PREDICTED GROUND MOTIONS FOR MAKRAN SUBDUCTION INTERFACE BASED ON A STOCHASTIC FINITE-FAULT MODEL

Studies concerned with estimating earthquake hazard analysis require the prediction of strong ground motion. It is well known that some of the larger uncertainties in earthquake hazard analysis are caused by uncertainties in seismic wave attenuation. Predictive attenuation relationships have been developed for peak ground acceleration based on simulated records for Makran subduction interface. A suite of ground motions has been simulated for a range of magnitude and distances based on the stochastic finite fault ground-motion model (Motazedian and Atkinson, 2005). The theoretical attenuation relationship, which has been developed for the peak ground acceleration and spectral acceleration, is applicable to earthquakes of Mw 7.5 to 9 at a distance up to 200 km. The stochastic finite-fault model was validated against some recorded events such as; 1985 M 8.0 Michoacan, Mexico, the 1985 M 8.0 Valpariso, Chile, and the 2003 M 8.1 Tokachi-Oki, Japan earthquakes (Yagi, 2004). These subduction zone megathrust earthquakes were recorded at several rock sites located near the fault rupture. The result was compared with global studies of subduction zone megathrust such as Cascadia Subduction Zone (Gregor et al., 2002; Atkinson and Macias, 2009). For the Makran megathrust earthquakes, four different rupture geometries were used to model the M 7.5 to 9 events. The geometries only differ in their respective fault lengths. A fault dip of 8 to the north with a rupture width of 90 km was selected to represent average properties of the Makran subduction zone geometry. A regional crustal attenuation (Qs=63f 0.98) and velocity model was used with the stochastic nite-fault model simulations. The parametric uncertainties associated with the variation in source, path, and site effects were included in the development of the ground motions. A functional form was t to the ground-motion model simulations to develop region-specic attenuation relationships for the Makran megathrust rupture zone for both rock and soil site conditions.

کلیدواژه ها:

Stochastic finite-fault model ، Subduction zone megathrust ، Makran