Forecasting the future
Goldfinger and his colleagues have evidence that the Cascadia Subduction Zone, which stretches from Northern California to British Columbia, is also in the middle of an earthquake supercycle.
Over the past 10,000 years, 19 superquakes and four supercycles have occurred along the zone, Goldfinger said.
"These would typically be of a magnitude from about 8.7 to 9.2, really huge earthquakes," Goldfinger said. "We've also determined that there have been 22 additional earthquakes that involved just the southern end of the fault. We are assuming that these are slightly smaller, more like 8.0, but not necessarily. They were still very large earthquakes that if they happened today could have a devastating impact," he said.
The present cycle seems like it's gently ratcheting downward, Goldfinger said. "This would suggest that we're not due for a giant anytime soon, but the model has no predictive value," he said.
The battery model of earthquake energy storage and discharge makes it difficult for scientists to forecast future earthquakes, as there's no explanation yet for why faults would behave this way, Goldfinger said. Plus, it's hard to say how much energy a fault's battery stores. "We haven't yet figured out how to effectively put a voltmeter on a fault and say how charged it is," Goldfinger said.