A mysterious jolt that shook residents from the San Fernando Valley to the South Bay early Thursday probably was a sonic boom and not an earthquake, scientists said.
Kate Hutton of the Caltech Seismological Laboratory said readings from a recording station on Catalina Island showed what appears to be a sonic boom. Sonic booms are explosive sounds usually caused by aircraft traveling at or above the speed of sound. They may rattle windows but do not cause damage.
"You see a wiggle on the Richter (scale) but it looks different from an earthquake," Hutton said in explaining how a sonic boom shows up on seismological instruments. The early morning jolt prompted telephone calls to authorities from nervous residents who believed a quake had hit.