ShakeMovie Computer Simulation of the M6.7 1994 Northridge, CA Earthquake

At the time of its occurrence, the 1994 Northridge earthquake produced one of the most comprehensive datasets of earthquake ground motion recordings to date. In spite of this, the spatial locations of instrumental observations do not provide sufficient resolution to fully visualize many of the important ground shaking features that occurred during this earthquake. To augment the seismic recordings, this ShakeMovie animation utilizes sophisticated computer models to predict how seismic waves were generated along the fault as it broke, and how those waves would have traveled through the complex three-dimensional sub-surface geology in the greater Los Angeles region. The animation clearly illustrates the phenomena of rupture directivity – the strong build-up of shaking in the direction the rupture is propagating – which in this case creates very large amplitude motions in the region north of the fault. Additionally, the channeling of waves into the deep sedimentary basins in San Fernando, Los Angeles and Ventura is also quite evident. As the waves are channeled into these basins, they begin to propagate more slowly, and their amplitudes and shaking durations increase significantly.