Seismic Interactions Between Northern Terminus of Ornahc-Nal and Hoshab Faults Based on Source Mechanism Investigation of 06 May 2022 Mw 5.4 Khuzdar Earthquake

Abstract

Moment tensor inversion was performed for earthquake of moderate magnitude occurring in May 2022 near Khuzdar, Pakistan. According to local news agencies, the event caused damages to engineered structures and collapse of several mud houses. Faulting style depicted from inversion implies that the event may be associated with Ornach-Nal strike-slip fault which is part of western boundary of Indian plate. To understand the tectonic setting of the area, the present study was augmented by inclusion of results from similar studies. Principal stress axis (S_Hmax) was determined by performing stress inversion. Based on 38 events focal mechanism solutions from the global Harvard Centroid Moment Tensor (CMT) of the Khuzdar region depict NW–SE orientation of S_Hmax direction. On the basis of their stress homogeneity, reduced stress tensors obtained from formal stress inversion have been divided into two subsets resulting in thrust and strike-slip faulting. The present-day stress state conforms to the oblique convergence of Indian and Arabian plates beneath Eurasian. Shear strain produced by strike-slip movement of plate boundary (Chaman fault system) is being accommodated in Kirthar range within the Indian plate. Before this event, a lower b-value (0.7) and accelerated earthquake sequence were observed in the Khuzdar region, which is (in our view evidence of presence of stress loaded asperities along this fault system) representation of stress loaded asperities exist. The spatial distribution of b-value depicts the lowest value in this region before the occurrence of Awaran earthquake of 2013 that took place about 70 km west of the recent event.