A strong earthquake struck the western Atlantic this morning but there does not appear to be any imminent threat of tsunami to the U.S. East coast nor Gulf of America coast at this time. The National Weather Service National Tsunami Warning Center (NTWC) in Palmer, Alaska issued a Tsunami Information Statement a short time ago for the U.S. East Coast, the Gulf of America States, and eastern Canada that said, “Based on earthquake information and historic tsunami records, the earthquake is not expected to generate a tsunami.”
“This will be the only U.S. National Tsunami Warning Center message issued for this event unless additional information becomes available,” the NTWC said.
At 10:50 am Eastern Time today, a magnitude 6.1 earthquake struck near the Leeward Islands in the Caribbean Sea from a depth of 39 miles. Specifically, the epicenter was at 17.6 North and 61.0 West.
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.
