EARTHQUAKE / DEEP CRUSTAL STUDIES

1. LATUR EARTHQUATE REGION, MAHARASHTRA :  

Latur Earthquake has occurred in aseismic region and it is important to know the deep crustal signature of the region. MT results in this region has brought out anomalous conductivity anomaly at a depth of about 7-10 km and indicated the presence of FLUIDS. Seismic and gravity data also supported for the presence of fluids that might have triggered the Latur earthquake. The new evidence from this study paved a way for possible identification of such zones in other seismic regions of the world as indicated recently from Kobe seismic epicentral zone (Ref: H.K.Gupta et al , Geophysical Research Letters, 23, No.13, 1569 1572,1996).

2. NARMADA-SON LINEAMENT ZONE ( JABALPUR EARTHQUAKE), MADHYA PRADESH.

Unlike above, this area is seismically active and has a series of E-W trending faults. However, it is important to know and distinguish between active and relatively passive faults. Magnetotelluric studies across the NSL zone cross both the Narmada South and North faults. Modeling results of MT data have clearly brought out the ACTIVE nature of the NSL SOUTH FAULT as compared to NORTH fault with a distinct conductivity contrast. This study thus gave evidence and a new way that it is possible to identify the active and relatively passive faults, which in turn helps to identify the hazardous zones as active faults that are associated with seismic activity. These results are presented in two international workshops (Ref: Harinarayana et al, Chapman conf., NGRI, and EM workshop, Romania, 1998).

3. BHUJ and CHAMOLI EARTHQUAKE REGIONS

MT studies were taken up during May-June 1999 in Chamoli epicentral region, Garwal Himalayas and during March 2001 in Kutch region. The studies were carried out by establishing 23 stations in Chamoli region and 36 (21+15) stations in Bhuj region. The stations occupied are oriented mainly along three different profiles in each region. Three profiles in Chamoli region are northeast-southwest (NE-SW) oriented profile from Gaucher towards southwest to Joshimath towards northeast direction, two east-west oriented profiles from Nijmula towards east and Mandal towards west and Chamtoli towards east and Appala towards west. The profiles occupied in Bhuj region are a northeast-southwest profile from Mundra towards southwest to Rapar towards northeast, from Mundra towards south and Kavda towards north and from Kodki towards west and Manaba towards east. The data have been processed using robust processing techniques and modeling exercises have been carried out using 1D and 2D modeling schemes to derive the subsurface geoelectric structure. (Ref: Gupta, H.K, Harinarayana, T and others, 2001, Geo. Soc. Of India , 57, 3,275-278.; Begum S.K., Ph.D Thesis, O.U. 2002; .)

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