Seismicity of Tehri Area of the Himalayan Region, India  

作　　者：Ashok Anand Nazeel Sabah Daya Shanker Ashok Anand;Nazeel Sabah;Daya Shanker(Department of Civil Engineering, Indian Institute of Technology, Roorkee, India;Department of Earthquake Engineering, Indian Institute of Technology, Roorkee, India)

机构地区：[1]Department of Civil Engineering, Indian Institute of Technology, Roorkee, India [2]Department of Earthquake Engineering, Indian Institute of Technology, Roorkee, India

出　　处：《International Journal of Geosciences》2024年第11期911-926,共16页地球科学国际期刊（英文）

摘　　要：A database for the seismicity of the Tehri region (29.5˚N - 31.5˚N and 77.5˚E - 79.5˚E) from November 1, 1853, to March 31, 1989, has been prepared using a Compatible Personal Computer System. The seismicity database is complete for events with mb ≥ 4.5 only since 1963. It is inferred that the general seismicity of the area is considerably low, which is associated with four main tectonic features identified based on the spatial distribution of events in the area. Earthquakes in the Tehri area is of shallow focus, and maximum seismic activity is confined in the region beyond 60 km east and northwest of Tehri. The cumulative Number of Events as a Function of Time (CNET) for the period from 1963 to 1988 has indicated that precursory swarms do not precede the medium-sized earthquakes of the Tehri area. However, the CNET curves for total events and those with mb ≥ 4.6 have indicated a sharp 2-fold seismicity rate increase from 1986 compared to the preceding period. The October 20, 1991 (IST) earthquake of mb = 6.5 of Uttarkashi is believed to be associated with this seismicity rate change. The continuous increasing trend of the CNET curve before 1986 has been attributed to the detection changes.A database for the seismicity of the Tehri region (29.5˚N - 31.5˚N and 77.5˚E - 79.5˚E) from November 1, 1853, to March 31, 1989, has been prepared using a Compatible Personal Computer System. The seismicity database is complete for events with mb ≥ 4.5 only since 1963. It is inferred that the general seismicity of the area is considerably low, which is associated with four main tectonic features identified based on the spatial distribution of events in the area. Earthquakes in the Tehri area is of shallow focus, and maximum seismic activity is confined in the region beyond 60 km east and northwest of Tehri. The cumulative Number of Events as a Function of Time (CNET) for the period from 1963 to 1988 has indicated that precursory swarms do not precede the medium-sized earthquakes of the Tehri area. However, the CNET curves for total events and those with mb ≥ 4.6 have indicated a sharp 2-fold seismicity rate increase from 1986 compared to the preceding period. The October 20, 1991 (IST) earthquake of mb = 6.5 of Uttarkashi is believed to be associated with this seismicity rate change. The continuous increasing trend of the CNET curve before 1986 has been attributed to the detection changes.

关 键 词：Himalayan Seismicity B-VALUE Earthquake Precursors Seismicity Rate 

分 类 号：P31[天文地球—固体地球物理学]