Partial coupling in low-seismicity subduction areas: an example of the western Makran subduction zone

Geodetic imaging of interseismic coupling in subduction zones enhances our understanding of seismic potential and hazard assessments, particularly in low-seismicity regions where tectonic risks may be underestimated or remain unrecognized. This study focuses on the Western Makran Subduction Zone (WMSZ), where the Arabian plate converges with the Eurasian plate. The WMSZ shows no significant thrust events at shallow depths, with most seismicity occurring at intermediate depths within the downgoing plate. Our approach begins with isolating the interseismic deformation signal, through an InSAR time series analysis method that targets the estimation and filtering of atmospheric effects. Then we utilize the corrected deformation rates to estimate the spatial distribution of interseismic coupling in the (WMSZ). This approach employs Bayesian inference for modeling interseismic coupling without imposing rigid smoothing constraints, allowing for improved model flexibility to capture localized variations in coupling distribution. The results reveal a partially locked zone in the WMSZ, notably at intermediate depths (35-40 km) beneath the southern Jazmourian plain. This area coincides with a cluster of moderate-magnitude earthquakes observed at approximately 40 km depth. Furthermore, pre-event coupling was detected in the region affected by the Mw 5.1 earthquake of March 5, 2024 (Fanuj). The presence of dip-elongated partially locked zones suggests the potential existence of local asperities along the subducting slab at intermediate depths, which may have significant implications for seismic hazard assessment in the WMSZ. These findings provide a basis not only for understanding the seismic potential in WMSZ but also offer insights applicable to other subduction zones, advancing methodologies that enhance geodetic monitoring and risk assessment in tectonically similar environments.