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Gulf earthquake

The Gulf of Mexico has many fault areas

By JEAN HELLER and KEVIN GRAHAM
Published September 11, 2006

It doesn't happen often, but a strong earthquake occurred in the Gulf of Mexico on Sunday morning about 260 miles west southwest of Clearwater and 330 miles southeast of New Orleans. Here are answers to some questions about this unusual occurrence.

Q: Was the quake widely felt?

A: Reports said people felt it from the West Coast of Florida through Alabama, Georgia and into North Carolina. There were no reports of damage or injury.

Q: Was there ever any danger of a tsunami hitting Florida?

A: Not with this quake. It measured a magnitude of 6, which is a strong quake, but not strong enough to produce massive wave action.

Q: How did this quake compare with the one that produced the 2004 tsunami that devastated the Indian Ocean region?

A: No comparison. That one measured between 9.1 and 9.3 on the magnitude scale, more than 1,000 times more powerful than Sunday's quake in the gulf.

Q: How does the magnitude scale work?

A: It is a logarithmic scale related to the amount of seismic energy released by a quake. Each whole number is 10 times greater than the one below it. (Some experts say the actual amount of energy released may be 30 times greater.) So a quake measuring 9 is 10 times stronger than an 8, 100 times stronger than a 7 and 1,000 times stronger than a 6.

Q: What caused Sunday's quake?

A: No one is certain. But the Earth's relatively thin crust is cross-hatched with fractures. The moving molten core of the planet creates gases and other stresses that build up below the crust. When the stress becomes great enough, it releases in the form of quakes and volcanoes.

Q: Where do the most violent quakes occur?

A: Generally along the boundary of tectonic plates. These are the massive sections of the Earth's crust that move slowly and rub against one another violently. Sometimes one will dive under another. These gargantuan movements cause the world's worst earthquakes, but they are not the only places where quakes occur. The stretching and compression of the Earth's crust causes minor cracking, called faults, and the bottom of the Gulf of Mexico has many fault areas.

Q: Was Sunday's quake along a plate boundary?

A: No. According to the U.S. Geological Survey, it was centered well away from the nearest active plate boundary. Such mid plate quakes are much less common than those on plate boundaries and probably represent the release of long-term stresses that originate at the boundary.

Q: Have there been other quakes in the gulf?

A: Yes. The Geological Survey says Sunday's was the largest of more than a dozen shocks recorded in the eastern Gulf of Mexico in the past three decades. The most recent, and the second largest, was recorded Feb. 10 at a magnitude of 5.2. Few people even noticed that one.

Q: Besides fault areas in the gulf, are there any fault areas near us on land?

A: Yes. Fault areas run along the Gulf of Mexico and well inland in Mexico, South and East Texas, Louisiana, Mississippi, Alabama and the extreme western Florida Panhandle.

Q: Are we in danger of ever having a major quake or tsunami?

A: The odds are against a tsunami. Experts say it takes the energy output of a major tectonic plate shift to create a tsunami, and there are no plate boundaries nearby. Quakes are a different matter. The New Madrid fault of northeast Arkansas and southern Missouri and Illinois has produced intense quakes that could be felt as far away as Central Florida. Less intense quakes have occurred in Georgia and Alabama. Only parts of North Dakota and extreme northern Wisconsin seem safe from the impact of quakes.

Q: Were there any indications that animals sensed the quake before it struck?

A: While there were reports around Tampa Bay of pets acting strangely before it struck, animal handlers at the Lowry Park Zoo and at Busch Gardens said they saw nothing out of the ordinary.

[Last modified September 11, 2006, 05:13:48]