February 27, 2016 – 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
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.
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. (mostly pirates?)
On November 18, 1867, a magnitude 7.5 earthquake occurred in the Anegada trough, located between the US Virgin Islands of St. Croix, and St. Thomas.
The first tsunami wave struck the town of Charlotte Amalie, on the island of St. Thomas, approximately 10 minutes after the first shock, and the second wave approximately 10 minutes after the second shock. Both waves struck the harbor at Charlotte Amalie first as a large recession of water, followed by a bore, which eyewitness accounts describe as a 4.5 to 6.1 ( 14 to 20 feet) meter wall of water. At the southern point of Water Island, located approximately four kilometers from Charlotte Amalie, the bore was reportedly 12.1 ( 39. feet) meters high!
The waves destroyed many small boats anchored in the harbor, leveled the town’s iron warf, and either flooded out or destroyed all buildings located along the waterfront area. The waves also damaged a United States Navy ship De Soto, that happened to be anchored in the harbor at the time of the event. The tsunami produced an estimated 2.4 ( 8 feet) meters of runup at Charlotte Amalie, and a maximum 75 meter (246 feet) inland inundation.
Fredriksted St. Croix was struck by two large tsunami waves, each approximately 7.6 meters (25 feet) high, according to eyewitness accounts.
These waves caused severe damage along the waterfront, washing several wooden houses and other structures a considerable distance inland.
The waves destroyed many of the smaller boats anchored in the harbor, and beached a large United States Navy ship, the Monongahela.
A total of five people died as a result of the tsunami, the populat was no where near what it is today.
Eyewitness accounts from Frederiksted indicate that the water withdrew from the harbor almost immediately after the earthquake, which suggests that the first wave to strike here might have been a local tsunami produced by a submarine landslide.
Reports from Christiansted, St. Croix, indicate that the tsunami inundated an area up to 91 meters ( 298 feet )inland. The greatest damage here occurred at Gallows Bay, where the waves destroyed 20 houses and beached many boats.
Puerto Rico is located along the northern boundary of the Caribbean plate, the expression of which is manifested as the Puerto Rico Trench, located immediately north of the island.
At the Puerto Rico Trench (the deepest location in the Atlantic Ocean), the North American Plate is being obliquely subducted beneath the Caribbean Plate to the south.
This oblique subduction is accommodated by a series of active fault zones, which lie very close to Puerto Rico’s northern coast. The presence of these large, active fault zones located just off shore of the island, creates a substantial tsunami threat for the Puerto Rican coast.
On October 11, 1918, the island of Puerto Rico was struck by a magnitude 7.5 earthquake, centered approximately 15 kilometers off island’s northwestern coast, in the Mona Passage. In addition to causing widespread destruction across Puerto Rico, the quake generated a medium sized tsunami that produced runup as high as six meters (19 – to 20 feet ) along the western coast of the island.
The tsunami caused an estimated 4 million dollars in property and other damages to the coastal communities of Puerto Rico.
Of the 116 people killed by the earthquake, 40 of those were victims of the tsunami.
The largest earthquakes to occur in this region were the October 29, 1900 M7.7 Caracas earthquake, and the July 29, 1967 M6.5 earthquake near this same region.
Just imagine the lost of life and economic damage when a larger earthquake happened today.