1 A New Approach for the Automatic Measurement of Shear-wave Splitting Parameters
This paper introduces a new approach for the automatic detection from microearthquake seismograms of two crucially important shear-wave splitting (SWS) parameters, fast wave polarization and delay time between split waves. The method is based on the analyses of multiple time windows that include the...
| Main Authors: | , , |
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| Other Authors: | |
| Format: | Text |
| Language: | English |
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.571.9740 http://www.unc.edu/~chhtang/paper_auto.pdf |
| Summary: | This paper introduces a new approach for the automatic detection from microearthquake seismograms of two crucially important shear-wave splitting (SWS) parameters, fast wave polarization and delay time between split waves. The method is based on the analyses of multiple time windows that include the shear wave arrivals. An automated SWS algorithm is performed for each specified window. Hundreds of estimates of the two parameters (polarization and time delay) are obtained from all windows, and unsupervised cluster analysis is applied to locate the region in phase space with the most stable estimate, the optimal cluster being that with the lowest variance. The mean value of the optimal cluster is regarded as the best estimate of polarization and time delay. The estimates are relatively easy to derive from large seismic datasets and show high reliability. We compare the results with manually estimated values of the SWS parameters from seismic data collected at the geothermal fields of The Geysers and Coso in California, and Hengill, Iceland, and show that the method outperforms all others, providing up to 90 % reliability (polarization) and 85% reliability (delay time) without human intervention. 2 |
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