Long-Term Seismic Hazard Analysis in Northeast Himalaya and Its Adjoining Regions

Northeast Himalaya and its adjoining region India, has been delineated into nineteen seismogenic sources on the basis of certain seismological and criteria for the estimation of repeat times of earthquakes, to apply a regional time- and magnitude-predictable model for all these sources to study the future seismic hazard. For this, published earthquake data since 1906 to 2008 from different available earthquake catalogues and books have been used. Considering the inter-event time between successive mainshocks, the following two predictive relations were computed: logTt = 0.01 Mmin + 0.22 Mp - 0.05 log m0 + 0.98 and Mf = 0.89 Mmin – 0.26 Mp + 0.29 log m0 - 5. Multiple correlation coefficient and standard deviation have been calculated as 0.50 and 0.26, respectively for the first relation and 0.75 and 0.41, respectively for the second relation. The positive dependence of Tt on Mp indicates the validity of time predictable model on the area considered in this study.on the basis of these relations and using the magnitude and time of occurrence of the last mainshocks in each seismogenic source, time dependent conditional probabilities of the next mainshocks and their occurrence during the next 10, 20 and 30 years as well as the magnitude of the expected main shocks are forecast.