Experts plumb depths for earthquake clues
New research focused off the West Coast of North America is giving seismologists a better understanding of what one scientist describes as “the single greatest geophysical hazard to the continental United States.”
Zach Eilon, a geophysicist at the University of California Santa Barbara, has developed a new method that uses an array of scientific instruments spread across the sea floor to measure shock waves that travel through the planet’s crust.
The waves, which are called attenuation, provide clues about rock temperatures deep below the surface of the Earth, which is important for understanding the friction that builds up between tectonic plates as they rub against one another, he said. The amount of friction affects the size of an earthquake created when the plates give way, as well as the destructiveness of an accompanying tsunami.
Eilon’s research targets the Juan de Fuca plate, which runs several hundred kilometres off the coast between southern B.C. and Northern California, and is the youngest and smallest of the planet’s 13 major tectonic plates.
The collision zone in this region has the potential to generate massive quakes and destructive tsunamis, which occur when the plates overcome friction and slip past one another, quickly displacing huge amounts of water.
His data suggests the interior of the Juan de Fuca plate is cooler than previously believed, meaning the edge that is being pushed westward below the North American plate is able to bring with it more water. The water acts as a lubricant and increases the likelihood of the slipping that leads to a quake.
Geoff Abers, an earth-sciences professor at Cornell University who co-authored the paper with Eilon, said improvements in sea-floor technology and the sheer number of sensors that were deployed make this project the first time researchers have been able to study an entire tectonic plate in the ocean.
“We’re not directly looking at the big-earthquake cycle, but we’re looking at the broader, theoretical framework for how the Earth works and getting a much better handle on that,” Abers said. “The relevance is it helps us calibrate a lot of the models that we have.”
The work, which was published in the journal Science Advances, will help with more accurate seismic modelling and improves hazard assessment and emergency preparedness.
West Coast residents have long been warned about the threat of a large quake, which scientists have been forecasting for decades.