Source parameter variability of intraslab earthquakes as determined from the empirical Green's function method

Shanna Chu, Gregory C. Beroza, & William L. Ellsworth

Published August 15, 2018, SCEC Contribution #8633, 2018 SCEC Annual Meeting Poster #078

The mechanism of intraslab earthquakes are still incompletely understood. In particular, the relative importance of dehydration embrittlement, thermal shear runaway, hybrid dehydration-induced stress transfer, or some combination, and how these influences might vary in different subduction zones is unclear. To understand the contribution from these mechanisms, we investigate earthquake source parameters from data in the two subduction zones in Japan: the older and colder Pacific Plate east of Hokkaido, and the younger and warmer Philippine Plate south of Kyushu.

We estimate stress drops, radiated energies, and radiated efficiencies of earthquakes greater than M3.6 over a 12-year period using the method of empirical Green’s functions (eGfs). Because intraslab earthquakes produce few aftershocks and because the signal-to-noise-ratio is low for small events, special attention must be given to eGf selection. We also consider the variation in high frequency fall-off rate between different events, noting that the standard omega-2 models used in such studies may be inappropriate for intraslab events. The methods we use are generally applicable to datasets of earthquakes in all settings for the common situation of low signal to noise ratio and/or insufficient data.

We find, in addition to the generally agreed-upon results of a higher stress drop and lower radiated efficiency for intraslab earthquakes, that there appears to be a break in self-similarity in the source parameters for the Hokkaido region, which suggests that different mechanisms may be important in the two subduction zones.

Key Words
intraslab, source parameters, stress drop, radiated energy, scaling, empirical Green's functions

Citation
Chu, S., Beroza, G. C., & Ellsworth, W. L. (2018, 08). Source parameter variability of intraslab earthquakes as determined from the empirical Green's function method. Poster Presentation at 2018 SCEC Annual Meeting.

Related Projects & Working Groups
Seismology