Megathrust stress drop as trigger of aftershock seismicity in subduction zone forearcs: Insights from the 2011 Mw 9.0 Tohoku earthquake, Japan

• DOI: 10.5194/egusphere-egu23-8028
• Publication Date: 2023-02-25T21:46:27Z
• Authors: Armin DIelforder; Gian Maria Bocchini; Kilian Kemna; Andrea Hampel; Rebecca Harrington; Onno Oncken
• Keywords: Forearc

Large megathrust earthquakes like the 2011 Mw 9.0 Tohoku earthquake (Japan) are followed by numerous aftershocks in subduction zone forearc overlying seismogenic fault. The can include normal-faulting events despite thrust mechanism of main shock. Postseismic normal faulting has been explained stress changes induced coseismic drop along megathrust. However, details and aftershock triggering mechanisms remain poorly constrained. Here we use numerical force-balance models combined with Coulomb failure analysis to show that indeed supports faulting, but forearc-wide is feasible within a narrow range stress-drop values states only. We determine this for associated explain seismicity unprecedented detail. In particular, our reveals ~78% ~92% seismic moment release occurred areas where caused increase, detailed distribution was also governed spatial variability fault strength topography. Our findings provide new insights into help understand occur after great at zones.