Earthquakes and the Neo-Tectonic Framework of the Kutch-Hyderabad-Karachi Triple Junction Area, Indo-Pakistan

Abstract

    In order to better understand its components and the associated seismic risk, the tectonic framework of Kutch, Hyderabad, and Karachi triple junction area is considered. It is proposed that a major active graben, named the Hyderabad graben, underlies the Karachi arc, and extends eastward under the Indus alluvial cover. The boundary faults of the Hyderabad graben control the boundary faults of the Karachi arc on its northern and southern ends.
The Hyderabad graben contains the Luni-Sukhri River lineament and runs parallel to the Kutch graben on its north side, with the Nagar Parker uplift acting as the divide. Both grabens trend eastward, converge in the vicinity of Ajmer, and swing to the north as a prominent lineament. This lineament cuts across the Himalayan foot hills. Both grabens are actively subsiding under the tremendous Indus load, a process that may contribute to the eastward creep of the Karachi arc and also enhance the overall seismic risk.
The dynamics of the active Karachi triple junction (KTJ), ancient but active rift structures, river sediment loading, along with the ongoing plate collision in the north, are some of the complex factors that control the tectonics and seismicity of the entire region.
Due to the presence of major population centers within the subject area, that already has a disastrous seismic record, the importance of close monitoring, enforcing strict building codes, and further research, cannot be over emphasized. The study of known and hidden rift structures may also lead to the discovery of additional energy resources.