Skip to main content

At 2:28 pm local time a major M7.9 earthquake struck China near the city of Chengdu in Sichuan province.  BBC reports 8500 dead , but USGS  analysis shows that 200,000 people were exposed to violent to extreme shaking that could cause heavy damage in well built structures and very heavy damage in vulnerable structures.

Survivor struggles to escape.
Image Hosted by
By Reuters

Moreover, close to a million people lived where strong shaking could cause heavy damage in vulnerable structures. This USGS analysis suggests that early news reports many be underestimating the extent of this disaster.

The city of Chengdu,with about 11 million inhabitants, 55 miles east of the rupture, was spared from heavy damage because the thrust event concentrated the worst damage near the fault rupture.

The earthquake was a shallow thrust earthquake, similar to the 1971 San Fernando Valley California earthquake in it's fault mechanism and transfer of energy to the surface. However, it was an order of magnitude greater than the San Fernando earthquake, so much more damage over a much larger area can be expected. It was located on a fault in the mountains just northwest of the Sichuan basin.
Image Hosted by

90 km (55 miles) WNW of Chengdu, Sichuan, China
150 km (90 miles) WSW of Mianyang, Sichuan, China
360 km (225 miles) WNW of Chongqing, Chongqing, China
1545 km (960 miles) SW of BEIJING, Beijing, China

Image Hosted by

Fortunately for the millions of people living in the basin that strongest shaking was in the mountains along the fault. The aftershock sequence shows that the primary shock began on the southeastern end of the rupture zone and propagated northeast. The heaviest damage can be expected along that rupture path to the northeast of the epicenter because that's where the energy was focused on the surface as the rupture spread northeast.

Image Hosted by

The earthquake was felt in major cities across China including Shanghai as reported here, but those cities will have suffered only minor damage such as objects falling from shelves.

I'm sitting at my desk on the 19th floor in Shanghai doing work and listening to bad 80's music.  I started to feel a little woozy, as if I was dizzy and needed to lay down for a minute.  That's when I noticed that the cords on my window  shade were swinging back and forth.  Earthquake!

The swaying lasted about a minute or two here.  I'm sure it was much worse near the epicenter - no word on that yet.  

The cause of the earthquake is the thrusting of the mountain block of the Tibetan plateau over Sichuan basin caused by the tectonic compression related to India's northward motion.

Tectonic Summary

The Sichuan earthquake of May 12, 2008, occurred as the result of motion on a northeast striking reverse fault or thrust fault on the northwestern margin of the Sichuan Basin. The earthquake’s epicenter and focal-mechanism are consistent with it having occurred as the result of movement on the Longmenshan fault or a tectonically related fault. The earthquake reflects tectonic stresses resulting from the convergence of crustal material slowly moving from the high Tibetan Plateau, to the west, against strong crust underlying the Sichuan Basin and southeastern China.

On a continental scale, the seismicity of central and eastern Asia is a result of northward convergence of the India plate against the Eurasia plate with a velocity of about 50 mm/y. The convergence of the two plates is broadly accommodated by the uplift of the Asian highlands and by the motion of crustal material to the east away from the uplifted Tibetan Plateau.

The northwestern margin of the Sichuan Basin has previously experienced destructive earthquakes. The magnitude 7.5 earthquake of August 25, 1933, killed more than 9,300 people.

P.S. The Richter scale has been replaced by the moment-magnitude scale which directly relates to the energy release of an earthquake.

Update: See Shanghaiist for updates from China.

Originally posted to FishOutofWater on Mon May 12, 2008 at 07:26 AM PDT.

Your Email has been sent.
You must add at least one tag to this diary before publishing it.

Add keywords that describe this diary. Separate multiple keywords with commas.
Tagging tips - Search For Tags - Browse For Tags


More Tagging tips:

A tag is a way to search for this diary. If someone is searching for "Barack Obama," is this a diary they'd be trying to find?

Use a person's full name, without any title. Senator Obama may become President Obama, and Michelle Obama might run for office.

If your diary covers an election or elected official, use election tags, which are generally the state abbreviation followed by the office. CA-01 is the first district House seat. CA-Sen covers both senate races. NY-GOV covers the New York governor's race.

Tags do not compound: that is, "education reform" is a completely different tag from "education". A tag like "reform" alone is probably not meaningful.

Consider if one or more of these tags fits your diary: Civil Rights, Community, Congress, Culture, Economy, Education, Elections, Energy, Environment, Health Care, International, Labor, Law, Media, Meta, National Security, Science, Transportation, or White House. If your diary is specific to a state, consider adding the state (California, Texas, etc). Keep in mind, though, that there are many wonderful and important diaries that don't fit in any of these tags. Don't worry if yours doesn't.

You can add a private note to this diary when hotlisting it:
Are you sure you want to remove this diary from your hotlist?
Are you sure you want to remove your recommendation? You can only recommend a diary once, so you will not be able to re-recommend it afterwards.
Rescue this diary, and add a note:
Are you sure you want to remove this diary from Rescue?
Choose where to republish this diary. The diary will be added to the queue for that group. Publish it from the queue to make it appear.

You must be a member of a group to use this feature.

Add a quick update to your diary without changing the diary itself:
Are you sure you want to remove this diary?
(The diary will be removed from the site and returned to your drafts for further editing.)
(The diary will be removed.)
Are you sure you want to save these changes to the published diary?

Comment Preferences

democrattotheend, Mogolori, Phoenix Woman, Buckeye BattleCry, decembersue, DawnG, Iddybud, its simple IF you ignore the complexity, Avila, tommurphy, MsSpentyouth, tacet, waytac, eeff, platypus, MackInTheBox, elfling, acuppajo, zenbowl, Mumon, mataliandy, jancw, sclminc, bara, smugbug, petercjack, sarahnity, nyceve, srkp23, Scoopster, mkfarkus, Ignacio Magaloni, CodeTalker, BruinKid, jbdigriz, thingamabob, dmac, kport, lirtydies, wader, DemocracyLover in NYC, resa, Barbara Morrill, sockpuppet, salsa0000, mrkvica, laderrick, churchylafemme, houyhnhnm, chillindame, rlharry, barbwires, walkshills, JayBat, ybruti, smartgo, Lefty Mama, SanDiegoDem, vacantlook, bibble, oortdust, weelzup, radarlady, 3goldens, Treg, Elise, Simplify, JRG, boofdah, Blissing, lennysfo, dansk47, jimstaro, GreyHawk, Skid, Phil S 33, serrano, sbdenmon, loggersbrat, northanger, Pluto, sillia, Spathiphyllum, Ekaterin, Land of Enchantment, fhcec, drag0n, forbodyandmind, skywriter, SSMir, pmc1970, meghna, dus7, BachFan, danmac, Nightprowlkitty, PatsBard, rcbowman, RustyBrown, alefnot, sambar, borkitekt, koNko, KenBee, mango, mystery2me, fahrenheit2200, Sagebrush Bob, Preston S, Dreaming of Better Days, MadMs, Jbeaudill, Statusquomustgo, kurious, chesapeake, CharlieHipHop, Pandoras Box, AmericanRiverCanyon, One Pissed Off Liberal, Abraham Running For Congress When I Turn 25, pgm 01, dotdot, hockeyrules, Femlaw, blue armadillo, Wide Awake in NJ, VA02 femocrat, Great Uncle Bulgaria, edsbrooklyn, dotcommodity, tbirchard, SJLeonidas, Jimdotz, joyful, BetterTogether, dolphin777, vbdietz, cyncynical, jhop7, uciguy30, Got a Grip, gizmo59, rontun, zerone, BlueTape, Laughing Vergil, John Barleycorn, Rick Winrod, lineatus, OWCH, Jake Williams, mofembot, Rachel Griffiths, KimD, valsagem, echatwa, CeeusBeeus, debheadley, Scubaval, bijoudesigncom, pileta, Neon Vincent, Texanomaly, gdwtch52, cantelow, CanyonWren, FrugalGranny, vertexoflife, millwx, The Mort Man, ninshubur, Somewhereinasia, citisven, smileycreek, jerry in wisconsin, TruthandTrust, RhymesWithUrple, ornithology

Subscribe or Donate to support Daily Kos.

Click here for the mobile view of the site