MEHDI ZARE - International Institute of Earthquake Engineering & Seismology (IIEES), Tehran, P,O.Box: ۱۹۳۹۵/۳۹۱۳, I.R.IRAN
MOHSEN GHAFORY-ASHTIANY - International Institute of Earthquake Engineering & Seismology (REES), Tehran, P O,Box: ۱۹۳۹۵/۳۹۱۳, I.R.IRAN
PIERRE YVES BARD - Laboratoire de Geophysique Interne et Tectonophysique (LGIT), ۱RIGM, BP۵۳X, ۳۸۰۴۱ Grenoble Cedex, and Laboratoire Central des Ponts et Chaussees, ۵۸ Bd Lefebvre, ۷۵۷۳۲ Paris Cedex ۱۵, FRANCE

The attenuation of the Iranian strong motions is studied using the Iranian strong motions database. This database comprises ۴۶۸ three-components well recorded data (analog and digital) for which the teleseismic source parameters were available, or calculated from the strong motion records. The two-steps used attenuation model used in this study is log A=a.M-b.X-log X+c۱.S۱+σ.PWhere A is strong motion parameter, M is the moment magnitude, X is the hypocentral distance, and the coefficients a, h and c, are the coefficients of magnitude, distance and site effects (as ci, c۲, c۳, and ca for the four-class site classification) respectively. The sigma term represent the ۸۴ I% standard deviation with P=۱.