Phase-Weighted Stacking Applied to Low-Frequency Earthquakes

We apply phase-weighted stacking (PWS) to the analysis of low-frequency earthquakes (LFEs) in the Parkfield, California, region and central Cascadia. The technique uses the coherence of the instantaneous phase among the stacked signals to enhance the signal-to-noise ratio (SNR) of the stack. We find that for picking LFE arrivals for the Parkfield, California, region and for LFE template formation in central Cascadia, PWS is extremely effective. For LFEs in the Parkfield, California, region, PWS yields many more usable phases than standard linear stacking; and, for LFE detection in Cascadia, PWS produces templates with much higher SNR than linear stacking.