Strong Earthquake Shakes Gulf of Mexico
The magnitude 6.0 temblor, centered about 330 miles (530 kilometers) southeast of New Orleans, Louisiana, occurred at 8:56 a.m. local time (map of Louisiana). It was felt in parts of Florida, Georgia, Alabama, Louisiana, and Mississippi.
Damage, if any, was too light to be reported. The earthquake was also too weak to cause a tsunami.
And Sunday’s quake should have little to no effect on development of recently discovered oil reserves deep beneath the Gulf, says Randy Cox, an associate professor of earth science at the University of Memphis in Tennessee.
Powerful earthquakes are rare but not unheard of in the Southeast U.S.
In 1879 an earthquake near St. Augustine, Florida, rattled dishes off shelves and cracked plaster. And in 1886 a magnitude 7.3 temblor killed 60 people in Charleston, South Carolina, and rang church bells as far away as St. Augustine.
Unusual Occurrence
Most earthquakes take place near the edges of the tectonic plates that make up Earth’s crust. Stress builds as the plates slowly but steadily collide.
The mammoth tsunami-generating quake in Indonesia on December 26, 2004, occurred at such a plate boundary.
The recent Gulf of Mexico earthquake, however, occurred in the middle of a plate, not at an edge.
Such “mid-plate” earthquakes probably represent release of long-term stress originating from distant forces, the U.S. Geological Survey says on its Earthquake Hazards Program Web site, which tracks earthquakes around the globe.
The earthquake occurred along a region known as the Cuba fracture zone, Cox says. A magnitude 5.2 temblor that occurred on February 10, 2006, about 150 miles (240 kilometers) south of New Orleans may have involved the same fault zone, he adds.
The source of stress is far out in the Atlantic Ocean, where plate tectonics are causing the seabed to spread. This drives the North American plate westward, compressing it.
“All of eastern North America is in similar compression, presumably for the same reason,” Cox said by email.
A few weeks ago, Cox published a study of the tectonics of southern North America in the GSA Bulletin, a journal of the Geological Society of America.
“This thrusting event is consistent with prehistoric fault movements we found in the onshore Gulf Coast region,” he said by email.
“Until recently it was presumed that the eastern North American plate had a transition from compression in the interior to extension—or stretching—in the Gulf, but we’ve changed the stress maps of late, and this earthquake fits right in.”
Sunday’s quake was the second-largest temblor recorded in the past week. The largest, at magnitude 6.3, occurred on Saturday in the earthquake-prone country of Indonesia.
