What Does an Earthquake Sound Like?

In 1953, audio engineer Emory Cook released a unique album titled Out of this World. Upon playing it, listeners heard a reverberating boom and a narrator informing them: “This is a record of actual earthquakes.” Narration continued over a strange soundscape, explaining how tapes of earthquakes were sped up to make them audible. Those tapes came from the experiments of Victor Hugo Benioff, a seismologist who helped bring both seismological and musical instruments into the electronic age.

According to historian Matthias Dörries, these projects were deeply intertwined. Benioff had started in astronomy in 1917, working at both the Mount Wilson and Lick observatories. During downtime, Benioff practiced violin and tried to reconcile his love of music with his understanding of science.

Over the next couple of decades, Pasadena became “a major worldwide center for geophysical research,” Dörries explains. By 1926, Caltech was running the Seismo Lab with the Carnegie Institution, where seismologists like Beno Gutenberg and Charles Richter would deepen our understanding of earthquakes. Benioff began work in seismology at Caltech in 1924.

While Gutenberg and Richter focused primarily on theory, Benioff concentrated on instrumentation. At the time, seismometers primarily used weighted pendulums connected to pens or light beams that recorded vibrations on photosensitive paper. But these instruments had limited sensitivity.

Benioff began to experiment with electromechanical sensors, using a suspended weight connected to a transducer and a galvanometer. Then, in 1932, Benioff invented a new way of listening to the Earth: the strain seismometer. Dörries describes the first instrument, installed “in the basement of the laboratory in the San Rafael Hills, with piers firmly fixed to the granite underneath the laboratory and cemented in with concrete.” The piers were 24 meters apart, with an iron pipe between them.

Benioff left a tiny gap between one of the piers and the pipe. As vibrations and other changes in the Earth altered the size of the gap, Benioff recorded the changes with a transducer. Greater sensitivity meant the instruments picked up other sources of vibration and strain: ocean surf, storms, traffic, and even sunrises.