Site-specific response analysis & development of time series for near-fault sites

Infrastructure such as bridges, dams and buildings are often built at locations near activefaults (MW>6, D< 10 km), such that the projects can be classified as Near-Fault Sites (NFS). This paper presents case history of designing a bridge near Opak fault (M6.9, D5.5 km) where the analysis of the bridge structure requires seven sets of earthquake time series in the horizontal and vertical directions. For locations at near-fault, it must consider the effect of forward directivity that may cause pulse and fling-step. The effect of forward directivity is the occurrence of wave propagation in the normal fault direction (FN) which is stronger than the direction of the fault parallel (FP). Accordingly, the design of the response spectrum is distinguished in the direction of normal fault (FN) and parallel fault (FP). This paper discusses the selection of seven sets time series, where four pairs of no-pulse motions representing active faults and subduction earthquakes and three pairs of pulse motions representing near-faults where Ground Velocity (PGV) and Pulse Period (Tp) are more controlling than the acceleration response spectrum.