Dr.Afroz Ahmad Shah
Much has been written about the science of earthquakes in Jammu Kashmir and now authorities are aware about the magnitude of future earthquake disasters in the region. However, what is totally missing is the action on ground. And surprisingly whenever a medium to large magnitude earthquake occurs in any part of the planet Earth it always sends panic waves, and in Jammu and Kashmir it does exactly the same.
The earthquake of magnitude 6.1 that struck Hindu Kush region on 31th January 2018 has caused collapse of a newly constructed flyover in Srinagar. This is surprising because the epicenter of earthquake is more than 400 kilometers away, and the depth of the earthquake was more than 180 kilometers. This should not cause severe shaking to damage building in Kashmir. If a medium magnitude earthquake, that has occurred far off from Kashmir, has caused collapse of an under construction government building, one can image the impact of a major earthquake that could originates at shallow crustal depths and under Jammu Kashmir.
Complete disaster, and a total loss of life and property. Are we waiting for one? We know the current earthquake waves will jolt authorities for a very little while, and swiftly they ought to return back to the normal routine of waiting for a major disaster to come and challenge our unconsciousness! I hope that moment never comes.
I will remind them again that the cause of earthquakes in Jammu Kashmir region is primarily because Indian plate is continuously trying to push harder to dive under the Eurasian plate, and in doing so it often breaks via earthquakes. Since the tectonic plates are solid and thus one cannot simply expect a solid to make a smooth dive under another solid. Think about rubbing of two rock units, thus the sliding journey will not be smooth, and friction will hold it tight, and once the applied forces overcome the frictional forces the movement will occur along a fracture, which we call a fault. Recently the Moment Magnitude (Mw) 7.8 earthquake ruptured a portion of this plate boundary fault on 25th April 2015 in Nepal in which unfortunately we lost more than 15000 people.
This fault is named as Main Frontal Thrust (MFT) fault, and it a megathrust fault that accommodates on an average some ~2 cm/year of the regional convergence between India and Eurasia plates. The total length of this fault is more than 2000 kilometer, and it marks the present day active plate boundary along which accumulated strain is occasionally released through medium to large magnitude earthquakes. Thus, it is not surprising that the ongoing collision has resulted in more than 8 major earthquakes along the Himalayan arc in the past 100 years.
Jammu Kashmir sits on top of the magathrust fault, and it passes under shallowly under Jammu city, however, no trace of this fault has been mapped on surface in this region yet, and thus it is assumed that it runs under as a blind structure (have not ruptured the surface). It largely controls the frontal-fold thrust belt in Jammu region, and has shaped the morphology of the entire region.
The latest research demonstrates that there is a possibility of a major earthquake on this fault, which could happen anytime because currently in Jammu, Kashmir region the tectonic stress is ripe to host such an earthquake.
Recently another major fault, known asRiasi fault system, has been mapped in south of the Kashmir basin, and this fault been seismically quite for some time, and thus there is a possibility that this fault could also host a major earthquake anytime soon. Importantly this fault merges at depth with the frontal blind thrust, and thus there is possibility that major earthquake could either occur on the Riasi fault system or the frontal fold-thrust belt, or both. Such an earthquake is estimated to be of (Mw > 8) or even bigger, a much bigger event than the Mw 7.6 earthquake that occurred on the Balakot- Bagh fault in Pakistan Azad Kashmir in 2005.
A well-documented major fault system cuts through Kashmir basin, and has the potential to host Mw 7.6 or greater earthquake. This fault system has not been studies in details, thus there are greater uncertainties in understanding of this very fault.
Although, geomorphic studies clearly suggest that the fault is active, and has recently moved however, only a detailed work in the future will shed more light on its activity, and how much strain energy has been released through the faulting in the past. Since it is located north of the magathrust fault and one would expect it to be a bit quitter than the frontal faults, but to answer this we have to understand it in greater details.
A number of faults have also been mapped to the northwest and southeast of the basin, and most of these fault run parallel to the Muzaffarabad fault on which the deadly 2005 earthquake occurred and resulted in more than 80,000 deaths and lost/destruction of property worth millions. These faults could pose a lot of danger and could potentially nucleate earthquake in the near future.
Thus with our current understanding of the tectonic skeleton of the Jammu Kashmir still remain largely unknown and we are learning to understand how, what and why we have faults in this part of the world, and when they are going to slip and how. This is a difficult journey and hopefully we will get into this soon. It surely needs a lot of hard work and a dedicated team of experts to evaluate the possible causes of faulting in the region.
With many uncertainties that we are still unable to understand, for example nucleation, propagation, behavior, and stress accumulation on faults, and unknown active faults, it is safe to conclude that major/mega earthquake disaster is Kashmir is unavoidable. And for a reliable seismic hazard and risk evaluation some detailed paleoseismological studies are extremely necessary to determine the current status of strain accumulation on faults/folds or fault-segments.
Please understand that the earthquake threat in Jammu Kashmir is real and, it should not be taken lightly. Since the earthquake science is at a stage where scientists more or less understand the cause of earthquakes but are not very confident about the prediction of an incoming event. This means that there is a need to understand how to live with earthquakes without a successful prediction in sight. This can be achieved if we strictly abide by the strict construction standards, careful geological evaluation of building sites, and public education. This should be done now.
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