Tectonic stress field in the epicentral zone of the Latur earthquake of 1993 |
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| Authors: | S V Srirama Rao K B Chary T N Gowd F Rummel |
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| Institution: | (1) National Geophysical Research Institute, 500 007 Hyderabad, India;(2) Institute for Geophysics, Ruhr University Bochum, Bochum, Germany |
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| Abstract: | In situ stress measurements by hydraulic fracturing were carried out in the 617 m deep borehole specially drilled in the epicentral
zone of the 1993 Latur earthquake for the purpose of research. The stress measurements carried out at 592 m depth in this
borehole are the deepest of all such measurements made so far in the Indian shield. The maximum and minimum principal horizontal
stresses (S
H max andS
h min) have been derived from the hydrofracture data using the classical method. TheS
H max andS
h min are found to be 16.5 and 9.6 MPa at 373 m depth, and 25.0 and 14.1 MPa at 592 m depth, indicating that the vertical gradients
ofS
hmax andS
hmin in the epicentral zone are 39 MPa/km and 21 MPa/km respectively. The principal horizontal stresses in the epicentral zone
are comparable with those at Hyderabad and 30% higher than in most other comparable intra-continental regions. Analysis of
the results indicate that the stresses in the focal region of the 1993 Latur earthquake have not undergone any significant
change following its occurrence and this is in agreement with a similar inference drawn from the seismic data analysis. It
appears that the Latur earthquake was caused due to rupturing of the overpressured fault segment at the base of the seismogenic
zone. |
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| Keywords: | Stress magnitude stress orientation hydrofracture seismicity Latur reactivation mechanism |
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