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Regional waveform calibration in the Pamir-Hindu Kush region

Zhu, Lupei and Helmberger, Donald V. and Saikia, Chandan K. and Woods, Bradley B. (1997) Regional waveform calibration in the Pamir-Hindu Kush region. Journal of Geophysical Research B, 102 (B10). 22,799-22,813. ISSN 0148-0227. doi:10.1029/97JB01855.

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Twelve moderate-magnitude earthquakes (m_b 4–5.5) in the Pamir-Hindu Kush region are investigated to determine their focal mechanisms and to relocate them using their regional waveform records at two broadband arrays, the Kyrgyzstan Regional Network (KNET), and the 1992 Pakistan Himalayas seismic experiment array (PAKH) in northern Pakistan. We use the “cut-and-paste” source estimation technique to invert the whole broadband waveforms for mechanisms and depths, assuming a one-dimensional velocity model developed for the adjacent Tibetan plateau. For several large events the source mechanisms obtained agree with those available from the Harvard centroid moment tensor (CMT) solutions. An advantage of using regional broadband waveforms is that focal depths can be better constrained either from amplitude ratios of Pnl to surface waves for crustal events or from time separation between the direct P and the shear-coupled P wave (sPn + sPmP) for mantle events. All the crustal events are relocated at shallower depths compared with their International Seismological Centre bulletin or Harvard CMT depths. After the focal depths are established, the events are then relocated horizontally using their first-arrival times. Only minor offsets in epicentral location are found for all mantle events and the bigger crustal events, while rather large offsets (up to 30 km) occur for the smaller crustal events. We also tested the performance of waveform inversion using only two broadband stations, one from the KNET array in the north of the region and one from the PAKH array in the south. We found that this geometry is adequate for determining focal depths and mechanisms of moderate size earthquakes in the Pamir-Hindu Kush region.

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Additional Information:© 1997 American Geophysical Union. Received 24 October 1996; revised June 12, 1997; accepted 20 June 1997. We thank M. W. Hamburger and two anonymous referees for their constructive criticism and comments which helped us to improve the manuscript substantially. Seismic data from the Pakistan Experiment were collected in a collaborative effort between the Pakistan Government, New Mexico State University, and Rensselaer Polytechnic Institute. We also thank the IRIS Data Center for providing KNET data. This work has been supported by ARPA contract F19628-95-C-0093 at Woodward-Clyde Federal Services and by the Department of Defense as monitored by the Air Force Office of Scientific Research under contract F19628-95-C-0096 at Caltech. Contribution 5735, Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California.
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Air Force Office of Scientific Research (AFOSR)F19628-95-C-0096
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Caltech Division of Geological and Planetary Sciences5735
Issue or Number:B10
Record Number:CaltechAUTHORS:20121129-101823799
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Official Citation:Zhu, L., D. V. Helmberger, C. K. Saikia, and B. B. Woods (1997), Regional waveform calibration in the Pamir-Hindu Kush region, J. Geophys. Res., 102(B10), 22,799–22,813, doi:10.1029/97JB01855.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:35726
Deposited By: Ruth Sustaita
Deposited On:29 Nov 2012 18:37
Last Modified:09 Nov 2021 23:17

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