GEOLOGICAL FACTOR CONTROL IN SPATIAL DISTRIBUTION OF LANDSLIDES IN HIMALAYAS

The seismic region of Himalayas undergoes geomorphological changes in the landscape on account of landslides. The two major thrusts i.e., the Main Boundary fault and Main central thrust are two fundamental lines of fracture which are consistently present in the entire E-W length of Himalayas across several countries of south Asia. These two thrusts are active and the plate movement from south to north has been a continuous mechanism available to the geodynamic process of Himalayas. The rate of uplift and rate of movement of the Indian plate is in consonance with each other. In this geodynamic system the geological parameters that contribute to landslides have to be identified. Several parameters have been identified and correlation found with factors like distance from fault, and ridge, relative relief and draiange patterns and density. This leads us to assessment of hazard zones in high relief terrain of Himalayas. This is a unique feature of the mountainous terrain of Himalayas where earthquakes have also contributed to erosion of slopes through the process of landslides. Example of an area close to Main Central Thrust is presented as a case study.

The work is an outcome of several years of study on landslides and has a bearing an application to other mountain terrains of other parts of the world.