Tsunami Regional Exercise Set for March 21. One Scenario is an earthquake East of North Eastern Antilles

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Tsunami Regional Exercise Set for March 21. One Scenario is an earthquake East of North Eastern Antilles

SINT MAARTEN/CARIBBEAN - The Intergovernmental Coordination Group for Tsunami and Other Coastal Hazards Warning System for the Caribbean and Adjacent Regions (ICG/CARIBE EWS) of the United Nations Educational, Scientific, and Cultural Organization’s (UNESCO) Intergovernmental Oceanographic Commission (IOC), the U.S. National Oceanic and Atmospheric Administration (NOAA), and the Caribbean Regional Emergency Management Stakeholders (CEPREDENAC, CDEMA, and EMIZ) will be conducting the CARIBE WAVE tsunami exercise on March 21, 2017.

The purpose of this exercise is to advance tsunami preparedness efforts in the Caribbean Region. Three exercise scenarios are planned. The first scenario simulates a tsunami generated by a magnitude 7.9 earthquake located off the Caribbean coast of Costa Rica, in the southern Caribbean Sea.

The second scenario is a tsunami generated by a magnitude 8.2 earthquake located off the south-eastern coast of Cuba, in the north-western portion of the Caribbean Sea. The third scenario is a tsunami generated by a magnitude 8.5 earthquake located East of the North-eastern Antilles.

This tsunami exercise is being conducted to assist tsunami preparedness efforts throughout the Caribbean region. Recent tsunamis, such as those in the Indian Ocean (2004), Samoa (2009), Haiti (2010), Chile (2010, 2014, 2015), and Japan (2011), attest to the importance of proper planning for tsunami response.

Historical tsunami records from sources such as the NOAA National Centers for Environmental Information (NCEI) show that over 75 tsunamis have been observed in the Caribbean over the past 500 years.

These represent approximately 7-10% of the world’s oceanic tsunamis. Earthquake, landslide, and volcanic tsunami sources have all impacted the region. According to NCEI, in the past 500 years 4,561 people have lost their lives to tsunamis in the Caribbean and Adjacent Regions.

Since the most recent devastating tsunami of 1946, there has been an explosive population growth and influx of tourists along the Caribbean and Western Atlantic coasts increasing the tsunami vulnerability of the region (von Hillebrandt-Andrade, 2013).

In addition to tsunamis, the region also has a long history of destructive earthquakes. Historical records show that major earthquakes have struck the Caribbean region many times during the past 500 years. Within the region there are multiple fault segments and submarine features that could be the source of earthquake and landslide generated tsunamis.

The perimeter of the Caribbean plate is bordered by no fewer than four major plates (North America, South America, Nazca, and Cocos). Subduction occurs along the eastern and north-eastern Atlantic margins of the Caribbean plate. Normal, transform thrust and strike slip faulting characterize northern South America, eastern Central America, the Cayman Ridge and Trench and the northern plate boundary (Benz et al, 2011).

In addition to the local and regional sources, the region is also threatened by tele-tsunamis/trans-Atlantic tsunamis, like that of 1755 from Lisbon. With nearly 160 million people (Caribbean, Central America and Northern South America) now living in this region and a major earthquake occurring about every 50 years, the question is not if another major tsunami will happen, but when it happens will the region be prepared for the impact.

The risk of earthquakes generating tsunamis in the Caribbean is real and should be taken seriously.

North-eastern Antilles Scenario Along the North-eastern Antilles arc, the Atlantic plate subducts below the Caribbean at a rate of 2 cm per year. The subduction turns nearly perpendicular to the trench at latitudes 12°N and 19°N. Here, in 1843 a major earthquake with estimated magnitudes between M 7.0-M 8.7 and a rupture length between 100-300 km affected the Lesser Antilles region (Hayes et al., 2013).

This event produced a tsunami with maximum water height of 1.2 m at Antigua (https://www.ngdc.noaa.gov). For this exercise a 10 m slip results in a M 8.5 event located at 17°N and 67°W that ruptures a segment 200 km long and 65 km wide, located at 40 km depth.

Based on Bilek and Lay (1999), and the depth of 35 km, a shear modulus of 50 GPa was used. The scenario produces waves of maximum amplitudes larger than three meters, mostly locally, and waves up to three meters at a regional scale.

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