UPDATE: You can click through to see individual seismometer outputs here: http://www.iris.washington.edu/cgi-bin/wilberII/wilberII_EnO_page4.pl?evname=20111023_104121.3.spyder
It’s going to be while before we have a proper handle on depths and magnitudes of the aftershocks, but enough data has been collated to start drawing up the focal mechanism (a plot that shows us what direction the fault moved in). USGS preliminary assessment suggest a low-angle thust fault http://earthquake.usgs.gov/earthquakes/eqarchives/fm/neic_b0006bqc_wmt.php. That makes it typical mountain-building activity, and the implication is that most off the aftershocks will be at a similar depth (thrust faults are generally dipped at between 0-30 degrees, so any other movement is likely to be along a similar plane). It’s a little unusual in that the plate boundaries are actually strike slip, but thrust faulting is necessary to accomodate the wedge movement (and growth of the mountain ranges which characterise much of the Turkish landscape). For more information on how to read and interpret these diagrams have a look here: http://en.wikipedia.org/wiki/Focal_mechanism
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Global Disaster Alert and Co-Ordination System (GDACS) report is here: http://w3.gdacs.org/reports.asp?ID=112337
Initial reports have it as a 7.2 Magnitude (expect this to vary over the next few days as data from more seismic stations is evaluated) at 20km depth, at a little after 10GMT this morning. Fatalities are estimated to be in the 500-1000 range. Below is the image my friend was circulating showing what remains of an 80 story tower block. Another 25-50 or so buildings are believed to have come down.
Remains of an 80 story office block, Van, Turkey. AFP
http://www.iris.edu/seismon/zoom/?view=eveday&lon=56&lat=36 shows seismic activity in the area over M4. There have been reports of 20+ aftershocks (the Kandilli Observatory website has a more detailed and excellent map and data list here http://www.koeri.boun.edu.tr/sismo/map/en/index.html). Turkey has a couple of plate margins crossing it roughly E-W (see the USGS map below), and is part of an active mountainbuilding belt. This is connected with the Aegean subduction system (the most seismically active area in the world), so seismic activity is not unexpected. This is a big one, however, and few buildings in Turkey are prepared for this kind of event.
Tectonic map of Turkey. Source: USGS. Click through for bigger
http://twitter.com/#!/aliarikan is keeping the updates flowing. I’ll be updating this as more becomes available.
Guardian article here (although basically just repeating the stuff that the Kandilli Observatory put out int heir press statement) http://www.guardian.co.uk/world/2011/oct/23/earthquake-hits-eastern-turkey
BBC Coverage here: http://www.bbc.co.uk/news/world-europe-15421633
More pictures from Time http://www.time.com/time/photogallery/0,29307,2097582_2319080,00.html
