Today's Magnitude 6.9 Earthquake, Yushu, China

An earthquake measuring 6.9 on the Moment-magnitude scale has struck southern Qinghai,
China, near the city of Yushu in the Tibet Autonomous Region.  Using the Hazard Viewer tool
on this web site, together with the Recent Earthquakes display, it can be determined that the ground
shaking resulting from the earthquake in Yushu was between 8% g and 12% g, equivalent
to Modified Mercalli Intensity V to VI.  Shaking of this intensity is enough to collapse some buildings
constructed of unreinforced masonry, as might be common in the region.

While it is possible that this event is related to the magnitude 8.0 Wenchuan earthquake that struck
near Chengdu, China on May 12, 2008, the distance between the two events and the elapsed time
would tend to suggest otherwise. The fact that yet another potentially destructive earthquake has occurred
near a populated area is not unexpected.  As discussed on this site in previous blogs, human exposure
to major earthquakes is growing, as populations move into seismically active areas.  Moreover,
earthquakes having magnitude greater than 7.0  occur approximately once every 3 weeks somewhere
on earth. 

UPDATE 1:  Reports from the region now indicate that more than 400 persons have been killed, with many thousands injured.  Widespread collapse of buildings have occurred, as the calculations here suggested might happen. (April 14)

UPDATE 2: It has now been reported that over 1100 persons may have died in the earthquake, with tens of thousands injured.  While not on the scale of the May 12, 2008 Wenchuan earthquake, in which 80,000 persons died, the Yushu earthquake is nonetheless a major disaster in China. (April 16)

UPDATE 3:  As of April 20, it is now reported that over 2000 persons have died in this earthquake.

A screen shot showing use of the Hazard Viewer is below: