Current Science

Utpal Saikia ¹, S. S. Rai ¹, M. Subrahmanyam ², Satyajit Dutta ¹, Somasish Bose ¹, Kajaljyoti Borah ¹, Rishikesh Meena ¹

Affiliations
1 CSIR-National Geophysical Research Institute, Hyderabad 500 007, IN
2 Department of Geophysics, Andhra University, Visakhapatnam 530 003, IN

Abstract

Earthquake waveform from a new temporary network of 21 seismic stations in South India has been used to significantly improve the detection threshold and parameters of small earthquakes near Idukki Reservoir, Kerala. We present here precise location of 16 earthquakes in this region with a local magnitude of 1.5-3.6 and focal depth 7.2-9.9 km. Fault plane solutions of the selected best six earthquakes show strikeslip faulting and right lateral movement. Reservoir loading usually leads to generation of stress and therefore earthquakes in the shallow depth (< 5 km), that are absent in the region of Idukki Reservoir. Recorded earthquakes are confined to a NW-SE trending fault close to Karur-Kamabam-Painavu-Trichur (KKPT) shear zone. These observations suggest that the earthquakes in Idukki region are tectonic in nature and have no linkage with the reservoir.

Keywords

Earthquake Location, Fault Plane Solution, Reservoir, Tectonics.

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R. Divya Bharathi ¹, M. Subrahmanyam ¹, D. S. Ramesh ², S. Rajendran ³

Affiliations
1 Department of Geophysics, Andhra University, Visakhapatnam 530 003, IN
2 Indian Institute of Geomagnetism, Kalamboli Highway, New Panvel, New Mumbai 410 218, IN
3 Department of Earth Sciences, Kerala University of Fisheries and Ocean Studies, Panangad, Cochin 682 506, IN

Abstract

Nine total magnetic profiles in the S–N direction of the Central Indian Ocean (CIO) have been interpreted with spectral and Werner deconvolution techniques to obtain approximate depths to shallow (magnetic basement) and deeper (Curie isotherm) interfaces of the oceanic crust. From these preliminary depths, tentative crustal models for all these nine profiles are prepared. These tentative models of the area show varying thickness of the oceanic crust, supporting the deformation history. It is inferred from these tentative models that deformation extends beyond the zone identified south of 8°S latitude. There is good agreement between the spectral and Werner deconvolution depths.

Keywords

Deformation Zone, Deconvolution Techniques, Magnetic Anomaly, Oceanic Crust, Tentative Model.

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