Journal of Geological Society of India (Online archive from Vol 1 to Vol 78)

A. K. Mundepi ¹, Kamal ¹, Ajay Paul ²

Affiliations
1 Wadia Institute of Himalayan Geology, 33, General Mahadeo Singh Road, Dehra Dun - 248 001, IN
2 Kumaun University, Nainital - 263 002, IN

Abstract

This note is a result of an off-shoot study carried out of a reconnaissance Seismic noise survey to establish broadband seismological stations. The survey was conducted in Kumaun Himalaya for the purpose of characterizing background seismic noise characteristics. This paper deals with the estimation of local site effects at various locations with varying geological and tectonic environments in the region. The effects of the various litho units on the site's predominant frequency are depicted here it is seen that the character of the top sedimentary column and its compaction plays a vital role in the estimation of site response. The level of tectonic complexity is also reflected in the noise spectra of the studied regions. The region in close proximity of the MCT zone exhibits high background seismic noise level.

Keywords

Seismic Noise, Site Amplification, Lithological Effect, Kumaun Himalaya.

Full Text

     

Charu C. Pant ¹, Ajay Paul ¹

Affiliations
1 Department of Geology, Kumaun University, Nainital - 263 002, IN

Abstract

The seismic network in Kumaun Himalaya has recorded nearly three thousand earthquakes events since April 1999. The data has been analysed to study the seismicity pattern, seismicity rate, stress drop and focal depth pattern. The detailed analyses of 388 events have been carried out. The magnitude of the events is less than 4.2, the focal depth for most of the events lie between 10-25 km and the stress drop values are low. An attempt has been made to delineate seismically active zones and the seismicity pattern indicates that the strain energy is being released along NW-SE direction almost parallel to the regional thrust viz. Main Central Thrust/Munsiari Thrust/Berinag Thrust/North Almora Thrust and orthogonally along N-S/NNW-SSE directions. Considering the fact that the strain energy is continuously building up along the Himalayan front due to convergence of Indian and Eurasian Plates and the region lying between Bihar-Nepal border (1934 earthquake MS 8.4) and Kangra (1905, earthquake MS 8.6) has not experienced a major earthquake (M ≥8). The evaluated low value of seismicity rate and stress drop in the Kumaun Himalaya may be indicative of possible major earthquake in near future.

Keywords

Seismotectonics, Stress Drop, Seismicity, Uttaranchal Himalaya.

Full Text

     

Ajay Paul ¹, P. D. Pant ¹

Affiliations
1 Department of Geology, Kumaun University, Nainital - 263 002, IN

Abstract

No Abstract.

Full Text

   

Ajay Paul ¹

Affiliations
1 Wadia Institute of Himalayan Geology, Dehradun - 248 001, IN

Abstract

The Garhwal-Kumaun region continues to accumulate the built-up of strain energy like the other regions of the Himalaya. But this sector unlike the other sectors is yet to release this accumulated strain energy which can be in the form of great earthquake. The region has sufficient strain energy to generate earthquake of M>8. The analysis of seven hundred ten local events recorded by ten station broad band network between August'07 to February'10 shows that most of the seismic events recorded in this region continue to occur from shallow depths (< 25 km). The evaluation of source parameters from p-wave spectral analysis indicates that the events have low stress drop values. The region continues to release energy in the form of smaller magnitude earthquakes. The epicentral location map indicates that Munsiari Thrust, which is located south of the Main Central Thrust is more active.

Keywords

Seismicity, Strain Energy, Earthquake, Garhwal-Kumaun, Himalaya.

Full Text