World's Largest Wheatstone Bridge

Typical Cahill comic book nonsense.

Two gps stations on both sides do the same trick

You cannot get a good enought temperature (and other factors) compensation with such a setup. A bird sitting on the wire would trigger a massive earthquake alarm, and the evacuation of San Francisco and Los Angeles and every clay hut in between, for example.

Sorry Bret, to disappoint you.

w.

What's the smallest displacement -- not movement but actual change in _distance_ between two points -- they can measure?

Bret Cahill

Compensation for temp. and other factors is easy: Just loosely wrap another identical wire around the taught wire and shield and insulate it for another leg of the bridge.

They may have to use fake owls or bury it underground.

isco and Los Angeles and every

The data wouldn't be made available to the general public until after it was studied and determined to be useful in predicting earthquakes.

Supposing 95% of a certain kind of fault line gives some kind of micro displacement warning an hour or so in advance of an M 8.0?

Wouldn't that be worth an investigation?

The World's Largest Strain Gage might turn out to be pretty cost effective at saving lives and property.

Bret Cahill

Wind.

Yet more silly, comic book engineering to solve a problem solved a long time ago.

The challenge to monitoring such stuff isn't an engineering problem, it is an economic problem.

They measure continental drift with them in cm's per year....

Use a laser and a mirror.

They already measure the distance from earth to the moon that way to a few cm.

What you are trying to make is a strain gauge. This scheme wont work because the gauge has to be attached to the substrate along it's whole length not just strung up like a power line. But attaching it to the earth in any meaningful way over distance would be next to impossible. Yes, you can compensate for the temperature coefficient of resistance but how do you compensate for the change in length due to temperature, coefficient of expansion, a very different animal. I can't see a strain gauge being a solution for seismic motions.

The best way is a laser interferometer for small displacements and GPS or gross measurements. Only two points need to be attached to the earth with these schemes.

Differential GPS and laser rangefinders make a lot more sense.

John

Sense? You're talking to Cahill, here.

oh. sorrreee.

John

And still, sensing the earth shake, doesn't tell you ... . .??? there is all sorts of low level shaking going on. How many 5.0 earth quakes per year? And how big is the shake from a 18 wheel semi going by your site.. or logging going on near by....(tale from Ligo)

George H.

The warning might be in microns.

Bret Cahill

AKA: The world's biggest loaded dummy.

use

Tie it down every few feet.

If you know the coefficient of expansion then you can correct for it, either mechanically or later in the calculations.

Is there any other way to measure very low frequency / very small displacements?

What's the accuracy?

Bret Cahill

Laser rangefinders can work over dozens to hundreds of miles in a dust storm or rainstorm?

To the nearest few microns?

Bret Cahill

What warning? Faults creep all the time. Knowing the rate of creep has zero useful predictive value.

John