Aseismic slip history after the 2011 Tohoku earthquake in the Suruga Trough, Central Japan

Abstract

Listen

Translate article

Summary Detailed investigations of aseismic slow slip events (SSEs) are crucial for estimating the strain budget and SSE mechanisms within subduction zones. The Suruga Trough, which includes the Tokai seismic gap, is an important area in Japan from a hazardous perspective. However, the aseismic slip history of this trough following the 2011 Tohoku earthquake is difficult to determine as a result of post-seismic deformation caused by the earthquake. In this study, we provided detailed imaging of the interplate aseismic slip in the Suruga Trough after the 2011 Tohoku Earthquake by applying a network inversion filter to global navigation satellite system data and considering viscoelastic deformation and afterslip caused by the earthquake. The analysis revealed the 2012 Shima long-term SSE (l-SSE), 2013-2016 Tokai l-SSE, 2017-2020 Shima l-SSE, and 2023-2024 Atsumi+Tokai l-SSE, with the slip area expanding to the area adjacent to the Tokai seismic gap from July 2023, consequently changing the stress state to promote the anticipated Tokai earthquake. The findings of this study suggest that the recurrence interval of the Tokai slow slip ranges from 10 to 13 years, with a duration of approximately 4-5 years and a total magnitude ranging from 6.5 to 7.1. The l-SSE zone shows that the upper-limit temperature threshold, which is the temperature at the upper bound of the l-SSE zone aligning the 350°C isothermal line in the Tokai segment, does not hold in the Suruga Trough. The change in strike direction of the l-SSE zone suggests that a discontinuous factor controls the l-SSE occurrence, such as high pore pressure caused by fluid infiltration to the plate interface. Furthermore, we explored a gap between the short-term SSE (s-SSE) and l-SSE zones, and the findings indicated a non-continuous transition from l-SSE to s-SSE, thus providing insights into the discontinuous factors that regulate l-SSE and s-SSE generation. The recurrence interval (10–13 years) and duration (4-5 years) of the Tokai SSEs are long, and their moment rates (1015.8Nm/day) are low compared to those of the l-SSEs in other regions. The SSE parameters suggest that the scaling law may not apply to SSEs in the Suruga-Nankai Trough with the prolonged duration.