Elaine Meinel Supkis
The latest earthquake to strike the US is, like most of them, associated with the Juan de Fuca plate. This one is the biggest so far and was very near to Mt. Shasta, an active volcano of the Cascades system. There are no fault lines near where this latest shake occurred. But if we look at earthquake maps, we can see clearly over time that the quakes are growing rapidly in number and violence. The section of the San Andreas between LA and San Jose is nearly totally frozen and doesn't even have micro shakes: a very bad sign. The Juan de Fuca plate is directly responsible for volcanic activity as well as a springboard for great quakes to the south. Also, the hinge between North and South America has been hammered by significant but sub-7.0 mag quakes this past month. The chances of a major event rises.
A moderate earthquake has hit a mountainous region of Northern California. There are no immediate reports or injury or damage.
The U.S. Geological Survey says a magnitude-5.2 temblor struck at 8:03 p.m., centered about 11 miles southeast of the town of Willow Creek in the Shasta-Trinity National Forest.
Shasta County Sheriff's Detective Mark Haslam says the department has received no calls about the earthquake.
The fact that this happened where there are no faults is problematic. I suspect the stresses caused by the North American plate overriding the Juan de Fuca plate is causing these things to jerk violently. Even if we see the Juan de Fuca plate going under at the subduction zone where the plates meet, the plate going under doesn't vanish, it actually probably folds and flops under the continental plate. It trails downwards through the mantle according to recent research. This under-the-continent folding process destabilizes the geology of the continent and thus, we get volcanoes. I suppose this is due to the folds causing flexing below the 10 km level of the continent and the fissures and cracks created by this opens up space for lava to gush out. This is due to a classic 'between a hot mantle and a hot ocean plate' situation.
Volcanoes have this habit of snoozing for long, long times. Then, they shake and rattle. Sometimes this fades. But all too often, it ends with a loud roar or a terrible blast. Some of the richest lands are around volcanoes which process new mineral wealth into the continental plates or onto islands. But the turnover in life forms is severe. Everything is destroyed and then life creeps back in, bit by bit.
I went to Mount St. Helen's two years after the eruption there. The landscape was as barren as Antarctica and just as dazzlingly white. Today, trees and animals have slowly returned and will build their lives there until they are all wiped out yet again.
The coast adjacent to the Juan de Fuca plate is scoured of all life, too, regularly. These tsunamis are caused by underwater changes in the landscape as the North American continent lurches over the plate being squeezed ruthlessly by the Pacific plate which is being shove northwards by an out of control Australian/Indian plate. Even as the Indian half slows down as it plows into Asia, Australia is still shooting forwards faster than any plate on earth, by far.
“It was sort of like a sonic boom,” said Brenda Simmons of SkyCrest Lake resort in Burnt Ranch. “It was a very loud noise before the house started shaking. It was pretty scary, the biggest thing I’ve ever felt here. (It) lasted 10 seconds max. I didn’t feel the aftershock.”
I have been in quakes before and never heard any 'boom' sounds. I wonder about this. It wasn't a quake due to two plates grinding on each other. This was more like the New Madrid Quake where people reported loud booms like distant cannon fire. I wonder if this is due to a drum-like effect of the earth rising and falling? Interesting subject.
Our studies tell us a lot about how Mount Shasta has behaved in the past, going back as far as an older volcano that was destroyed by an enormous landslide about 300,000 years ago and coming up to our own experiences of recent debris flows. Have we come to some conclusions about whether Mount Shasta is dangerous? Yes, we have.
It seems fair to assume that Mount Shasta's most likely future activity will be similar to its past behavior. We know that it has undergone periods of major cone building; these were periods of nearly continuous lava-flow eruptions and associated explosive and other disruptive events that lasted for centuries or millennia. If some of these events were to occur in the future, they are likely to affect nearby communities, air routes and other transportation corridors in the area, and rivers that head on the volcano. Clearly, future eruptions pose a potential danger to people. We also know the volcano generates debris flows every now and then and these are capable of causing serious damage along streams draining the volcano even without an eruption. At the same time, we think that repetition of the most drastic past event that we know about—a catastrophic landslide that destroyed ancestral Mount Shasta—while possible, is rather unlikely.
Finally, we know that Mount Shasta is an active volcano—it erupted only about 200 years ago and has erupted many times in the past few thousand years. According to our studies, the volcano has erupted on average at least once every 600 years in the past 4,500 years. With such an active record of recent volcanism, we have every reason to think it will erupt again.
When Mt. St. Helen's blew up, the geological survey didn't take it all too seriously until much too late. The State of Washington was furious when the geologists tried to remove park visitors. Quite a few tourists died when this one blew up. Not to mention, scientists. These volcanoes are not like Iceland or Hawaii, these tend to blow their tops.
This is a map of California and Nevada, screen shot taken today. I have watched this map for several years. I have not seen, even ONCE, so many micro quakes at once, across the entire region! Not even close! Nevada is shivering as if this is January and the top and bottom of the San Andreas is trembling like an aspen in a violent windstorm. Seen close up or from afar, it is striking how shaky things are this month.
2.0 2008/04/29 22:08:14 40.875N 123.445W 17.3 21 km (13 mi) E of Willow Creek, CA
2.4 2008/04/29 20:54:38 40.838N 123.490W 26.3 18 km (11 mi) ESE of Willow Creek, CA
2.0 2008/04/29 20:08:05 40.899N 123.390W 5.0 25 km (16 mi) E of Willow Creek, CA
5.2 2008/04/29 20:03:06 40.837N 123.499W 28.5 18 km (11 mi) ESE of Willow Creek, CA
Here is a close up of the latest quake as well as the data. These quakes are all at the very dangerous 10 km level. There is no evading this fact: the biggest quakes are generated at this vital level!
We can see from the bigger planetary map, the Aleutian Islands have had some major quakes. And all of Asia has been incredibly active since the Boxing Day Great Quake.
And this map shows how the quakes are creeping northwards from Panama. Geologists are finally beginning to issue some warnings. But as usual, California is snoozing and won't wake up unless Mother Nature gives us a huge shaking. And we know that this usually happens at a bad time. If we think we are seeing housing problems now, just wait until a quake renders a huge number of homes worthless! And in the most expensive sector of the US economy outside of Manhattan's Tri State Region and DC!