~By Quinn Bender
A magnitude 6.0 tremor in late January near Craig, AK, was just one of tens-of-thousands of aftershocks that researchers are monitoring as part of a new scientific study to better assess the likelihood of where the next earthquake will strike, and with what force.
Dr. John Cassidy, an expert in earthquake seismology with Natural Resources Canada, has zeroed in on the rare research opportunity to study two powerful temblors that struck just 70 days and 300 kilometres apart—a 7.7-magnitude earthquake near Haida Gwaii last October, and the 7.5-magnitude earthquake Jan. 4 off the coast of Alaska. One of the research goals is to determine whether these two events are somehow related.
“You don’t know if it will be some amazing new discovery,” said Cassidy, “or some run of the mill thing. That’s just the nature of research.”
Additional instruments have been installed on Haida Gwaii to measure surface movements from the smaller aftershocks to get an accurate picture of the seismic fault and how it slipped. For the past month newly-placed instruments on the sea floor have also been collecting data, which will help determine whether the quakes have added pressure to the fault.
“The goal of the monitoring and the research is to understand where earthquakes are more likely to occur in the future, how the ground will shake and for how long you can expect it to shake,” he said.
Cassidy confirmed there has been more seismic activity than usual in the region, but it’s mostly attributable to aftershocks rather than new earthquakes.
The 6.0 aftershock last week occurred at almost the precise location as the 7.5 quake in January. It struck shortly before 1 a.m. Jan. 31, roughly 100 kilometres west of Craig, AK, and 10 kilometres beneath the surface. There were no reports of damage and the United States Geological Survey stated there was no danger of a tsunami. Cassidy said aftershocks like this are finally subsiding and should cease within four weeks.
“Haida Gwaii has seen almost non-stop shaking for months. A lot of those wouldn’t be felt, but there have been a number of four- and five-magnitude aftershocks for the first few weeks or month that people would have felt every few days. Very, very frightening for the people there.
“And now after the 7.5 earthquake in Alaska, many of those aftershocks have been felt on Northern Haida Gwaii—Masset. so they’re now feeling aftershocks from the South and the North.”
Since October’s earthquake, Haida Gwaii has experienced more than 40,000 aftershocks.
“All of that information will help us be able to better model tsunamis and predict tsunami effects, to what controls earthquakes and where we can expect them in the future,” Cassidy said.
“What we learn from Haida Gwaii… will help us better calibrate our models so we can be better prepared.”
Following a peer review from seismologists around the world, Cassidy hopes to publish the results of his research in the next few months.