Probabilities for the occurrences of medium to large earthquakes in northeast India and adjoining region |
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| Authors: | R B S Yadav J N Tripathi D Shanker B K Rastogi M C Das Vikas Kumar |
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| Institution: | (1) Institute of Seismological Research (ISR), Raisan, Gandhinagar, Gujarat, 382009, India;(2) Present address: Indian National Centre for Ocean Information Services (INCOIS), Ministry of Earth Science, Government of India, Near ALEAP, Pragathi Nagar, Near JNTU, Kukatpally, Hyderabad, India;(3) Department of Earth and Planetary Sciences, University of Allahabad, Allahabad, 211002, India;(4) Department of Earthquake Engineering, Indian Institute of Technology Roorkee, Roorkee, Uttaranchal, 247667, India;(5) Shiv-Vani Oil and Gas Exploration Ltd, Agartala, India |
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| Abstract: | The return periods and occurrence probabilities related to medium and large earthquakes (M
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4.0–7.0) in four seismic zones in northeast India and adjoining region (20°–32°N and 87°–100°E) have been estimated with
the help of well-known extreme value theory using three methods given by Gumbel (1958), Knopoff and Kagan (1977) and Bury (1999). In the present analysis, the return periods, the most probable maximum magnitude in a specified time period and probabilities
of occurrences of earthquakes of magnitude M ≥ 4.0 have been computed using a homogeneous and complete earthquake catalogue prepared for the period between 1897 and 2007.
The analysis indicates that the most probable largest annual earthquakes are close to 4.6, 5.1, 5.2, 5.5 and 5.8 in the four
seismic zones, namely, the Shillong Plateau Zone, the Eastern Syntaxis Zone, the Himalayan Thrusts Zone, the Arakan-Yoma subduction
zone and the whole region, respectively. The most probable largest earthquakes that may occur within different time periods
have been also estimated and reported. The study reveals that the estimated mean return periods for the earthquake of magnitude
M
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6.5 are about 6–7 years, 9–10 years, 59–78 years, 72–115 years and 88–127 years in the whole region, the Arakan-Yoma subduction
zone, the Himalayan Thrusts Zone, the Shillong Plateau Zone and the Eastern Syntaxis Zone, respectively. The study indicates
that Arakan-Yoma subduction zone has the lowest mean return periods and high occurrence probability for the same earthquake
magnitude in comparison to the other zones. The differences in the hazard parameters from zone to zone reveal the high crustal
heterogeneity and seismotectonics complexity in northeast India and adjoining regions. |
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