A very strong earthquake occurred in Eastern Iran close to the Iran-Pakistan border. USGS reports a magnitude of 7.8 and a shallow depth of 15 km, EMSC data suggest M7.7 and 50 km depth. Preliminary shake maps estimate intensities around MSK VIII, which would be enough to make traditional adobe buildings to collapse. Reports confirm the event was felt as far away as Muscat, Oman (600 km distance!). Update: USGS now also reports a depth of 80 km.
USGS shake map (source: http://earthquake.usgs.gov)
Quick moment tensor solution indicate that normal faulting happened, despite the region is situated in a compressive regime where thrust or reverse faulting could be expected. However, historic seismicity also showed normal mechanisms.
EMSC compilation of Moment Tensor Solutions (data source: http://www.emsc-csem.org)
Historic moment tensor solutions indicate normal faulting:
Historic moment tensor solutions (source: http://emsc-csem.org)
Felt reports show that the event was felt as far as Muscat, Oman:
Felt reports indicate intensity IV-V even in Muscat (Data source: http://emsc-csem.org).
Updated: Up to now there are reports of 40 fatalities and some damages, but the hypocentral depth and the magnitude of the event suggest that there will be at least local destruction.
A connection to the M6.3 event that rattled SW Iran on 9 April does not exist as far as I know. The only thing that connects both earthquakes is the fact that they occurred in the same plate collision zone, but it would not be good science to guess that one event triggered the other. The distance between the two events is very large, around 1000 km.
My colleague Gösta Hoffmann from GUtech told me that the university campus has been evacuated after strong shaking has been felt: “The member of the geoscience department were outside the building in 2 minutes and then we called the management. They evacuated the building. We felt no aftershocks and went back in after 30 minutes. The evacuation was smooth, no one panicked and the people assembled in front of the building.” Of course, I am back to Germany again so I haven’t felt the earthquake myself.
As I’ve written in one of my last posts, Gösta, his colleagues and me are also conducting field studies for finding out if there are active faults in Oman itself. The last earthquake that has been felt in Muscat occurred in 1945. This event was a large event (>M8.0) that happened offshore at the Makran Subduction Zone and this event also caused a tsunami that reached the Omani coast…
By the way, as the following map from EMSC illustrates, such strong events are well known from this area:
Historic seismicity, 1960-today (Source: http://emsc-csem.org)
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