IDENTIFICATION OF PROBABLE EARTHQUAKE EPICENTRES IN THE KUMAON HIMALAYA A PATTERN RECOGNITION APPROACH

Abstract

The work presented In the following pages relates to pattern recognition study of a part of the Himalaya, designed to distinguish the seissmac ay dangerous parts of the region from those vh .ch may be comparatively safe* The approach followed In this investigation is a logical- bated oh its statiatical one and algorithm- 'CLUST B$, applied for a similar purpose to the California. region by Gelfand et al (1976) It was initially planned to make a compre. hansive study of the entire Himalayan chain which furnishes a wealth of learning material to be subsequently used In recognition. However, this exercise had to be restricted only to a part of the 1iamalaya. and to the use of only a few geological associates, as the computer cost began rising* The eel ection of this region was based on two main c oneiko derationg: I) Firstly$ the Kumaun region happens to be one of the most active seismic segments of the Himalayan arc and also geologically one of the best explored. ii) Secondly, it already happened to be.region rkod for an intensive geoinvestigations bye muitii disciplinary group of scientists of the Department of Geology and Geopbgeice,University of Roorkee. It was naturally felt that this study carried out for this region would constitute a welco1e support to the larger project. The most notable results that a~i erge fro!- the study can be su arised as follows: 1) The Main Central Thrust in the region narks a zone of high seimicity except for stretches toto11in8 about 150 iCr s. - it) It was further observed that in general points near the concave bends (with respect to the. Indian subcontinexn t) were more likely to be dangerous than those at the convex bends* iii) The Main Boundary Paul t which to a major line-ament running along the Himalayan chain is found to be largely nondangerous except a stretch of Jb0,1w, !v) A noteworthy feature that is revealed is that to the eegtment in which the Main central Thrust shows greater probability of being active, the Main Boundary Fault shows relative 'Quiet' and viceeversa. This would constitute an interesting mechanism for crustal shortening conjunctively accomodate i by two parallel lineaments., v) A third fairly dangerous zone is delineated along the Foot ill Thrust which es at a distance of about 10 Krns. to the south of the Hain Boundary Fault, vi.) Two transverOO faults passing respectively near Rarduar and Muesoorie curiously turn out to be dangerous and nondongerouo respe eti..vely,* The above conclusion must of course be viewed in the light of limitations imposed on the extent of the learning uateriel used and absence of control experiments. ts, But the study does point out interesting implication of these results f to the problet s of siting and design of complex engineering projects in the region. ?ina ly it is felt that the logic of the technique has much wider applicability lity and can be used to obtain ueeAxl inforration in respect of variety of complex processes and ,phenomena. For example, these technique may be applied fruitfully in tbo search for the most probab'e occurrence of ear#, -resourcea were adequate learning material, furnished by associated geological and ,copbyaioal featLreo can be obtaine