Tag Archives: Global Tsunami Scenario Catalogue

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.”

RMS To Launch Global Tsunami Scenario Catalog

The 2011 Tohoku earthquake and its accompanying mega-tsunami highlighted how a single magnitude 9.0 (Mw9) tsunami could impact multiple regions and lines of business. The size of the earthquake was considered beyond what was possible on this plate boundary, and there are many areas worldwide where a massive earthquake and accompanying tsunami could impact coastal exposures over a very wide area.

Global coastal exposure is increasing rapidly including port cities, refineries, power plants, hotels and beach resorts. On regions around the Pacific and parts of the Indian and Atlantic Oceans, some of these exposure accumulations are at frontline risk from the mega-tsunamis that would accompany magnitude 9.0 (Mw9) earthquakes.

Later this year, RMS will release a Global Tsunami Scenario Catalog to provide (re)insurers with a broad and relevant set of tsunami scenarios that include both local and ocean-wide impacts. The tsunamis scenarios have been generated by modeling fault rupture and sea floor deformation associated with earthquakes on the principal subduction zones worldwide, with magnitudes ranging between M8.0-9.5.

For each scenario the tsunami is modeled in three stages – a) the initial generation of the water level changes caused by sudden movements in the configuration of the seafloor, b) tsunami wave propagation, and c) the flooding inundation of coastlines.

For each scenario the tsunami flood is represented as the elevation of the water level at each onshore location in the path of a tsunami. The tsunami flood data also includes the maximum expected inundation depth of tsunami flooding so that users can estimate the level of destruction to different building categories. The tsunami modeling capability has been extensively tested to show the method reproduces the observed coastal water heights from recent tsunamis.

A key element of the work to create the new Global Tsunami Scenario Catalog involved identifying where Mw9 earthquakes had the potential to occur, and hence which were the coastal regions at risk from mega- tsunami. These regions include cities with high insurance penetration such as Hong Kong and Macao, the main Taiwanese port of Kaohsiung, the island of Barbados, as well as Muscat, Oman. Our research also shows that a mega-tsunami as large as Tohoku could even occur in the Eastern Mediterranean – and in fact a mega-tsunami was generated in this region in 365 A.D. A repeat of such a tsunami could impact a wide stretch of coastal cities from Alexandria, Egypt to Kalamata, Greece and Antalya, Turkey.

The Tohoku earthquake and tsunami surprised the world because it occurred on a plate boundary that was not considered capable of producing a giant earthquake. The lessons from Tohoku should be applied to other ‘dormant’ subduction zone plate boundaries worldwide where M9 earthquakes have the potential to occur even though they have not previously been experienced in the past few hundred years of history. The region-wide loss correlations associated with some of these events have the potential to affect multiple lines of property and marine exposures in diverse coastal locations, potentially spanning several countries in a single loss. (Re)insurers wishing to manage their regional coastal exposures should be testing their exposure accumulations against a credible set of the largest-scale earthquake and tsunami scenarios.