EarthquakesAfter the Big One: Understanding aftershock risk
In early September 2018, a powerful earthquake on the island of Hokkaido in northern Japan triggered landslides, toppled buildings, cut power, halted industry, killed more than 40 people and injured hundreds. The national meteorological agency warned that aftershocks could strike for up to a week following the main event. “A large earthquake will typically have thousands of aftershocks,” said Stanford University’s Gregory Beroza. “We know that a big earthquake changes something in Earth’s crust that causes these aftershocks to happen.”
In early September 2018, a powerful earthquake on the island of Hokkaido in northern Japan triggered landslides, toppled buildings, cut power, halted industry, killed more than 40 people and injured hundreds. The national meteorological agency warned that aftershocks could strike for up to a week following the main event.
“A large earthquake will typically have thousands of aftershocks,” said Gregory Beroza, the Wayne Loel Professor of geophysics in the School of Earth, Energy & Environmental Sciences (Stanford Earth) at Stanford University, and co-director of the Stanford Center for Induced and Triggered Seismicity (SCITS). “We know that a big earthquake changes something in Earth’s crust that causes these aftershocks to happen.”
The rarity of big quakes, however, makes it difficult to document and statistically model how large earthquakes interact with each other in space and time. Aftershocks could offer a workaround. “Aftershocks occur by the same mechanism, on the same geological faults and under the same conditions as other earthquakes,” Beroza explained in a recent article in the journal Nature. As a result, interactions between the largest earthquake in a sequence, known as a mainshock, and its aftershocks may hold clues to earthquake interactions more broadly, helping to explain how changes on a fault induced by one earthquake may affect the potential site of another.
Beroza, in a conversation with Josie Garthwaite, associate director of communications at Stanford University, discusses the culprits behind destructive aftershocks and how scientists forecast them; why scientists are harnessing artificial intelligence to gain new insights into earthquake risks and build better models for the future.
Josie Garthwaite: What are the current methods for predicting foreshocks and where do they fall short?
Gregory Beroza: When a large earthquake slips, that changes the forces throughout the Earth’s crust nearby. It’s thought that this stress change is most responsible for triggering aftershocks. The stress is what drives earthquakes.
