Probabilistic seismic hazard analysis (PSHA) is a technique for estimating the annual rate of exceedance of a specified ground motion at a site due to known and suspected earthquake sources. PSHA integrates the contributions from all potential seismic sources to the annual frequency of exceedence (AFE) of an Intensity measure of ground motion at a given site. The main disadvantage of PSHA is that the concept of a "design earthquake" is lost; i.e., there is no single event specified by magnitude M, distance R, and epsilon ε, which is the number of standard deviation from the median intensity measure predicted by an attenuation relation. This disadvantage results directly from the integrative nature of PSHA. The disaggregation technique of seismic hazard provides the relative contribution to hazards from sources of different magnitude, M, distance, R, and ε, as predicted by an attenuation equation. Tehran is a large, rapidly growing and important city located at the foothills of the Alborz Mountains and is bounded by several active faults. Historical earthquake are associated with the Mosha, Talegan, Parchin and Garmsar faults with the largest events on the Garmsar fault (an Ms ~ 7.6 during the third century BC) and on the Taleqan fault (an Ms ~ 7.7 in the 10th century). The shape of the ground motion spectrum and, therefore, the response spectrum is strongly dependent upon distance, magnitude, and ground motion deviation. In the central part of metropolitan of Tehran, different seismic sources dominate the hazard at different frequencies, so that contributions to the hazard come from significantly different magnitudes, distances, and ε, therefore a single design earthquake is not appropriate. We have disaggregated the seismic hazard analysis for ground motions having a 10% chance of exceedance in 50 years. This probability value was chosen because the Iranian seismic code proposes this probabilistic ground-motion value as a basis for design values. In here, values of
