An incident similar to the 2004 Indian Ocean tsunami might also be a potential risk for the Caribbean region, according to seismologists at the SSA 2018 Annual Meeting.
The Caribbean Islands lie in a tectonic setting where the North American plate is sinking beneath the Caribbean plate giving rise to earthquakes and volcanic activity. In this setting, earthquakes that rupture the crust may generate tsunamis. Volcanic eruptions and landslides (coastal or beneath the ocean) may also generate tsunamis. As a consequence, the entire arc may be considered a potential source for tsunami generation. Tsunamis have been observed in the Caribbean and its adjacent seas since the 16th century. Both local and distant (tele-tsunamis) tsunamis have affected this region at the rate of one or more severe occurrences per century. Indeed in the year 1755 the Great Lisbon earthquake near Portugal caused a tele-tsunami "as high as the upper storey's of houses" on the east coast of Martinique. Waves 2m high were also observed at the east coast of Barbados.
Christa von Hillebrandt-Andrade of the National Oceanic and Atmospheric Administration (NOAA) states: "It's been a long time since a big earthquake and tsunami have hit the region, but almost 3500 people have lost their lives in the past 500 years from tsunamis in the Caribbean. The vulnerability is just huge because so much of our population and infrastructure is located right along the coast''. She also notes: "Before 2004, we thought an earthquake of about 8.0 was about right for the largest we might see in the Caribbean, based on the history of earthquakes there and the length and motion of the faults, but now some think that several faults in the region could be capable of producing earthquakes of 8.6, and the catastrophic planning by our emergency management community is considering 8.5 and 9.0 earthquakes".
The region contains several large subduction zones and faults, most of which are located offshore and are challenging to study. One particular focus is the subduction zone associated with the Puerto Rico Trench, located north of Puerto Rico and roughly on the border of the Caribbean Sea and Atlantic Ocean. A large earthquake on the Trench could produce a tsunami that reaches Puerto Rico within 20 minutes, and might be felt as far away as the U.S. Eastern seaboard. There is no historical evidence of any megathrust 9.0 earthquakes taking place on the trench, and the fault there has "a bit of oblique motion that takes up some of the energy and doesn't create the big offset of the seafloor creating the tsunami" that would be expected from a straightforward subduction zone, von Hillebrandt-Andrade said.
For the researchers it would really be helpful to have more ocean bottom seismology where they can place seismometers on the seafloor close to these faults so that we can appreciate more of their movement. ''More Caribbean paleoseismology- Identifying and analyzing the evidence of past earthquakes- would also help researchers pinpoint the recurrence times of possible large earthquakes'', von Hillebrandt-Andrade points out.
Tsunamis have impacted the region in the past thus they are expected in the future. Therefore, the community should be alerted in order to be prepared for such an incident.
Sources: Sciencedaily.com, Whoi.edu
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