Paleoseismology: Why can't earthquakes keep on schedule?

Robert S. Yeats

Published September 2007, SCEC Contribution #1140

Our neighbors and the media ask us when the next large earthquake is due. In our response, we follow Shakespeare: “what's past is prologue.” But projecting the past into the future is tricky because earthquakes, unlike tides and Halley's comet, don't follow a regular schedule, as shown by 1) the earliest multiple-event paleoseismological studies at Pallett Creek on the San Andreas fault (Sieh, 1978), 2) trenching studies on the Wasatch fault (Machette et al., 1992) and elsewhere, and 3) analysis of a 50,000-yr-long record of lake sediments in the Dead Sea graben (Marco et al., 1996). Lack of periodic behavior in earthquakes should not surprise us because Earth's crust is complicated, with many unknowns at depths where we cannot observe directly. But, like volcanism and changes in sea level, there ought to be broad geological patterns that can help us improve our ability to assess seismic hazards.

Citation
Yeats, R. S. (2007). Paleoseismology: Why can't earthquakes keep on schedule?. Geology, 35(9), 863-864. doi: 10.1130/focus092007.1.