At 8:43 PM Thursday 9th September 2021, a preliminary light magnitude 4.9 (Md or Mt) earthquake occurred approximately 79.0 km NE of Point-à-Pitre, Guadeloupe, 84.0 km SE of Saint John’s, Antigua and Barbuda, and 173.0 km N of Roseau, Dominica. This event was located at 16.84N and 61.14W and at a depth of 10 kilometers.
This information (above) is preliminary from the U.W.I. Seismic Research Centre, the authority for seismic and volcanological information in the Eastern Caribbean. Quake parameters such as location, depth, and magnitude may change upon review from a seismologist at the SRC.
This event was widely reported felt across Guadeloupe, Antigua and Barbuda, St. Kitts and Nevis, and Montserrat. 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).
None of these conditions occurred.
Note that across the globe, different seismic monitoring agencies use different methods, or several methods, for processing quake parameters. Each method has its limitations and will likely produce different results within the ranges of the uncertainty of that data. This is generally accepted within the scientific community.
The United States Geological Survey registered this earthquake in a similar location and at a deeper depth compared to the U.W.I. Seismic Research Centre.
The EMSC also registered this earthquake in a similar location and at a deeper depth compared to the U.W.I. Seismic Research Centre.
Seismicity in this area is common, with over 400 quakes occurring with 20 kilometers of the epicenter of this quake since 1960. The strongest event occurring within this 20-kilometer area was a magnitude 5.8 quake on March 10th, 1976. If today’s M5.3 magnitude is not revised, it would be tied with May 15th, 1969, and January 18th, 1966’s M5.3 quakes to become the third-highest magnitude event in this area. Near all other quakes in the past have registered below magnitude 4.0. Depths of earthquakes in this area are variable, generally occurring under 50-kilometer depth, as deep as 113.9 kilometers within the subducting slab of the North American plate under the Caribbean plate.
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. See here for more details.