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

[SCG58-P19] A physical model of tremor response to periodic external stresses in poroelastic medium

*坂本 龍之輔¹、田中 愛幸¹ (1.東京大学　大学院理学系研究科)

キーワード：微動、多孔質弾性体、バネブロックモデル

It is known that tectonic tremors are generated by the rupture of small rata-weakening asperities which is caused by slow slip on the surrounding plate interface. In most cases, tectonic tremors occur in areas where the pore fluid pressure is higher. Because high-pressure fluids reduce the effective normal stress significantly, tectonic tremors can be triggered by weak perturbing external stresses such as tidal stresses. Previous studies show that the rate for tremor occurrences exponentially changes [e.g., 1]. Other studies show that the peak of the tremor occurrence rate advances/delays relative to the peak of tidal stresses [2 & 3].So far, no model has been constructed that could explain all of the above observations with realistic fault parameters. Most of tidal response models did not take the presence of pore fluids into account. In this study, we reveal how the pore fluids behave under periodic external stresses by considering fluid pressure change due to dilatancy within fault core (fig) and show that this model could explain the observations reported above [1-3].In addition, we will discuss which kinds of material parameters affect the tidal sensitivity based on our model. Furthermore, we will investigate how the behavior of the system changes under multiple periodic perturbations.

[1] S. Yabe, Y. Tanaka, H. Houston and S. Ide, J. Geophys. Res. Solid Earth, 120, 7587–7605 (2015)
[2] R. Nakata, N. Suda and H. Tsuruoka, Nature Geosci. 1, 676-678 (2008)
[3] Thomas, A. M., R. Bürgmann, D. R. Shelly, N. M. Beeler, and M. L. Rudolph, J Geophys Res. 117, (2012)