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Authors: Mate, Shonkholen
Keywords: HIMALAYA
Issue Date: 2012
Abstract: The attenuation characteristics of the Kinnaur area of the North West Himalayas were studied using local earthquakes that occurred during 2008-2009. Most of the analyzed events are from the vicinity of the Main Boundary Thrust (MBT) and the Panjal Thrust (PT), which are well-defined tectonic discontinuities in the Himalayas. The frequency dependent attenuation of P and S waves were estimated using the Coda Normalization Method. Data from 64 earthquakes recorded at 10 stations were used. The Coda Normalization of the spectral amplitudes of P and S waves was done at central frequencies of 1.5, 3, 6, 9 and 12 Hz. Qp increases from about 58 at 1.5 Hz to 706 at 12 Hz and Qs increases from 105 at 1.5 Hz to 1207 at 12 Hz. The results show that the quality factors for both P and S waves (Qp and Qs) increases as a function of frequency according to the relation Q=Qof' where Qo is corresponding Q value at 1 Hz frequency and "n" is the frequency relation parameter. The QO and n values show that the region is seismically very active and the crust there is highly heterogeneous. There was no systematic variation of values of Qp and Qs at different frequencies from one tectonic unit to another. As a consequence average values of these parameters were obtained for each frequency for the entire region and these were used for subsequent analysis. Qp values lie within the range of values observed for some regions of the world, whereas Qs values were the lowest among the values compared for different parts of the world. Qs/Qp values were greater than 1 for the entire range of frequencies studied. All these factors indicate that the crust is highly heterogeneous in the study region. 0
Other Identifiers: M.Tech
Appears in Collections:MASTERS' DISSERTATIONS (Earth Sci.)

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