Baro Olympa, Kumar Abhishek (2017), Seismic Source characterization for the Shillong Plateau in Northeast India, Journal of Seismology, DOI: 10.1007/s10950-017-9664-2

(a)Seismotectonic map of the SP showing the four seismic source zones, tectonic features, past EQs and beach ball solutions of some of the significant EQs in the different zones; (b) Frequency vs. percentage rupture plot showing the variation of rupture percentage of faults during past EQs across the seismotectonic region
(a)Seismotectonic map of the SP showing the four seismic source zones, tectonic features, past EQs and beach ball solutions of some of the significant EQs in the different zones; (b) Frequency vs. percentage rupture plot showing the variation of rupture percentage of faults during past EQs across the seismotectonic region

 

Present study aims at understanding the seismotectonic province of the Shillong Plateau (SP) by identifying the potential seismic source zones within a radius of 500km from the centre of the SP. From existing literature and earthquake (EQ) data the seismotectonic region is found to vary in terms of seismicity, tectonic features, geology, thickness of overburden, rupture characteristics, rate of movement. Thus, entire 500km radius seismotectonic region is divided into four seismic source zones namely; 1) the Shillong Plateau – Assam Valley Zone (SP-AVZ), 2) the Indo-Burma Ranges Zone (IBRZ), 3) the Bengal Basin Zone (BBZ) and 4) the Eastern Himalaya Zone (EHZ). EQ catalogues for each source zone is analysed for completeness of magnitude and time. Seismic parameter ‘b’ estimated using maximum likelihood method are found as 0.91±0.03 0.94±0.02, 0.80±0.03 and 0.89 ± 0.03 for SP-AVZ, IBRZ, BBZ and EHZ respectively. In addition, maximum likelihood method is used to estimate the mean annual activity rate, maximum possible magnitude (mmax), return period and probability of exceedence for the four zones. The ‘b’ values estimated suggest that BBZ is seismically more active; however the rate of occurrence of EQs is highest in the IBRZ. Findings from this study are in indication of the relative contribution from each of the four seismic source zones towards seismic hazard of SP.

 

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