Uncertainties in Teleseismic Earthquake Locations: Implications for Real-Time Loss Estimates

Abstract

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 ≈ 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.

Report estimated quake death tolls to save lives

“…Once aftershocks outline the direction and extent of a rupture, more-accurate losses can be estimated. For example, my initial prediction of fatalities in the 2003 magnitude-6.7 earthquake in Bam, Iran, was 2,500 because the epicentre was at first thought to be in a remote location 9 . In reality, more than 26,000 perished.…”

Rapid kinematic finite-fault inversion for anMw7+ scenario earthquake in the Marmara Sea: an uncertainty study

“…Using the Monte Carlo approach, we generate totally 500 Gaussian distributed sets of a priori parameters with standard deviations shown in Table 1. The uncertainties of the hypocentre location and focal mechanism are based on the statistical results from the Marmara network and other regional seismic networks around the world (Karabulut et al 2011;Wyss et al 2011). Then the synthetic data are inverted using each set of the a priori parameters, but all based on the same structure model (LM_1).…”

Rapid Earthquake Loss Assessment After Damaging Earthquakes

“…PAGER and QLARM) rely on teleseismic determinations of epicenters. This reliance can create error in loss estimations, especially in populated areas, since the mean errors in real-time teleseismic epicenter solutions, provided by U.S. Geological Survey (USGS, the PDE) and/or the European Mediterranean Seismological Center (EMSC), can be as large as 25-35 km (Wyss et al 2011).…”