Source Spectra Variability of earthquakes preceding the 2011 Mw 9.0 Tohoku-Oki megathrust
Abstract
Observations of seismic sequences preceding recent large megathrust ruptures suggest that aseismic and seismic slip can coexist in the same region of the subduction interface. Such complex interactions that could cause the initiation the rupture of large earthquakes. We study here the spectral characteristics, and their temporal variations, of foreshock sequences.
First, we detect temporal anomalies of ground motion generation during seismic sequences preceding 2014 Iquique and 2011 Tohoku megathrust ruptures. These temporal anomalies seem to be associated to the occurrence of transient slow slip events before the mainshocks. This suggests that the conditions that propitiate the transient aseismic slip on the seismogenic zone of the subduction interface could affect the source radiation patterns at frequencies higher than 1 Hz. In complement, we analyze the variation of the earthquake spectra before the 2011 Mw 9.0 Tohoku-Oki Earthquake. We use the records of earthquakes of Mw 5.0 and higher between 2000 and 2011, including the seismic sequence preceding the Tohoku Earthquake. A Hamiltonian Monte Carlo algorithm (HMC), was implemented to adjust a Brune's displacement source spectrum to the records, inverting for the corner frequency (fc), the amplitude at low frequencies (A0) and the high frequency power decay law (ω). Then the spatial and temporal variability of the high frequency content radiation is analyzed using as a proxy the variability of the retrieved model parametersω and fc.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.S21F0586P
- Keywords:
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- 1242 Seismic cycle related deformations;
- GEODESY AND GRAVITY;
- 7209 Earthquake dynamics;
- SEISMOLOGY;
- 7215 Earthquake source observations;
- SEISMOLOGY;
- 8118 Dynamics and mechanics of faulting;
- TECTONOPHYSICS