The present work deals with the development and evaluation of landslide hazard zonation techniques which have been applied to parts of Garhwal Himalaya. The binary relationships between the factors and landslides have been determined. These relationships revealed the degree of susceptibility to landslide occurrence. The two techniques developed for landslide hazard zonation are the Subjective Rating Technique (SRT) and Objective Rating Technique (ORT). Although the SRT employs the inferred relationships between the landslide occurrence and the terrain factors to assign ratings to the factor categories, yet the rating assignment to the individual factors is subjective. The ORT reduces the impact of subjectivity in rating assignment, by deriving these from the frequency distribution of landslides. In this technique an attempt has also been made to judiciously classify the different hazard classes. Finally, the maps prepared from two different techniques have been validated and compared. The work presents a systematic approach to a comprehensive landslide hazard assessment of a large region.
earthquake on the basis of recording the P (longitudinal) waves. Longitudinal waves travel at a velocity of about 7 km/sec. Maximum damage is done by S (transverse) waves that are slower and travel with a velocity of about 4 km/sec. About one minute prior to effects of the Sendai earthquake being felt in Tokyo, the Earthquake Early Warning System connected to over 1000 seismometers in Japan sent out a warning message on television about the anticipated accelerations in Tokyo region to millions. It is believed that this early warning saved many thousands of lives.
