by Curlan Campbell, NOW Grenada
Tuesday night, around 9:49 pm, a 4.9 magnitude earthquake tremor about 84 km northwest of Trinidad’s capital, Port of Spain and 113 km southwest of St George’s, Grenada rattled the two countries, causing no damage. The depth recorded was 23 km.
I was at home following up on emails when I felt the house shake and reached out to friends nearby to find out if they had also felt the tremor. The next day, I sought the expertise of The University of the West Indies Seismic Research Centre via email.
Clevon Ash, responsible for education and outreach at the centre indicated that Tuesday’s tremor felt in both countries does not necessarily precursor a much larger event, but should serve as a reminder that earthquake hazards are real, and should be factored in regional development plans.
The islands of the Eastern Caribbean including Grenada, as well as Trinidad and Tobago, lie on the eastern boundary of the Caribbean plate, which is interacting with the North American and South American plates in a process call subduction, which gives rise to the earthquake and volcanic activity characteristic of the region.
Ash stated that in “the Trinidad and Tobago area, at the south-east corner of the Caribbean plate, earthquake activity is significant, and we can expect to record annually, on average, 250 located earthquake events. More than 40 of those have the potential to be felt.”
“While, in general, the background earthquakes that may be felt are usually well spaced, maybe once a month, sometimes they come in bursts. This is in and of itself not necessarily precursory to a much larger event. However, our reality is that a significant magnitude event can occur at any time and small earthquakes that are being felt should be used as little reminders that the earthquake hazard is real and should be addressed not only in our development plans but in the routine of our lives.”
Research conducted in the US has shown that there exists a link between drilling for oil by petroleum companies and rise in seismic activities. According to information contained in an article published by PBS news hour entitled ‘Scientists study link between US oil drilling and rise in earthquakes’ state policymakers in Kansas and Oklahoma have experienced a vast reduction from ‘feeling an average of about 2 earthquakes a day, down from about 6 last summer, and Kansas is feeling about a quarter of the tremors it once did after restricting oil and natural gas operations in certain hotspots”.
The question of whether this may be contributing to the frequent tremors felt annually was posed and although Ash confirmed the authenticity of the report, he said this is not the case in the region.
“In recent years, oil companies, especially in the US, are using a technique where they inject fluid at a very high pressure to fracture shale formations and release the oil that is then recovered. This affects the stability of the subsurface, resulting in an increase in local seismicity. In areas like Oklahoma and Kansas, there has been a significant increase in induced earthquakes during the past decade. The term used for this method in the oil industry is called fracking. While, in general, the earthquakes so induced are of low magnitude, many have been large enough to be widely felt in the area, mainly due to the fact that they occur on land and at a shallow depth. It is also possible that some of the larger magnitude events recorded are from the activation of faults in the area.”
He continued that “In this context, fracking is not a technique being employed in petroleum exploration in Trinidad currently. Further, earthquakes have been occurring in the Trinidad and Tobago area long before activities associated with oil exploitation.”
Grenada’s National Disaster Management Agency (NaDMA) remains extremely concerned due to the frequency of tremors felt in recent times. This has prompted NaDMA to initiate its pilot project in the parish of St Patrick to get Grenada ‘Tsunami Ready’ in conjunction with the National Oceanic and Atmospheric Administration (NOAA) and UNESCO.
NaDMA indicated that St Patrick was chosen to pilot the project due to its proximity to the only live submarine volcano in the Eastern Caribbean, Kick ‘em Jenny, with plans to later replicate the project throughout the island.
According to the seismic centre’s site, “Kick ‘em Jenny is a submarine volcano located 8 km north of Grenada (12.18°N, 61.38°W). The volcano is about 1300 metres high and 300 metres wide at its summit, which is currently thought to be about 180 metres below the surface of the sea. As far as we know, Kick ‘em Jenny is the only ‘live’ (likely to erupt again) submarine volcano in the Eastern Caribbean. It is also the most frequently active volcano in the region, erupting at least 14 times since it was discovered in 1939. The most recent eruption of Kick ‘em Jenny occurred in April 2017.”
NaDMA’s Public relations Officer Oslyn Crosby said, “The project, which costs US$40,000 includes the creation of maps from Davey all the way up to Bathway, identifying the areas that will be affected by a tsunami, and evacuation routes, the erection of warning signs in 60 sites throughout the parish and public awareness campaigns aimed at ensuring every parishioner within knowing something about tsunamis, the importance of heeding warnings and what to do in the event of one…that project started last year.”
Crosby said NaDMA would increase its public awareness campaign going forward. “We will also start going door to door engaging our districts, and we also will be utilising the various media to ensure that every household in St Patrick knows what to do in the event of a tsunami. At the end of the programme, the board of directors will ensure that all the necessary proactive measures were implemented before internationally certifying St Patrick as ‘Tsunami Ready.’ Once that leg of the process is finished, then we can replicate the procedure in other parts of the island.”