资源环境科技发展态势分析平台

Fluids play a prominent role in the genesis of earthquakes, particularly in intraplate settings. In this study, we present evidence for a highly heterogeneous nature of electrical conductivity in the crust and uppermost mantle beneath the Kachchh rift basin of northwestern India, which is host to large, deadly intraplate earthquakes. We interpret our results of high conductive zones inferred from magnetotelluric and 3-D local earthquake tomography investigations in terms of a fluid reservoir in the upper mantle. The South Wagad Fault (SWF) imaged as a near-vertical north dipping low resistivity zone traversing the entire crust and an elongated south dipping conductor demarcating the North Wagad Fault (NWF) serve as conduits for fluid flow from the reservoir to the middle to lower crustal depths. Importantly, the epicentral zone of the 2001 main shock is characterized as a fluid saturated zone at the rooting of NWF onto the SWF.

Plain Language Summary Fluids play a significant role in generation of earthquakes in intraplate and interplate settings. However, knowledge of the nature, origin, and localization of crustal fluids in stable continental interiors (intraplate) remains uncertain. The Kachchh rift basin of northwestern India is host to large, deadly intraplate earthquakes like those in 1819 (M(w)7.8) and 2001 (M(w)7.7). In the present study we carried out extensive geophysical investigations to understand the cause for seismic activity in the region. The study provides the evidence for the presence of fluids in the seismically active intraplate region of northwest India. This study demonstrates that the dynamics of mantle fluids controlled by geological faults could lead to large and moderate-sized earthquakes.