3 September 2010

Updated: The New Zealand earthquake

Posted by Dave Petley

Bizarrely, I am currently sitting in the QANTAS lounge at Sydney Airport waiting for a flight to New Zealand, where the IAEG Congress starts on Monday.  The theme of the conference is “Geologically Active”…

So, what do we know about the earthquake so far.  The best source of information is the Geonet site – http://www.geonet.org.nz/ – which puts seismic data online in real time.  They are reporting that the earthquake occurred at 4:35 am local time 30 km west of Christchurch at a depth of (now updated to) 10 km.  The reported magnitude is (now updated to) 7.1 – USGS is reporting 7.0, but this is probably a moment magnitude.  This is the isoseismal map from Geonet:

This suggests that some damage in the Christchurch area is likely, which seems to be confirmed by the initial news reports.  Hopefully the timing of the earthquake, and the high level of preparation for earthquakes in New Zealand, will mean that casualties will be light and damage manageable.  Perhaps the most interesting data at this stage is the map of locations in which people have reported they felt the earthquake.  This looks like this at the time of writing.  The dark orange dots represent an intensity sufficiently large to cause significant damage:

GEONET shake map
There are no reports of landslides as yet, but given the proximity of the Southern Alps some landslides are likely:
More later.