Thursday, October 29, 2009


Do you still use listservs? They used to be one of the coolest things online. Now we have Twitter (coughs, still unconvinced about Twitter).

It was 20 years ago that the 6.9 magnitude earthquake known as the "Loma Prieta" hit the San Francisco and Monterey Bay regions of California. The USGS has a brief description and collection of photos available at among many other sites. This was the World Series quake that occurred while the Giants were playing the A's.

Marty Hoag reports that after he heard about the quake, he wondered what we could do in the middle of the country. As an administrator of our LISTSERV(tm) service he decided to create an e-mail list. He expected it would be a temporary list and then disappear. But it is still running, as QUAKE-L.

You can review the entire archive and search the text of the postings at 

At first the focus was on the impact on computer networks (BITNET and the rather young Internet). For a few years there were discussions about earthquakes but early in the 1990 James Fisher started to provide the list with timely earthquake reports from the USGS. These are the main items on the list now. Currently there are 131 subscribers to the list. (I'm still one of them.)

Times are changing, though. If you haven't done so, just type the word "earthquake" into your Google search engine, and see what you come up with as the first hit. 

My son tells me that Twitters will be good in real-time emergency reaction and response. He is probably right, if the right Tweets can be heard over the technobabble.

To join the QUAKE-L list simply send e-mail to LISTSERV@LISTSERV.NODAK.EDU with SUBSCRIBE QUAKE-L in the BODY of the e-mail. 

Sunday, October 25, 2009

Second largest Dillsburg quake

The 2.8 magnitude quake occurred at 7:21 a.m. about two miles southeast of the York County town, according to the USGS Web site.
This was the biggest quake since the 2.9 event of 24 April, 2009.

Speaking of things rumbling in Pennsylvania ... well, see the image!

Friday, October 23, 2009

Earthquake early warning systems

There was an  interesting story on NPR a few days ago about the development of s seismic early warning system for California. Note that this is not earthquake forecasting or prediction, which might give days to years of warning about the possibility of a quake. Nor is it a tsunami warning system, which can give hours of warning that water waves may arrive across the ocean after an earthquake has already occurred.

Earthquake early warning systems use the travel time of seismic waves (around 5 miles per second!) to give a few seconds of warning before they arrive. So, in Japan, high-speed Shinkansen trains might be automatically slowed. Elevators could be forced to stop at the next floor.  Or, upon hearing sirens in the U.S. after the waves were sensed, you might have time to get below your desk. (Brings back memories from my youth of duck and cover drills).

As the article tells us, this effort is probably less effective than good earthquake planning and engineering, but a lot less costly then completely retrofitting San Francisco and Los Angeles.

Sunday, October 18, 2009

IRIS Seismographs in Schools Program

IRIS’s Seismographs in Schools Program serves teachers across the country and around the world using seismic instruments or real-time seismic data in K-16 classrooms. Additionally, the web site includes tools to share seismic data in real-time, classroom activities, and technical support documents for seismic instruments. The hope is to bridge the gap between science classrooms to create an international educational seismic network.

Join a growing movement of teachers using seismic data to engage students in science.

Friday, October 16, 2009

Report on the Dillsburg earthquake swarm

A new Open-File report presents information on the earthquake swarm in Dillsburg, York County, which began in October 2008. Data on microearthquakes were collected by an array of portable seismographs placed and operated by Lamont-Doherty Geological Observatory of Columbia University from October 24 to December 11, 2008. Results and interpretations based on this data are presented here. The Pennsylvania Geological Survey assisted in placement and monitoring of a later array from May to September, 2009. Data from that installation are still in processing and interpretation. A follow-up study, conducted by the Pennsylvania Geological Survey, Penn State University, Charles Scharnberger and Jeri Jones, will investigate the spatial and temporal distribution of seismic events during the summer of 2009, based upon the small array of seismographs that were in place during that period.

similar swarms in Pennsylvania, Maryland, Connecticut, South Carolina, Maine, Ontario, and elsewhere, have not led up to a big earthquake.  Rather, the activity has died away after several months.  Thus, it seems most likely that this is what will also happen with the Dillsburg swarm.
Full disclosure: I was the outside reviewer for this report.

Tuesday, October 13, 2009

Twenty years since the World Series Earthquake

My week on the Hayward Fault went without incident. Twenty years ago, California was not so lucky.  The World Series between the San Francisco Giants and the Oakland A's was interrupted by the Loma Prieta earthquake.

October 17, 2009 marks the 20th anniversary of the Loma Prieta Earthquake. At Stanford University, a panel of experts will reflect on what happened in 1989, the likely impact of future Bay Area earthquakes, progress in earthquake science and engineering, how the Bay Area can become more earthquake resilient, and earthquake preparedness.

Speaking of the World Series, go Phillies. And Yankees. What will I do if they face each other?

Thursday, October 8, 2009

Three magnitude 7's in one day

According to the list of earthquakes from the USGS, there were three magnitude 7 quakes on Oct. 7.

These all occurred near Vanuatu, so are probably not independent. But if we take the annual global magnitude statistics, there are typically 17 quakes per year with magnitudes above 7. What are the chances of getting three independent magnitude 7's on the same day?

The chance of getting one is 17/365 = 4.6%. I think (correct my joint probabilities, please) that the chances of three in one day would then be this probability cubed, or 1 chnce in 10,000,

If you are more energetic than I am, go back and check when was the last time this happened.

Or, would it make more sense to simply consider the probability of a magnitude 8 quake, which would release more energy than three magnitude 7's anyway?

Image from

Monday, October 5, 2009

My week on America's most dangerous fault?

I am visiting my sons and working for a week in Berkeley, California. So I've moved from the not so worrisome Lancaster Seismic Zone to

The Hayward Fault: Is It America’s Most Dangerous?

It passes right through the Cal football stadium:


The Cal team received quite a shock from USC on Saturday. But I was out at the best Americana music festival in the country, Hardly Strictly Bluegrass.