Applying Array Methods to Multiscale Imaging of Slow Earthquakes in Nankai Subduction Zone.

Abstract:

Slow earthquakes are a family of phenomena spanning a wide range of seismic moment and duration. This family comprises tectonic tremors, low-frequency earthquakes (LFE), very low-frequency earthquakes (VLFs) and slow-slip events (SSE). Recent studies showed a common spatio-temporal scaling between the different types of slow earthquakes, suggesting that they are different manifestations of a single process. Detecting, locating, and understanding the relation between the seismic energy release associated to the different types of slow earthquakes are fundamental for understanding the dynamics of active deformation processes in the Earth lithosphere.

Here we further develop the new methodology of Poiata et al. (2013) exploiting the frequency selective coherence of the wave field at dense seismic arrays and local antennas. We investigate a signal-processing scheme based on multi-band higher-order statistics for detecting and locating LFE and tectonic tremor sources, using the backprojection algorithm.

We assess the capability and performance of the method on a reference dataset from western Shikoku, Japan, composed of recordings from the Hi-net velocity seismometers, and high-sensitive accelerometers provided by NIED. The results are discussed and compared with locations of tectonic tremors and LFEs from NIED and JMA catalogs, respectively.

We then present preliminary results for applying our extended methodology to detection and location of VLFs in the same target area. Thus aiming to demonstrate the capability of the method to provide an integrated framework for detection, location, and analysis of very broadband seismic sources.