Seismicity depth distribution analysis in southern Pakistan
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ORIGINAL PAPER
Seismicity depth distribution analysis in southern Pakistan Muhammad Jahangir Khan 1 & Mubarik Ali 1 Received: 16 April 2020 / Accepted: 26 October 2020 # Saudi Society for Geosciences 2020
Abstract This study is focused on analytical analysis of spatial dispersion of seismicity depth in southern Pakistan. The southern Pakistan spreads over Sindh, Balochistan, and frontal offshore areas of the Arabian Sea. Thereby, earthquake-prone sources are diversified in their seismotectonic characteristics such as active Makran subduction zone, transform boundary along Murray ridge and Chaman-Ornch-Nal fault system. The drifting mosaic of lithospheric platform is adding elastic fuel at a rate of 1.5–4 mm/year to the potential faults at shallow, intermediate, and deep levels. Unlike conventional approach, we have fragmented the composite catalog of earthquakes (during 325 BC to 25 February 2020) into different depth slices to reckon comparative seismicity changes at various depth intervals. Seismicity depth patterns are found significant to delineate potential seismotectonic plate boundaries and associated fault network in their intraplate regions. The changes in seismicity characteristics are comprehended with b-value variations for segregated depth windows. The interplate seismicity is observed in various clusters of shallow to deep focal depths, reflecting the seismically active zones of respective plate margins. Critical analysis of focal depths unveiled some anomalous deep focal depths for several intraplate earthquakes located in southern Sindh region. It is suggested to re-estimate focal depth anomalies by identifying uncertainties in data recording procedures or investigate physical mechanisms which synchronized with seismotectonic environments of the region. Keywords Seismicity . Southern Pakistan . Focal depth . Murray ridge . b-value
Introduction During the past two decades, the earthquakes are studied with more care and critic in Pakistan. The potential earthquakeprone sources are diversified in study area which make it seismically sensitive (Ambrasseys and Bilham 2003; Smith et al. 2013; Waseem et al. 2019). Recent studies place the entire coastline of southern Pakistan including populous city Karachi in a zone of “noticeable seismically active area” (Ahmed et al. 2016; Khan et al. 2018a, b). Ali and Khan (2015) suggested that active plate kinematics primarily control Responsible Editor: P. Anbazhagan Supplementary Information The online version contains supplementary material available at https://doi.org/10.1007/s12517-02006160-6. * Muhammad Jahangir Khan [email protected] 1
Department of Earth & Environmental Sciences, Bahria University Karachi Campus, Karachi, Pakistan
seismicity depth characteristics and its surficial distribution in study area over the last century (post-1900). Active lithospheric mosaic of Arabian, Eurasian, and Indian plates is adding elastic fuel to generate seismicity and has contributed to inimical thin-to-thick-skinned crustal deformation in different seismote
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