Slip distributions based on tilt change data for short-term slow slipevents in western Shikoku, southwest Japan
Abstract
Since recurrence of slow slip events (SSEs) on the plate interface are thought to be related with the generation cycle of large earthquakes in subduction zone (e.g., Matsuzawa et al., 2010), SSEs provide useful information for understanding the strain balance not only at the SSE area but also at the source area of the megathrust earthquakes. In order to discuss the strain balance, it is necessary to estimate the spatial slip distributions of SSEs systematically and to make their catalog as complete as possible. In this study, we develop a method to estimate the spatial slip distribution of a short-term SSE in western Shikoku where one of the most active SSE areas in the world (e.g., Obara and Kato, 2016).This method is intended to apply to tilt change data which has been widely used to detect short-term SSEs in southwest Japan (e.g., Hirose and Obara, 2005). Our method does not use information on temporal change unlike Hirose and Obara (2010), but only use information on spatial variation of tilt changes, because it is expected that this will increase the number of data sets that can be applied. In this method, tilt change vectors are inverted with a least squares method with spatial smoothness constraints and non-negative constrains based on the analytic formulae of crustal deformation due to fault slip in a homogeneous elastic half-space (Okada, 1992) . We apply this method to tilt change data for short-term SSEs in western Shikoku in November 2003 and April 2004. The previous study estimates the spatial slip distribution of April 2004 SSE (Hirose and Obara, 2010) but could not estimate that of November 2003 SSE because of the limitation in the data quality. We successfully obtain the spatial slip distributions for both of the SSEs. Estimated seismic moment of both events are approximately 5.9 and 6.1, respectively. These are similar sizes with those in Hirose and Obara (2005). For both of the slip distributions, slip in the western part of the modeled area is larger than that in the eastern part. This slip distribution for the April 2004 SSE is consistent with that of Hirose and Obara (2010). In addition, we can estimate the slip distribution of November 2003 SSE that could not be estimated in the previous study (Hirose and Obara, 2010) by using our method. This demonstrates that we can obtain more slip distributions of the short-term SSEs in the area.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.T33E0458T
- Keywords:
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- 1242 Seismic cycle related deformations;
- GEODESY AND GRAVITYDE: 7230 Seismicity and tectonics;
- SEISMOLOGYDE: 8118 Dynamics and mechanics of faulting;
- TECTONOPHYSICSDE: 8163 Rheology and friction of fault zones;
- TECTONOPHYSICS