Hypocenter location of mixed events in real-time processing systems |
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Authors: | Vladimir Pinsky Shigeki Horiuchi |
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Institution: | (1) Geophysical Institute of Israel, Lod, Israel;(2) National Research Institute for Earth Science and Disaster Prevention, 3-1 Tennodai, Tsukuba 305-0006, Japan |
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Abstract: | Automatic pickings in earthquake real-time monitoring systems often contain noise bursts and/or phases of different event(s)
occurring almost simultaneously. Typically, a locator uses these picks as P and S waves arrival times coming from a single
event and, therefore, should be complemented by a distinctive phase association logic. The method we propose manages to automatically
associate data related to different events and eliminates the influence of spoiled data from single events. The method is
based on “network beamforming”, a robust and stable algorithm, which utilizes a hypocenter grid search for the stack maximum
of a set of complex exponents applied to the P phase readings. The algorithm separates the residual outliers and then uses
them for location. If successful, a hypocenter is established for the interfering event. The solutions obtained are overall
robust and independent from the estimate of origin times. The preliminary epicenter for the grid search is provided by the
intersection of perpendicular bisectors in the modified “arrival order algorithm” or by the modified “Tnow” algorithm, which uses non-arrival information. We applied this method to automatic first arrival phase readings of 915 events
registered by the Hi-net Japan seismic network and our results are statistically promising. Here, we present two interesting
and complicated examples. |
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Keywords: | Seismic event location Robust procedures Real-time processing Early warning Automatic phase picking |
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