Calculations run on supercomputers show that deep sedimentary basins, such as those in the greater Los Angeles area, receive greater shaking than standard methods predict. This visualization, courtesy of Amit Chourasia, San Diego Supercomputer Center, depicts a magnitude-8 earthquake in the northern San Andreas Fault. Seismic waves propagate from the epicenter and move toward population centers built on basins in Southern California, with peaks representing shaking severity. Researchers hope that realistic simulations can improve building safety, hazard policies and emergency planning.