Estimation of Coda‐Wave Attenuation in the Central and Eastern Alborz, Iran

Abstract

The quality factor of coda ( Q c) waves has been estimated by using single backscattering and single isotropic scattering models. The earthquakes used were recorded by three permanent and one temporary network located in the central and eastern Alborz, Iran. The database was composed of 746 local earthquakes with local magnitude from 1.1 to 5.7. The estimated Q c has been found to be similar for lapse times greater than twice the S ‐wave travel time (2 t S ) for both methods. The estimated Q c for central frequencies <1.0 Hz shows less frequency dependency compared with the higher frequencies. By using a Q f n relation, the average frequency dependence of Q c for the whole area has been estimated as 59 f 1.03, 69 f 0.97, 78 f 0.97, 105 f 0.93, 123 f 0.89, 159 f 0.79, and 203 f 0.68 for central lapse times 30, 40, 50, 65, 85, 110, and 155 s, respectively. We found the value of Q decreases at an average depth of 78 km, which may be the result of high dissipating media at this depth. The average Q c values, estimated for central and eastern Alborz and their frequency‐dependent relationships are similar to those of tectonically active regions.