Evaluation of strong motion acceleration for embankment dam design considering local seismotectonics

A probabilistic method is used to evaluate the seismic hazard of Adassiya dam site on the Yarmouk river in Jordan. A line source model developed by McGuire (1978) is used in this study. An updated earthquake catalogue covering the period from 1 A.D. to 1996 A.D. is used for this purpose. This catalogue includes all earthquakes that occurred in Jordan and adjacent areas, more specifically between latitudes 27.0degrees-35.5degreesN and longitudes 32.0degrees-39.0degreesE. Nine distinct seismic sources of potential seismic activities are identified. The seismic hazard parameters are determined using the method suggested by Kijko and Sellevoll (1989). The Peak Ground Acceleration (PGA) is selected as a measure of ground motion severity. Esteva (1974) attenuation relationship is used in evaluating PGA values at each dam site. Analysis is carried out for 50%, 90%, and 95% probability that is not being exceeded in a life time of 50, 100, and 200 years. Results of analysis indicate that PGA values at the dam site are as follows: Operating Basis Earthquake (OBE) (50% probability of non-exceedance for a design life of 100 years-corresponding to a return period of 145 years) is 133.6 cm/sec(2). An earthquake with 90% probability of non-exceedance for a design life of 50 years corresponding to a return period of 475 years is 214.9 cm/sec(2). Maximum Credible Earthquake (MCE) (Return period of 900 years) is 283.0 cm/sec(2). Strong motion acceleration time history of these earthquakes are given based on strong motion records of the November 1995 Gulf of Aqaba earthquake. Local site effect analysis for Adassiya Dam site using SHAKE program showed no amplification. Normalized site-specific acceleration response spectra for OBE and MCE design earthquakes is also given.