Determination of Short-term SSE Slip Extent by Small BSM Observations

Abstract:

Among crustal deformation observations, borhole strainmeters (BSM) are the most sensitive. However, its observation density is low. Various slow earthquakes have been found in the Nankai Trough. Highly sensitive BSM is effective for short-term SSE detection. For example, in the southern part of the Kii Peninsula, BSM has been used to successfully detect short-term SSEs that could not be detected (Itaba et al., 2010). However, compared to GNSS and tiltmeters, the observed density of BSM is lower. We have developed a small BSM and installed this small BSM in an existing unused well in January 2020.

The new BSM station is located in the BSM blank area in eastern Shikoku island, near the eastern end of the short-term SSE tremor zones. There is no BSM station in eastern Shikoku island, and the extent of short-term SSE is not well understood. The installation of new BSM station is expected to contribute to the improvement of short-term SSE fault model estimation accuracy in eastern Shikoku island. In the poster, we will introduce short-term SSE detection cases and fault model estimation results in eastern Shikoku island using new BSM station.

Reference

Itaba S, Koizumi N, Matsumoto N, Ohtani R (2010) Continuous observation of groundwater and crustal deformation for forecasting Tonankai and Nankai earthquakes in Japan. Pure Appl Geophys. 167:1105-1114. doi:10.1007/s00024-010-0095-z