earthquakes

Source: FEMA

The official blog for The Great Southern California ShakeOut has been posting a series of informative articles about earthquakes and what you should do. Their latest post on the subject deals with the popular myth that says doorways are the safest place to be during an earthquake.

In modern houses, doorways are no stronger than any other part of the house. You are safer under a table.

I remember growing up in Southern California and talking about always present danger of large earthquakes and having elementary and junior high school teachers propagate this myth. You’re more likely to get injured while trying to get to a doorway (or have the door swing into you during violent shaking).

More information is available at The Great Southern California ShakeOut website.

The Great Southern California ShakeOut is a week of special events featuring the largest earthquake drill in United States history, organized to inspire Southern Californians to get ready for big earthquakes, and to prevent disasters from becoming catastrophes. What we do now, before a big earthquake, will determine what our lives will be like after. The ShakeOut drill will occur in houses, businesses, and public spaces throughout southern California at 10AM on November 13, 2008.

Free registration at www.ShakeOut.org/register will pledge an individual’s or a group’s participation in this important preparedness event. Participants will receive information on how to prepare for the inevitable major earthquake in the region and what actions to take during and after the shaking.

Earlier this week, I was browsing through the list of recently added applications on Apple’s App Store when a small little icon caught my eye. It was for a new program called Seismometer.

Basically, this application uses the iPhone’s (or iPod Touch’s) built in accelerometer to display a seismogram onscreen that shows real-time data.

While it’s an interesting program in concept, it isn’t very useful. For one, the iPhone’s accelerometer is way too noisy to get any clean data back. The following screen shot was taken when the iPhone was sitting flat on my desk (and no, there weren’t any earthquakes going on this time!).

Secondly, as far as I can tell, it uses some sort of funky combination of the X, Y and Z axises to produce the data on screen. While I agree that it simplifies things (especially with the relatively small viewing screen available on the iPhone), it’d be nice to have the option to view movement on just one particular axis. (A program for Apple laptops that uses their accelorametors called Seismac does this. We briefly mentioned it before in this article.)

The last concern I have with it is that it only shows the most recent 5 seconds of data on screen at any one time. It’d be nice to be able to see more data. The needle takes up a large majority of the screen.

This application was originally free when I downloaded it, but as of today they are charging 99 cents for it. Relatively cheap in the scheme of things, but for something with a fairly limited utility, I don’t think I can justify the price. It’s more of a novelty item for people interested in geology and geophysics.

That said, the developer did say they will be releasing an updated version shortly with new features and improvements based on user feedback. They believe the 99 cent price will justify this. Stay tuned to find out!

[This review details Seismometer 1.0 - An application for the iPhone/iPod touch originally released on August 28th, 2008]

About an hour and a half ago, we had a fairly small earthquake here in the San Francisco Bay Area.

While it only had a magnitude of 4.0, it was interesting to see the reaction on various social networks such as Facebook and Twitter. In fact, when I first felt our building shake, I wasn’t sure if there had actually been an earthquake, so I checked my Twitter account.

Only a few minutes later, this is what my feed looked like.

And here is the shake map for the earthquake:

According to the USGS, it was centered on an unnamed fault located near the Calaveras Fault:

A light earthquake centered near Alamo shook the Bay Area Friday evening. Reported at 9 p.m., it was a magnitude 4.0, said the U.S. Geological Survey.

The Contra Costa and Alameda County sheriff’s offices said they had no reports of damage.

The quake was felt in Petaluma to the north and in Gilroy and Turlock to the south and southeast, said David Oppenheimer, a seismologist with the geological survey. He said it occurred on an unnamed fault about 2.5 miles from the larger Calaveras fault and two miles north-northeast of Alamo, on Serafix Road.

A cluster of quakes occurred on the same fault in April 1990, with 18 registering at 3.0 or higher in a three-week period, Oppenheimer said. He said the larger quakes in that sequence caused minor structural damage to nearby homes.

Friday’s earthquake took place about 10 miles underground, more than twice as deep as the 1990 quakes, and thus is probably less likely to be part of a cluster or cause damage, Oppenheimer said.

Bummer, I predicted that it was actually on the Calaveras Fault itself.

Anyway, not really a big deal in the end. But the fusion of social media and science is always interesting. We’ve written about Twitter before as well, also in terms of earthquakes and disseminating information.

Kris Pankow, a seismologist at the University of Utah, analyzed 15 major M7.0 or greater earthquakes that have occurred since 1992 and found that in many cases, the quakes were directly responsible for causing smaller earthquakes hundreds or thousands of miles away.

Source: Aaron Velasco, University of Texas at El Paso

“Previously it was thought seismically active regions or geothermal areas were most vulnerable to large earthquake triggers,” says Kris Pankow, a seismologist at the University of Utah Seismograph Stations and a co-author of the new study.

But Pankow and colleagues analyzed 15 major earthquakes stronger than magnitude-7.0 since 1992, and found that at least 12 of them triggered small quakes hundreds and even thousands of miles away, according to the findings published online Sunday, May 25, 2008 in the journal Nature Geoscience.

“We conclude that dynamic triggering is a ubiquitous phenomenon,” they wrote.

Pankow conducted the study with seismologist Aaron Velasco and undergraduate student Stephen Hernandez, both at the University of Texas at El Paso; and seismologist Tom Parsons, of U.S. Geological Survey in Menlo Park, Calif.

They analyzed data from more than 500 seismic recording stations five hours before and five hours after earthquakes that registered more than 7.0 on the “moment magnitude” scale, which scientists say is the most accurate scale for large earthquakes. (The frequently cited Richter scale measures only relatively small, nearby quakes).

The data – obtained from the Incorporated Research Institutions for Seismology, a consortium of universities – included 15 major earthquakes from 1992 through 2006, including the 1992 Landers quake in California 800 miles southwest of Yellowstone, the magnitude-7.9 Denali fault quake in Alaska in 2002, and the magnitude-9.2 Sumatra-Andaman Islands quake near Indonesia in 2004 that generated a catastrophic tsunami blamed for most of the quake’s 227,898 deaths in South Asia and East Africa.

Scientists previously noted that those three major quakes triggered not only nearby aftershocks, but small quakes at great distances. The new study is the first to systematically analyze all the world’s big quakes during 1992-2006 and find that most of them triggered distant, smaller tremors. These are different than aftershocks, which occur fairly close to the main quake. After the devastating 2004 Sumatra earthquake, triggered quakes even occurred in Ecuador, on the opposite side of the Earth.

[Via Eurekalert]

The fourth episode of the Goodschist PodClast is out today. This episode features Chris Town and myself. Due to technical difficulties, Chris and I decided to each record a separate segment of the PodClast, dealing with topics we were planning on discussing.

Show notes for Episode 4 are available on Chris’ webpage and relevant links will posted on the PodClast del.icio.us account.

Discussions this week feature a brief discussion on the Sichuan earthquake in China and the pending landing of the Mars Phoenix Lander.

Chris is always looking for new voices from the geoblogosphere to join in on the PodClast. If you’d like to participate next time, check out his information on joining the PodClast.

[Via GoodSchist]