Tiny, deep earthquakes under Washington less powerful than before, scientists saySEATTLE — The rash of tiny, deep earthquakes doesn't predict earthquake risk in Seattle. But this time they are less robust and scientists want to know why.
First discovered by Japanese scientists, these so-called "silent earthquakes" are deep tremors around the earthquake prone Pacific Rim. A little over 20 years ago, we didn't know they existed.
"Every 14 months for 20 years, we've been seeing regular clockwork events," said Harold Tobin, Washington state's seismologist and head of the Pacific Northwest Seismic Network based at the University of Washington.
Tobin said they've noticed an interesting shift in this batch of silent earthquakes. The change this time is that the pattern of deep earthquakes is not as robust as other events which have been watched since the late 1990s.
"We don't know if that's a major change, or [if] the next one will cycle back to the normal pattern," he said.
Scientists have only known about the quakes for 20 years, yet we know subduction and the drift of continental plates has gone on for billions of years. In that context, the last two decades are a mere peek into a much, much longer time horizon.
"This is a deviation from that pattern," said Tobin. "I can't draw any conclusion from that until we learn more."
The same plate that makes for interesting science 40 miles underground, is connected to a system where the upper plate can lead to the world's biggest earthquakes. When those magnitude 8.0-9.0 earthquakes are triggered, massive tsunamis follow. Such was the case in northeastern Japan in Marcy of 2011, when an estimated 16,000 people were killed, mostly by the tsunami waves, Japanese authorities said.
[
link to www.king5.com (secure)]
~*Ride the Wave*~