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.”