I got a kick out of this story. Hollister is known as “the earthquake capital of the world.” They get dozens of earthquakes every day.
The hundred or so geologists and seismologists who turned up for the informal monthly meeting of California’s Pick and Hammer Club expected an evening of socializing and routine gossip about faults, core samples and volcanoes. Instead, they heard scientific history in the making. As part of his work for the U.S. Geological Survey’s Earthquake Research Center, Seismologist Malcolm Johnston had just finished analyzing data from seven monitoring stations set up along the San Andreas Fault in the quake-prone Hollister area. His figures, Johnston told his colleagues, showed that the strength of the local magnetic field had suddenly risen between two of the stations, then gradually subsided over a period of one week. Furthermore, the surface of the earth in the same area had undergone slight but noticeable changes in tilt. Those changes, he said, were just “the sort one would expect to see before a quake.” John Healy, another USGS scientist, was even more emphatic. Johnston’s data, he said, left little doubt that Hollister could expect a moderate earthquake of up to magnitude 5 on the Richter scale.* When? “Maybe tomorrow,” said Healy.
The next afternoon, Nov. 28, 1974, while residents of Hollister were sitting down to their Thanksgiving Day dinners, the earth began to sway and rumble beneath them. The brief 1-to 2-sec. quake measured 5.2 magnitude and did little damage.