EGU2020-2550, updated on 12 Jun 2020
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Enhancement of Interplate Coupling after Recent Megathrust Earthquakes

Mohammad Yuzariyadi and Kosuke Heki
Mohammad Yuzariyadi and Kosuke Heki
  • Space Geodesy Laboratory, Hokkaido University, Hokkaido, Japan (

Enhanced interplate coupling has been found for segments adjacent along-strike to megathrust faults after the 2003 Tokachi-Oki and the 2011 Tohoku-Oki earthquakes, NE Japan, and was interpreted as acceleration of the subducting Pacific Plate slab. A similar enhanced coupling was also reported for the segments to the north of the rupture area of the 2010 Maule earthquake, central Chile. We utilize available GNSS data to find such enhanced coupling in worldwide subduction zones including NE Japan, central and northern Chile, Sumatra, and Mexico to investigate their common features. Our study revealed that the accelerations of landward movement of 2.1-9.0 mm per year appeared in adjacent segments following the 2014 Iquique (Chile), the 2007 Bengkulu (Sumatra), and the 2012 Oaxaca (Mexico) earthquakes. We also confirmed that the enhanced coupling is associated with the increase of seismicity for all these six cases. We found that the degree of enhancement depends on the length of the slab and the magnitude of the earthquake, which is consistent with the simple 2-dimensional model proposed earlier.

How to cite: Yuzariyadi, M. and Heki, K.: Enhancement of Interplate Coupling after Recent Megathrust Earthquakes, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2550,, 2020


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displays version 1 – uploaded on 04 May 2020
  • CC1: Comment on EGU2020-2550, Jonathan Bedford, 04 May 2020

    Dear Authors,

    Thank you for the interesting contribution.  I enjoyed reading this.

    Many in this field suggest a viscosity drop in the postseismic (e.g. using a Burgers rheology).   Have you considered this in your conceptual model?  What is interesting is that the velocity changes do not seem to recover (i.e. are sustained) - what is this telling us?  If I understand correctly, slide 5 indicates that the interface coupling is reduced in the postseismic (and this is facilitated by increased side resisitance Fsr) - if interface coupling is reduced then shouldn’t we expect sustained higher rates of background seismicity?  Furthermore, some postseismic studies suggest that relocking of the plate interface can be anywhere between instantaneous and 3 years (Remy et al. 2016; Bedford et al., 2016; Hobbs et al., 2019).

    Is there any along-strike dependence on the slab acceleration (e.g. as a function of distance to the coseismic slip centroid)?  If, for example, the locked slab in the mainshock region is now subducting faster than before the earthquake, but with postseismic effective mantle viscosities identical to the interseismic,  one might expect this faster subduction at the adjacent segments to start tapering off with distance (typical of an elastically controlled process).  So, establishing the wavelength of this postseismic slab acceleration might help us to better understand the controlling processes.

    Kind regards,
    Jonathan Bedford

    • AC1: Reply to CC1, Mohammad Yuzariyadi, 05 May 2020

      Dear Mr. Bedford

      Thank you very much for your interest in our presentation.

      So far, We have not considered the viscoelastic relaxation in our conceptual model.
      All we know is the concept that tries to explain the phenomenon using viscoelastic relaxation is an abstract from the 2019 AGU fall meeting by D'Acquisto et al.
      Could you inform us which paper that provides the new concept/model with viscoelastic relaxation?

      Yes, there is along-strike dependence of the acceleration. In slide 17, we show the spatial decay of the acceleration after the 2011 Tohoku-Oki earthquake, Japan, and after the 2010 Maule earthquake, Chile.

      Best regards,
      Mohammad Yuzariyadi.