Tracking unilateral earthquake rupture by P-wave polarization analysis

Bayer, B., Kind, R., Hoffmann, M., Yuan, X. and Meier, T. (2012) Tracking unilateral earthquake rupture by P-wave polarization analysis Geophysical Journal International, 188 (3). pp. 1141-1153. DOI 10.1111/j.1365-246X.2011.05304.x.

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Abstract

Rapid estimation of earthquake rupture propagation is essential to declare an early warning for tsunami-generating earthquakes. An increasing number of seismological methods have been developed to determine rupture parameters, such as length, velocity and propagation direction, especially since the occurrence of the Sumatra-Andaman earthquake that resulted in a devastating tsunami in the Indian Ocean region. Here, we present a new method to follow the rupture process in near real time by a polarization analysis of local and regional P phases that permits a faster determination of rupture properties than using teleseismic records. The new technique has the capability to provide detailed information in less than 10 min. Originally, the method stems from a single-station earthquake location method and is expanded here to monitor P-phase polarization variations through time. As the earthquake source moves away from the hypocentre, the backazimuth of an incoming P phase is expected to change accordingly. With polarization analysis we may be able to monitor the temporal change in P-wave backazimuth to follow the rupture process in near real time. Three component P phases are scanned to determine the azimuthal variation as a function of time. The backazimuth of a moving rupture front is determined by the first eigenvector of the covariance matrix. The linearity of the particle motion is used as a measure of the quality of the data. Seismic stations at local and regional distances (graphic) are used. We tested the new method with a theoretical simulation and observed seismograms of the Sumatra-Andaman earthquake (2004 December 26, Mw= 9.3), and we were able to follow the rupture for the first 200 s. For larger ruptures, stations at more than 30° epicentral distances would be required. The method is also successfully applied to the Wenchuan earthquake (2008 May 12, Mw= 8.0).

Document Type: Article
Keywords: Time-series analysis, Earthquake source observations, Early warning
Research affiliation: OceanRep > The Future Ocean - Cluster of Excellence > FO-R06
Kiel University
OceanRep > The Future Ocean - Cluster of Excellence > FO-R09
OceanRep > The Future Ocean - Cluster of Excellence
Refereed: Yes
DOI etc.: 10.1111/j.1365-246X.2011.05304.x
ISSN: 0956540X
Projects: Future Ocean
Date Deposited: 04 Oct 2017 15:35
Last Modified: 04 Oct 2017 15:35
URI: http://eprints.uni-kiel.de/id/eprint/39638

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