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
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Creator |
Parvez, Imtiyaz A
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Subject |
Computational Seismology
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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.
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Publisher |
CSIR Centre for Mathematical Modelling and Computer Simulation
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Date |
2001-09
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Type |
Monograph
NonPeerReviewed |
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Format |
application/pdf
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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) |
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Relation |
http://cir.cmmacs.ernet.in/208/
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