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Sunday, 15 December 2019

2019 has seen several earthquake swarms but a swarm close to the mag 7.0 Haiti strike in 2010 killing more than 150,000 people has recorded 3,068 mag 2.5 quakes or higher this year

Map, USGS

As this year is about to come to an end, 2019 has had several earthquake swarms, in November, an earthquake swarm was reported, under the Askja volcano, in Iceland. Over 1,000 earthquakes were recorded at the volcano, in less than a week. Around the same time, a new swarm of earthquakes struck near the California-Mexico border underneath the town of El Centro in Imperial County. 
Also in November, a total of almost a 1,000 quakes, rocked the Californian city of Ventura in just 7 days. And who can forget the July "swarmageddon" when1250 quakes of all magnitudes rocked Southern California bringing the total to 2,750 in just 48 hours with another 100 small quakes rocking the Coso Volcanic Field?

However, probably the most impressive swarm of 2019 is the mega-swarm in and around the Dominican Republic, Puerto Rico and the Caribbean Sea, just how many quakes have occurred there this year is impossible to know because my computer is too small to load all the info, however, 3,068 magnitude quakes or higher have been recorded this year so far.

The swarm is in the area where the devastating magnitude 7.0 struck Haiti in 2010 killing more than 150,000 people along with the total destruction of 250,000 buildings and 30,000 commercial buildings. The nation's history of the national debt, prejudicial trade policies by other countries, and foreign intervention into national affairs contributed to the existing poverty and poor housing conditions that increased the death toll after the disaster. Wikipedia

Should we expect another big one?

Extensive diversity and complexity of tectonic regimes characterize the perimeter of the Caribbean plate, involving no fewer than four major plates (North America, South America, Nazca, and Cocos).

Since 1900, the two largest earthquakes to occur in this region were August 4, 1946, M8.0 Samana earthquake in northeastern Hispaniola and the July 29, 1943, M7.6 Mona Passage earthquake, both of which were shallow thrust fault earthquakes. A significant portion of the motion between the North America plate and the Caribbean plate in this region is accommodated by a series of left-lateral strike-slip faults that bisect the island of Hispaniola, notably the Septentrional Fault in the north and the Enriquillo-Plantain Garden Fault in the south. Activity adjacent to the Enriquillo-Plantain Garden Fault system is best documented by the devastating January 12, 2010, M7.0 Haiti strike-slip earthquake, its associated aftershocks and a comparable earthquake in 1770.

Moving east and south, the plate boundary curves around Puerto Rico and the northern Lesser Antilles where the plate motion vector of the Caribbean plate relative to the North and South America plates is less oblique, resulting in active island-arc tectonics. Here, the North and South America plates subduct towards the west beneath the Caribbean plate along the Lesser Antilles Trench at rates of approximately 20 mm/yr. As a result of this subduction, there exists both intermediate focus earthquakes within the subducted plates and a chain of active volcanoes along the island arc.

Although the Lesser Antilles is considered one of the most seismically active regions in the Caribbean, few of these events have been greater than M7.0 over the past century. The island of Guadeloupe was the site of one of the largest megathrust earthquakes to occur in this region on February 8, 1843, with a suggested magnitude greater than 8.0. The largest recent intermediate-depth earthquake to occur along the Lesser Antilles arc was November 29, 2007, M7.4 Martinique earthquake northwest of Fort-De-France. USGS

Major Quakes

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