Tuesday, April 8, 2008

Whole lot of shaking going on

Ahh! how exciting to this former geologist. Real, down to earth, geology news to rock your world.

I'm sure this came as a great shock to many folks in South Central Texas but there can be earthquakes here, like California, just fortunately not as large.

My thought? I agree with those that say it was probably caused by pumping of oil, gas ansd maybe even water from the aquifer.

Of course we all know that the large feature of uplifted hills is called the Balcones fault. That should be a small clue. Its not "active" though. (Yet, hee hee)

Small earthquake jolts South Texas
Sara Inés Calderón: Express-News

FALLS CITY — Diana Sherman was startled awake Monday morning by a loud thud that sounded to her like someone had fallen out of bed.

"I heard a boom, a shake and rattling of my walls and windows. I thought my sweetheart had done fallen out of the bed," Sherman said.

In fact, it was a small earthquake that rattled her and others in Karnes County. According to the U.S. Geological Survey, an earthquake registering 3.7 on the Richter scale was recorded about six miles southwest of Falls City.

The quake didn't cause any injuries or damage, but it did startle residents in Karnes City, Kenedy, Floresville, Poth and Jourdanton, where many reported hearing loud noises and rattling they thought was caused by strong winds.

"I've been through a flood, never an earthquake," said Sherman, who tends the local convenience store, the Busy Beaver. "It's something that's been talked about all day."

The earthquake that occurred at 4:51 a.m. was relatively shallow and was caused by the release of stress from tectonic plate movement, said Don Blakeman, a seismologist with the U.S. Geological Survey.

But there was wide speculation by other seismologists Monday that the quake was due to oil and gas extraction, since Texas lies far from the boundaries of tectonic plates — West Texas is closest to active faults and can get real temblors.

Blakeman, who doesn't buy into the theory that it was caused by fluid extraction, said that while earthquakes in South Texas may not be normal, they're not unheard of. Since 1983 there have been at least eight earthquakes within a 50-mile radius of this one, Blakeman explained; the most recent earthquake was in 2000 and the strongest registered 4.3.

During the last century, Texas has had about 100 earthquakes that could be felt, seismologists said.

A 3.7 magnitude earthquake is equivalent to about 15 tons of TNT. The two largest temblors in Texas were about 1,000 times more powerful.

In contrast to these events, the most powerful earthquakes in the world are equivalent to about 475 million tons of TNT, or 25,000 nuclear bombs. Since 1900 there have been four of these earthquakes, each with a magnitude above 9.0, including the event that precipitated the 2004 tsunami.

Monday's earthquake may have been felt as far as Austin, Blakeman said, but it was not a very big earthquake and the likelihood of aftershocks was slim. Because of its size, Blakeman said the earthquake would be felt as a "sharp jolt" and last only a few seconds; it would seem as though something heavy had been dropped, he said.

"I was asleep at the time and it sounded like the rattling of the windows, and that woke me up," said Dawn Johnson, who lives six miles west of Falls City, very near to the epicenter of the earthquake.

"I thought it must have been the wind blowing," Johnson said. "But there was no wind, it was not much more than that."

But not all residents were roused from their slumber Monday morning.
Laramie Lewis said his mother burst into his room in the morning to ask if he felt the quake.

"Go back to sleep," he recalled telling her, adding that he slept right through it.

Lewis' mother described the earthquake as feeling "like a car ran into the house."

All in all it was a very short experience, he said, although the earthquake scared the family horses and dogs.
Sherman noted the earthquake wasn't all bad news; she said it gave the town something productive to do.
"It'll be gossip for a week now," she said.