25 September 2019
The Mirpur earthquake in Pakistan: images of lateral spreading
On 24th September 2019 an M=5.6 earthquake struck Mirpur in NW Pakistan. Whilst the Mirpur earthquake was comparatively small, it was also shallow, meaning that a significant area will have suffered high peak ground accelerations. The USGS has generated a map of earthquake intensity (the contours on the map), enhanced by the shading, which shows areas of liquefaction potential:-
At the time of writing, over 30 people have been reported to have been killed, whilst at least 450 people were injured. Interestingly, the area with the highest intensity of shaking coincides with both the banks of the major Jhelum River and the margins of part of the huge Mangla reservoir:-
Thus, whilst this earthquake is not large, it has the potential to generate both liquefaction and lateral spreading. Early images coming out of Pakistan show that the earthquake has had just this effect. For example, this image (from the Independent), clearly shows lateral spreading on the banks of the river. Note that the material appears to be made ground:-
Whilst this image, also from the Independent, also appears to show this area of lateral spreading:-
As usual, it is difficult at the moment to ascertain the full extent of these types of impacts – this should become apparent in the days ahead. It will also be interesting to find out the proportion of the building collapses that are associated with these lateral spread events, rather than simple structural failure under high peak ground accelerations.