For more than a century, a guiding principle in seismology has been that earthquakes recur at semi-regular intervals according to a “seismic cycle.”
For more than a century, a guiding principle in seismology has been that earthquakes recur at semi-regular intervals according to a “seismic cycle.” In this model, strain that gradually accumulates along a locked fault is completely released in a large earthquake. Recently, however, seismologists have realized that earthquakes often occur in clusters separated by gaps, and one research group now argues that the probability of a tremor’s recurrence depends upon whether a cluster is ongoing—or over.
On Monday, 23 Sept. 2019, at the GSA Annual Meeting in Phoenix, Seth Stein, the Deering Professor of Geological Sciences at Northwestern University, will present a new model that he and his co-authors believe better explains the complexity of the “supercycles” that have been observed in long-term earthquake records. “One way to think about this is that faults have hot streaks—earthquake clusters—as well as slumps—earthquake gaps—just like sports teams,” says Stein.
In the traditional concept of the seismic cycle, Stein explains, the likelihood of a large earthquake depends solely upon the amount of time that has elapsed since the most recent large tremor reset the system. In this simple case, he says, the fault has only a “short-term memory.”
“The only thing that matters,” says Stein, “is when the last big earthquake was. The clock is reset every time there’s a big event.”
Read more at Geological Society of America
Image: The ancient Israeli city of Susita was destroyed in 749 AD. Fallen columns all pointing in the same direction indicate the damage was due to an earthquake on the Dead Sea transform fault. The earthquake history on this fault is one of the world's longest. (Credit: Seth Stein)
