New Underground Map of the Los Angeles Region Tracks Seismic Shaking

In computer simulations of The Big One—a large magnitude earthquake that may occur along the San Andreas Fault in California—seismic waves ripple from a magnitude 7.8 epicenter near the Salton Sea up into the Los Angeles Basin. For minutes in this simulation, the ground beneath downtown Los Angeles shakes like Jell-O because the region is built upon a deep basin of soft sediments, which can amplify seismic waves. The structure and composition of the ground make a large impact on the strength of seismic shaking and whether it is felt as a quick jolt or a long reverberation.