October 26, 2015

expert reaction to earthquake in north Afghanistan

A powerful earthquake of magnitude 7.5 has struck northern Afghanistan, with reports of tremors being felt in India and Pakistan.

Prof. John McCloskey, Professor of Geophysics, University of Ulster, said:

“A magnitude 7.5 earthquake in an area like Afghanistan would be expected to generate high numbers of casualties; the type of construction used in these areas makes their populations very vulnerable to earthquake shaking. In this region the topography is very steep and therefore landslides are likely to pose a particular threat. In this case, however, the depth of the earthquake at over 200 km has reduced the amount of shaking experienced at the surface. Additionally, the main areas of high-intensity shaking were only sparsely populated so whereas the 2005 magnitude 7.6 Kashmir earthquake killed more than 75,000 people, this event is likely to be much less destructive. The USGS PAGER system, which uses a well-tested algorithm to forecast the number of deaths and economic impact of earthquakes, for example, quotes a peak probability of somewhere between 1,000 and 10,000 expected deaths for this event so it is still likely to be a significant earthquake.

“Earthquakes are always followed by other earthquakes, which are known as aftershocks. Bath’s Law, a useful rule of thumb in seismology, states that, in general the largest aftershock tends to be about one order of magnitude less on the Richter scale than the main shock. However this is not always the case, for example an aftershock to the recent Nepal magnitude 7.8 earthquake had a magnitude of 7.3, significantly larger than expected. In this case, we can certainly expect several magnitude 6 aftershocks, but an aftershock of magnitude 7 is a significant probability. Should an event like this happen closer to the surface, it could make a very significant contribution to the death toll. It is extremely important that people in the source region are properly advised with respect to the continuing hazard. They should not, for example, sleep in their houses, particularly if these houses have suffered visible damage during the main shock.”

Prof. Simon Redfern, Professor of Mineral Physics, University of Cambridge, said:

“The large earthquake, estimated as magnitude 7.5 by the US Geological Survey, that occurred in the Hindu Kush, Afghanistan, this-morning is the latest in a series of such quakes that have occurred in the region over historic times. Seven earthquakes at magnitude 7 or more have struck within 250 km of the latest event in the last century. The focus of today’s earthquake is placed at more than 200 km below the surface, and as such it will have been felt over a very wide area, from the borders of Tajikistan through north-eastern Afghanistan into Pakistan.

“This earthquake appears to be consistent with previous ones in the Hindu Kush that have been interpreted as originating from the near-vertical thrusting and faulting at the surfaces of a huge subterranean slab of rocky lithosphere that is being forced down deep beneath central Asia, as the Indian subcontinent moves northwards into Eurasia.

“The subterranean slab beneath the Hindu Kush appears to be being drawn down vertically like a giant rocky sausage in a tectonic process called “boudinage”, according to earthquake models reported in Nature Geoscience: http://www.nature.com/ngeo/journal/v1/n3/full/ngeo132.html.”

Dr Ilan Kelman, Reader in Risk, Resilience and Global Health, UCL, said:

“Communications appear to have gone down in the worst-affected areas, so it will be some time before we know the full impact. In the meantime, at this stage in the hours afterwards, it will be the locals rescuing people from the rubble, treating the injured, setting up temporary shelter, and catering for immediate physical and psycho-social needs. This situation illustrates the importance of local training for disaster response and of disaster education for everyone, from before kindergarten until after retirement.”

Prof. David Rothery, Professor of Planetary Geosciences, The Open University, said:

“Today’s earthquake in the Hindu Kush region of northeast Afghanistan was a result of the northward collision of India with central Asia. With a magnitude of 7.5 on the Richter scale it had the potential to be very damaging but fortunately it occurred at a depth of more than 200 km (as they usually are in this area) and so the shaking of the ground surface was less than it would have been for a shallower earthquake of the same magnitude. (The Ghorka earthquake in Nepal on 25 April was magnitude 7.8 and only 8 km deep).

“Even so, poorly-constructed homes may have been badly damaged, and in such a mountainous region landslides could have occurred.”

Declared interests

Prof. John McCloskey: “I work in a university have no voluntary appointments or memberships with conflict in any way with making a comment on this event. I have no financial interests in this whatsoever. I will likely work advising some aid agencies, particularly Concern Worldwide, who will deploy in the region, and will likely be in touch with the government SAGE committee in the next day or two.”

Dr Ilan Kelman: Co-director of the NGO Risk RED (Risk Reduction Education for Disasters).

Prof. David Rothery: “My current grant funding is for work on the planet Mercury.  Relevant to this story I am author of ‘Volcanoes, Earthquakes and Tsunamis: A Complete Introduction’ (aka Teach Yourself Volcanoes, Earthquakes and Tsunamis) (Hodder & Stoughton 2001, 2010, 2015) and I run the Open University’s short course S186 Volcanoes, Earthquakes and Tsunamis.”

None other received.