Offshore Gulf 3.9-Magnitude Earthquake Shakes the Region: TAMUG Expert Explains Why Not All Quakes Are the Same
Geoscientist Dr. Timothy M. Dellapenna explains what the offshore quake means – and why magnitude alone doesn’t tell the full story
An earthquake was reported in the Gulf of Mexico on March 29, hundreds of miles away from Louisiana’s coastline, according to the U.S. Geological Survey.
The small 3.9-magnitude earthquake was located 220 miles from Venice, LA with a depth of 10 kilometers. A similar earthquake was reported in the Gulf in 2023.
While it may seem like earthquakes are happening with a greater frequency, Dr. Timothy M. Dellapenna, Professor, Department of Marine and Coastal Environmental Science, College of Marine Science and Maritime Studies at Texas A&M University at Galveston noted that the earthquake in the Gulf was nothing like those that fire up along the San Andreas fault in California.
“That was a pretty small earthquake, 3.9 and 220 miles offshore. I doubt anyone really felt it,” Dr. Dellapenna said. “Since the Gulf is what we call a passive continental margin, meaning it not part of a tectonic plate, we are not prone to earthquakes. However, there are still faults in the Gulf and occasionally, they experience small adjustments.”
When these small adjustments occur, an earthquake results. While California and other areas of the country are known for major earthquakes, the Gulf region is less of an earthquake hot zone. The last significant earthquake in the Gulf of Mexico was in 2006. That earthquake, which was felt by nearly 3,000 people, measured 6.0 on the Richter scale and was centered about 260 miles southwest of Tampa, FL.
In addition to the shaking of the earth and everything on it, earthquakes that take place underwater can lead to the formation of a tsunami. When a tsunami forms, columns of water rush onshore creating a path of destruction. People living along the Gulf coast who might be worried about an earthquake leading to a tsunami can take some solace in the fact that Gulf quakes are normally below the threshold where a tsunami would form. Earthquakes with a magnitude of 6.5 or higher are generally required to trigger a tsunami, with significant or destructive tsunamis typically resulting from shallow earthquakes measuring 7.6 or greater.
“The recent earthquake was too small for a tsunami,” Dr. Dellapenna said.
It is entirely plausible that there will be more quakes in the Gulf as fault lines undergo adjustment. However, the risk of the type of terrain altering quakes that are experienced along major fault lines is low for the Gulf region.
While people in California are still bracing for the “Big One,” residents along the Gulf Coast are more likely to experience a small one from time to time. Or, as the recent quake demonstrates, some quakes might be so small and so far offshore that they barely notice it at all.
