Tuesday, December 30, 2008

Shaking earth causes vibrating butt

The Sunday report in the Lancaster Newspapers on the earthquake began its article as follows:

[Name withheld by me] of Ridge Road, Mount Joy Township, was in the bathtub when, he said, "I felt it in my butt. It vibrated."

I'm not kidding - who could make this up?

I know animals are reputed to sense impending earthquakes. I wonder if this is a corresponding human trait? Or was that guy just playing around in the bathtub at midnight on a Saturday?

And how could a reporter and an editor possibly let an article start that way? I guarantee, you would never find that particular wording about an earthquake here in the SF Bay area where I'm spending the week.

Hoping the New Year brings you all good vibrations!

Sunday, December 28, 2008

Another view of the Lancaster earthquake

This one is from the Millersville seismograph. You can look up Millersville's current and archived seismograms here.

click above for larger image

Seismologists, what say ye about this event?

Saturday, December 27, 2008

Hometown earthquake!

How ironic! While I am spending the week virtually on top of the Hayward Fault in the East Bay area, a magnitude 3.4 earthquake happens back home in Lancaster.

At least I have F&M's seismogram to look at.

click above for larger image

Our current daily seismogram can be found here, and our archives can be found here.

Does this count as a holiday quake?

More on the hilarious reporting of this event by the Lancaster Newspapers later.

Sunday, December 21, 2008

My holiday earthquake theory

Two blogs back I wrote on earthquake (seismicity) patterns. Well, I have a pet theory that earthquakes tend to occur on holidays. Cases in point:
  1. Lisbon earthquake, 1755 - All Saint's Day. According to Rob Zaretsky, professor of French history at the University of Houston, over 100,000 people died. The earthquake also pounded Europe's political and cultural landscapes. The brightest light of the Enlightenment, Voltaire, used the earthquake in his wonderful satire, Candide. From a ship in Lisbon harbor, Candide watched helplessly as the good drowned and the wicked survived.
  2. Alaskan earthquake, 1964 - Good Friday. This is the second biggest earthquake ever recorded, surpassed only by the 1960 Chile quake. According to the Alaska Earthquake Information Center, the area of significant damage covered about 130,000 square kilometers. It was felt over 1,300,000 square kilometers (all of Alaska, parts of Canada, and south to Washington). The four minute duration of shaking triggered many landslides and avalanches. Major structural damage occurred in many of the cities in Alaska. The damage totaled $300-400 million dollars. You betcha.
  3. Sumatra-Andaman earthquake, 2005 - day after Christmas (that's kind of a holiday, isn't it?). The IRIS special report states that approximately 1200 kilometers of the India-Burma plate boundary slipped, with an average displacement on the fault plane of about 15 meters. The resulting tsunami claimed 250,000 lives.
  4. Lancaster, Pennsylvania, 1984 - Easter Sunday. This is actually the only earthquake I have ever experienced. It was studied by our own group's Charlie Scharnberger (see booklet on Earthquake Hazard in Pennsylvania) and John Armbruster. Actually, this is my favorite kind of earthquake - sensible, exciting, and useful for scientific research, yet it only caused a little bit of cracked plaster.
I like the web site at left, Today in Earthquake History. Check out other holidays. What do you think - does my theory amount to anything?

Hoping your solstice and upcoming holidays are disaster-free.

Wednesday, December 17, 2008

Wired at the AGU

Wired News is an online technology news website, on the hip side, at least in my aged opinion. The American Geophysical Union is a scientific society with a membership of 50,000 researchers, teachers, and students. The AGU has two meetings a year, the December meeting in San Francisco, and a Spring meeting in the eastern U.S. (or, in recent years, a joint meeting in Mexico, Europe, or Canada. Wired is currently running a blog from the AGU conference. Read about global warming, coal and oil resources, magmas, mooning, and so much more, at Wired Science Rocks AGU.

Friday, December 12, 2008

Random events?

See that link on the left for Recent Northeast quakes?

I took all 52 events listed there, and imported the data into Excel.

I made a graph of simply when the events occur. Is this a random sequence? Shouldn't they be evenly spaced? (Hint: no.)

click above for a better image

By the way, I love Excel, or at least used to. I think that after word processing, email, and web browsing, spreadsheets are the next most essential type of software for general geophysics. And I make my intro geology students learn to use Excel as well. The latest release of Excel 2008 has lots of horrific defaults and cumbersome menus, though. Thank you, Microsoft for your sucky improvements. Next year when I am on leave I will seriously look into alternatives, including open source freeware. Any suggestions?

Tuesday, December 9, 2008

Seismic time - change your watches

Earthquake information is given in UCT, coordinated universal time, which is, more or less, the same as Greenwich Mean Time. (The letters are backwards thanks to the French, which is why the abbreviation for the metric International System of units is also backwards, SI). You can read about time systems at the excellent web pages of the United States' official timekeeper, the U.S. Naval Observatory.

The graph above shows how many milliseconds the length of day varies from 86,400 seconds, or 24.00 hours. The length of day is now about 2 milliseconds less than it was since I graduated from college in 1972 - no wonder I always seem behind the times. What about those shorter variations in the LOD (length of day): fodder for another blog.

The Earth, like me, is slowing down, due to the braking action of the tides, by about 1.4 milliseconds per day per century on the average. This is equivalent to 1 second every 714 days. Periodically, a leap second is added to account for this. The last leap second was added at the end of 2005.

So, if 2008 was a good year for you, you're lucky, because an extra leap second will be inserted once more on December 31, 2008.

Thursday, December 4, 2008

Monday, December 1, 2008

LCSN seismologist Kim wins award

Dr. Won-Young Kim, chief scientist for the Lamont Cooperative Seismic Network, the 25-station system that monitors most of the northeastern United States, has been named 2008 recipient of the Jesuit Seismological Association Award.

This award is presented annually by the Eastern Section of the Seismological Society of America.
"Won-Young Kim combines the traditional skills of the classical observational seismologist with the modern skills necessary to obtain good scientific results from the many different types of broadband digital data in use today. Whether he is working on exotic core phases or on commonly-recorded regional phases, his goals are always to achieve a scientific explanation for interesting phenomena that can be observed on seismograms. Sometimes he has put his efforts into development of methods, sometimes into field deployments to acquire new data with new instruments. He has had recent successes with use of waveform fitting to estimate accurate depths and focal mechanisms for earthquakes in eastern North America" (read more at the web site of the Lamont-Doherty Earth Observatory ).