For those of you who missed it -- and you weren’t alone if you did --there was an earthquake in the Gulf of Mexico this past February.
That it may fuel ongoing debates on issues ranging from long-term geo-political concerns to safety of area residents to a new understanding of the geologic footprint of the entire region is one story.
That it happened at all is another.
What we do know is this: At around 10 p.m. on Friday, Feb. 10, a 5.2 magnitude quake, approximately 160 miles south of New Orleans, struck in the Gulf of Mexico. Its recorded depth was five kilometers.
What we don’t know is why.
The quake, while noted by academia and those who get paid to notice such things, was barely mentioned in the mainstream media -- it received a mere two paragraphs on MSNBC online.
Jack Reed, a retired Texaco geologist/geophysicist and something of a Don Quixote on the issue of an active tectonic plate in the Gulf of Mexico, wasn’t surprised by the quake or, for that matter, the reaction to it.
“It happened 123 miles offshore -- who cares?” he said, reflecting the media and public’s apathy rather than his own.
But according to Louisiana State University geologist Roy Dokka, who should care are the people of the region. Saying it was one of the most significant quakes to hit the region, Dokka told a local New Orleans television reporter that it should provide a warning to erosion officials that Louisiana’s coastline is shifting fault lines throughout the region.
“These faults are moved largely because south Louisiana is very unstable ground,” Dokka said. “It’s kind of oozing in the Gulf.”
An Active Topic
Reed, this time reflecting himself, has a more technical explanation.
“Simply stated, the linear Cretaceous shelf edge was the separation point of the Gulf of Mexico plate from North American plate,” he said.
According to Reed, this movement started near the end of the Early Cretaceous and, to date, the plate has moved south. The exterior salt basin was formed in the ever-widening gap between these plates by allochthonous salt pressure forced from under the moving plate into the gap.
The trailing edge of this south moving plate is undergoing tensional forces accompanied by outward and upward moving salt into the basin, Reed explained, which creates fractures (faults) along the trailing edge of the plate and these fracture lines are filled with the highly pressurized salt.
This movement, in turn, separates fault blocks from the moving plate, which are then suspended in the ever-expanding exterior basin salt mass. This action, or something very similar, is the source of 11 earthquakes that have struck the northern Gulf, according to Reed. Seven of these quakes are located along the trailing edge of the south moving plate.
“This action, or something very similar, is the source of the earthquakes that occur in the northern Gulf,” he said.
Moreover, for Reed the quake may help prove the existence of plate movement, and could be a new piece of evidence for a tectonically active Gulf.
“This MS=5.2 quake alone does not prove the Gulf is active,” he admits, “but when it is placed in line with other evidence, it’s a major nail supporting the active Gulf structure.”
Reed, who is retired and admits he is not an expert on earthquakes, has theorized for years there was an active tectonic plate in the region that, among other things, is connected to the New Madrid seismic center. This active seismic center is located on a possible tensional continental spreading fault zone that parallels the Appalachians and connects with the St. Lawrence seismic center, located in Canada (see November 2002 EXPLORER).
Asked whether we will see a significant quake along New Madrid, he says, “It’s not a matter of if, but when.”
He is the first to admit, though, that his theory is in stark contrast to others -- and still something of a novelty.
“I developed the active tectonic theory and then realized that this thory would be opposite from the passive theory, and, therefore, I would have an uphill battle trying to prove it,” he said.
“The passive theory (no tectonic activity) has been accepted in our geological community for decades,” he said, “and very few earth scientists would like to change their position. I know I wouldn’t.”
This quake may indicate he doesn’t have to.
Other explanations are still being formulated, a fact of which Reed became aware while talking to other earth scientists who were also trying to come up with an explanation.
There was a report circulating immediately following the quake that since the activity occurred near the huge salt domes where much of the oil and gas is being extracted, Shell Oil helped cause it with its drilling activity in and around its Brutus platform. One report, published in Pure Energy System News, attributed the quake to the unsettling of rock formations as a result of extraction of massive quantities of oil, gas and brine.
Reed laughs off this suggestion.
“I think it is nothing more than a theory cooked up by environmentalists,” he said. “Of all the thousands of wells drilled, both onshore and offshore, not one has caused anything like an earthquake. Why should it happen now? A 5.2 quake is a significant tremor that releases a large amount of energy and the shift would cover several miles or more.
“There is no way a small, insignificant drilling platform could cause the release of this force,” he said, “even though the rig is named Brutus.”
For years, Reed has been espousing a view that the Gulf region north of Cuba resembled other active tensional areas, and when asked if the current quake proved him right, he said, “Gee, I hope so!”
“I know of no other rift areas that have split a salt basin in two parts like the Gulf,” he said. The way I see it, listric fault action similar to the Gulf of Suez region could not happen here. The separating fault blocks, as they break away, would be supported by the upwelling surrounding salt mass.”
The conventional wisdom up to this point is that, unlike the Pacific, the Atlantic and the Gulf were passive regions.
February’s quake may restart the debate again.
An active Gulf, some maintain, suggests the conditions there are eerily similar to those that brought about the earthquake and tsunami in Aceh, Indonesia.
Reed dismisses this argument, regardless of which theory is ultimately proved true.
“If the passive theory (no tectonics) is correct, then there are no significant lateral or vertical forces to cause earthquakes, he said. “Again, I am talking about the Gulf of Mexico, not the Caribbean,” where he does see some similarities.
Reed says the Aceh quake was caused by compressional and accompanying lateral forces.
“If the active theory (tectonics) is correct, the forces acting are mostly tensional and not compressional, he continued. “Tensional forces of the trailing edge of a moving plate are considered much weaker than compressional forces of the leading edge.”