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  • Seismological Society of America  (2)
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  • 1
    Publication Date: 2011-09-26
    Description: Seventy-two local earthquakes were analyzed and the quality factor (Q (sub c) ) was calculated for three regions of Georgia using the single-scattering model in the frequency range of 1-32 Hz. Standard International Association of Seismology and Physics of the Earth's Interior (IASPEI) routines for the coda Q (sub c) determination have been used. The coda window varied from 35 to 45 s, and the lapse time was up to 63 s. The epicenter distances and the focal depths of the earthquakes were up to 50 km and 20 km, respectively. Local magnitudes ranged from 1.7 to 4.1. These earthquakes were recorded by three digital seismic stations equipped with broadband Guralp CMG40T seismometers. The Q (sub c) values show strong frequency dependence for three regions. The value of Q (sub c) at frequency 1 Hz varies from 35.1 + or - 5.3 to 83 + or - 8.2, and the frequency parameter, n, increases from 0.890 + or - 0.062 to 1.095 + or - 0.056 depending on the model of the coda generation and the considered region. Observed Q (sub c) values reflect the average attenuation property of the whole crust beneath each region and are correlated with the seismicity pattern and geology in the studied regions.
    Print ISSN: 0037-1106
    Electronic ISSN: 1943-3573
    Topics: Geosciences , Physics
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  • 2
    Publication Date: 2011-05-29
    Description: For estimating fatalities and injured within minutes after an earthquake worldwide, we rely on real-time teleseismic determinations of epicenters. To estimate the teleseismic location errors, we computed the difference between the local epicenters of the dense seismograph networks of Japan, Italy, and Taiwan with those given by the PDE, those distributed in real time by the U.S. Geological Survey (USGS), and the European Mediterranean Seismological Center (EMSC). The average difference is 16 and 8 km between PDE teleseismic epicenters and those by the local networks for Japan/Taiwan and Italy, respectively. For EMSC epicenters, the average difference is 13 km for Italy. The average difference between real-time USGS parameters and those listed in the PDE is 12 km (median 9 km) for 30 earthquakes in Japan. Comparisons of real-time USGS epicenters and the Japan Meterological Agency (JMA) locations yield an average difference of 31 km (median 26 km). Estimates indicate that the epicenter errors in the local catalogs are typically 1 and 3 km for Japan/Italy and Taiwan, respectively. Assuming that the differences in earthquake locations are mostly due to teleseiseismic errors, we conclude that the mean errors in real-time epicenter solutions are in the range of 25 to 35 km. This implies that for earthquakes of M approximately 6.7 in the vicinity of a medium-sized city (80,000), the fatality estimates using QLARM in real time have to range from near 0 to 10,000 in the developing world and from 0 to 500 in an industrialized country. These results were verified by comparison with observed numbers of fatalities in the cases of the 2003 M 6.7 Bam, Iran, and the 2008 M 6.9 Iwate-Miyagi, Japan, earthquakes.
    Print ISSN: 0037-1106
    Electronic ISSN: 1943-3573
    Topics: Geosciences , Physics
    Location Call Number Expected Availability
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