Yes, Dillsburg, PA, you just felt another one

LCSN Earthquake Alert

Lamont-Doherty Earth Observatory (4/30/2009 22:16 EDT)

Origin time: 4/30/2009 18:36:11.3 EDT
4/30/2009 22:36:11.3 UTC

Location: 40.073 N, 77.013 W Depth= 1 km
(40 deg 4.4 minutes North, 77 deg 0.8 minutes West)

Magnitude: Mc=2.0

On Thursday evening, April 30, 2009 at 18h 36m 11s EDT,
a minor earthquake of magnitude 2.0 occurred near Dillsburg,
Pennsylvania (25 km southwest of Harrisburg, Pennsylvania).

There are felt reports from Dillsburg and Franklintown.

Pennsylvania's largest earthquake this week

is now a

Arlen has long been pretty moderate for a Republican. But at 79, isn't it about time he retires to "spend more time with his family," as they say?

Six months of south-central Pennsylvania seismicity

The figure and the list below are from the LCSN:

    Date        Time      Lat     Long   Depth Magnitude
year-mo-dy  hh:mm:sec    (N)     (W)    (km)  (Mc)
--------------------------------------------------
Lancaster County, PA
1972-12-08  03:00:32.5  40.150   76.220   4  0.0
1978-07-16  06:39:39.6  39.900   76.220   0  0.0
1984-04-19  04:54:55.1  39.946   76.323   7  2.9
1984-04-23  01:36:02.0  39.946   76.323   4  4.1
1984-04-23  02:46:00.5  39.946   76.323  10  2.5
1994-01-16  03:03:31.3  40.532   76.247   4  2.0
1995-03-11  21:10:16.0  40.100   76.400   5  2.7
1997-11-14  03:44:11.7  40.164   76.276   6  3.0
2000-03-22  20:48:00.0  40.070   76.300   1  1.8
2000-10-05  23:33:59.0  40.080   76.300   7  2.0
2001-07-17  14:41:20.2  39.937   76.340   1  1.8
2008-12-27  05:04:34.5  40.114   76.403   3  3.4

Adams County, PA
1994-05-26  17:21:58.2  39.950   77.187  11  2.8

Dillsburg, York County, PA

1997-06-16  05:43:16.6  40.098   76.967   5  1.9

2008 (21 events)
2008-10-05  22:36:48.1  40.054   76.967   2  2.0
2008-10-06  01:06:13.4  40.120   77.025   0  1.2
2008-10-06  06:15:38.4  40.069   76.992   0  1.1
2008-10-19  08:21:22.7  40.080   77.019   5  1.9
2008-10-19  08:22:07.3  40.078   76.963   5  2.1
2008-10-19  08:26:20.5  40.168   77.038   5  1.2
2008-10-19  08:28:09.0  40.087   76.998   5  1.5
2008-10-19  08:58:31.7  40.092   76.974   3  1.8
2008-10-19  09:06:01.5  40.091   77.018   5  1.0
2008-10-19  09:08:20.7  40.056   76.962   5  0.8
2008-10-19  09:08:44.3  40.092   76.987   5  1.1
2008-10-19  09:17:34.8  40.100   77.009   5  1.7
2008-10-19  09:49:19.1  40.095   77.002   5  1.0
2008-10-19  09:49:51.7  40.075   76.973   5  1.5
2008-10-19  09:50:11.4  40.091   76.989   5  1.6
2008-10-20  00:08:26.6  40.159   77.107   5  1.2
2008-10-20  00:14:03.9  40.075   77.005   5  1.1
2008-10-20  02:16:02.4  40.090   76.984   5  1.5
2008-10-23  15:55:32.3  40.068   76.962   5  1.2
2008-11-07  04:07:03.0  40.096   77.006   1  1.4
2008-12-31  05:34:08.8  40.107   77.003   1  2.1

2009 (3 events)
2009-04-22  13:21:14.1  40.073   77.002   1  1.1
2009-04-23  22:26:04.4  40.085   76.998   1  2.4
2009-04-24  05:36:48.8  40.064   77.026   1  2.9

See any patterns here? Maybe I'll try that next.

Holiday quake hypothesis - Earth Day in Dillsburg

from http://www.dillsburg.com/

You may remember my hypothesis that earthquakes tend to occur on holidays. If not, it doesn't matter, because I'm just kidding. But, from the York Daily Record:

Dillsburg marks Earth Day with another earthquake
By TERESA ANN BOECKEL
Daily Record/Sunday News
Updated: 04/23/2009 12:38:30 AM EDT

An earthquake that registered 1.1 on the Richter Scale shook the Dillsburg area about 9:21 a.m. Wednesday, according to the U.S. Geological Survey.

"Boy, did we have one this morning," Carroll Township resident Michael McCaffrey said.

He was taking a shower and heard a thunderous boom. He thought that his wife, Kathleen, who recently had surgery, might have fallen out of bed. He ran to check on her, and she was fine.

The couple figured it was another earthquake.

"It makes you wonder when they're going to stop - probably never at this point," he said.

The seismic activity in the Dillsburg area - several earthquakes and nearly 460 tremors since Oct. 3 - had seemed to be dwindling in recent months.

The last measurable earthquake shook the area New Year's Eve.

Residents reported booms during the weekend, preceding Wednesday's earthquake, said Jeri Jones of Jones Geological Services.

Jones said he has noticed that the rumblings, which were occurring during the night, are now happening more during the day.

He'll be meeting with township supervisors next month to discuss placing portable seismographs in the area.

Scientists with the Lamont-Doherty Earth Observatory of Columbia University placed portable seismographs in the area last fall to record the tremors and analyze the data.

Senior research scientist Won-Young Kim said in an e-mail Monday that their work is still going on, and he hopes to finalize it in the next couple of weeks.

DILLSBURG QUAKES

An earthquake that shook the Dillsburg area Wednesday morning is the 19th one that has been measurable since the fall, said Jeri Jones of Jones Geological Services.

The earthquake at 9:21 a.m. Wednesday measured 1.1 on the Richter Scale.

Three earthquakes measuring 2.0 or greater on the Richter scale have hit the Dillsburg area since the fall. Nearly 460 tremors have been reported in the area since Oct. 3.

Latest Dillsburg quakes - LCSN at the ready

A seismology team from Columbia University set up portable seismographs in the area. Retired Millersville University professor emeritus of geology Charles Scharnberger holds a map showing earthquake intensity zones. Zone III in center is the most intense with decreasing intensity outside the zone (photo credit: Dan Gleiter, The Patriot-News/2008).

From PennLive.com:

Friday April 24, 2009, 10:28 AM
2 earthquakes reported in Dillsburg area
by LARA BRENCKLE, Of The Patriot-News

A 2.9-magnitude earthquake rattled residents around the Franklintown, Pa., area early this morning, setting off concerns that the series of temblors that rocked northern York County in the fall and early winter have returned. The U.S. Geological Survey reported today's quake occurred at 1:36 a.m.

On Thursday, residents of Dillsburg also experienced tremors, with a 2.4 magnitude quake startling residents there. Dillsburg Borough manager Karen Deibler was in her office when Thursday's quake struck.

"I don't think a lot of people knew what was going on last night because it's been such a long time (since we've had one)," Deibler said.

The last spate of earthquakes occurred from October to January.

It's been quiet, however, and Deibler said people figured they were over. "Nobody really knows what to think at this point," she said.

New quakes in Harrisburg, Pennsylvania, area

There have been three small earthquakes in the Harrisburg area in the last few days. I'm returning tonight from the Society for American Archaeology meeting in Atlanta, flying into Harrisburg. Maybe I'll get to feel one?

I like the way the above graphic present four dimensions of information - latitude, longitude, earthquake magnitude, earthquake time - on a two dimensional map.

Update time = Sun Apr 26 12:19:15 EDT 2009
Here are the earthquakes appearing on this map, most recent at top ...

 MAG    DATE    LOCAL-TIME  LAT     LON    DEPTH    LOCATION
      y/m/d     h:m:s     deg     deg     km

2.9  2009/04/24 01:36:48 40.064N 77.026W  1.5   23 km (14 mi) SW  of Harrisburg,PA
2.4  2009/04/23 18:26:04 40.085N 76.998W  1.0   20 km (12 mi) SW  of Harrisburg,PA
1.1  2009/04/22 09:21:14 40.073N 77.002W  1.0   21 km (13 mi) SW  of Harrisburg,PA
2.1  2008/12/31 00:34:08 40.107N 77.003W  1.0   18 km (11 mi) SW  of Harrisburg,PA
3.4  2008/12/27 00:04:34 40.114N 76.403W  4.0    9 km ( 6 mi) W   of Lancaster,PA
1.4  2008/11/06 23:07:03 40.096N 77.006W  1.0   19 km (12 mi) SW  of Harrisburg,PA

Figure and data from Lamont-Doherty Cooperative Seismograph Network.

Happy Earth Day, 2009

from NASA

Today is the 39th anniversary of the first Earth Day, which I remember from when I was an undergraduate.

May we continue to use the Earth's burps to learn more about our planet, and minimize the dangers posed to our fellow inhabitants.