Identification of potential areas for the occurrence of strong earthquakes in Himalayan arc region

Abstract

Morphostructural zoning (MSZ) scheme of the Himalayan arc region as obtained from a joint study of topographic, geological and tectonic maps as well as satellite imagery is analysed. Three types of morphostructures have been determined: territorial units (blocks of different ranks), linear zones limiting these blocks (lineaments) and intersections of the lineaments (knots). Comparison of MSZ scheme with the known seismicity indicates epicenters of strong earthquakes (M/> 6.5) clustered around some of these knots. Pattern recognition method is used to determine seismically potential areas for the occurrence of strong earthquakes of magnitude i> Mo. We have carried out two such studies for the Himalayan arc region, one for Mo = 6.5 and the other for Mo = 7.0. Out of a total number of 97 knots, 48 knots are found to be seismically potential for the occurrence of earthquake of M I> 6"5. The results of the study for M o = 6.5 were presented in the symposium on "Earthquake Prediction" held in Strasbourg, France, March 1991 (Gorshkov et al 1991). The epicenter of Uttarkashi earthquake of magnitude, M b = 6-6 that occurred in the late hours of 19th October 1991 (UTC) lies in the vicinity of one such knot. The second study carried out subsequently shows that only 36knots are potential for the occurrence of earthquakes of M t> 7.0, which include the knot associated with the Uttarkashi earthquake.

Identification of seismically susceptible areas in western Himalaya using pattern recognition

“…Other knots also partially overlap some parts of Area A. Dangerous knots of Bhatia et al (1992) are either within area A or are at boundary of A, which implies a similarity in identification of almost same areas by different methods. In addition, Area A is much larger than the area encompassed by knots.…”

“…These are located in Doda district of J&K and Chamba district of HP. Bhatia et al's (1992) qualitative study for the occurrence of strong earthquakes identifies potential areas as dangerous knots in the Himalayan arc. The quantitative approach of the present study has identified three kinds of seismically susceptible areas in western Himalayas where Area A is the most susceptible.…”

“…The quantitative approach of the present study has identified three kinds of seismically susceptible areas in western Himalayas where Area A is the most susceptible. The susceptible area map was superimposed on the map of potential knots for earthquakes M w ≥ 6.5, identified by Bhatia et al (1992), and compared as shown in figure 12. Several dangerous knots #10, 18, 19, 23, 24, 25, and 34 are located totally within Area A, and major parts of several other knots partially overlap Area A.…”

“…The dangerous areas identified were characterized by proximity intersections or ends of major faults and by relatively low elevation or subsidence against a background of weaker uplift Varunoday et al 1979 Kumaon Himalayan Out of the 51 objects considered, 33 appear as dangerous and 18 as nondangerous Caputo et al 1980 Italy Two clusters of dangerous points were observed in north and central Apennines Bhatia et al 1992 Himalayan Arc Two studies were carried out for M ≥ 6.5 and M ≥ 7.0. Out of 97 knots 48 knots are seismically potential for M ≥ 6.5 and 36 knots are seismically potential for M ≥ 7.0.…”

Earthquake prediction activities and Damavand earthquake precursor test site in Iran

“…For this purpose, the methodology developed by IIEPT&MG that has been applied to many seismic regions of the world for the identification of seismogenic nodes has been employed (Bhatia et al 1992;Gelfand et al 1972Gelfand et al , 1976Gorshkov et al 1991Gorshkov et al , 2000Gorshkov et al , 2002Gorshkov et al , 2003Gorshkov et al , 2004Gvishiani et al 1986Gvishiani et al , 1987Gvishiani et al , 1988. Recent earthquakes in each of the regions studied have proven the reliability of the results obtained.…”