Improving earthquake location resolution through dynamic time warping-based crosscorrelation

ABSTRACT Crosscorrelation methods for seismic event location use the differential traveltime of the signals presented in the crosscorrelation records for positioning, eliminating the necessity of scanning the earthquake occurrence time, thereby ensuring efficient calculation of event locations. The finite-frequency characteristics of the signal can cause a decrease in the time resolution of the correlation recordings, resulting in a decrease in the spatial resolution of the location. Exploration of various combinations of station pairs, often referred to as imaging conditions, have been commonly used to enhance the positioning resolution. Instead of modifying the imaging conditions, we develop a dynamic time warping-based crosscorrelation method aimed at enhancing the time resolution of the crosscorrelation records. This innovative approach uses the Pearson correlation coefficient as a distance metric to conduct a global search to obtain time shifts for different seismic signals, providing an optimal correlation coefficient. Our workflow enables the transformation of the differential time and the Pearson correlation coefficients into high-resolution crosscorrelation records. It not only enhances the time resolution of individual seismic event crosscorrelation records but also captures the time differences of distinct signals across multiple events. Simulations show that our method markedly improves the time resolution of crosscorrelation records and the spatial resolution of locations, effectively handling multievent locations with varying magnitudes. A case study reveals that the new method is effective in handling complex waveforms from regional seismic networks and serves as a significant improvement in the precision of seismic event location.