Though Earthquake Detection Has Improved, Gaps Remain
Just five years after statehood, Alaska endured the largest earthquake recorded in North America. The quake devastated communities around the Southcentral portion of the state, but in the years that followed it also made Alaska the epicenter of extreme seismic studies.
When the quake struck on March 27, 1964, earthquake detection was in its infancy and scientists didn’t understand much about the correlation between seismic events and tsunamis.
But, according the U.S. Geological Survey’s Peter Haeussler, a geologist noticed a particular pattern in the disaster’s aftermath, which has been the key to understanding how this type of event happens.
“As a result of this particular idea, which was brand new at the time and really quite revolutionary, we now understand that these plates are converging and coming together along the southern Alaska margin,” Haeussler said. “And this type of earthquake that occurred in 1964, we now refer to as a ‘mega thrust earthquake.’ It’s the largest type of earthquake on the planet and these are particularly devastating.”
The energy created when the tectonic plates converged was also found to be the driving force behind certain types of tsunamis – forging a scientific link between earthquakes and tsunamis for the first time.
Haeussler says this discovery gave scientists the fingerprint of the worlds-largest earthquakes.
“It occurred at a pivotal time in earth science history. It helped lead to this acceptance of this brand new theory of plate tectonics. It showed the world largest earthquakes are caused at these convergent margins where plates are coming together. It provided a mechanism for launching trans-oceanic tsunamis,” Haeussler said. “And, in many ways, all of the giant mega-thrust earthquakes are now understood in the shadow of what was learned from 1964.”
Though massive earthquakes are a relatively rare occurrence in Alaska, the ’64 quake emphasized the dire need for understanding and tracking seismic events.
“In 1964, there were two seismic stations in Alaska,” Michael West, the director of the Alaska Earthquake Center, said. “The closest one to the earthquake was in Fairbanks, and there was one in Sitka.”
Today, West says the state has around 400 seismic monitoring stations.
“About half of those are clustered on volcanoes in the Aleutians and the other half are distributed generally around the state,” he said.
West says the Earthquake Center’s ability to detect and pinpoint earthquakes varies widely depending on where in the state it occurs.
“Southcentral in sort of a triangle with Fairbanks as the apex, that area has, I think, very robust, very good monitoring,” West said. “And what that allows us to do, it allows us to detect smaller-magnitude earthquakes and it allows us to locate them with great accuracy.”
But, that’s not the case in more remote sections of the state. West says there has been an interesting sequence of five, magnitude four or larger earthquakes recently in the same spot in the Arctic National Wildlife Refuge.
“They’re quite puzzling to us and we are not able to get a good depth constraint,” West said. “So we don’t know if this is on some very shallow fault or some very deep fault; in fact we have little understanding of why they’re occurring because there’s an area up there the size of Oregon that has no instrumentation.”
Even though earthquake and tsunami science has improved by leaps and bounds in the years since the 1964 earthquake forever changed the Alaska landscape, there are still huge gaps to fill and a lot of ground to cover.