9:35 AM – Light M4.0 Earthquake NW Of Trinidad

At 9:35 AM Wednesday 23rd September 2020, a preliminary light Magnitude 4.0 (Md or Mt) earthquake occurred 41.2 km NW of Güiria, Venezuela, 82.7 km WNW of Port of Spain, Trinidad and Tobago and 109.3 km NW of San Fernando, Trinidad and Tobago.

This event occurred at a depth of 78.43 Kilometers. This information (above) is preliminary by the U.W.I. Seismic Research Centre, the authority for seismic and volcanological information in the Eastern Caribbean. This information may change when additional data is processed by a seismologist.

Preliminary information from the University of the West Indies Seismic Research Centre concerning the M4.0 Earthquake west of Trinidad and Tobago.
Preliminary information from the University of the West Indies Seismic Research Centre concerning the M4.0 Earthquake west of Trinidad and Tobago.

This event has not been reported felt, likely due to its deep depth and low magnitude. 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:

  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).

None of these conditions occurred.

Seismic signal recorded at Grenville, Grenada for the light magnitude earthquake northwest/west of Trinidad Wednesday morning.
Seismic signal recorded at Grenville, Grenada for the light magnitude earthquake northwest/west of Trinidad Wednesday morning.

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.

Preliminary information from FUNVISIS concerning the M3.3 (UWI SRC M4.0) Earthquake northwest of Trinidad.
Preliminary information from FUNVISIS concerning the M3.3 (UWI SRC M4.0) Earthquake northwest of Trinidad.

The Venezuelan Foundation for Seismological Research (FUNVISIS) also recorded this quake at a much lower magnitude, 3.3 (Mw) at a shallower depth of 20.9 kilometers, much further north, away from Trinidad, compared to the UWI SRC solution.

This area records some of the highest seismicity in the Trinidad and Tobago region, with at least 752 located quakes occurring with 10 kilometers of the epicenter of this quake since 1960. The strongest magnitude earthquakes occurring within this 10-kilometer area were two magnitudes 5.1 earthquakes on December 12th, 1981 and more recently, March 5th, 2020. Most quakes in this area register below magnitude 5.0.

This quake like occurred in seismic zone 1, in the Paria Peninsula.

Seismic zone one is a complex, and without a doubt, the most seismically active area near Trinidad. Within zone one, the South American plate is beginning to rapidly descend into the Earth’s mantle as the detached oceanic lithosphere exists at depths between 50 to 300 kilometers. (Russo et al. 1993). This zone is one of the most active seismogenic sources in the Eastern Caribbean and has the potential to generate earthquakes up to Magnitude 8.0.

At shallower levels the North Coast Fault Zone, as well as the El Pilar Fault, part of the Boconó-San Sebastian-El Pilar Fault system, run across Zone 1. These fault systems compensate for the stress built up as the Caribbean plate slides past the South American plate. Hence, most of these earthquakes from these fault systems are shallow to moderate between 0 to 70 kilometers.

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.

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