| Abstrakt: |
To ensure the seismic safety of important buildings and infrastructure facilities in seismically active areas, it is necessary that, in addition to the various ground motion parameters, the seismic hazard is also characterized in terms of many other destructive natural effects of earthquakes like soil liquefaction and permanent fault displacement for example. The probabilistic seismic hazard analysis methodology can in principle be applied to quantify any of the destructive effects of the earthquakes in a region, provided a formulation has been developed to compute the probability with which a specified level of that effect can be exceeded at a site of interest due to given earthquake magnitude and location. Several investigators have developed necessary relationships and methodologies to estimate this probability for the permanent fault displacement, which may be a potential and primary cause of damage to long structures like bridges, tunnels, pipelines, dams and buried structures, if an active fault happens to cross or pass by such a structure. Based on a comprehensive literature survey and critical analysis of the results obtained for various possible alternatives, we have finalized a methodology for probabilistic fault displacement hazard analysis suitable for a 257 km long strand of the main boundary thrust (MBT) in the Garhwal-Kumaon Himalaya. Formulations are proposed for estimation of both the on-fault principal displacement and the off-fault distributed displacement, which can also be applied to any other thrust fault in any other segment of the Himalaya. The application of the proposed methodology to obtain the on-fault displacement estimates for a site at the midpoint of the selected strand of the MBT is found to provide physically realistic displacement values for very long return periods of upto 100,000 years. The off-fault displacements are found to decrease very fast with distance from the site on MBT and become practically insignificant at a distance of only two km. [ABSTRACT FROM AUTHOR] |
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