Source characteristics of the 18 September 2011 Sikkim earthquake and zoning

Main Article Content

Rajesh Prakash
Ravi Kant Singh
https://orcid.org/0000-0002-9721-216X
Gaddale Suresh
Jia Lal Gautam
Sanjay Kumar Prajapati
Hari Narain Srivastava

Abstract

Using detailed waveform analysis of Pn, sPn depth phases from the nearby seismic stations, attempts were made to resolve the focal depth of the 2011 Sikkim earthquake. Focal depth of 46.8 km thus determined was found closer to the GCMT source mechanism solution as compared to ISC solution (29.6 km). Re-examination of its source mechanism with the spatial/ depth distribution of its aftershocks sug- gested that both the nodal planes oriented WNW or ENE, initially ruptured but the orientation of meizoseismal area and larger concen- tration of its aftershocks parallel to the Tista lineament conformed WNW striking nodal plane relatively more active. The large value of the stress drop derived from S-wave spectra based on the data of Indian stations was attributed to its strike-slip mechanism and deeper focal depth. The stress drop of its foreshock was much lower than that the main shock. The b-value also showed a decrease during the last decade prior to the main earthquake.The recent Sikkim earthquake (Mw 6.9) has brought out the limitations of the microzoning of the Sikkim region attempted earlier.

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How to Cite
1.
Prakash R, Singh RK, Suresh G, Gautam JL, Prajapati SK, Srivastava HN. Source characteristics of the 18 September 2011 Sikkim earthquake and zoning. Ann. Geophys. [Internet]. 2018Aug.2 [cited 2021Dec.4];61(4):SE451. Available from: https://www.annalsofgeophysics.eu/index.php/annals/article/view/7585
Section
Seismology
Author Biographies

Rajesh Prakash, National Centre for Seismology, Ministry of Earth Sciences

Scientist

Ravi Kant Singh, National Centre for Seismology, Ministry of Earth Sciences

scientist

Gaddale Suresh, National Centre for Seismology, Ministry of Earth Sciences

scientist

Jia Lal Gautam, National Centre for Seismology, Ministry of Earth Sciences

scientist

Sanjay Kumar Prajapati, National Centre for Seismology, Ministry of Earth Sciences

scientist

Hari Narain Srivastava, Retired Additional DG, India Meteorological Department, New Delhi

Scientist