Mexico earthquake: What do we know?


Baja California — that’s in Mexico, you European readers — got hit with a large earthquake tonight, a 7.2 on the logarithmic Richter Scale according to some early reports. At least one person died; Mexicali, on the border with California, reports many people trapped.  A state of emergency has been declared.

BBC gives the facts:

A 7.2 magnitude earthquake has hit the Mexican peninsula of Baja California, killing at least one person and causing tremors as far away as Nevada.

The quake struck at 1540 (2240 GMT), 26km (16 miles) south-west of Guadalupe Victoria in Baja California, at a depth of 32km, said the US Geological Survey.

Some people are still trapped in their homes in the city of Mexicali, where a state of emergency has been declared.

It was the worst quake to hit the region for many years, officials said.

The US Geological Survey said some 20 million people felt tremors from the largest quake to hit the area since 1992.

My students with Mexico connections tend to come from farther east, and higher in the mountains — I don’t think I have a single student who visits Baja California on breaks.  But the news will prompt questions from them tomorrow.

The U.S. Geological Survey (USGS) tracks earthquakes around the world.  It should have solid information.  Data on the April 4 7.2 quake are here.

Here’s the tectonic summary:

A magnitude 7.2 earthquake occurred at 3:40:40 p.m. (local time at the epicenter) on Sunday, 4 April 2010 in Baja California, approximately 75 km south of the Mexico-USA border. The earthquake occurred at shallow depth (approximately 10 km) along the boundary zone between the North American and Pacific plates. Since earthquakes have been recorded instrumentally, only two similar sized earthquakes have been recorded in the area. The first was the 1892 earthquake estimated at magnitude 7.0-7.2 along the Laguna Salada fault just south of the USA-Mexico border. The second was the 1940 Imperial Valley magnitude 6.9 earthquake which occurred in southernmost California. Today’s event is located nearly in line with these earthquakes along the plate boundary, but is situated farther to the south. There are several active faults in the vicinity of today’s earthquake, and the particular fault that generated this quake has not yet been determined. Faulting is complex in this region, because the plate boundary is transitional between the ridge-transform system in the Gulf of California and the continental transform system in the Salton Trough. Most of the major active faults are right-lateral strike-slip faults with a northwest-southeast orientation, similar in style to the San Andreas fault to the north. Other faults in the vicinity with the same orientation include the Cerro Prieto fault and the Laguna Salada fault.

USGS hosts good maps, too, like this “shake map” (click the map to go to the USGS site for more information):

USGS "shake map" for the April 4 7.2 quake near Mexicali, Mexico

USGS "shake map" for the April 4 7.2 quake near Mexicali, Mexico - Click to go to USGS site

What other questions can we anticipate?  Somebody will ask whether this quake is related to the Haiti and Chilean quakes (probably not closely related).  Somebody will wonder about the Pacific Ring of Fire, and this quake’s relation to volcanoes and general earthquake activity around the Pacific (high relationship).  Someone will want to know about quakes in your area.  Is this the precursor to “the Big One?”

The USGS site is a good place to start on all of those questions.

2 Responses to Mexico earthquake: What do we know?

  1. Ed Darrell says:

    As of this morning, two known dead.

    Contrast that with Turkey, Chile, and Haiti — clearly there are advantages to good planning, good regulations on building standards, and careful building.

    Like

  2. Tsu Dho Nimh says:

    I faintly felt it in Phoenix as a prolonged feeling of vertigo … more so if you were in a high building or lying – as one woman was – on her waterbed.

    The photos I have seen are showing damage from poor construction. Facades detached, poorly connected floors separated, the usual stuff.

    Like

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