According to USGS, 13 earthquakes have struck in and around Puerto Rico and the Virgin Islands within the last 24 hours; there was also a sizeable quake near Haiti too. Despite the seismic activity, there is no threat of a tsunami for the region, for the U.S. East Coast, or for the coast around the Gulf of America.
From oldest to newest, the earthquakes include a magnitude 4.1 near Anse a Galets in Haiti, a 3.5 in Charlotte Amalie in the U.S. Virgin Islands followed by another there as a magnitude 3.4. A 3.6 then hit Suarez, Puerto Rico. Next was a magnitude 3.5 event near Cruz Bay in the U.S. Virgin Islands. A 2.4 magnitude earthquake then hit La Parguera, Puerto Rico, followed by a 3.5 in Punta Cana in the Dominican Republic. Those were followed by a 2.6 in Indios on Puerto Rico followed by another 3.6 in Punta Cana. A 2.3 then hit Maria Antonia in Puerto Rico followed minutes later by a magnitude 2.4 there. The last two earthquakes today were a 3.6 event in Cruz Bay again followed by a magnitude 2.1 event in Fuig, Puerto Rico.
According to USGS, earthquakes with a magnitude of 2.0 or less are rarely felt or heard by people, but once they exceed 2.0 , more and more people can feel them. While damage is possible with magnitude 3.0 events or greater, significant damage and casualties usually don’t occur until the magnitude of a seismic event rises to a 5.5 or greater rated event.
A few of these Puerto Rico earthquakes aren’t far from the epicenter of a strong earthquake that hit in January 2020. That 6.4 created extensive damage in Puerto Rico, including widespread power failures across much of the island.  An earthquake swarm started here in December 2019 and unrest has continued since.
Haiti is also no stranger to severe earthquakes. A catastrophic 7.0 earthquake struck 16 miles west of Haiti’s capital of Port-au-Prince in 2010. According to the Haitian government, roughly 220,000-316,000 people were killed while 250,000 homes and 30,000 businesses collapsed or were severely damaged. All in all, roughly 3 million people were directly impacted by that earthquake.
These earthquakes are occurring near the northern edge of the Caribbean Plate, a mostly oceanic tectonic plate underlying Central America and the Caribbean Sea off of the north coast of South America. The Caribbean Plate borders the North American Plate, the South American Plate, the Nazca Plate, and the Cocos Plate. The borders of these plates are home to ongoing seismic activity, including frequent earthquakes, occasional tsunamis, and sometimes even volcanic eruptions.
USGS continues to monitor earthquake activity in and around Puerto Rico while the National Weather Service Tsunami Warning Center is keeping an eye on any tsunami threats.
Tsunamis are giant waves caused by earthquakes or volcanic eruptions under the sea. Out in the depths of the ocean, tsunami waves do not dramatically increase in height. But as the waves travel towards the coast, especially within shallow coastal waters, they build up to higher and higher heights as the depth of the ocean decreases. The speed of tsunami waves depends on ocean depth rather than the distance from the source of the wave. Tsunami waves may travel as fast as jet planes over deep waters, only slowing down when reaching shallow waters. While tsunamis are often referred to as tidal waves, this name is discouraged by oceanographers because tides have little to do with these giant waves.
An earthquake causes a tsunami when it abruptly shifts the seafloor vertically during a major underwater or coastal earthquake. This sudden motion pushes a massive column of water upward or drops it downward. Gravity then forces the displaced water to regain its balance, sending powerful waves racing outward in all directions.
While the Pacific is better known for tsunamis, tsunami can and does occur in the Atlantic basin too. As with the Pacific basin, earthquakes can trigger a tsunami threat for the U.S. East and Gulf coasts. According to USGS, submarine landslides can be one result of an Atlantic-based quake. An offshore earthquake with a magnitude 4.5 or greater can destabilize the continental shelf, causing massive underwater avalanches. These landslides displace large volumes of water and can generate significant, localized tsunamis. This was the case during the 1929 Grand Banks earthquake near Canada, which caused a destructive localized tsunami. Distant tectonic earthquakes can also create problems; massive earthquakes along faults further away in the Atlantic, such as the Azores-Gibraltar Transform Fault near Portugal or the Puerto Rico Trench in the Caribbean, are capable of generating tsunami waves that travel across the ocean. While the infamous 1755 Lisbon earthquake created a trans-Atlantic tsunami that was recorded on the East Coast, the height of the waves reaching the US mainland was relatively small but different earthquake intensities and locations can trigger very different results.
