This highly unusual quake happened many hours ago and has generated multiple ‘aftershocks’ easily in the range of 5.9 – 6.1 ever since it occured. I preferred to wait as long as possible on the USGS for their analysis and insight on this – but as usual – THEY HAVE NOTHING SIGNIFICANT TO ADD OR TO SAY ALMOST 12 HRS. LATER!!!!! 😳😠😡
AND.. much to my surprise they have not done their USUAL and now NORMAL DOWNGRADE of significant earthquakes. Trust me – 7.7 magnitude earthquake is very significant. I personally experienced the 1989 Loma Prieta earthquake while in SFO in a 70 year old brick and mortar building that had been ‘earthquake upgraded to the max’ and that one was only 6.9. I was trapped on the 3rd floor of that building (top floor) watching the corners of the ceiling and the walls separate every 2 seconds while plaster hit the desk that I was under for more than 30 seconds! It was then and still is today the largest earthquake I have experienced in life – and it scared the Holy Shxt out of me for more than 6 weeks as the aftershocks slowly diminished – finally disappearing. I cannot imagine a 7.7 magnitude earthquake that would be more than 70 times more powerful. https://en.wikipedia.org/wiki/1989_Loma_Prieta_earthquake
But I digress.. back to the USGS and their neglect of their critical mission they are NOT fulfilling. Following is the latest I could find from them on this unusual and very significant quake..
On January 28, 2020, a magnitude 7.7 earthquake struck in the Caribbean Sea, roughly equidistant from the coasts of Jamaica, Cuba and the Cayman Islands. Seismic instruments immediately detected the earthquake that originated at a depth of about 6.2 miles (10 km).
The U.S. Geological Survey continues to monitor the seismic activity in the region. The earthquake is a strike-slip event consistent with it occurring along the Oriente Fault. Aftershocks, which are already occurring, are normal and expected.
Despite the large size of the earthquake, the fact that it occurred offshore and away from high population areas lessened its societal impact. USGS estimates moderate shaking occurred on parts of Cuba and Jamaica, the two islands closest to the epicenter, and light to weak shaking across other parts of these islands. Light shaking was also reported from some parts of the Florida mainland.
USGS scientists report that this earthquake confirms what is already known about this part of the world: large earthquakes can and do happen in the Caribbean region. Given what we know about earthquake behavior, and given the distance between the magnitude 7.7 quake and the activity occurring in southwestern Puerto Rico, it is unlikely there is any relationship between these two seismic events. Typically, a M 6.4 event (the largest in the Puerto Rico sequence) will only influence activity within a few tens of kilometers or miles around itself. Nor do USGS earthquake experts expect the M7.7 earthquake to change the behavior of the earthquake sequence in Southwestern Puerto Rico. The distance between the earthquakes in southwestern Puerto Rico and today’s M 7.7 is approximately 1,250 kilometers or nearly 800 miles.
Five other earthquakes of M 6 or larger have occurred within 248 miles (400 km) of the January 28, 2020, event over the past half-century. They include a M 6.8 earthquake in December 2004, 174 miles (280 km) west of today’s earthquake, and a M 6.2 event in May 1992, almost 62 miles (100 km) east of today’s quake. None of these earthquakes are known to have resulted in shaking-related damage or fatalities, likely because of their location away from land and major population centers.
A USGS map of Caribbean tectonics is available here: https://www.usgs.gov/media/images/map-north-american-caribbean-tectonic-plate-boundary