8:57 PM – Moderate Earthquake Felt Across Trinidad

At 8:57 PM Friday 4th September 2020, a preliminary Magnitude 5.5 (Md or Mt) earthquake occurred 64 km WNW of Port of Spain, Trinidad and Tobago, 89 km WNW of Arima, Trinidad and Tobago, and 92 km NW of San Fernando, Trinidad and Tobago

This event occurred at a shallow depth of 10 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.

There have been no initial reports of damages or injuries.

Preliminary information from the University of the West Indies Seismic Research Centre concerning the M5.5 Earthquake west of Trinidad and Tobago.
Preliminary information from the University of the West Indies Seismic Research Centre concerning the M5.5 Earthquake west of Trinidad and Tobago.

This event was widely reported felt across parts of Trinidad, Northeastern Venezuela, Grenada and St Vincent and the Grenadines. 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 to moderate magnitude earthquake northwest/west of Trinidad Friday night.
Seismic signal recorded at Grenville, Grenada for the light to moderate magnitude earthquake northwest/west of Trinidad Friday night.

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 the EMSC concerning the Earthquake west of Trinidad.
Preliminary information from the EMSC concerning the Earthquake west of Trinidad.

The European Mediterranean Seismological Centre (EMSC) also recorded this quake at a magnitude 5.4 (Mww) at a moderate depth of 79.7 kilometers, slightly closer to Trinidad but much deeper than the UWI SRC solution.

Reviewed information from the USGS concerning the Earthquake west of Trinidad.
Reviewed information from the USGS concerning the Earthquake west of Trinidad.

The United States Geological Service (USGS) also recorded this quake at a magnitude 4.7 (Mwr) at a moderate depth of 48.4 kilometers, slightly further south from the UWI SRC solution.

Preliminary information from FUNVISIS concerning the M4.3 (UWI SRC M5.0) Earthquake northwest of Trinidad.

The Venezuelan Foundation for Seismological Research (FUNVISIS) also recorded this quake at a magnitude 4.7 (Mw) at a deeper depth of 4.7 kilometers, much further east and south, closer to Trinidad, from the UWI SRC solution.

Seismicity in this area is very common, with 184 quakes occurring with 10 kilometers of the epicenter of this quake since 1960. The strongest event occurring within this 10-kilometer area was a magnitude 4.6 earthquake on July 27th, 1978. Most quakes in this area register below magnitude 5.0, making this quake the strongest quake within a 10 km in recent recorded history.

This quake like occurred in seismic zone 1, in the Paria Peninsula. Focal mechanisms show that this quake likely occurred on a normal fault.

USGS Regional Moment Tensor (Mwr) for Friday night's earthquake west of Trinidad, showing normal faulting. (USGS)
USGS Regional Moment Tensor (Mwr) for Friday night’s earthquake west of Trinidad, showing normal faulting. (USGS)

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, where this quake occurred, 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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