11:00AM Wednesday 6th March 2019 Final Update: A reviewed solution has been published by the U.W.I. Seismic Research Centre. This post has been updated.
At 8:12PM Tuesday 5th March 2019, a Magnitude 4.1 earthquake occurred 12 KM NNW of Arima, Trinidad and Tobago and 25.7 KM ENE of Port of Spain, Trinidad and Tobago. This event occurred at a shallow to moderate depth of 48.0 KM. No damage or injuries were reported.
It was widely reported felt across parts of Northern & Central Trinidad, Western Tobago and Grenada with 2 brief jolts. If you felt this earthquake, you can report it to the U.W.I. Seismic Research Centre here.
The United States Geological Survey reported a body wave magnitude of 4.4 mb. The U.W.I. Seismic Research Centre’s magnitude was calculated using the duration magnitude scale, resulting in a magnitude of Mt. 4.1. Discrepancies of magnitude and other earthquake parameters occur amongst seismic organizations and this is generally accepted in the scientific community. You can read more about it here.
Beyond the difference in magnitude, the USGS has this earthquake located slightly further west and south, in the Maracas Valley, well below the Loango community, at 10.722°N 61.423°W. UWI SRC reported this earthquake at 10.73°N and 61.30°W, located below a ridge of the Northern Range, just north of the Asa Wright Nature Centre.
Depths from both the UWI SRC and USGS were comparable, 48 kilometers and 57 kilometers respectively.
Based on the depth and location of this earthquake, it likely occurred within seismic zone 6, on-land Trinidad.
Trinidad is a highly faulted area, with several fault systems running across the island – all due to compensation of the lateral movement of the Caribbean and South American plates. There are several major fault systems that run across, on land, Trinidad including the El Pilar Fault system, the Central Range Fault, Northern Range Fault, Darien Ridge, Los Bajos Fault and the Arima Fault. Earthquakes on-land across Trinidad are typically less than 50 kilometers.
From the exact, reviewed location and depth of this quake, it likely occurred at or near the interface of the subducting slab of the South American plate under Trinidad. The hypocenter (depth) of the earthquake was 48 kilometers according to UWI SRC. Based on the Slab 2.0 model, the subducting slab at the location of the quake starts at 48 kilometers +/- 10.5 kilometers.
Looking at seismicity in the area of this earthquake, quakes are generally less than magnitude 4.5, dating back to the mid-1900’s.
Generally, in Trinidad and Tobago, a seismically active area, earthquakes of this magnitude, up to M8.0 and greater, are possible in area, and this statement has been repeated by seismologists at the U.W.I. Seismic Research Centre for decades.
Each year, over 2,200 seismic events are recorded in the Eastern Caribbean. On average, the Eastern Caribbean has seen a pattern of major (M7.0-M7.9) quakes every 20 to 30 years. That pattern has stayed true. The last major (M7.0-7.9) quake occurred north of Martinique in 2007.
Historical patterns indicate great earthquakes (M8.0+) on the Richter Scale have occurred every century or so in the region. The probability of another event at that level is high since the last >M8.0 earthquake occurred in 1843.
Now is the time to create or go over your earthquake preparedness plan and know what to do during, before and after an earthquake. See here for more details.
This event has been reviewed by an analyst at the U.W.I. Seismic Research Centre.