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closeDuring the past five and a half years, my hometown, Paso Robles, has moved in a northwesterly direction, compared to most of the rest of North America. We moved about 9.25 inches. Other land in this county is also shifting.
All the land that’s moving lies west of the San Andreas Fault. In fact, all the rest of California that lies west of that fault is also on the move.
It’s grinding upward along the western edge of North America at varying speeds.
How do I know Paso Robles moved about 9.25 inches? Well, teams of scientists have installed Global Positioning System devices to detect movement in the Earth’s crust. They’ve been placed mainly in Western states and Alaska.
One of the GPS devices was installed Jan. 9, 2004, on bedrock west of Paso Robles on a ranch in Adelaida. Chris Walls is regional engineer for this GPS program. He told me that device has since moved northwest about 91⁄4 inches. He also said the Paso Robles area has moved about the same.
Strangely enough, as you get closer to the San Andreas Fault, the movement gets slower. But he said when the fault finally “pops a big one,” the slower territory will catch up.
You probably know that GPS devices receive data by radio from more than 24 satellites that orbit Earth. A really high-precision GPS device can use that data to tell you exactly where on earth it is.
Some of you probably have GPS devices in your cars or cell phones. And they’re used in those ankle bracelets some paroled prisoners have to wear.
Walls works for PBO, UNAVCO Inc. PBO stands for Plate Boundary Observatory. “Plates” are what scientists call the huge chunks of Earth’s crust that slowly slide around on top of the planet’s hot, molten interior.
The San Andreas Fault is a boundary between the North American Plate and the Pacific Plate, where they grind against each other.
UNAVCO is a nonprofit corporation founded by several universities to apply GPS to earth science. It gets money from the National Science Foundation and NASA.
This current PBO project was organized about five and a half years ago. That was around the time when an earthquake on Dec. 22, 2003, took the lives of two women in Paso Robles. A PBO brochure says its first GPS station was the one installed 18 days later on the ranch in Adelaida.
Next week I’ll write more earth-shaking stuff, including the connection between that 2003 quake and the 4.4-magnitude quake we had three weeks ago.
Contact Phil Dirkx at phild2008@sbcglobal.net or 238-2372.
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