Universal marketed Earthquake as more than a movie by making the theater itself part of the disaster. Its Sensurround system used enormous Cerwin-Vega speakers and BGW amplifiers to produce sub-audible infrasonic waves at roughly 120 decibels, creating a physical rumble that audiences could feel in their seats. During testing at Grauman's Chinese Theatre in Hollywood, the vibrations reportedly cracked plaster in the ceiling. The damage became an awkward publicity and engineering problem when the same theater was selected to premiere the film: a newly installed net was placed over the audience to catch any falling material. The stunt was not simply an advertising legend; Sensurround was a real theatrical system and was subsequently used for Midway, Rollercoaster, and Battlestar Galactica. Its legacy was an early example of Hollywood attempting to turn exhibition technology into a physical attraction, even when the effect threatened to damage the venue presenting it.
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