[S-CG46] Uncovering stress accumulation and fault strengthening of megathrust earthquakes

[SCG46-P12] Stress Changes Effects on Mentawai Segment of Sumatra Megathrust Seismic Gap for Seismic Hazard Assessment

*Fermiro Faza Haribowo¹, Shinji Toda² (1.Graduate School of Science, Tohoku University, 2.International Research Institute of Disaster Science, Tohoku University)

Since the Enggano Earthquake in the year 2000, Sumatra has experienced several large megathrust earthquakes with the 2004 Great Sumatra Earthquake being the largest with magnitude reaching 9.1 Mw. Along the Sumatra Subduction Zone, the Mentawai Segment on the coast of Padang has not released its megathrust earthquake for almost 200 years based on previous studies, with the last known events being the 1797 M 8.7 and 1833 M 8.9 earthquakes. Geological and geodetic observations suggest that this segment remains locked, accumulating stress that could lead to a future large rupture. An inversion of ground-based GPS velocity data from the Sumatra GPS Array (SuGAr) estimates the current slip deficits on the subduction interface. Cumulative stress contribution from neighboring ruptures in adjacent segments is also calculated to the total stress on the interface. The resulting secular stress calculations for the subduction plane are then compared with observed seismicity to validate spatial patterns of stress buildup. Finally, the calculated stresses are used to infer an approximate return period for the Mentawai Segment, providing insights into the seismic hazard potential in the region.