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from the I'll-have-that-in-16oz-please dept.
The granite rocks, called Precariously Balanced Rocks, or PBRs, form when tectonic processes allow a big chunk of rock, tattooed with patterns of fractures, to ascend from beneath the surface of the Earth. As the rock rises, wind, water and other natural processes erode bits and pieces of it away, eventually chiseling out the remaining delicately balanced rocks, said study co-author Julian Lozos, a postdoctoral researcher at Stanford University.
PBRs typically develop over thousands or tens of thousands of years, and they can be found around the globe, including in other earthquake-prone spots in the United States and New Zealand, the researchers said. There are more than 1,200 PBRs just in California and western Nevada, they added.
In the new study, the researchers focused on PBRs that are approximately 10,000 years old, located in the middle of the San Bernardino Mountains, about 90 miles (145 km) east of Los Angeles.
Locating PBRs near active faults could help officials plan for future earthquakes. To prepare infrastructure — including the water supply, telecommunications and energy systems — in areas prone to shaking, "you would really like to have an idea of what to expect," said Lisa Grant Ludwig, lead author of the study and an expert on the San Andreas Fault at the University of California, Irvine.
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The researchers used 3D modeling to simulate how different kinds of shaking would affect various shapes and sizes of rock. Although some rocks are easily knocked over by fast, small shakes, other rocks topple to slow, big shakes, Lozos said.
The researchers in this Live Science article use PBRs to measure earthquakes. The submission title used PBRs to measure Soylent's Hipster Quotient...
(Score: 2, Interesting) by anubi on Sunday August 09 2015, @07:35AM
The main thing PBR studies bring to my mind is that the rocks, being massive as they are, would be quite sensitive to very low frequency seismic activity... like in the hertz region.
That is to say having the ground shift over by an inch over the period of a few minutes may not be detectable by human senses, but may impart enough inertial force to the rock to topple it.
PBR's aren't the only things sensitive to this, though. Tall buildings also have a long time constant. I would think laser interferometry to tops and bottoms of large buildings would deliver a wealth of seismic info. Of course you would have to account for winds and moving loads within the building, but that what DSP is for.
My guess is putting tension sensors on the guy wires supporting AM radio transmitter towers ( seems like the countryside is full of them ) would also provide a lot of seismic data as the base of the tower ( and guy wires ) are subject to ground seismic activity while the top of the tower is more of a dead weight. Again, probably have to use DSP to compensate for wind loading.
Just speculation and conjecture on how I would use existing stuff to get low frequency seismic data... I do not know if any of what I speak of is done or not.
"Prove all things; hold fast that which is good." [KJV: I Thessalonians 5:21]
(Score: 0) by Anonymous Coward on Sunday August 09 2015, @12:37PM
I love the DSP hand-waiving. All you gotta do is some DSP. You could also just use your smart phone. Just lay it on the ground and read the accelerometers to measure ground vibrations. Just use a little DSP to get rid of the background signals you don't want. Profit!
(Score: 1) by anubi on Monday August 10 2015, @08:22AM
Quite correct!
You may have to use multiple phones sampling simultaneously so your DSP can use beamforming and correlation algorithms to determine which signal is of interest and which is noise.
I believe most of us here have seen some pretty amazing things which can be done with DSP. I know I have seen stuff that simply blew me away. Recovery of signals I thought were forever buried in noise.
Ever seen a raw OTA TV signal? Especially one with multipath reflections. Or the data stream coming off of the magnetic head on a 1TB drive? I would see these and marvel how anyone could recover anything meaningful from it.
And its done. Everyday. As a mainstream technology. QAM. Transversal filters. Adaptive equalizers. Blows me away. And I thought FFT was big stuff not too long ago. I was toying with that to listen to motor bearings to see how well it correlated with prediction of bearing failure.
"Prove all things; hold fast that which is good." [KJV: I Thessalonians 5:21]