A double-correlation tremor-location method

TL;DR

This paper introduces a double-correlation method for accurately locating tremor sources using complex, doubly-correlated seismic records, demonstrating robustness and improved focus over traditional single correlation techniques.

Contribution

The paper presents a novel double-correlation approach for tremor source localization that enhances robustness and resolution, especially under imprecise velocity information and noisy data.

Findings

Effective suppression of noise and inconsistent signals.

Improved source mapping focus compared to single correlation.

Method applicable to surface and body waves with additional data.

Abstract

A double-correlation method is introduced to locate tremor sources based on stacks of complex, doubly-correlated tremor records of multiple triplets of seismographs back projected to hypothetical source locations in a geographic grid. Peaks in the resulting stack of moduli are inferred source locations. The stack of the moduli is a robust measure of energy radiated from a point source or point sources even when the velocity information is imprecise. Application to real data shows how double correlation focuses the source mapping compared to the common single correlation approach. Synthetic tests demonstrate the robustness of the method and its resolution limitations which are controlled by the station geometry, the finite frequency of the signal, the quality of the used velocity information and noise level. Both random noise and signal or noise correlated at time shifts that are inconsistent with the assumed velocity structure can be effectively suppressed. Assuming a surface-wave velocity, we can constrain the source location even if the surface-wave component does not dominate. The method can also in principle be used with body waves in three dimensions, although this requires more data and seismographs placed near the source for depth resolution.