[S-GD02] Crustal Deformation

[SGD02-P05] Examination of slow slip events in the shallow part of the Suruga Trough

*Yuji Kikuchi¹, Yuta Mitsui² (1.Graduate School of Science and Technology, Shizuoka University, 2.Department of Geosciences, Shizuoka University)

Keywords:Slow slip events, Suruga Trough, Baseline change

Many slow slip events (SSE) have occurred at the Nankai subduction zone in southwestern Japan. Deep SSE have been detected by GNSS and tiltmeters (e.g., Sakaue et al., 2019; Okada et al., 2022; Yabe et al., 2023), and recently SSE detection has also been attempted even in the shallow part near the trench. For example, a previous study (Kano and Kato, 2020), which attempted to detect short-term slow slip events (S-SSE) by stacking GNSS data with reference to low-frequency earthquakes, estimated shallow fault slip occurring simultaneously with deep S-SSE in the shallow part of the Suruga Trough.

To investigate the shallow fault slip, this study examines the changes in GNSS baseline length between the upper and lower Suruga Trough before and after the occurrence of deep S-SSE. The results show that the baseline length in the southern part of the shallow part of the Suruga Trough was shortened for about 100 days. We further investigate the timing of shallow SSE with a duration of about 100 days by comparing the correlation peaks between the moving averages of the baseline length and the template signal. As a result, several candidate SSE periods are estimated for 2002-2022. The changes in the baseline length during these periods show a statistically significant shortening.