Recent studies have shown that deep tremor in Shikoku consists of a swarm of low frequency earthquakes (LFEs) that occur as slow, shear slip on the down-dip extension of the primary seismogenic zone of the Nankai Trough. In this study, we develop a method for identifying LFEs within tremor. The method is a matched-filter algorithm, similar to the technique used to infer that tremor in parts of Shikoku is comprised of LFEs. In our case, however, we do not know the origin times and locations of the LFEs a priori. We search for LFEs using a running autocorrelation of the tremor waveforms for all Hi-Net stations in the vicinity of the tremor source. We apply this method to Hi-Net recordings of tremor and demonstrate that it allows us to extract both known and previously unidentified LFEs. Lags showing a high degree of similarity in the autocorrelation are either repeats, or near repeats, of LFEs within the tremor. Once LFEs are identified, we apply waveform cross-correlation to measure arrival times and locate them. This approach allows us to extend the analysis of Shelly et al.  to parts of the Nankai Trough that have only sparse LFE coverage. It should also allow us to extend our analysis to other regions that experience deep tremor, but where LFEs have not yet been identified. Shelly, D. R., G. C. Beroza, and S. Ide, Non-volcanic tremor and low frequency earthquake swarms, Nature, 446, doi:10.1038/nature05666, 2007.
AGU Fall Meeting Abstracts
- Pub Date:
- December 2007
- 1031 Subduction zone processes (3060;
- 1207 Transient deformation (6924;