Study: Winter snow, spring melt triggers earthquakes in CA

[rlown]

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Study: Winter snow, spring melt triggering earthquakes in California

CAROLYN WILKE | THE SACRAMENTO BEE | June 16, 2017, 10:05AM | Updated 18 minutes ago.

The Sierra Nevada and Coast ranges are pushed down by fractions of an inch each winter by the weight of rain and snow and then rise after melt and runoff, tugging on California’s earthquake faults and triggering small temblors, according to a new study by seismologists at UC Berkeley and Bowling Green State University.

The researchers traced the up-and-down motion of the earth’s crust using nine years of GPS measurements, which stresses the underlying faults by pushing and pulling on them. The study, published Thursday in Science magazine, was able to calculate how much water is stored in the ground and how this weight loss and gain stresses the faults. When the stresses change, the number of roughly 2.0 magnitude earthquakes grows, the researchers found. California experienced thousands of quakes of that magnitude last year, with most of them going unnoticed by humans.

Although the size of those quakes seems insignificant, studying them helps researchers understand the causes of earthquakes and the timing of their formation, said UC Berkeley researcher Christopher Johnson, the lead author of the paper. “We’re using all the big faults throughout the states as a giant experiment,” he said.

The Sierra Nevada saw a record snowpack this past season after four years of drought. The exact way the seasonal water cycle unleashes earthquakes differs from fault to fault, the researchers found. For instance, the weight of water on the Sierra Nevada causes the San Andreas fault to clamp together. When the water weight diminishes, the fault unclamps and causes an increase in small earthquakes in late summer and early fall.

Many small earthquakes would have occurred without the water cycle’s influence, Johnson said, but the nudges cause the earthquakes to rupture earlier than they would otherwise.

“This is a subtle push. It’s kind of like the straw that broke the camel’s back,” he said.

Paul Segall, a professor of geophysics at Stanford University, said the earthquakes caused by the phenomenon shouldn’t be a cause for worry.

“It’s an intriguing correlation, but I wouldn’t say that anybody should do anything differently,” Segall said. The threat of earthquakes in California is always present and people should be prepared, he said.

Source: http://www.pressdemocrat.com/news/71070 ... artslide=0

[Jimr]

You'd think they would mention the positive aspect of this. Stress relief from many 2.0 quakes is much better than a huge stress relief from a 6.0 or higher.

[rlown]

And that some of that is caused from lubrication by the water. Santa Rosa has been pumping water from the sewer plants for a decade or two into "The Geysers" steam/power generation station, and they are a LOT of 3.0-4.0 quakes there.

[maverick]

You'd think they would mention the positive aspect of this. Stress relief from many 2.0 quakes is much better than a huge stress relief from a 6.0 or higher.

Exactly, always trying to create drama.

[rlown]

Ok.. I'll add this tid-bit.. https://www.sciencedaily.com/releases/2 ... 142245.htm

Old but understanding what is going on is always helpful.

Point was really that there's a great pic up there for Ellery Lk. More condition info.

[maverick]

Point was really that there's a great pic up there for Ellery Lk. More condition info.

Well, you should have said so Russ.

[rlown]

A picture is worth a thousand words.. Didn't need to say anything but show the pic. I've been in earthquakes in the back country. Very interesting experience based on where you camp. One was a 4.3. Rocks were falling all night.

[Jimr]

Years ago, I remember discussions of the possibility of injecting water into key areas of the San Andreas Fault to create slippage and reduce pressure along areas of the fault zone in an attempt to keep "The Big One" at bay. One big issue arose and that was with respect to lawsuits due to damage caused by those who created the quake. Interesting theoretical approach with practical issues.

[wildhiker]

You'd think they would mention the positive aspect of this. Stress relief from many 2.0 quakes is much better than a huge stress relief from a 6.0 or higher.

Except that the magnitude scale is logarithmic, so it would take about 10,000 magnitude 2 earthquakes to release the same amount of energy as one magnitude 6 earthquake.
-Phil

[Jimr]

I understand the logarithmic Richter scale, but California averages somewhere around 10,000 quakes per year. Most of them are very small. I chose 6.0 because anything under that just doesn't seem like much. Unless, of course, you're very near the epicenter. The point being....... you know.