Happy Earth Day

I still remember the first one 40 years ago!

Editorial Cartoon by John Sherffius

 From AAES (The Association of American Editorial Cartoonists)

May the Earth and us have a more  benign relationship together!

Safe travels, everyone.

China earthquake, magnitude 6.9

From the Christian Science Monitor:

Striking around dawn while many locals were at home, the quake collapsed buildings in Jiegu Township, near the epicenter, trapping hundreds under rubble, Huang Limin, deputy secretary-general of the Yushu Tibetan Autonomous Prefecture, told the state-run Xinhua News Agency.

More than 85 percent of the houses in Jiegu, a town of 100,000 people, were destroyed, Zhuo Huaxia, a prefectural official told Xinhua: "The streets in Jiegu are thronged with panicked, injured people, with many bleeding in the head. Many students are buried under the debris due to building collapse at a vocational school."

With memories of the 2008 earthquake in neighboring Sichuan Province still strong, the government’s response to this disaster will be closely watched, particularly since the quake zone is in a poor area largely inhabited by ethnic Tibetans.

Location map from USGS

Here is the seismogram as recorded on the Franklin & Marshall College seismograph:

Accelerographs for PCs

There was a question to one of my old posts about the availability of motion sensors for PCs, like Seismac for the Macintosh, which could turn your PC into an accelerograph.

Our friend IRIS (Incorporated Research Institutions for Seismology) comes through with a posted activity, 

Exploring three-component seismic data with accelerometers.

This exercise refers you to the QCN site at Stanford which allows you to download software. The software not only works with a Mac laptop (2006 or later), but also a Thinkpad (2003 or later), or a desktop with a USB sensor.

In addition, you can purchase an external USB accelerometer (for Macs, PCs and Linux) can be purchased from the Quake Catchers Network (request a sensor on right hand menu).

(Or, buy a Macintosh!)

Mexicali earthquake poster

The USGS has produced another in its fine series of posters on significant earthquakes.

The latest is on the magnitude 7.2 Mexicali quake.

Click on the image for a larger version

I won't dissect it in detail as I did for the Chile quake, but in the next post, we'll look at the fault plane solution, and its relation to the San Andreas Fault.

Mexicali quake magnitude same as Haiti quake

Here is the usual good story (text and audio) from NPR, explaining in part why despite the similar magnitudes for these two quakes, damage in Mexicali was less. Many aftershocks are still occurring.

Mexicali is the capital of the Mexican state of Baja California, with a metropolitan population close to 1 million people.

Earthquake coverage in the LA Times

For recent updates on the Mexicali quake, see the LA Times.

More soon - I have ballet tickets.

Quake near California-Mexico border

  == PRELIMINARY EARTHQUAKE REPORT ==
California Integrated Seismic Net
USGS/ Caltech/ CGS/ UCB/ UCSD/ UNR
Version #3: This report supersedes any earlier reports of this event.
This event has been reviewed by a seismologist.

A major earthquake occurred at 3:40:41 PM (PDT) on Sunday, April 4, 2010.
The magnitude 7.2 event occurred 26 km (16 miles) SW of Guadalupe Victoria, Baja California, Mexico.
The hypocentral depth is 10 km ( 6 miles).

---

Magnitude	7.2 - regional moment magnitude (Mw)
Time	Sunday, April 4, 2010 at 3:40:41 PM (PDT) Sunday, April 4, 2010 at 22:40:41 (UTC)
Distance from	Guadalupe Victoria, Baja California, Mexico - 26 km (16 miles) SW (225 degrees) Mexicali, Baja California, Mexico - 60 km (37 miles) SSE (165 degrees) Calexico, CA - 64 km (40 miles) SSE (163 degrees) San Luis, AZ - 65 km (40 miles) SW (231 degrees) Tijuana, Baja California, Mexico - 167 km (104 miles) ESE (105 degrees)
Coordinates	32 deg. 7.7 min. N (32.128N), 115 deg. 18.2 min. W (115.303W)
Depth	10 km (6.2 miles)
Location Quality	unknown
Location Quality Parameters	Nst=315, Nph=315, Dmin=112.1 km, Rmss=0 sec, Erho=0 km, Erzz=0 km, Gp=79.2 degrees
Event ID#	ci14607652
Additional Information	map with fault names Google Earth KML (Requires Google Earth.) Did you feel it? ShakeMap shaking intensity maps Waveforms SCSN Moment Tensor Solution Tsunami Information Statement from the WC/ATWC

Shake/intensity map:

The magnitude 8 earthquake that did not happen

Yesterday, I got the following messages from the QUAKE-L listserv:

First
Date: Sat, 3 Apr 2010 00:45:46 +0000 (UTC)
From: ens@usgs.gov (USGS ENS)

PRELIMINARY EARTHQUAKE REPORT

Region: NORTH ATLANTIC OCEAN
Geographic coordinates: 19.053N, 68.052W
Magnitude: 8.0 M
Depth: 13 km
Universal Time (UTC): 2 Apr 2010 05:38:55
Time near the Epicenter: 2 Apr 2010 01:38:55
Local standard time in your area: 2 Apr 2010 05:38:55

Second
 Date: Sat,  3 Apr 2010 01:16:57 +0000 (GMT)
From: ens@usgs.gov (USGS ENS)

DELETED: Event DR 2

                      == EVENT DELETED NOTIFICATION ==

***This event has been deleted after review by a seismologist.***

Geographic coordinates:        19.053N,  68.052W
Magnitude:                    8.0
Universal Time (UTC):          2 Apr 2010  05:38:55
Time near the Epicenter:       2 Apr 2010  01:38:55

And here is the explanation:

Users of the USGS Earthquake Notification System received a message reporting a magnitude 8.0 earthquake near the Dominican Republic. This was a mistake. In an effort to increase our ability to detect smaller earthquakes in the Caribbean region following the January 12th earthquake in Haiti, the USGS began accepting earthquake locations and magnitudes from additional sources in the region. The message reporting a magnitude 8.0 earthquake near the Dominican Republic was incorrect and resulted in the distribution of the errant e-mail. We acknowledge this was a serious mistake and have issued a correction.

Temblor predicted for Los Angeles in 2.5 years

Or, see the video here in YouTube.

Enjoy the beginning of April!