At 10:17 PM Friday 26th March 2021, a light (reviewed) Magnitude 4.0 (MLv) earthquake struck approximately 43.9 km NE of Roseau. This event was located at 61.010°W and 15.420°N, at a depth of 117 Kilometers.
This information has been reviewed by seismologists at BCSF-RENASS (French Central Seismological Office – National Seismic Monitoring Network).
Note that this quake likely fell below the magnitude 3.8 threshold for public reporting from the U.W.I. Seismic Research Centre based on their automatic calculations. The UWI-SRC is the authority for seismic and volcanological information in the Eastern Caribbean.
This event was not reported felt. You can submit felt reports to the University of the West Indies Seismic Research Centre.
There is no tsunami threat.
There are four conditions necessary for an earthquake to cause a tsunami:
- The earthquake must occur beneath the ocean or cause material to slide in the ocean.
- The earthquake must be strong, at least magnitude 6.5.
- The earthquake must rupture the Earth’s surface and it must occur at shallow depth – less than 70 KM below the surface of the Earth.
- The earthquake must cause vertical movement of the seafloor (up to several meters).
These conditions were not met.
Note that different seismic monitoring agencies use different methods, or several methods, for processing quake parameters across the globe. Each method has its limitations and will likely produce different results within the ranges of the data’s uncertainty. This is generally accepted within the scientific community.
Based on the location and depth of this quake, it is tectonic in origin. In this area, the South American plate is beginning to descend into the Earth’s mantle as the detached oceanic lithosphere exists at depths between 50 to 300 kilometers. (Russo et al. 1993).
Earthquakes *cannot* be predicted – meaning the precise time, date, magnitude, depth, etc. cannot be known ahead of time based on current research and technology.
Generally, across the Eastern Caribbean, a seismically active area, quakes of this magnitude, up to M8.0 and greater, are possible 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 quakes (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.