31 August 2008

UPDATED 4th Sept: Magnitude 5.7 earthquake in China

Posted by Dave Petley

The USGS is reporting today that there was a Mw=5.7 (Xinhua is reporting M=6.1) earthquake in China at 4:30 pm local time yesterday. News reports this morning suggest that 25 people have been killed and a further 100 injured. I wouldn’t normally post on an earthquake of this size as the likelihood of triggering extensive landslides is limited. However, in this case there may be an interesting landslide angle to this.

The terrain in which the earthquake struck is pretty mountainous as the following Google Earth image perspective shows. The location is the estimated epicentre, as derived by the USGS:

This is clearly the type of terrain in which landslides occur, and of course this region received a good shake in the Wenchuan event. However, of particular concern this time is the weather at the time of the earthquake. NASA TRMM data are very useful for looking at the locations of heavy rainfall. Their latest image shows that SW China has been having some pretty intense precipitation of late:

Given that material may have been loosened by the Wenchuan earthquake, the shallow depth of the earthquake and the rainfall at the time, there must be a reasonable chance that some landslides have occurred. It will be interesting to see if reports of landslides emerge.

UPDATE: The official news agencies are now reporting that there were 40 fatalities, but is not specifying how these occurred. However, Xinhua has released the following incredibly sad and poignant image showing soldiers recovering two bodies. There seems to be little doubt that these people were buried in a landslide.

UPDATE 4th SEPTEMBER: It does appear that landslides have proven to be a substantial problem. CCTV is now reporting that:
“Local residents say there are areas in the remote mountainous regions that suffered even more severe devastation than Huili. But quake-triggered landslides have damaged roads leading to those areas, hampering relief efforts. And it takes several hours at the very least…for relief supplies to get through.”