Frictional and structural controls of seismic super-cycles at the Japan trench

Abstract

The diverse mechanical behaviors of subduction zones during the seismic cycle emerge from the nonlinear dynamics of a complex mechanical system with interacting brittle and ductile deformation. The 2011 Tohoku mega-quake represents the culmination of a super-cycle of partial and full ruptures of the plate interface, but the physical controls on the down-dip segmentation of the megathrust remain unclear. Here, we propose a two-dimensional rheological model of the Japan trench to explain the variability of earthquake size at the Miyagi section, in northern Honshu, during the last century. We simulate seismicity in a continuum with a physics-based rate-and state-dependent constitutive law for fault slip, producing aperiodic earthquake sequences with a power-law distribution of rupture sizes. Although some partial ruptures of the megathrust are the result of self-emergent behavior, others are structurally controlled. The 1978 and 2005 Mj∼ 7 interplate earthquakes took place in a metamorphic belt in the mantle wedge corner bounded up-dip by the arc Moho that constitutes a permanent structural boundary. We explain the succession of the great 1981 Mw = 7.1 and 2003 Mw = 6.9 earthquakes within the forearc and the 2011 giant earthquake as the natural response of a large continuously velocity-weakening fault with a small nucleation size. The shallow segment below the frontal prism only slips in giant through-going ruptures that unzip the whole velocity-weakening interface. The model consistently explains the size, recurrence time, and hypocenter location of historical earthquakes in the Miyagi segment, the slow-slip and foreshock preparatory phase of the 2011 Tohoku earthquake, the large slip near the trench during the giant rupture, and important features of its postseismic deformation. The complex patterns of seismicity at the Japan trench can be better understood by assimilating geological and geophysical observations at various periods of the seismic cycle within an explicative physical framework.

The stop-start control of seismicity by fault bends along the Main Himalayan Thrust

“…However, partial coupling and interseismic creep are predominant at the base of the MFT (Supplementary Fig. 3), as is often found at fault bends 8,10,11 . The transition zone between velocity-strengthening and velocityweakening friction is characterised by high stresses (Fig.…”

“…The development of seismic super-cycles may be controlled by several factors, such as particular frictional properties 5,6 , geometric complexity 7 , off-fault deformation in the hanging wall 8 , and residual stress from past earthquakes 9 . The remaining challenge is to assess the relative contribution of these factors at specific plate boundaries 10,11 .…”

Presence of interplate channel layer controls of slip during and after the 2011 Tohoku-Oki earthquake through the frictional characteristics

“…Barbot 17 focused on down-dip segmentation of rupture styles; partial ruptures at the deeper part and a giant, super-cycle rupture at the entire velocity-weakening interface. Barbot 17 presented two-dimensional simulations, which suggested that the rupture styles at the middle segment of the Japan Trench are controlled by both structural and frictional heterogeneity. Therefore, the spatial distributions of slip along the trench may also be explained by structural and frictional heterogeneity.…”

Static Source Properties of Slow and Fast Earthquakes

“…The earthquake phenomenon includes a wide spectrum of rupture styles associated with different source characteristics (Beroza & Ide, 2011; Barbot, 2019b; Leeman et al, 2016; Scuderi et al, 2017; Obara & Kato, 2016; Veedu & Barbot, 2016). The stress change on a fault produced by an earthquake is one of the fundamental physical properties that govern the seismic cycle, impacting the style of rupture, that is, slow or fast earthquake, and the magnitude of the event (Aki, 1967, 1979; Barbot et al, 2020; Kanamori & Anderson, 1975; Kanamori et al, 1993; Poli & Prieto, 2016; Sobolev et al, 2017; Venkataraman & Kanamori, 2004; Ye et al, 2016a). The scaling relationship between stress drop and various other source parameters depends on the tectonic setting (e.g., Romanowicz, 1992; Scholz et al, 1986; Walsh & Watterson, 1988) and on the rupture style (Beeler et al, 2001; Cocco et al, 2016; Cattania & Segall, 2018; Gomberg et al, 2016; Kato, 2012; Liu‐Zeng et al, 2005; Peng & Gomberg, 2010).…”