New earthquake probability model improves prediction of seismic events

Northwestern University researchers have developed a new model to help seismologists better predict when the next big earthquake will occur on a fault. The study, conducted by a team of seismologists and statisticians, aims to address the major problem of seismology: determining when to expect the next big earthquake.

Traditionally, seismologists have assumed that big earthquakes on faults are relatively regular and that the next quake will occur after approximately the same amount of time as the previous two. However, this assumption has proven to be inaccurate as earthquakes can sometimes occur sooner or later than expected.

The new model developed by the Northwestern team takes into account the specific order and timing of previous earthquakes, rather than just relying on the average time between past earthquakes to forecast the next one. This comprehensive and realistic approach helps explain why earthquakes sometimes occur in clusters, with relatively short intervals between them, separated by longer periods without earthquakes.

The researchers hope that their new model will be a useful tool for seismologists as they work to improve earthquake prediction and better prepare for future seismic events.

“Considering the full earthquake history, rather than just the average over time and the time since the last one, will help us a lot in forecasting when future earthquakes will happen,” said Seth Stein, William Deering Professor of Earth and Planetary Sciences in the Weinberg College of Arts and Sciences. “When you’re trying to figure out a team’s chances of winning a ball game, you don’t want to look only at the last game and the long-term average. Looking back over additional recent games can also be helpful. We now can do a similar thing for earthquakes.”

The study, titled “A More Realistic Earthquake Probability Model Using Long-Term Fault Memory,” was published recently in the Bulletin of the Seismological Society of America. Authors of the study are Stein, Northwestern professor Bruce D. Spencer and recent Ph.D. graduates James S. Neely and Leah Salditch. Stein is a faculty associate of Northwestern’s Institute for Policy Research (IPR), and Spencer is an IPR faculty fellow.

Learn more in Northwestern Now’s article, “Forecasting earthquakes that get off schedule.”