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Teleseismic and strong-motion source spectra from two earthquakes in eastern Taiwan

Hwang, Lorraine J. and Kanamori, Hiroo (1989) Teleseismic and strong-motion source spectra from two earthquakes in eastern Taiwan. Bulletin of the Seismological Society of America, 79 (4). pp. 935-944. ISSN 0037-1106.

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The 20 May and 14 November 1986 Hualien earthquakes occurred in a seismically active region of Taiwan. Locally determined focal mechanisms and aftershock patterns from the Taiwan Telemetered Seismographic Network indicate that both earthquakes occurred on steeply dipping reverse faults that trend NNE. This agrees with teleseismic first-motion data for the May event but not for the November event. This discrepancy is due to a moderate foreshock before the November event. Surface-wave analysis gives a solution for the November event of: dip 57°, rake 100°, and strike 43°, which is similar to the locally reported focal mechanism. The seismic moment of the November event is M_0 = 1.7 × 10^(27) dynecm and the magnitudes determined from WWSSN data are m_b = 6.4, M_s = 7.3. Teleseismic source spectra show that the two events also have similar spectral signatures above 0.15 Hz. Reference acceleration spectra are computed from the average teleseismic source spectra and compared to the averaged acceleration spectra computed from strong-motion stations for both events. Correlations between the spectral amplitudes of the strong-motion spectra obtained from the main portion of the SMART 1 array and the teleseismically estimated reference spectra are poor above 0.2 Hz. Data from the hard-rock site situated outside of the basin indicates that amplification of the ground motion between 0.17-1.7 Hz is due to the alluvial valley where the SMART 1 array is located. The amplitude of the observed spectrum is five times the reference spectrum at the hard-rock site. This is consistent with similar observations from the 1985 Michoacan and 1983 Akita-Oki earthquakes. The analysis of these and more teleseismic and strong-motion records will lead to a better understanding of the relationship between their spectra.

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Kanamori, Hiroo0000-0001-8219-9428
Additional Information:© 1989, by the Seismological Society of America. Manuscript received 4 August 1988. We thank the personnel from the WWSSN stations and the USGS for making their data available to us. Thanks to Frances Wu and Kuo-Liang Wen who kindly shared aftershock data from TTSN with us and to Heidi Houston and Y.T. Yeh who made preprints available. The SMART 1 Array data were made available by Bruce Bolt through the Seismographic Station of the University of California at Berkeley and the Institute of Earth Sciences of the Academia Sinica in Taipei. This research was supported by USGS Grant No. 14-08-0001-G1356 NSF EAR-86-18189 and an NSF Graduate Fellowship. Contribution No. 4662, Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125.
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NSF Graduate FellowshipUNSPECIFIED
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Caltech Division of Geological and Planetary Sciences4662
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Official Citation:Lorraine J. Hwang and Hiroo Kanamori Teleseismic and strong-motion source spectra from two earthquakes in eastern Taiwan Bulletin of the Seismological Society of America, August 1989, v. 79, p. 935-944
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:49162
Deposited By: Ruth Sustaita
Deposited On:03 Sep 2014 14:43
Last Modified:09 Mar 2020 13:18

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