Broadband synthetic time histories for central and eastern United States are generated using a proposed hybrid broadband simulation technique. The low‐frequency (LF) portion of synthetics is calculated using kinematic source modeling and deterministic wave propagation. Using the COMPSYN software package (Spudich and Xu, 2003), a discrete wavenumber/finite‐element method is implemented for the LF Green’s functions generation. The procedure makes use of the reciprocity theorem and numerical techniques to assess the representation theorem integrals on a fault surface. Spatial random field models are employed to characterize the complexity of the slip distribution on the heterogeneous fault. In this study, the variability of some of the kinematic source modeling’s parameters (e.g., hypocenter locations, slip distribution, source time function, and rupture propagation) is taken into account to produce multiple seismograms that contain a broader range of intensity measures such as peak ground motions and spectral accelerations. A stochastic finite‐fault simulation model is employed to attain the high‐frequency (HF) portion of synthetics. Combining HF and LF synthetics in a magnitude‐dependent transition frequency, the broadband seismograms are constructed for M 5.5, M 6.5, and M 7.5 earthquakes in a distance range of 2–200 km.

Broadband synthetics will be compared with some of the existing ground‐motion prediction equations for spectral accelerations at 0.2, 1.0, and 3.0 s, and the results will be discussed. A compatibility assessment of the stochastic point source and the finite source is performed. The generated seismograms could be implemented in engineering seismology applications such as structural seismic analysis/design and seismic‐hazard analysis.

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