POSSIBLE ROLE OF DELHI-HARIDWAR SUBSURFACE RIDGE IN GENERATION OF UTTARKASHI EARTHQUAKE, GARHWAL HIMALAYA, INDIA

Himalayan orogen, a product of continued NE-SW compression, has certai n zones in its foreland, which frequently experience seismicity. Geoph ysical and aeromagnetic data suggest extension of Peninsular rocks as NE-SW trending ridges in the Himalaya in these zones. The epicentral z one lying above the ridge end, has generated many NE-SW extensional st ructures within the NE-SW compressional field. As the Himalayan orogen y has not vet ceased and the compression continues, the resultant geol ogical phenomena are manifestation of basement-cover interaction. The authors visualize a structural high at shallow depth at the ridge end. The release of stresses, retained by such structures under elastic st rain causes seismicity in the Himalayan belt.