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Published November 2012 | Published
Journal Article Open

Real-time Finite Fault Rupture Detector (FinDer) for large earthquakes

Abstract

To provide rapid estimates of fault rupture extent during large earthquakes, we have developed the Finite Fault Rupture Detector algorithm, 'FinDer'. FinDer uses image recognition techniques to detect automatically surface-projected fault ruptures in real-time (assuming a line source) by estimating their current centroid position, length L, and strike θ. The approach is based on a rapid high-frequency near/far-source classification of ground motion amplitudes in a dense seismic network (station spacing <50 km), and comparison with a set of pre-calculated templates using 'Matching by Correlation'. To increase computational efficiency, we perform the correlation in the wavenumber domain. FinDer keeps track of the current dimensions of a rupture in progress. Errors in L are typically on the same order as station spacing in the network. The continuously updated estimates of source geometries as provided by FinDer make predicted shaking intensities more accurate and thus more useful for earthquake early warning, ShakeMaps, and related products. The applicability of the algorithm is demonstrated for several recorded and simulated earthquakes with different focal mechanisms, including the 2009 M_w 6.3 L'Aquila (Italy), the 1999 M_w 7.6 ChiChi (Taiwan) and the M_w 7.8 ShakeOut scenario earthquake on the southern San Andreas Fault (California).

Additional Information

© 2012 The Authors. Geophysical Journal International © 2012 RAS. Accepted 2012 August 20. Received 2012 June 29; in original form 2012 January 10. Article first published online: 14 Sep. 2012. Strong-motion records of the 2009 Mw 6.3 L'Aquila earthquake recorded by RAN were downloaded from the Italian strong-motion database ITACA (http://itaca.mi.ingv.it; last visited 2012 April); strong-motion records of the 1999 M_w 7.6 ChiChi earthquake recorded by TSMIP were downloaded from the COSMOS Virtual Datacenter (http://db.cosmos-eq.org, last visited 2011 December). We would like to thank Dr. Georgia Cua for providing codes to simulate ground motion envelopes and amplitudes used in this study. Most figures in this paper were generated with Matlab 7.8; maps in Fig. 5 were made with the Generic Mapping Tools version 4.2.1 (www.soest.hawaii.edu/gmt;Wessel & Smith 1998). We would like to thank Brad Aagaard and Robert Graves for data and discussions on the ShakeOut scenario earthquake. We are very grateful for the helpful comments and suggestions by two anonymous reviewers and the Editor, Dr. Frank Krüger. This work is funded through contract G09AC00258 from USGS/ANSS to the California Institute of Technology (Caltech). Funding was also provided by a grant from the Gordon and Betty Moore Foundation to Caltech. This is contribution #10068 of the Seismological Laboratory, Geological and Planetary Sciences at Caltech.

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August 22, 2023
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