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Strong Motion Amplitudes in Himalayas and Deterministic Approach towards First Order Microzonation Studies in a Part of Delhi City

IR@C-MMACS: CSIR-Centre for Mathematical Modelling and Computer Simulation, Bangalore

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Title Strong Motion Amplitudes in Himalayas and Deterministic Approach towards First Order Microzonation Studies in a Part of Delhi City
 
Creator Parvez, Imtiyaz A
 
Subject Computational Seismology
 
Description The interdependence among the strong-motion amplitude, earthquake magnitude and hypocentral distance was established1 for the Himalayan region using the dataset of six earthquakes, two from western and four from Eastern Himalayas (Mw = 5.2-7.2) recorded by strong-motion networks in the Himalayas. The significant result of this study was that the level of peak strong motion amplitudes in the Eastern Himalayas are three fold larger than those in the Western Himalayas, in terms of both the peak acceleration and peak velocities. In the present study, we have included the strong motion data of Chamoli earthquake (Mw=6.5) of 1999 from the western sub-region to see whether this event supports the regional effects and we found that the new result fits well with our earlier prediction in Western Himalayas. The minimum estimates of peak acceleration for the epicentral zone of Mw=7.5-8.5 events is Apeak=0.25-0.4 g for the wetsern Himalayas, and as large as Apeak=1.0 – 1.6 g for the Eastern Himalayas. Similarly, the expected minimum epicentral values of Vpeak for Mw=8 are 35 cm/s for Western and 112 cm/s for Eastern Himalayas. The presence of unusually high levels of epicentral amplitudes for the eastern subregion also agrees well with the macroseismic evidence1, and therefore, these results represent systematic regional effects, and may be considered as a basis for future regionalized seismic hazard assessment in the Himalayan region. Many metropolitan and big cities of India are situated in the severe hazard zone just south of the Himalayas. A detailed microzonation study of these sprawling urban centres is therefore, urgently required for gaining better understanding of ground motion and site effects. An example of the study of site effects and microzonation of a part of metropolitan Delhi is presented based on a detailed 2-D modelling along NS cross sections from the Inter State Bus Terminal (ISBT) to Sewanagar. Full synthetic strong motion waveforms have been computed using the hybrid method, a combination of modal summation and finite difference techniques, for the earthquake source of July 15, 1720 (MMI=IX, M=7.4), and mapped all along the cross section. The response spectra ratio (RSR), i.e. the response spectra computed from the signals synthesized along the laterally varying section normalized by the response spectra computed from the corresponding signals synthesized for the bedrock reference regional model, have been determined as well.
 
Publisher CSIR Centre for Mathematical Modelling and Computer Simulation
 
Date 2001-09
 
Type Monograph
NonPeerReviewed
 
Format application/pdf
 
Identifier http://cir.cmmacs.ernet.in/208/1/rrcm0105r.pdf
Parvez, Imtiyaz A (2001) Strong Motion Amplitudes in Himalayas and Deterministic Approach towards First Order Microzonation Studies in a Part of Delhi City. Technical Report. CSIR Centre for Mathematical Modelling and Computer Simulation , C-MMACS,Bangalore 560037,India. (Unpublished)
 
Relation http://cir.cmmacs.ernet.in/208/