Multi-band array backprojection method for detection and location of seismic sources associated to deformation processes

Detection, location and characterization of the seismic energy release associated to deformation processes in active subduction zones are fundamental for understanding the dynamics of active deformation and the mechanisms of generation and rupturing of large subduction earthquakes. The analysis of this seismic energy release, spanning a wide range of space and time scales, as well as phenomena, (e.g., earthquakes, seismic repeaters, low and very low-frequency earthquakes, tectonic tremors) can provide original insides to the problem. We developed a methodology for detection and location of seismic sources exploiting the frequency selective coherence of the wave field at dense seismic arrays and local antennas. The methodology consist of: (1) a signal processing scheme yielding a simplified representation of a seismic signal by an adaptive time-frequency characterization of its statistical properties; (2) an imaging algorithm based on back projection of stacked local cross-correlations of the simplified signals. This new approach has been developed and tested on the Shikoku region in Japan, which represent an exceptional field laboratory, due to its high seismic activity comprising a wide variety of phenomena observed by the dense Hi-net seismic network operated by NIED. We present the results evaluating the capability and potential of the proposed methodology to detect and locate the energy release associated to possibly overlapping seismic radiation from earthquakes and low-frequency tectonic tremors in Shikoku, Japan. As a potential direction, its application to detection and location of seismic sources at a different observational scale, such as mine-induced seismicity is also discussed.