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A comprehensive analysis of 101 major earthquakes around the Pacific ring of fire between 1990 and 2016 shows that most of the aftershock activity occurred on the margins of the areas where the faults slipped a lot during the main earthquakes. The findings support the idea that the area of large slip during a major earthquake is unlikely to rupture again for a substantial time.
The idea that earthquakes relieve stress on faults in the Earth's crust makes intuitive sense and underlies the common assumption that the portion of a fault that has just experienced an earthquake is relatively safe for some time. But not all studies have supported this, according to Thorne Lay, professor of Earth and planetary sciences at UC Santa Cruz.
Intuition - Treatments - Data - Clustering - Earthquakes
"This intuition has been challenged by statistical treatments of seismic data that indicate that, based on the clustering of earthquakes in space and time, the area that has just slipped is actually more likely to have another failure," Lay said. "The truth appears to be more nuanced. Yes, the area that slipped a lot is unlikely to slip again, as the residual stress on the fault has been lowered to well below the failure level, but the surrounding areas have been pushed toward failure in many cases, giving rise to aftershocks and the possibility of an adjacent large rupture sooner rather than later."
In the new study, published February 14 in Science Advances, Lay and other seismologists at UC Santa Cruz and Caltech took advantage of advanced slip-imaging methods applied...
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