By David Jacobson, Temblor
At 1:23 a.m. local time, a M=5.6 earthquake shook the eastern rim of the Caribbean near Antigua and Barbuda. Several aftershocks were also recorded, including a M=4.8 approximately one hour after the mainshock. Fortunately, this region is sparsely populated, and according to the USGS, no greater than light shaking was felt. Having said that, over 100,000 people were exposed to shaking and 42 people reported feeling the quake on the USGS website.
In the area around today’s quake, which is known as the Lesser Antilles, much of the seismicity is the result of subduction of the North American plate beneath the Caribbean plate at a rate of approximately 20 mm/yr. This subduction has not only caused earthquakes within the subducting plate, but helped form a chain of active volcanoes. According to the USGS, today’s earthquake occurred at a depth at 20 km, while the European-Mediterranean Seismological Centre assigned it a depth of 40 km.
Even though the Lesser Antilles is one of the most seismically active portions of the Caribbean, over the last century, few earthquakes have exceeded M=7.0. Having said that, on November 29, 2007, a M=7.4 quake shook the region, and in 1974, a M=7.5 quake caused significant damage in Antigua and Barbuda. Therefore, the region can experience damaging earthquakes.
Based on the Global Earthquake Activity Rate (GEAR) model, which is available in Temblor, this M=5.6 earthquake should not be considered surprising. The model, which uses global strain rates and seismicity since 1977 forecasts that a M=5.75 earthquake is likely in your lifetime. To check what the likely earthquake magnitude is in your lifetime anywhere on earth, click here. Should any more aftershocks occur or should there be new developments, we will update this post.
European-Mediterranean Seismological Centre
National Office of Disaster Services
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