[S01-1] Open session I

[S01-1-04] A tremor location method using products of cross correlations

Ka Lok Li¹, Hamzeh Sadeghisorkhani¹, Giulia Sgattoni^1,2,3, ^○Olafur Gudmundsson¹, Roland Roberts¹ (1.Uppsala University, Uppsala, Sweden, 2.University of Iceland, Reykjavik, Iceland, 3.University of Bologna, Bologna, Italy)

We introduce a back-projection method to locate tremor sources using products of cross-correlation envelopes of signals between seismic stations. Tremor is characterized by signals which lack a clear onset. For such signals it is usually not possible to use first-arrival picks to locate a source. Instead, inter-station cross-correlation is commonly used for this purpose. We introduce a method which resembles high-order cross-correlations, but it is much less computationally expensive. In this method we calculate up to the (n-1)th-order products of cross-correlation envelopes for a given subset of n stations. The products are back projected to hypothetical source locations in a geographic grid and the resulting maps are stacked over combinations of station subsets. We show that compared to existing correlation methods and for realistic signals and noise characteristics this way of combining phase information can significantly suppress the effects of correlated and uncorrelated noise and therefore give a robust estimate of source locations. We present synthetic examples which demonstrate the robustness of the method and apply the method to tremor at Katla volcano, Iceland in 2011.