Static Stress Transfer from The 2010 Mw 7.8 Sinabang Earthquake and Its role in Triggering the Mw 7.2 Meulaboh Event

Jhon Eric Natanael Hutabarat (Geophysical Engineering Study Program, Sumatera Institute of Technology, Indonesia)
Sendy Diego M.P Lubis (Geophysical Engineering Study Program, Sumatera Institute of Technology, Indonesia)
Yudha Styawan (Geophysical Engineering Study Program, Sumatera Institute of Technology, Indonesia Earthquake and Tsunami Disaster Mitigation Center, Sumatera Institute of Technology)
Rizki Wulandari (Geophysical Engineering Study Program, Sumatera Institute of Technology, Indonesia Earthquake and Tsunami Disaster Mitigation Center, Sumatera Institute of Technology)

Jurnal Fisika FLUX
Vol 23, No 2 (2026): Jurnal Fisika Flux: Jurnal Ilmiah Fisika FMIPA Universitas Lambung Mangkurat

This study investigates the mechanical relationship between the 6 April 2010 Sinabang earthquake (Mw 7.8) and the subsequent 9 May 2010 Meulaboh earthquake (Mw 7.2) along the Sumatra–Andaman Subduction Zone (SASZ) using static Coulomb Stress Change (ΔCFS) analysis. Earthquake source parameters and focal mechanisms were obtained from the United States Geological Survey (USGS) catalog. Aftershock sequences associated with the Sinabang earthquake were identified using the Gardner and Knopoff declustering algorithm, while fault geometry was constrained using focal mechanism solutions and empirical scaling relationships. Static stress transfer was modeled using Coulomb 3.3 assuming a homogeneous elastic half space. The results indicate that the Sinabang earthquake generated a positive ΔCFS lobe extending toward the Meulaboh segment, with stress increases penetrating the seismogenic depth range of approximately 20–40 km. Receiver-fault analysis yielded positive ΔCFS values of 0.022 bar and 0.011 bar for Meulaboh Nodal Plane 1 (NP1) and Nodal Plane 2 (NP2), respectively, with NP1 showing better agreement with the regional tectonic setting and aftershock distribution. Validation using 107 aftershocks showed that 63 events (58.88%) occurred within positive ΔCFS regions, supporting a spatial association between stress increase and postseismic seismicity. Although the calculated stress perturbations remain below the commonly adopted static triggering threshold of 0.1 bar (0.01 MPa), the positive ΔCFS values suggest that static stress redistribution may have increased the failure potential of the Meulaboh fault. The 33-day interval between the Sinabang and Meulaboh earthquakes further implies that additional time-dependent postseismic processes may have influenced the timing of fault failure, although these mechanisms were not explicitly modeled in this study. These findings highlight the probabilistic nature of earthquake interactions within active subduction systems and provide insights for future investigations of delayed earthquake triggering and seismic hazard assessment.