Lompoc Earthquake – California – November 4, 1927

All places within fifty miles of Lompoc suffered damage and a tsunami from the earthquake was recorded on the tidal gauges at San Francisco and San Diego.

An area offshore, west of Lompoc, California, experienced an earthquake of magnitude 7.1 on November 4, 1927. The most severe damage occurred north and west of Lompoc. Chimneys were wrecked in several towns in these areas, including Guadalupe and Arroyo Grande, all places within fifty miles of Lompoc.

There were sand craters and cracks in numerous buildings where water-soaked soil had weakened foundations. The Southern Pacific Railroad tracks, running close to the coast west of Lompoc and near Vandenberg Air Force Base, were thrown out of alignment. A tsunami from this earthquake was recorded on the tide gages at San Francisco and San Diego.

Late in the morning of November 4, the captain of a ship at sea a few miles west of Point Arguello was startled to discover great quantities of dead or stunned fish floating on the surface of the ocean. He was unaware that he was viewing the aftermath of an earthquake that had struck underneath him a few hours earlier that day. Other signs of trouble had come an hour after midnight on the fourth when residents of a coastal community were awakened. Others soon followed because of the strength of the earthquake, powerful enough to awaken most of the inhabitants of Lompoc. Several other ships at sea were shaken.

At the Roberds Ranch southwest of Lompoc ten to twenty sand blows appeared. These sand blows occur when shaking from an earthquake causes the pore pressure of water trapped between sand particles to suddenly increase. The result is a fountain of water and sand coming straight out of the earth. The Lompoc office of the Los Angeles National Trust building had all of its furniture and equipment broken and scattered around the rooms. Hundreds of residents of Lompoc, probably recalling the recent earthquake damage in downtown Santa Barbara, hurried to downtown Lompoc to check on buildings.

This was one of the largest Californian earthquakes of the twentieth century and a great deal of interest persisted about it for a long time, particularly questions concerning its epicenter. The quest for this location was heightened because the earthquake was the third largest occurring offshore of California since 1900 and because, over the years, many questions remained unanswered about the earthquakes and tsunamis that had been reported from areas offshore from coastal locations around Santa Barbara.

Some indications of the range of opinions about the Lompoc epicenter were documented in 1977, fifty years after the earthquake, each no doubt influenced by the growing body of information and technological expertise that had accumulated over the years. The earliest estimate had placed the epicenter more than forty miles west of Point Arguello and others had followed with a range of alternatives closer to the coast. Still later reassessments of the epicenter placed them along a fault, defined as the Hosgri Fault, stretching for a hundred miles along the coast but with ruptures that may have triggered earthquakes farther west of the defined fault.