[J06-3] The spectrum of fault-zone deformation processes (from slow slip to earthquake) III

[J06-3-03] Analyzing tectonic tremor and low-frequency earthquakes' activity in western Shikoku using automatic detection and location scheme

^○Natalia Poiata¹, Jean-Pierre Vilotte², Kazushige Obara³, Pascal Bernard² (1.National Institute for Earth Physics, Romania, 2.Institut de Physique du Globe de Paris, France, 3.Earthquake Research Institute, University of Tokyo, Japan)

Slow earthquakes, spanning a wide range of duration and amplitude scales, unify a broad class of events generating seismic signals that are significantly different from classical earthquakes. These events include weak, long-duration and low-amplitude, nonstationary signals such as tectonic tremors, low-frequency earthquakes and very-low frequency earthquakes. While the physical mechanism underlying the generation of slow earthquakes is not fully understood, they are considered to represent different manifestations of the same process associated with fluid-enabled shear transients at brittle–ductile transition zones of active faults. The ability to outline in fine detail the space-time pattern of slow earthquakes' energy release activity and to clarify the relationship between its different components represents a key to understanding the physics of underlying phenomena.
We present here an automatic scheme for detection and location of tectonic tremor and low-frequency earthquakes based on the method of Poiata et al. (2016). The method is a computationally efficient array-type detection and location scheme making use of multi-scale, frequency-selective coherence of signals' statistical features recorded across the stations of seismic network. We demonstrate the efficiency of the automatic scheme in detecting large number of low-frequency earthquakes during the energetic tectonic tremor sequences in western Shikoku and providing the details about their space-time activity patterns (i.e., migration and tidal modulation). The obtained low-frequency earthquake catalogs are compared against the existing tectonic tremor catalogs, as well as the catalog of low-frequency earthquakes provided by JMA. We also discuss the potential capabilities of the developed system to provide a basis for continuous monitoring and characterisation of tectonic tremor and low-frequency earthquakes' activity.