Figure above shows locations of major events along the Himalayan arc. The pink areas are the rupture zones of damaging earthquakes (magnitudes 7.3-8.6) in the past two centuries, and the grey areas are the inferred enormous rupture zones of Medieval megaquakes.
Kashmir Observer: Estimates of the magnitudes of past seismic events foretell a very shaky future for this pastoral Valley writes Dr Afroz Ahmad Shah.
The earthquake studies in the state of Jammu of Kashmir, and primarily in the valley is still quite juvenile. Any kind of conclusion or opinion at this point of time will be dangerous and unscientific, if not provided with proper evidences or references of authentic scientific work.
Until now, the most authentic sources are a few publications from Roger Bilham and his research group. He is a well known earthquake scientist and a professor of geology in the University of Colorado, USA. His work about the past earthquakes in the valley is based on the historical data, and therefore, NOT a fully reliable scientific source of information.
This was also felt by Professor Bilham himself and therefore, he consistently mentions it in his findings. I will follow his conclusions based on the scientific evidences he suggested in those publications, which until now remain the most authentic, scientifically reviewed and detailed work in the Kashmir valley. One of his papers, titled “Kashmir Valley Megaearthquakes”, published in an international science magazine, American Scientist in 2009, is the first detailed scientific publication on the earthquakes of Kashmir. I will quote him, “History as well as geology tells us that the Himalaya arc will experience much bigger earthquakes than the 2005 event-bigger than the damaging moderate earthquakes that have struck the Kashmir Valley in recent centuries. Given the massive scale of faults in this part of the world, and the enormous forces, earthquakes in the range of magnitude 8.5, maybe even greater, will inevitably strike..”
He further goes on saying that “..recent calculations moreover suggest that megaquakes, with magnitudes well above 8.0, are not just possible along the Himalayan arc; they are necessary to relieve the stresses generated by the continuing northward motion of India into Eurasia”. We know from the GPS measurements that no part of the Himalaya can be out of danger as the Indian plate moves northwards and continuously builds up the energy.
The two major earthquakes, which Bilham and his group reported, have occurred in the years 1554/5 and 1886. About the first major event, they write “..the 1554/5 earthquake may have been the most recent of the irregular large earthquakes in the Kashmir region. Again, more by inference than by force of evidence, we suspect that the 1554/5 event focused at the base of the Pir Panjal Range. This is the westernmost expression of the Himalaya, and the region that has not slipped in a large earthquake since 1555 is roughly 400 kilometers by 80 kilometers-big enough to host an M8 earthquake, The GPS data tell us convergence in the region is now more than 15mm/year. If this convergence has been continuous since 1555, we have more than enough potential slip (6.8 meters) ready right now to drive another quick of the similar size….The uncomfortable conclusion is thus that a repeat of the 1555 earthquake may be close at hand, and one cannot dismiss the specter of a future megaquake extending well beyond the confines of the Kashmir Valley. How close, unfortunately, the unknowns currently far outweigh the knowns, and the mechanisms of earthquakes contain none of the elements characteristic of a clock. We note, however, that stresses generated by the 2005 Kashmir earthquake, although only a relatively modest one at Mw 7.6, have not dissipated stresses already stored near the 1555 rupture zone. Indeed, they serve to enhance them. Looking at other major faults around the world, it is clear that adjacent fault segments sometimes break sequentially, like toppling dominoes, with major earthquakes separated by days, months, years…sometimes a few decades. If the Kashmir segment is the next domino to topple along the Himalayan arc, the future earthquake will unleash devastating ground motions on a corner of the world that is, in every sense of the phrase, one perilously shaky ground. The magnitude could be 7.6-7.8 or even bigger, it was not a megaquake”.
About the 1884 quake
Bilham and his group in a paper published last year, in The Geological Society of American, report historical evidences of 1884 earthquake. It says “Srinagar, the capital city of Kashmir, has been shaken numerous times by earthquakes in the past millennium, most recently by damaging earthquakes in 1885 (M 6.2, 30 km to the west). They however, are unsure about the magnitude or size of the earthquake and therefore, in their conclusions, they reflect it by saying“….our findings are thus clearly insufficient to draw conclusions about the magnitudes of earthquakes that have shaken Kashmir Valley in the past millennium, nor do our results provide upper limits to the shaking experienced in historical times in nearby Srinagar, where thick sediments in the Jhelum River valley and around lakes are likely to amplify shaking significantly. Careful analysis of other ancient monuments in the valley, in particular dating of damage, may usefully supplement the sparse historical record.
We note in closing that the Pandrethan Temple serves as both an encouraging and a cautionary case study: encouraging to the extent that the structure does provide useful clues that help elucidate the earthquake history of the region; cautionary to the extent that, if not for the fortuitous existence of repeat historical photographs, one could easily be led to the same obvious but mistaken conclusion implied by R.D. Oldham’s 1887 photograph, that damage to the temple evident in 1887 was caused by the 1885 earthquake..”
This above mentioned data are the most authentic scientific investigations and hence, reflect the current scenario of earthquake studies in the Kashmir valley. It is therefore safe to argue that a big earthquake can hit this region anytime. I have also identified a number of locations where active faults have uplifted and tilted young sediments and still carry strong evidences of past earthquakes. What however remains unknown is when and how big a earthquake can hit the region. That is what should be done in the coming years. I am aware there are a number of people currently working and will possibly publish their findings soon.
They have excavated some trenches to supplement the historical records. I would also recommend a thorough paleoseismilogical investigation on these identified active faults, so that the “unknowns” can be scientifically turned into “reliable knowns”. This will however, require the concerned authorities to channelize funds for the earthquake research projects and provide adequate facilities, so that earthquake research ambition of a global standard can be achieved in the valley.
Author is a Research Fellow, Tectonics Group, Earth Observatory of Singapore, Nanyang Technological University, Singapore . He can be reached at: afroz@ntu.edu.sg
