Microearthquake observations around Thien Dam in northwest Himalayas |
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| Institution: | 1. CSIR-National Geophysical Research Institute, Hyderabad 500 007, India;2. Institute of Seismological Research, Gandhinagar, Gujarat 382009, India;3. Earth and Climate Science Program, Indian Institute of Science Education & Research, Pune 411008, India;1. Department of Earth Sciences, Indian Institute of Technology Kanpur, Kanpur 208016, India;2. Department of Civil Engineering, Indian Institute of Technology Kanpur, Kanpur 208016, India;3. Department of Geography, Faculty of Letters, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8522, Japan |
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| Abstract: | A microearthquake survey has been conducted around Thien Dam (32°26.5′N, 75°43.5′E) during March–April 1983 by operating seven high gain stations. The data recorded at these stations have been supplemented by other seismological stations in the region under the Beas and Salal Projects. Surficial velocity structure has been obtained from waves generated from blasts in the dam area and hypocentres were determined using the program HYPO 71.Microearthquake distribution shows four main zones of active seismicity. Deeper microearthquakes with focal depths greater than 10 km below the dam were attributed to the Satlitta fault. Composite focal mechanism solution shows that the Satlitta fault at this depth is of normal type. Shallow microearthquakes below the dam are due to the Suruin-Mastgarh anticline which is of the thrust type. Microearthquakes located northeast of the dam are apparently associated with a ‘back’ thrust. |
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