Event-Feature-Based Clustering Reveals Continuous Distribution of
Tectonic Tremors of 0.3-100 s: Application to Western Japan
Abstract
We develop a methodology to compile an objective tremor catalog by
combining the envelope cross-correlation method with clustering,
utilizing distinctive event features that can differentiate tectonic
tremors from non-tremor events. This approach enables tremor extraction
without subjective criteria, allowing for the detection of
short-duration tremors overlooked in previous studies. The event
features are depth, the mean amplitudes at high and low frequencies, the
ratio of these two amplitudes, and event duration, which is defined as
the minimum period within which 50 % of the seismic energy is
concentrated. The application of this method for western Japan detects
1.7 times more tremors compared with previous studies, with durations of
0.3 to ~100 s. The events with short durations are
considered to be low-frequency earthquakes. The relationship between
seismic moment and the duration of the detected tremors adheres to the
scaling law of slow earthquakes.