High precision timing of permanent surface dislocation in regional distance after a megathrust earthquake
Abstract
The 2011 MW9.0 Tohoku-Oki megathrust earthquake deformed regional-area surface. The earthquake caused coseismic surface dislocation in a large regional-distance area that includes Japanese islands, Korean Peninsula, and eastern Eurasian Plate. The Korean Peninsula is located in a stable intraplate region where the seismicity is low. However, there is an increase in moderate-sized earthquakes after the 2011 Tohoku-Oki megathrust earthquake, which may be associated with lithospheric displacement around the Korean Peninsula. The static surface dislocation can be measured effectively using GPS data. However, it is difficult to retrieve the dynamic displacement history from GPS data due to the positioning errors induced by transient waves. We determine the onset time of coseismic dislocation in sequential arrivals of transient seismic waves from the earthquake using broadband velocity seismic records in the Korean Peninsula. The Korean Peninsula is located ~1200 to ~1600 km from the megathrust earthquake. We collected unclipped seismic data. The dynamic range of STS-2 sensor is 1.3 cm/s. We focus on the anelastic motion that leads to the coseismic dislocation. We apply a time-domain deconvolution method for instrument response correction to restore the ground velocity. We then integrate the velocity motions to obtain displacement motions, which causes a cubic baseline drift in deconvolved data. We correct the baseline drift using a 4th order polynomial function. Gradual surface deformation starts to occur at the time of P arrival, continuing for about 310-410 s until the time of peak surface-wave amplitude. Rapid deformation occurs during the passage of surface waves. The entire duration of the coseismic deformation is about 450 s for the western Korean Peninsula. The amount of the surface displacement after the signal is about 1 cm less than the amount measured for 1 day by GPS data, and the direction of the displacement is similar to the GPS data. Broadband seismic data is useful to detect minute surface dislocations during the passage of transient waves. The analysis enables us to understand the detailed process of anelastic surface dislocation over a regional-distance area after a megathrust earthquake.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.T13D0300K
- Keywords:
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- 1209 Tectonic deformation;
- GEODESY AND GRAVITY;
- 1294 Instruments and techniques;
- GEODESY AND GRAVITY;
- 8118 Dynamics and mechanics of faulting;
- TECTONOPHYSICS;
- 8120 Dynamics of lithosphere and mantle: general;
- TECTONOPHYSICS