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A new hypothesis for the deep subsurface structures near the Bhuj 2001 earthquake (Mw 7.6) hypocentre zone and its tectonic implications

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Title A new hypothesis for the deep subsurface structures near the Bhuj 2001 earthquake (Mw 7.6) hypocentre zone and its tectonic implications
 
Creator CHANDRASEKHAR, E
MATHEW, G
HARINARAYANA, T
 
Subject Magnetotelluric
Seismicity and tectonics
Continental tectonics: compressional
Asia
WESTERN INDIA
SEISMOTECTONIC IMPLICATIONS
MAGNETOTELLURIC DATA
KUTCH BASIN
26 JANUARY
KACHCHH
CRUSTAL
BENEATH
DECOMPOSITION
AFTERSHOCKS
 
Description We provide a new hypothesis for the deep subsurface structures near the Bhuj 2001 earthquake region based on magnetotelluric (MT) investigations carried out close to the epicentre zone. 2-D inversion of broad-band MT data of two profiles of lengths 32 km (AA') and 52 km (BB') revealed a thick (similar to 3 km) highly conductive (14 O-m) surface layer of fluvio-marine MesozoicCenozoic sediments. The models delineate the hypocentre zone located at similar to 2025 km depth that manifests the high resistivityconductivity transition zone. The accumulation of compressive stresses post-rifting along this weak zone has resulted in the reverse slip of Bhuj 2001 earthquake. The reverse fault (F1) associated with the earthquake is believed to be an ancient normal fault formed during the rifting phase. Contrary to earlier suggested theories, we suggest that F1 got initiated along the high resistivityconductivity transition zone causing the Bhuj 2001 event. The geoelectric models revealed a laterally extending partially resistive zone at 2030 km depth range showing a tendency to extend further deep. Model calculations using synthetic data also support this observation. Therefore, we hypothesize the presence of a basal detachment, marking the transition zone between the continental crust and the lithospheric upper mantle at similar to 40 km depth, intersected by the F1. The geoelectric models suggest that the crustal thinning caused the asthenospheric upwelling and/or serpentinization leading to the ascent of volatiles and melts. The subsurface geometry in Kachchh basin suggests the thick-skinned deformation.
 
Publisher WILEY-BLACKWELL
 
Date 2014-10-16T15:34:48Z
2014-10-16T15:34:48Z
2012
 
Type Article
 
Identifier GEOPHYSICAL JOURNAL INTERNATIONAL, 190(2)761-768
http://dx.doi.org/10.1111/j.1365-246X.2012.05532.x
http://dspace.library.iitb.ac.in/jspui/handle/100/15916
 
Language en