Probing the Complex Interaction of Makran Subduction Zone with Regional Tectonic Features: Insights from Gravity and Seismic Source Parameters

Abstract

Unraveling the intricate tectonic framework of the Makran subduction zone is essential for enhancing our understanding of seismic risks and developing effective mitigation strategies. This study delves into this complexity by analyzing gravity data and stress states derived from earthquake focal mechanisms. In this endeavor, the distribution and nature of seismic activity were compared with lateral gravity variations observed through vertical changes at the near-surface, intermediate, and regional levels. This analysis revealed a strong correlation between abrupt gravity changes and earthquake occurrences. This study reveals contrasting stress regimes across subduction zones and associated tectonic elements. Along the deformation front of the subduction zone, predominantly north−south compression occurred, and greater coupling in the eastern part was inferred based on gravity data. Northward, an anti-clockwise rotation of the stress axis is consistent with regional tectonics and deep structures within the Afghan Block, possibly influenced by the Chaman Transform Boundary to the east. The same northeast−southwest trend is followed by a deep normal faulting band related to the flexure of the subducted Arabian plate, which exhibits complex behavior, particularly in the west, where it seems to detach from the eastern part and interact with the deep root of the Sistan Suture. The same interaction may be responsible for the comparatively higher seismic activity in the western part of the flexural structure. The presence of a low-density zone below 100 km depth implies that two deep earthquakes occurring underneath the Chaghi volcanic arc discordant with the general trend of tectonic features and the stress axis may be associated to contortion in the subducting Arabian Plate under the effect of deep root’s Indo-Eurasian plate boundary.