Instances of normal intervals between earthquakes of comparable magnitudes have been noted somewhere else, including Hawaii, but these are the exception, not the rule. Way more often, reoccurrence intervals are given as averages with large margins of error. For areas vulnerable to large earthquakes, these intervals might be on the size of lots of of years, with uncertainty bars that also span lots of of years. Clearly, this approach to forecasting is removed from a precise science.
Tom Heaton, a geophysicist at Caltech and a former senior scientist on the USGS, is skeptical that we are going to ever have the option to predict earthquakes. He treats them largely as stochastic processes, meaning we are able to attach probabilities to events, but we are able to’t forecast them with any accuracy.
“By way of physics, it’s a chaotic system,” Heaton says. Underlying all of it is important evidence that Earth’s behavior is ordered and deterministic. But without good knowledge of what’s happening under the bottom, it’s unattainable to intuit any sense of that order. “Sometimes if you say the word ‘chaos,’ people think [you] mean it’s a random system,” he says. “Chaotic implies that it’s so complicated you can not make predictions.”
But as scientists’ understanding of what’s happening inside Earth’s crust evolves and their tools turn out to be more advanced, it’s not unreasonable to expect that their ability to make predictions will improve.
Slow shakes
Given how little we are able to quantify about what’s occurring within the planet’s interior, it is sensible that earthquake prediction has long seemed out of the query. But within the early 2000s, two discoveries began to open up the chance.
First, seismologists discovered a wierd, low-amplitude seismic signal in a tectonic region of southwest Japan. It will last from hours as much as several weeks and occurred at somewhat regular intervals; it wasn’t like anything they’d seen before. They called it tectonic tremor.
Meanwhile, geodesists studying the Cascadia subduction zone, an enormous stretch off the coast of the US Pacific Northwest where one plate is diving under one other, found evidence of times when a part of the crust slowly moved in the other of its usual direction. This phenomenon, dubbed a slow slip event, happened in a skinny section of Earth’s crust positioned beneath the zone that produces regular earthquakes, where higher temperatures and pressures have more impact on the behavior of the rocks and the best way they interact.
The scientists studying Cascadia also observed the identical form of signal that had been present in Japan and determined that it was occurring at the identical time and in the identical place as these slow slip events. A latest variety of earthquake had been discovered. Like regular earthquakes, these transient events—slow earthquakes—redistribute stress within the crust, but they’ll happen over every kind of time scales, from seconds to years. In some cases, as in Cascadia, they occur usually, but in other areas they’re isolated incidents.
