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. | |
Dave Petley is the Vice-Chancellor of the University of Hull in the United Kingdom. His blog provides commentary and analysis of landslide events occurring worldwide, including the landslides themselves, latest research, and conferences and meetings.
Staff from Recent Earthquakes recently left New Zealand, having checked on Tsunami Alert Systems. They are totally needed. Dunedin has interest in improving its alert systems as does Wellington and Christchurch. Christchurch suffered tremendous damage in 1960 from a Tsunami. We pray for our friends in Christchurch and surrounding areas. http://recentearthquakes.net
Don't know where this is – Indian subcontinent I think from the language – but you might be interested in it, Dave. http://www.youtube.com/watch?v=25svE52rihcA recent landslide in perilous conditions, and I hope the driver jumped out in time.
From the local GNS Science group discussing their air recon:"They then flew to Rakaia Gorge where there were reports of landslides. The Rakaia River was very dirty and brown due to spall from steep cliffs on the sides of the gorge and at Big Ben. The landslides are small (hundreds of cubic metres) but restricted to steep cliffs. They saw small surface scars on the sides of Mount Hutt, but no major landslides or rock avalanches (and none had been reported to Mt Hutt helicopters who were flying in the area all day)."
GNS has provided an amazing flyover movie showing dextral displacement, vertical displacement, pressure ridging, surface cracking etc.http://www.youtube.com/watch?v=Npqx3WmNkv4
Thank you, Christoph. The flyover is well-worth the trip.
As we see, disasters continue to befall Christchurch. Just when progress was being made on the last quake cleanup, Christchurch gets hit again. Christmas 2011 will not be remembered for that new bicycle, for sure. I’m praying for a better 2012 for the citizens in those areas of New Zealand sitting on the “ring of fire.”
Bobby vassallo
Things have been quiet for the better part of the decade, so far. I am hoping that all remains calm. New Zealand is the finest place ever to visit. Nicest people and the nicest scenery anywhere in the world. Ring of Fire? Be calm! I’m visiting soon to work on the wireless network in Queenstown!
Bobby Vassallo