World's Largest Wheatstone Bridge
in [Basics]
|
From: Bret Cahill on 3 May 2010 23:01 > >> >>> String a wire back and forth across / along a fault line to measure > >> >>> very small displacements in the earth's surface. If the resistance > >> >>> and/or tensile strength needs to be higher than a common single alloy > >> >>> wire then structural steel cable could be wrapped around a insulated > >> >>> wire with a higher resistivity. It could be temperature compensated > >> >>> as usual, with another wire of the same length loosely supported > >> >>> nearby in another leg of the bridge. > >> >>> An abandoned power line may be good to go if it is properly located. > >> >>> Good info sometimes comes in small displacements. > >> >>> Bret Cahill > >> >> Two gps stations on both sides do the same trick > > >> > What's the smallest displacement -- not movement but actual change in > >> > _distance_ between two points -- they can measure? > > >> > Bret Cahill > > >> They measure continental drift with them in cm's per year.... > > >The warning might be in microns. > > >Bret Cahill > > What warning? Faults creep all the time. At constant speed? If that were true all the acceleration measurements published by USGS or Cal Tech on the web in real time would always be zero. There may be some characteristic behaviour of certain faults that could be highly reliable early warning info. > Knowing the rate of creep has > zero useful predictive value. Has this been proven over long distances measuring displacements of a few thousandths of an inch? Bret Cahill
From: Androcles on 3 May 2010 23:40 "Bret Cahill" <BretCahill(a)peoplepc.com> wrote in message news:cbd8dbe2-93eb-4ed1-ac8c-08b4e000ac69(a)11g2000prw.googlegroups.com... > > String a wire back and forth across / along a fault line to measure > > very small displacements in the earth's surface. If the resistance > > and/or tensile strength needs to be higher than a common single alloy > > wire then structural steel cable could be wrapped around a insulated > > wire with a higher resistivity. It could be temperature compensated > > as usual, with another wire of the same length loosely supported > > nearby in another leg of the bridge. > > > An abandoned power line may be good to go if it is properly located. > > > Good info sometimes comes in small displacements. > > > Bret Cahill > > 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. Tie it down every few feet. =========================================== Do manual work in a dust storm or rainstorm? That was one of your objections to laser ranging, right? 'Faced with changing one's mind, or proving that there is no need to do so, most people get busy on the proof.'- John Kenneth Galbraith 'There is nothing so easy but that it becomes difficult when you do it with reluctance.'- Marcus Tullius Cicero
From: John Larkin on 3 May 2010 23:49 On Mon, 3 May 2010 20:01:47 -0700 (PDT), Bret Cahill <BretCahill(a)peoplepc.com> wrote: >> >> >>> String a wire back and forth across / along a fault line to measure >> >> >>> very small displacements in the earth's surface. �If the resistance >> >> >>> and/or tensile strength needs to be higher than a common single alloy >> >> >>> wire then structural steel cable could be wrapped around a insulated >> >> >>> wire with a higher resistivity. �It could be temperature compensated >> >> >>> as usual, with another wire of the same length loosely supported >> >> >>> nearby in another leg of the bridge. >> >> >>> An abandoned power line may be good to go if it is properly located. >> >> >>> Good info sometimes comes in small displacements. >> >> >>> Bret Cahill >> >> >> Two gps stations on both sides do the same trick >> >> >> > What's the smallest displacement -- not movement but actual change in >> >> > _distance_ between two points -- they can measure? >> >> >> > Bret Cahill >> >> >> They measure continental drift with them in cm's per year.... >> >> >The warning might be in microns. >> >> >Bret Cahill >> >> What warning? Faults creep all the time. > >At constant speed? > >If that were true all the acceleration measurements published by USGS >or Cal Tech on the web in real time would always be zero. > >There may be some characteristic behaviour of certain faults that >could be highly reliable early warning info. > >> Knowing the rate of creep has >> zero useful predictive value. > >Has this been proven over long distances measuring displacements of a >few thousandths of an inch? > > >Bret Cahill Nobody is making useful earthquake predictions. It's probably impossible. A superficial surface measurement is obviously insufficient to understand an immensely complex and chaotic subsurface 3D system. John
From: Bret Cahill on 4 May 2010 00:02 > >> >> >>> String a wire back and forth across / along a fault line to measure > >> >> >>> very small displacements in the earth's surface. If the resistance > >> >> >>> and/or tensile strength needs to be higher than a common single alloy > >> >> >>> wire then structural steel cable could be wrapped around a insulated > >> >> >>> wire with a higher resistivity. It could be temperature compensated > >> >> >>> as usual, with another wire of the same length loosely supported > >> >> >>> nearby in another leg of the bridge. > >> >> >>> An abandoned power line may be good to go if it is properly located. > >> >> >>> Good info sometimes comes in small displacements. > >> >> >>> Bret Cahill > >> >> >> Two gps stations on both sides do the same trick > > >> >> > What's the smallest displacement -- not movement but actual change in > >> >> > _distance_ between two points -- they can measure? > > >> >> > Bret Cahill > > >> >> They measure continental drift with them in cm's per year.... > > >> >The warning might be in microns. > > >> >Bret Cahill > > >> What warning? Faults creep all the time. > > >At constant speed? > > >If that were true all the acceleration measurements published by USGS > >or Cal Tech on the web in real time would always be zero. > > >There may be some characteristic behaviour of certain faults that > >could be highly reliable early warning info. > > >> Knowing the rate of creep has > >> zero useful predictive value. > > >Has this been proven over long distances measuring displacements of a > >few thousandths of an inch? > > >Bret Cahill > > Nobody is making useful earthquake predictions. That's the problem. > It's probably > impossible. That may very well be somewhat true. > A superficial surface measurement is obviously > insufficient to understand an immensely complex and chaotic subsurface > 3D system. Maybe. Probably. But why leave any stone unturned when _my_ safety is at stake? Bret Cahill
From: Bret Cahill on 4 May 2010 00:16
> String a wire back and forth across / along a fault line to measure > very small displacements in the earth's surface. If the resistance > and/or tensile strength needs to be higher than a common single alloy > wire then structural steel cable could be wrapped around a insulated > wire with a higher resistivity. It could be temperature compensated > as usual, with another wire of the same length loosely supported > nearby in another leg of the bridge. > > An abandoned power line may be good to go if it is properly located. > > Good info sometimes comes in small displacements. > > Bret Cahill The problem is just to the East of Laguna Salada: http://maps.google.com/maps?f=q&hl=en&q=32.2006,-115.4625(M3.0+-+Baja+California,+Mexico+-+2010+May+04+02:35:27+UTC)&t=h&z=9&iwloc=A String a thin steel wire from Aqua Matias to Cucapa returning with a larger diameter copper wire with a resistance << than the steel. All those << M 1.0 movements can now be documented and studied. Bret Cahill |