DEVELOPMENT OF TIME-AND-MAGNITUDE PREDICTABLE MODEL AND PREDICTION OF EARTHQUAKE HAZARD IN CENTRAL HIMALAYAS

SUMMARY Earthquake prediction is one of the necessary components of seismic risk reduction in India. This is associated with the fact that owing to the subjectively underestimated seismic hazard in the territory of India earthquake resistance level of buildings and structures had appeared to be significantly lower than the seismic hazard level. Earthquake Prediction should be considered as a stage-by-stage seismic hazard assessment that consequently passes from long-term to current one when strong seismic event is under preparation. This will allow for making decisions that are adequate to the hazard data and reduce the seismic risk. Strong main shocks in six seismogenic sources of the Central Himalayas have been used to show that the interevent time, Tt (in years), between two strong shallow earthquakes and the magnitude, Mf , of the following mainshock are given by the relation: logTt = 0.46 Mmin + 0.09 Mp + 0.14 log mo – 5.79 Mf = - 0.69 Mmin – 0.08 Mp - 0.45 log mo + 22.52, where Tt is the interevent time, measured in years; Mmin the surface wave magnitude of the smallest mainshock considered; Mp the magnitude of preceding mainshock, Mf the magnitude of the following mainshock and mo the moment rate in each source per year. These relations may be used for earthquake hazard assessment in the region. A multiple correlation coefficient equal to 0.78 and a standard deviation equal to 0.22 for the first of the above relations were computed. The corresponding quantities for the second of these relations are 0.73 and 0.39. Time dependent conditional probabilities for the occurrence of the next large (Ms ≥ 5.5) shallow mainshocks during the next 30 years (2004-2034) in one of the sixseismogenic source are estimated, by use of the first of these relations. The magnitudes of the expected mainshocks are also determined, by the second of the above relations