UC Davis

Ground-motions from 14 well-recorded moderate magnitude (M3.0 - M4.9) Bay Area earthquakes were compared to predictions from Ergodic Ground-Motion Models (GMMs). The radiation pattern is part of the earthquake source, however, in current GMMs the radiation pattern is not modeled explicitly and is treated as part of the path term in the regression. Without the proper separation between the earthquake source parameters and path parameters, the true path effect can be obscured. Going forward, the radiation pattern should be removed from the path effect in GMMs and included as part of the anisotropic source term for moderate earthquakes. This can isolate the 3-D crustal structure path-effects from the radiation-pattern effects and the radiation-pattern corrected residuals can be used for evaluations and calibration of 3-D simulations.