Tsunamis and earthquakes*

Summary Tsunamis (“tidal waves,” “maremotos”) may be produced by submarine volcanic eruptions, submarine slides started by earthquakes, submarine faulting, and atmospheric conditions. The hypothesis that at least some of the largest tsunamis have been produced by submarine slides with earthquake waves as a trigger force has been advanced by a notable number of those seismologists who have studied tsunamis. The macroseismic as well as the microseismic data of the Atacama earthquake of November 11, 1922, indicate clearly that the fault movement occurred inland; the tsunamis originated from a submarine slide near a relatively feebly shaken stretch of the coast where the surface slopes steeply to a considerable depth. On gently sloping coasts, such as those of California, large tsunamis are rare and the relatively small tsunamis there are probably produced by faulting at the bottom of the ocean.