A scenario for the generation process of the 2011 Tohoku earthquake based on dynamic rupture simulation: Role of stress concentration and thermal fluid pressurization

Abstract

We perform dynamic rupture simulations to improve the understanding of the generation process of the 2011 Tohoku earthquake. We assume a dynamic weakening mechanism (dynamic thermal pressurization of pore fluid, hereinafter called TP) on the fault plane to represent nonlinear weakening friction, and take into account the shear stress changes before the Tohoku earthquake, due to the four M 7-class earthquakes that occurred during [2003][2004][2005][2006][2007][2008][2009][2010][2011]. To constrain the dynamic rupture simulation, the moment release rate obtained by seismic slip inversions is referred. The simulation result implies the following about the 2011 Tohoku earthquake: (1) The rupture around the hypocenter was enhanced by the stress accumulation due to the preceding M 7-class earthquakes. (2) The enhanced rupture triggered the TP mechanism in the near-trench area causing large slip, which promoted propagation of the rupture over a wide region including the source areas of the M 7-class earthquakes and surrounding conditionally-stable areas. (3) Without sufficient stress accumulation, the moment release of the Tohoku earthquake ended as an M 8-class earthquake. (4) TP in the near-trench area should be effective but moderate. The occurrence time of the next megaquake would be strongly affected by the nonlinear effects of TP and the stress conditions. Thus, our model may contradict the concept of the (quasi-)cyclic occurrence of M 9 earthquakes.

Fluid transport properties in sediments and their role in large slip near the surface of the plate boundary fault in the Japan Trench

“…6) shows that the stress drop is more abrupt at 720 mbsf in the fault zone than at 820 mbsf. This stress-drop behavior at 820 mbsf is more consistent with the suggestion by Mitsui et al (2012b) that thermal pressurization is moderately effective in explaining the moment release rate estimated from the slip inversion. However, our data are insufficient to explain the reduced effectiveness of thermal pressurization at greater depths that is necessary to explain large slips in shallow areas (Mitsui et al, 2012a).…”

“…Several mechanisms have been proposed to explain the giant earthquake in the Tohoku area (Mitsui and Iio, 2011;Kato and Yoshida, 2011;Mitsui et al, 2012aMitsui et al, , 2012b. Kato and Yoshida (2011) simulated the recurrence of rare giant earthquakes and frequent large earthquakes by assuming a persistent strong patch and a large characteristic slip distance Dc in friction law on the shallow plate interface.…”

Rupture Reactivation during the 2011Mw 9.0 Tohoku Earthquake: Dynamic Rupture and Ground‐Motion Simulations

“…The possibility of large slip near the trench can be further enhanced by dynamic stresses in the subduction wedge associated with seafloor effects (Kozdon and Dunham, 2013;Huang et al, 2014) and by dynamic weakening mechanisms operating at large slip or slip velocity in materials that are velocity strengthening at low speed (Mitsui, Kato, et al, 2012;Noda and Lapusta, 2013;Cubas et al, 2015). Enhanced high-frequency radiation at depth has been attributed to the presence of deep asperities on the megathrust (Mitsui, Iio, and Fukahata, 2012;Huang et al, 2013Huang et al, , 2014 and its deprivation at shallow depth to thermal pressurization (e.g., Noda and Lapusta, 2013) and inelastic failure in the wedge (Ma and Hirakawa, 2013).…”

Pressure dependence of fluid transport properties of shallow fault systems in the Nankai subduction zone

“…When a fault zone is impermeable, a sudden pore pressure rise due to frictional heating or shear compaction during a seismic slip increases fault instability (Lachenbruch 1980;Andrews 2002) and promotes large displacement (Tanikawa and Shimamoto 2009). A low permeable fault zone is also related to the generation of highly pressurized fluid in the megathrust induced by dehydration and fluid influx from oceanic crust (Yoshida and Kato 2011;Kimura et al 2012;Mitsui et al 2012). Fluid transport properties in a fault zone also play an important role in the generation of slowslip events and low-frequency earthquakes (Suzuki and Yamashita 2009), which have been observed in the Nankai accretionary prism (Ito and Obara 2006).…”