JpGU-AGU Joint Meeting 2020

Presentation information

[E] Oral

S (Solid Earth Sciences ) » S-CG Complex & General

[S-CG58] Science of slow earthquakes: Toward unified understandings of whole earthquake process

convener:Satoshi Ide(Department of Earth an Planetary Science, University of Tokyo), Hitoshi Hirose(Research Center for Urban Safety and Security, Kobe University), Kohtaro Ujiie(Graduate School of Life and Environmental Sciences, University of Tsukuba), Takahiro Hatano(Department of Earth and Space Science, Osaka University)

[SCG58-02] Seismic energy estimation for shallow tremors in the Nankai trough and Japan trench

*Suguru Yabe1, Masaru Nakano2, Takashi Tonegawa2, Satoru Baba3, Shunsuke Takemura3 (1.National Institute of Advanced Industrial Science and Technology, 2.Japan Agency for Marine-Earth Science and Technology, 3.Earthquake Research Institute, UTokyo)

Keywords:Shallow slow earthquakes, seismic energy, Scaled energy

After the deployment of wide ocean bottom seismometer networks in the Pacific off Japan, it has been revealed that tectonic tremors have repeatedly occurred on the shallow plate interface. As studies of deep slow earthquakes have shown that characteristics of tremor activities vary along the fault, spatial variations are expected for shallow slow earthquakes as well. As shallow seismic structure can be imaged in detail by seismic reflection surveys compared with deep structure, this study aims to clarify spatial variations of shallow tectonic tremor activities and to compare them with shallow seismic structures. We estimate seismic energy of tectonic tremors in order to characterize their sizes. We also compare the estimated seismic energy of tectonic tremors with the seismic moment of accompanying very low frequency earthquakes (VLFEs) to evaluate scaled energy of slow earthquakes.

Yabe et al. (2019, doi: 10.1029/2018JB016815) estimated seismic energy of shallow tectonic tremors in Kumano region off Kii Peninsula. We applied the same method to the entire Nankai trough (DONET) and Japan trench (S-net). In the Nankai trough, we refer shallow VLFE catalog by Nakano et al. (2018, doi:10.1038/s41467-018-03431-5) and estimate seismic energy of shallow tremors accompanying VLFEs. In the Japan trench, we refer tremor catalog by Nishikawa et al. (2019, doi:10.1126/science.aax5618) and estimate seismic energy of those tremors. In addition, we also estimate seismic moment of VLFEs accompanying tectonic tremors with large seismic energy, which can be observed using onshore F-net stations. We will report the spatial variations of the estimated seismic energy of shallow tremors and the scaled energy of shallow slow earthquakes.

This study used data from NIED F-net (doi:10.17598/NIED.0005), DONET (doi:10.17598/NIED.0008), and S-net (doi:10.17598/NIED.0007).