Caribbean subduction zones have catastrophic tsunami potential, study shows

NEWARK, California — Four years after the 9.0 magnitude Tohoku Earthquake in Japan, catastrophe risk management firm RMS has released a global tsunami risk study that identified twenty subduction zones around the world – some of which are in the Caribbean region – with the capability of generating magnitude 9.0 earthquakes – even in zones considered to be dormant or inactive.

A subduction zone is the boundary between two of Earth’s tectonic plates. An earthquake occurs when the Earth’s tectonic plates push away from, pull towards or grind against each other, releasing energy and causing vibratory movements.

The after effects of an earthquake include, among others, landslides, volcanic eruptions, tsunamis, floods, fires, injuries and fatalities, falling buildings and other structures.

In a quote, Chief Research Officer at RMS Dr. Robert Muir-Wood said that while the Puerto Rico Trench, among others, is dormant, RMS analyses revealed that they were capable of generating tsunami waves similar in scale to those produced along the Japan Trench in 2011, bringing with them unprecedented devastation.

“Future mega-tsunamis should no longer be considered black swan events, as we now know where these events can occur. While these events have very low occurrence rates, communities and businesses on the coastlines at frontline risk of these events should assess the risk accordingly”, he said.

The study determined that if a tsunami occurred on the dormant Puerto Rico Trench, it would not only cause flooding along the northern and western coast lines of Puerto Rico, but also generate nine meter waves around the neighbouring islands of the Dominican Republic and the U.S and British Virgin Islands.

Generally, earthquakes with a magnitude of 2.0 or below are considered ‘micro-earthquakes’ as they are not usually felt in the area in which it occurs. Those earthquakes measuring 4.5 or more tend to be strong enough to be noticed.

Earthquakes in the Caribbean: The most recently devastating earthquake to occur in the Caribbean happened in Haiti in 2010. The death toll for the 7.0 magnitude earthquake was estimated between 230,000 to 316, 000. 300,000 persons injured and a further 1.5 million displaced. While Haiti’s structural and economic circumstances differ greatly to that of many other Caribbean islands, there is no foreseeing the strength of, or consequences, following a potential earthquake in any other part of the region.

Historically, there have only been five years on record in which devastating earthquakes occurred in the region.

In 1692, 90% of Port Royal, Jamaica was obliterated by an earthquake, killing over 2,000 people. Over a century later, in 1843, an estimated 8.0 – 8.5 magnitude tremor occurred in the Eastern Caribbean, causing damage in islands from St. Maarten to Dominica. An 8.1 M earthquake in 1946 in the Dominican Republic generated a tsunami resulting in 75 deaths and leaving 20,000 people homeless. Aftershocks from this event were still being felt in 1947 and 1948.

In 1974, a 7.5 M earthquake occurred between St. Kitts & Nevis and Trinidad & Tobago. And between the months of April to July in 1997, the southern islands of the Caribbean were affected by a series of earthquakes which affected an estimated 200 people and caused damages costing approximately USD$3 million.

During the latter months of 2014 and early into the current year, the University of the West Indies Seismic Research Unit recorded several, frequent smaller tremors in and around the Southern Caribbean, prompting seismologists to caution Caribbean residents to prepare for a major earthquake sooner, rather than later.

Downloads: Coastlines at Risk of Giant Earthquakes & Mega-Tsunamis