Whole lotta shakin' going on!
Sept. 23, 2013 — Don’t look now, but the earth is moving beneath our feet in Northeastern California, and there is no way to determine what the future holds because we’re in uncharted territory.
Could a big shaker be coming soon? We just can’t know that.
Chester geologist Charles Watson, who submits the weekly Earthquake Report for the Feather Publishing newspapers, said despite what you might hear on some late night radio talk shows, it’s impossible for geologists to predict earthquakes.
“You never predict in the earthquake business,” Watson said. “If anybody does predict what’s going to happen, you have to look them straight in the eye, laugh and walk away.”
Still Watson said he’s been tracking earthquakes in this part of the world for 40 years, and he’s surprised by what he sees as he follows the recent earthquake activity.
Since the moderate 5.7-magnitude Canyon Dam earthquake shook the region in late May, Watson said, “there have been a slew of aftershocks, now more than 1,000 registering 1.5 or greater,” — activity he said is much different than normal.
Luckily, he said we’re past the three-week period in which the Canyon Dam quake would have been considered a foreshock of a larger event, according to conventional geologic wisdom.
“They happen that way about 93 percent of time,” Watson said.
But he was quick to point out he didn’t want to alarm area residents because the data doesn’t mean there’s going to be another temblor.
“If I have some kind of clue, if we start getting 3s and 4s and 5s, and they’re all happening on this line, you can go, well, it looks like this is just the beginning of the end of the earth,” Watson quipped, “but you can’t say until the event actually happens that it’s going to happen. You can’t predict (an earthquake). You just can’t.”
Watson said geologists can stand up on their soapboxes and pound their chests and shout, but if they have any professionalism or common sense, they don’t.
But something is happening under ground.
“We’ve also had a number of these other activities starting to sprout up elsewhere, including in the fringes of the aftershock zone closer to Chester and closer to Greenville, and increased activity near Portola … extending southeast to Lake Tahoe, Carson City and Reno,” Watson said.
Watson said there is a very strong northeast/southwest trend, and it defines the boundary of the Sierra Nevada. Last week there was a swarm of earthquakes on the western side of the mountains near Redding in the Palo Cedro area. These earthquakes are unusual because such temblors normally are located about 20 miles beneath the surface, but these are shallower — 10 to 11 miles deep.
“That means it’s in the upper crust,” Watson said, “so something is going on with the North American continental crust.”
Having said that, Watson did not want to create alarm.
“It could be just a little flurry that gets us all excited for a couple of months and then relaxes,” Watson said, “but this is different. It’s not just aftershocks of the Canyon Dam earthquake. This is the trend that governs our seismic lives in Northeastern California. To see this much, this active, even gives me pause.”
In fact, Watson said there’s been an increase globally in the past two weeks.
Statistically, Watson said the region experiences between 10 and 20 earthquakes a week. Sometimes the activity increases and sometimes it decreases. Sometimes Lassen Peak has a swarm of earthquakes, reminding residents it erupted a little over 100 years ago.
“There are people who remember the earthquake swarms of the 1940s and 1950s at Lassen that scared these people,” Watson said, “and it’s been relatively quiet until about 1999 when it started to progressively increase. Every year it’s produced more earthquakes than it did the previous year. This went all the way to about 2009, and it stopped for some reason.”
Watson noted the activity at Lassen Peak has been absent during these recent earthquake swarms.
“Lassen (Peak, the southern most volcano in the Cascades) is the dysfunctional child on the map,” Watson said. “If something’s going on, this should be the thing that reacts to it. This whole pattern is different, which means it’s a much, much bigger tectonic framework than the background activity.”
Despite that, Watson again pointed out there’s no way to predict what might happen in the future.
“As far as earthquakes go, what you can do is look at it (the data) and make personal evaluations on what you think you should do,” Watson said. “No one has been successful — ever — in predicting earthquakes. Sometimes they may get it right just by chance, but not even the best seismic minds can figure this out. The clairvoyants don’t even get it right.”
And here’s a mindbender for you.
“We’re not even sure of the fault that created this thing,” Watson said. “The distribution of activity is such that it shows there was a major fault trend, but then there was an enormous amount of aftershock activity that occurred on perpendicular structures, and the current activity is mostly on the extreme parts of it. The stress is still not gone. It’s not like the ground is trying to find a comfortable place to rest after it shifted. It’s beyond that. The activity’s progressing northward into Chester past the (Lake Almanor) peninsula into the north arm. That wasn’t part of the aftershock zone, but it is now because there’s more activity happening up there. Could this thing get larger in the long run? Those are the questions scientists are asking … We’ve never had an earthquake like this.”
Watson pointed out there have been big earthquakes in Northeastern California in the past, including one in the Honey Lake Valley as large as 7.4 about 2,500 years ago when “white guys were running around in togas. The Bronze Age was already going by then!”
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