Moderate M5.6 Early Morning Earthquake Shakes Barbados, St. Vincent

At 2:35 AM Monday 29th March 2021, a (preliminary) moderate Magnitude 5.6 (Mt) earthquake occurred approximately 130 km NE of Bridgetown, Barbados, 246 km E of Castries, Saint Lucia and 268 km ESE of Fort-de-France, Martinique. This event was located at 58.760°W and 13.920°N, at a depth of 10.0 Kilometers.

There have been no reports of damages or injuries. This event was widely reported felt across Barbados and St. Vincent. You can submit felt reports to the University of the West Indies Seismic Research Centre.

U.W.I. Seismic Research Centre preliminary solution for the M5.6 earthquake northeast of Barbados
U.W.I. Seismic Research Centre preliminary solution for the M5.6 earthquake northeast of Barbados

The above information is preliminary from the U.W.I. Seismic Research Centre, the authority for seismic and volcanological information in the Eastern Caribbean. Earthquake parameters may change as more data is received and reviewed by seismologists.

There is no tsunami threat.

There are four conditions necessary for an earthquake to cause a tsunami:

  1. The earthquake must occur beneath the ocean or cause material to slide in the ocean.
  2. The earthquake must be strong, at least magnitude 6.5.
  3. 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.
  4. 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.

Seismic waves from the moderate M5.5-M5.6 earthquake recorded at RéNaSS seismometers.
Seismic waves from the moderate M5.5-M5.6 earthquake recorded at RéNaSS seismometers.

The French Central Seismological Office’s National Seismic Monitoring Network, with stations in the French Antilles, recorded this quake preliminarily at a much lower magnitude of 4.8 (MLv) though in a similar location and depth.

Meanwhile, the United States Geological Survey recorded this event and reviewed the information, registering the quake as a magnitude 5.5 (mww), at a depth of 10 kilometers. The USGS located event at 58.484°W and 13.8270°N, slightly further east and south than the UWI SRC.

USGS reviewed solution for the M5.5 earthquake northeast of Barbados
USGS reviewed solution for the M5.5 earthquake northeast of Barbados

Based on the location and depth of this quake, it is tectonic in origin and occurred within the overriding Caribbean Plate. In this area, the South American plate is beginning to descend into the Earth’s mantle.

U.W.I. Seismic Research Centre preliminary solution for the M5.6 earthquake northeast of Barbados with historical seismicity
U.W.I. Seismic Research Centre preliminary solution for the M5.6 earthquake northeast of Barbados with historical seismicity

In this location, the subducting slab is at approximately 20-40 kilometers depth. Within 20 kilometers of the epicenter of this earthquake, since the 1970s, there have been 93 recorded events with varying depths – from 0 KM to 142 KM, with the majority of quakes occurring below a 10-kilometer depth. However, this area just northeast of Barbados is no stranger to large earthquakes, with over 400 events recorded. The largest of these were magnitudes 6.6 (Md) and 6.3 (Md) on July 16th, 2015 just south and east of the most recent seismic event.

Earthquakes *cannot* be predicted – meaning the precise time, date, magnitude, depth, etc. cannot be known ahead of time based on current research and technology.

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, earthquakes 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.

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