Seismic source zoning and maximum credible earthquake prognosis of the Greater Kashmir Territory, NW Himalaya

We present the seismic source zoning of the tectonically active Greater Kashmir territory of the Northwestern Himalaya and seismicity analysis (Gutenberg-Richter parameters) and maximum credible earthquake (m(max)) estimation of each zone. The earthquake catalogue used in the analysis is an extensive one compiled from various sources which spans from 1907 to 2012. Five seismogenic zones were delineated, viz. Hazara-Kashmir Syntaxis, Karakorum Seismic Zone, Kohistan Seismic Zone, Nanga Parbat Syntaxis, and SE-Kashmir Seismic Zone. Then, the seismicity analysis and maximum credible earthquake estimation were carried out for each zone. The low b value (< 1.0) indicates a higher stress regime in all the zones except Nanga Parbat Syntaxis Seismic Zone and SE-Kashmir Seismic Zone. The m(max) was estimated following three different methodologies, the fault parameter approach, convergence rates using geodetic measurements, and the probabilistic approach using the earthquake catalogue and is estimated to be M-w 7.7, M-w 8.5, and M-w 8.1, respectively. The maximum credible earthquake (m(max)) estimated for each zone shows that Hazara Kashmir Syntaxis Seismic Zone has the highest m(max) of M (w) 8.1 (+/- 0.36), which is espoused by the historical 1555 Kashmir earthquake of M (w) 7.6 as well as the recent 8 October 2005 Kashmir earthquake of M-w 7.6. The variation in the estimated m(max) by the above discussed methodologies is obvious, as the definition and interpretation of the m(max) change with the method. Interestingly, historical archives (similar to 900 years) do not speak of a great earthquake in this region, which is attributed to the complex and unique tectonic and geologic setup of the Kashmir Himalaya. The convergence is this part of the Himalaya is distributed not only along the main boundary faults but also along the various active out-of-sequence faults as compared to the Central Himalaya, where it is mainly adjusted along the main boundary fault.