlines At Risk of Tsunami

Tsunami and their deadly consequences have been with us since the beginning of mankind. What’s new, however, is the increasing awareness of the economic and insured losses that tsunami can cause. There are several mega cities in developed and emerging nations that are in the path of a future mega-tsunami, as reported by Dr. Robert Muir-Wood in his report Coastlines at Risk of Giant Earthquakes & Their Mega-Tsunami.

The 2011 earthquake and tsunami off the Pacific coast of Tohoku, Japan acted as a wake-up call to the insurance industry moving tsunami out of its quasi-niche status. With more than 15,000 lives lost, more than USD 300 billion in economic losses, and roughly USD 40 billion in insured losses, clients wanted to know where other similar high magnitude earthquakes and subsequent tsunami could occur, and what they would look like.

In response, RMS studied a multitude of high magnitude (Mw8.9-Mw9.6) event sources around the world and modeled the potential resulting tsunami scenarios. The scenarios are included in the RMS® Global Tsunami Scenario Catalog and include both historical and potential high-magnitude tsunami events that can be used to identify loss accumulations and guide underwriting decisions.

For example, below is an example output, showing the potential impact of a recurrence of the 1877 Chile Mw9.1 Earthquake (Fig 1a) and the impact of a potential future M9 scenario (Fig 1b) stemming from the Nankai Trough on the coast of Toyohashi, Japan.

Fig 1a: Re-simulation of the 1877 Chile Mw9.1 Earthquake. Coquimbo area shown. The inundation from this event would impact the entire Chilean coastline and exceed 9 meters inundation depth (further to the North). Fig 1b: M9 scenario originating on the Nankai Trough south of Japan, impacting the city of Toyohashi (population ~376 thousand), with inundation going far inland and exceeding 6 meters in height.

With rapid advances in science and engineering enabling a deeper understanding of tsunami risk, the insurance industry, city planners and local communities can better prepare for devastating tsunami, implementing appropriate risk mitigation strategies to reduce fatalities and the financial shocks that could be triggered by the next “big one.”

The 1960 Tele-tsunami: Don’t Forget the Far Field

On May 22, 1960 the most powerful earthquake ever recorded struck approximately 100 miles off the coast of southern Chile. The 9.5 Mw event released the energy equivalent to 2.67 gigatones of TNT (178,000 times the energy yielded from the atomic bomb dropped on Hiroshima) leading to extreme ground shaking in cities such as Valdivia and Puerto Montt, triggering landslides and rockfalls in the Andes as well as resulting in a Pacific basin wide tsunami. In Chile, 58,622 houses were completely destroyed with damages totalling $550 million (~$4 billion today adjusted for inflation).

However, the effects in the far field were also significant. While the majority of the damage and approximately 1,380 fatalities occurred in close proximity to the earthquake, a proportion of the tsunami death toll and damage occurred over 5,000 miles away from the epicentre and reached as far away as Japan and the Philippines.

Such tsunamis with the potential to cause damage and fatalities at locations distant from their source are known as tele-tsunamis or far-field tsunamis and require a large magnitude earthquake (>7.5) on a subduction zone to be triggered. Recent events, such as the 2011 Tohoku and 2010 Maule earthquakes, demonstrated that even if these criteria are met, the effects of any resulting tsunami may not be felt significantly beyond the immediate coastline. As such, it can be easy to forget the risks at potential far field sites. However, the 55th anniversary of the 1960 Chilean earthquake and tsunami provides a useful reminder that megathrust earthquakes can have far reaching consequences.

Across the Pacific, the 1960 tsunami caused 61 deaths and $75 million damage (~$600 million today) in Hawaii, 138 deaths and $50 million damage (~$400 million today) in Japan, and left 32 dead or missing in the Philippines.

Hilo Bay, on the big island of Hawaii, was particularly hard hit with wave heights reaching 35 feet (~11 meters), compared to only 3-17 feet or 1-5 meters elsewhere in Hawaii. Approximately 540 homes and businesses were destroyed or severely damaged, wiping out much of downtown Hilo.

Hilo aftermath copy   hilo tsunami copy
                          Aftermath of the event in Hilo (USGS)                                               Inundation extent of the 1960 tsunami in Hilo (USGS)

Despite an official warning from the U.S. Coast and Geodetic Survey and the sounding of coastal sirens, 61 people in Hilo died as a result of the tsunami and an additional 282 were badly injured. The majority of these casualties occurred because people did not evacuate, either due to misunderstanding or not taking the warnings seriously. Many remained in the Waiakea peninsula area, which was perceived to be safe due to the minimal damage experienced there during the event triggered by the 1946 Aleutian Islands earthquake.

Others initially evacuated to higher ground but returned before the event had finished. A series of waves is a common feature of far field tsunamis, with the first wave typically not being the largest. This was the case with the 1960 event with a series of 8 waves striking Hawaii. Thethird of these was most damaging, killing many of those who returned prematurely.

These avoidable casualties highlight the need for adequate tsunami mitigation measures, including education to ensure that people understand the warnings and the correct actions to take in the event of a tsunami. This is particularly important in areas exposed to far field tsunami hazard, where people may be less aware of the risk and there is enough time to evacuate. The introduction of a Pacific Tsunami Warning System in 1968 as a consequence of the event was a big step forward in improving such measures, the presence of which would no doubt substantially reduce the death toll were the event to reoccur today.

Mitigation efforts can also be supported by tools like the RMS Global Tsunami Scenario Catalog, which provides information on the inundation extent and maximum inundation depth for numerous potential tsunami scenarios around the globe. This can be used to identify areas at risk to far-field tsunami events, including those with no historical precedent, enabling the quantification of exposures likely to be worst impacted by such events.

A Decade Later – Reconsidering The Indian Ocean Earthquake and Tsunami

This December marks the 10-year anniversary of the Indian Ocean earthquake and tsunami, a disaster that killed more than 230,000 people in 14 countries. The disaster hit Thailand and Indonesia especially hard and is considered one of the ten worst earthquakes in recorded history based on damages.

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In advance of the anniversary on December 26, 2014, Dr. Robert Muir-Wood, RMS chief research officer, and Dr. Patricia Grossi, RMS senior director of global earthquake modeling, hosted their second Reddit Science AMA (Ask Me Anything). Back in October, Muir-Wood and Grossi hosted another AMA on the 25th anniversary of the Loma Prieta earthquake in the San Francisco Bay Area.

The latest Reddit thread generated almost 300 comments. Muir-Wood and Grossi discussed topics including: early warning systems for disasters like tsunamis, what variables are considered in catastrophe models, and if better building design can protect against natural disasters – particularly tsunamis. Highlights of the chat follow:

What kind of structural elements or configurations are best to combat or defend against these disasters?

Muir-Wood: There have been research studies on buildings best able to survive tsunamis. The key is to make them strong (from well engineered reinforced concrete) but with ground floor walls running parallel with the shoreline that are weak, so that the walls can be overwhelmed without threatening the whole building.

The 2004 Indian Ocean tsunami took a lot people by surprise due to the lack of a tsunami warning system even though there was a gap between the earthquake and the tsunami. If there was a tsunami warning system in place at the time would that have decreased the death toll by a lot, or not make too much of a difference considering how strong the tsunami was.

Grossi: Early warning systems are excellent tools for reducing the loss of life during an earthquake-induced tsunami event. But education is one of the easiest ways to reduce tsunami life loss. Such education needs to include knowledge of the cause of a tsunami and its association with the largest earthquakes to help individuals understand how their own observations can help them take appropriate action (e.g., seeing the water recede from the coastline). In essence, official warning systems can provide only part of the solution, as information can never be effectively disseminated to everyone along a coastline. With only 10 to 30 minutes warning in the nearfield of major tsunamis, it is imperative that people are taught to take their own action rather than wait for official instruction.

Show me the coolest tsunami video.

Muir-Wood: There are amazing videos of the Japan 2011 tsunami. I wouldn’t pick just one of them – but recommend you watch quite a few – because they are interestingly different. The most amazing feature of the tsunami is the way the water can continue to rise and rise, for five or ten minutes, apparently without end. And then how the people watching the tsunami, climb to higher locations and then realize that if it keeps rising there will be nowhere for them to go.

Was there anything we missed you wanted to discuss? Please let us know in the comments. 

Managing Risk 10 Years After the 2004 Indian Ocean Earthquake and Tsunami

On Sunday, December 26, 2004 at approximately 8 a.m. local time, a massive earthquake occurred along the Indian–Burma plate boundary off the coast of Sumatra, Indonesia. Rupturing over 1,200 km of the Sunda Trench, the magnitude of the earthquake has been estimated between M9.0 and M9.3—with the U.S. Geological Survey’s Centennial Earthquake Catalog estimating M9.1. Occurring at a fairly shallow depth—less than 30 km—the earthquake generated a basin-wide tsunami that inundated coastlines across the Indian Ocean and caused run-up waves farther afield, impacting the eastern coastline of Africa. By the end of the day, it was apparent that the event was going to emerge as one of the worst natural disasters in modern times.

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Economic Toll and Recovery

Overall economic losses from the 2004 disaster were approximately $10 billion, with the majority of loss attributed to the damage in the Indonesia, Thailand, Sri Lanka, and India. The large majority of property damage was caused by the tsunami waves. Along coastlines of most of the affected countries, buildings were situated closer to sea level than is typical of higher latitudes, exacerbating the impacts.

In the aftermath of the event, the international relief efforts across the Indian Ocean were seen as fairly effective. But the longer-term recovery work in certain regions has struggled—due to the overwhelming numbers of people displaced from their homes. There are, of course, examples of well-executed reconstruction efforts. Build Change—a partner organization of RMS—has worked with tsunami survivors in Banda Aceh, Sumatra to rebuild safe, sustainable homes. Ten years after the event, evidence of the destruction wrought by the tsunami remains in the high-impacted areas.

Humanitarian Impact 

While tsunami in the Indian Ocean have certainly occurred many times before, from the perspective of modern history, the human casualties from the 2004 Indian Ocean Earthquake and Tsunami have no historical equal. More than 225,000 people lost their lives in the disaster, with most of the loss of life occurring in the near field in Sumatra, Indonesia. In Indonesia, the tsunami destroyed virtually every village, town, road, and bridge along a 170-km stretch of coast less than 10 m above sea level. Sri Lanka’s Eastern and Southern provinces were severely impacted, with fatality rate among the population within 1 km of coast between 15% and 20%. In India, entire villages in Tamil Nadu were destroyed.

In Thailand, the tsunami affected local inhabitants and foreign tourists in the densely inhabited Phuket Island. The fatalities among the tourists were a significant proportion of the overall loss of life, as many were on the beach or in hotels near the sea at the time the tsunami waves struck. In addition, the initial tsunami wave in Phuket, which was east of the rupture, began with a receding wave. Many of the tourists (not indigenous to tsunami-prone coastal regions) were unfortunately not familiar with the nature of tsunami waves. In many (but not all) tsunami, the first movement of the sea is a withdrawal. Any occasion when the sea level recedes rapidly and inexplicably should be taken as a signal for immediate flight to higher ground.

Managing Tsunami Risk in the Aftermath

The 2004 Indian Ocean Tsunami highlighted inherent vulnerabilities in the world’s coastlines and the people who live there. Coastal populations are on the increase in many parts of the world, mostly due to the exploitation of sea resources or tourism-related activities. Adequate tsunami mitigation measures— such as tsunami warning systems, education, and land use planning—can be put in place to save lives, property, and the livelihoods of those living on the coast.

Although the impact of the 2004 disaster on the global insurance industry was minimal, it alerted the world to the dangers of tsunami hazards. Worldwide response to the 2004 disaster resulted in the establishment of the Indian Ocean Tsunami Warning and Mitigation System in 2006.

Ten years hence, the world has seen two more earthquake-induced tsunami events—in the 2010 M8.8 Maule, Chile Earthquake and in the 2011 M9.0 Tohoku, Japan Earthquake—causing many clients to inquire where else in the world can events like these happen?

Chennai, India

9:30 a.m. local time

On the Indian peninsula, the hardest-hit areas were on India’s southeastern coast, in the state of Tamil Nadu, where close to 8,000 perished. Chennai, the capital of Tamil Nadu, has rebounded to become one of the Rockefeller Foundations’ “100 Resilient Cities” for its commitment to minimizing the impact of flooding in low-lying coastal areas and adopting a tsunami early warning system.

Just north of the earthquake’s epicenter, India’s Andaman and Nicobar islands were struck by waves reaching 4 to 15 m (13 to 50 ft) within 10 minutes of the earthquake. The death toll reached 7,000, with many more missing and presumed dead.

Distance from Epicenter

2,020 km

(1,260 mi)

Wave Height

5 m

(16 ft)

Time from initial rupture

3 hours

Banda Aceh, Indonesia

8:30 a.m. local time

The first wave reached Sumatra, Indonesia’s largest island, approximately 30 minutes after the initial rupture. Banda Aceh, the area hardest hit by the tsunami and closest major city to the earthquake’s epicenter, sustained more than 31,000 casualties in the city alone. Entire towns in the surrounding areas, some with populations of more than 10,000, vanished. More than 600,000 people in Aceh’s fishery and agricultural sectors lost their livelihoods.

Four times more women than men were killed—not just in Indonesia, but India and Sri Lanka as well—as many men were fishing, while women were on the beach, waiting for the fishermen to return, or at home, minding their children.

Distance from Epicenter

260 km

(160 mi)

Wave Height

30 m

(100 ft)

Time from initial rupture

30 min

Patong Beach, Thailand

9:30 a.m. local time

Tourism is one of Thailand’s key economic sectors, comprising about 12% of its overall GDP, with the greatest economic development along Thailand’s western coast. Khao Lak, Ko Phi Phi, and Phuket, with their pristine beaches, placid waters, and coral reefs, are among some of the most visited places on Earth. They were also the areas hit hardest by the tsunami.

The earthquake struck during the height of Thailand’s tourist season, causing close to 5,400 confirmed deaths, with many thousands more missing and presumed dead.

Distance from Epicenter

580 km

(360 mi)

Wave Height

6 m

(20 ft)

Time from initial rupture

1.5 hours

Galle Port, Sri Lanka

10:00 a.m. local time

Before the tsunami hit, elephants were observed running away from Patanangala beach in Yala National Park, directly in the tsunami’s path. Flamingos, goats, and buffaloes also moved to higher ground. All but two water buffaloes were unharmed.

When the waves came, Sri Lanka’s eastern and southern provinces were the hardest hit. In the coastal town of Telwatta, the tsunami struck an overcrowded train packed with passengers for the Buddhist full moon and Christmas holiday weekend. More than 1,700 lives were lost in what became the worst humanitarian disaster in railroad history.

Distance from Epicenter

1,750 km

(1,100 mi)

Wave Height

6 m

(20 ft)

Time from initial rupture

3 hours

Wave Height

6 m

(20 ft)

Northern Sumatra, West Coast

7:58 a.m. local time

The M9.1 earthquake struck 160 km (100 mi) off the northwest coast of Sumatra, Indonesia, generating the deadliest tsunami in history. With a rupture length of more than 1,200 km (750 mi), the earthquake released energy equivalent to 475 megatons of TNT, and shot a massive water column into the air.

The water settled back into the open ocean as a barely perceptible swell of only 50 cm (1.6 feet)—but moved at speeds of more than 600 km/hr (370 mph). It slowed toward the coast, inundating Sumatra with waves of up to 30 m (100 feet), leaving more than 225,000 people missing or presumed dead, and displacing 1.5 million more.

Countries impacted

14

Total insured losses

$1 billion

Total economic losses

$10 billion

Canada Earthquake Risk 85 Years After the Grand Banks Earthquake and Tsunami

November 18 marked the 85th anniversary of one of the largest and deadliest earthquakes in Canadian history, one that reiterates the importance of managing all drivers of earthquake risk effectively in the region.

The 1929 Grand Banks earthquake and tsunami was a magnitude 7.2 event that occurred just after 5:00 p.m. NST approximately 155 miles south of Newfoundland and was felt as a far away as New York City and Montreal. The earthquake caused limited damage on land and water, including minor landslides, but triggered a significant tsunami that was recorded as far south as South Carolina and as far east as Portugal.

Sea levels near the Newfoundland coast rose between 6 and 21 feet, with higher amounts recorded locally through narrow bays and inlets, and the tsunami claimed 28 lives. Had this event occurred near a more populated region, such British Columbia or Québec, the impacts could have been much worse.

Figure 1: A home in Newfoundland gets dragged out of a nearby cove following the 1929 Grand Banks earthquake and tsunami. Source: Natural Resources Canada

An event like this shows just how complex the Canadian earthquake risk landscape can be and how important it is to keep that view of risk as up-to-date and accurate as possible. On average, Canada experiences approximately 4,000 earthquakes each year. Most are small, but some can be large, particularly along the west coast near Vancouver and Victoria. There, in what is known as the Cascadia Subduction Zone, the Juan de Fuca plate is sliding underneath North America, causing subduction earthquakes, which tend to be less frequent but more severe than other Canadian seismic sources.

RMS has been modeling Canadian earthquake risk since 1991, with the last model update in 2009. The model inherently or explicitly includes the impacts of nearly all drivers of earthquake damage in that part of the world, from ground shaking, landslides, and liquefaction to fire following.

In building, updating, and validating the model over the years, RMS has collaborated with leading Canadian researchers and engineers, including representatives from what is now known as Natural Resources Canada (NRCan). RMS also maintains strong relationships with key insurance organizations and regulatory bodies, such as the Office of Superintendent of Financial Institutions and the Insurance Bureau of Canada, to play a key role in influencing guidelines and practices throughout the Canadian earthquake market.

The next update to the RMS Canada Earthquake Model is targeted for 2016 as part of a larger RMS North America Earthquake Models update. Among other enhancements, the model will incorporate the latest seismic hazard data (2015), internal research by the RMS seismic hazard development team, and introduce a probabilistic earthquake-induced tsunami model that will include losses from inundation along impacted coastlines.

Together, these updates will reflect the latest view of earthquake hazard in Canada, enabling the market to price and underwrite policies more accurately, and manage earthquake portfolio aggregations more effectively.