Archives for July 2008

I have been meaning to write a short post about the small earthquake we experienced today. But every time I try it seems that I am interrupted by someone who thinks that it is fun to say “what’s shaking.”

You know, that used to be funny. It used to be kind of cool, in the same way that Mr. Microphone used to be cool.

Anyway, if you didn’t hear about the quake here is a short report from CNN. Let me share a few highlights from the report that warm the cockles of my heart. (Emphasis in bold is mine)

“This is a sample, a small sample,” said Kate Hutton, a seismologist at the California Institute of Technology.

“This is somewhere between small and moderate.” She said there is a 5 percent chance the quake could be a precursor to a larger earthquake. After 24 hours, she said, that chance will drop to 1 percent.

Isn’t that nifty, to know that this might be a warmup for the big show. Ok, here is some more about the earthquake that might interest you.

A 5.4 magnitude quake is considered by the USGS to be “moderate,” which can cause slight damage to buildings and others structures. So far this year, 39 “moderate” earthquakes of between magnitude 5.0 and 5.9 have occurred in the United States, and 790 globally.

The last moderate quake to strike California was a magnitude 5.4 in April in the northern part of the state. A magnitude 4.4 struck the greater Los Angeles area in August 2007.

There is a 99 percent chance of California experiencing a quake of magnitude 6.7 or larger within the next 30 years, according to the Uniform California Earthquake Rupture Forecast, sponsored by the U.S. Geological Survey, the California Geological Survey and the Southern California Earthquake Center and published in Science Daily in April.

“This earthquake reminds us to be prepared,” said California Gov. Arnold Schwarzenegger. “We were very fortunate that there were no serious injuries or property damage.”

He said he believes the state is “as prepared as anyone can be. We have continuous discussions about that. We are fanatics about emergencies and to be ready.”

The largest earthquake in recent years in California was a magnitude 7.1 in 1999, Hutton said. But it was centered in the desert, near Twentynine Palms, in a sparsely populated area.

Tuesday’s quake struck about 11:42 a.m., according to the USGS. Its epicenter was about 2 miles southwest of Chino Hills and about 5 miles southeast of Diamond Bar.

The epicenter was about 7.6 miles deep, making it a fairly shallow quake, according to CNN meteorologist Chad Meyers. In general, earthquakes centered closer to the surface produce stronger shaking and can cause more damage than those further underground. But most Southern California earthquakes tend to be fairly shallow, officials said.

Those of us who lived through the Northridge quake can tell you that it was far bigger than today’s temblor. If you want to learn more about that try reading USGS Response to an Urban Earthquake — Northridge ‘94. Or you can read this summary:

“At 4:30 on the morning of January 17, 1994, some 10 million people in the Los Angeles region of southern California were awakened by the shaking of an earthquake.
The earthquake, named for its epicenter in the town of Northridge, was a magnitude 6.7 (M = 6.7) shock that proved to be the most costly earthquake in United States history.
The shaking heavily damaged communities throughout the San Fernando Valley and Simi Valley, and their surrounding mountains north and west of Los Angeles, causing estimated losses of 20 billion dollars. Fifty-seven people died, more than 9,000 were injured, and more than 20,000 were displaced from their homes by the effects of the quake.
Although moderate in size, the earthquake had immense impact on people and structures because it was centered directly beneath a heavily populated and built-up urban region.
Thousands of buildings were significantly damaged, and more than 1,600 were later “red-tagged” as unsafe to enter. Another 7,300 buildings were restricted to limited entry (“yellow-tagged”), and many thousands of other structures incurred at least minor damage.
The 10-20 seconds of strong shaking collapsed buildings, brought down freeway interchanges, and ruptured gas lines that exploded into fires. Fortuitously, the early morning timing of the earthquake spared many lives that otherwise might have been lost in collapsed parking buildings and on failed freeway structures

Related posts:

Fourteen Years Ago The Earth Shook
Adult Pajamas
Just Another Earthquake
It Was Disconcerting- Whoa!