A megathrust earthquake cycle model for Northeast Japan: bridging the mismatch between geological uplift and geodetic subsidence

Abstract

In Northeast Japan, it remains a puzzle to reconcile the mismatch between long-term (geological) uplift and lateinterseismic and coseismic subsidence associated with the 2011 Tohoku earthquake. To explain this mismatch between different periods, we modeled the entire megathrust earthquake cycle in the Northeast Japan arc using a simple dislocation model with a two-layered lithosphere-asthenosphere structure in which we account for viscoelastic relaxation in the asthenosphere and tectonic erosion. The model behaves differently when the rupture stops within the lithosphere and when it cuts through the lithosphere to reach the asthenosphere. It is possible to explain the mismatch in the case where the rupture stops within the lithosphere. In the early interseismic stage, the viscoelastic response to the megathrust earthquake dominates and can compensate for late-interseismic and coseismic subsidence. In contrast, the late-interseismic stage is dominated by the locking effect with the steady slip below the rupture area. Tectonic erosion explains up to about half of the long-term uplift by landward movement of arc topography. The rest of the long-term uplift may be attributed to indirect effects of internal deformation in the arc.

Interseismic Loading of Subduction Megathrust Drives Long‐Term Uplift in Northern Chile

“…For comparison, typical vertical displacement rates over geological times for the coastal domain are generally one order of magnitude lower than typical interseismic uplift or subsidence rates (a fraction of millimeter per year vs several millimeters per year, e.g., Figure 1 Béjar- Pizarro et al, 2013;Hashima & Sato, 2017;Jolivet & Simons, 2018;Melnick, 2016;Regard et al, 2010). Comparatively, large megathrust earthquakes will generate meter-scale vertical displacements every time they occur (e.g., Simons et al, 2011;Vigny et al, 2011).…”

Lineaments and earthquake ruptures on the East Japan megathrust

“…Several of these works demonstrate patterns that suggest the existence of margin segments similar to those recognized by the seismotectonic results presented above. For example, Ozawa et al (2012), Hashima and Sato (2017), and Perfettini and Avouac (2014) highlight interesting aspects in the context of the segmentation inferred in this paper: (i) maximum coseismic and post-seismic displacement focused in the offshore prolongation of the Tohoku-oki compressional buttress (Fig. 1); and (ii) vertical acceleration focused within the Tohoku-oki buttress and the northern edge of the Joban buttress.…”

“…Later aftershocks within the northern reaches of the Joban buttress were also gently dipping thrust displacements, which explains the pattern of vertical uplift focused in or at the margins of the compressional buttresses. In contrast, extensional normal faulting at the seaward margin of the Tohoku-oki extensional channel requires either subsidence, or minimal vertical uplift, as observed (Hashima and Sato, 2017).…”

“…Numerous previous studies show the value of combining the analysis of satellite geodesy with mechanical modeling (Ikuta et al, 2012;Kato et al, 2012;Ozawa et al, 2012;Kyriakopoulos et al, 2013;Mavrommatis et al, 2014Mavrommatis et al, , 2015Hasegawa and Yoshida, 2015;Johnson et al, 2016;Loveless and Meade, 2016;Hashima and Sato, 2017;Yokota and Koketsu, 2015). Several of these works demonstrate patterns that suggest the existence of margin segments similar to those recognized by the seismotectonic results presented above.…”

“…To understand why the segment boundaries have focused the onset of the largest earthquakes in the past four decades in East Japan, we need to bring geology into the equation, at the scale involved in modeling subduction zone interactions (Bassett et al, 2016;Freed et al, 2017;Hashima and Sato, 2017;Hu et al, 2016). Geological architecture responds to loading just like any man-made construction.…”