Term
| as wavelength goes up, the signal's ability to penetrate the ground _____, and resolution _____ |
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Definition
| as wavelength goes up, the signal goes deeper, and resolution goes down |
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Term
| as wavelength goes down, depth of signal _____, and resolution _____ |
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Definition
| as wavelength goes down, the signal can't go as deep, but resolution goes up |
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Term
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Definition
| units of conductivity are 1/ohm |
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Term
| most rocks are poor conductors, so current is carried by ____ |
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Definition
| most rocks are poor conductors, so current is carried by fluids in pore water |
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Term
| most rocks are poor conductors, so _____ is carried by fluids in pore water |
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Definition
| most rocks are poor conductors, so current is carried by fluids in pore waters |
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Term
| in electrical surverys, low frequencies measure _____, while high frequencies measure _____ |
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Definition
| in electrical surveys, low frequencies measure conductivity while high frequencies measure dielectric constants |
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Term
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Definition
Archie's Law is
formation factor = F= (resistivity of rock)/(resistivity of pore water) = aΦ-m
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Term
| in Archie's Law, what does each symbol mean? |
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Definition
in Archie's Law, formation factor = a*Φ-m
Φ is porosity. "a" and "m" are dependent on lithology |
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Term
| when we say "high frequencies" of electronic surveys, what range of frequencies are we talking about? |
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Definition
| when we say "high frequency" for electronic surveys, we are looking at 10-1000 MHz |
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Term
| the goal of examining dielectric properties |
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Definition
| the goal of examining dielectric properties is to establish a relationship between physical properties of a layer and the radar wave velocity in that layer |
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Term
| what is dielectric permittivity the same as? |
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Definition
| dielectric permittivity is the same as dielectric constant |
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Term
| dielectric constant is a measure of what? |
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Definition
| dielectric constant is the measure of a material's ability to hold a charge |
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Term
| dielectric permittivity has units of what? |
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Definition
| dielectric permittivity has units of farads. A farad is a measure of capacitiance. Capacitance is how much electric potential it takes to acheive one unit of charge. Or how much charge results from one unit of electric potential. |
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Term
| what property of materials relates how much electric potential leads to how much charge? |
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Definition
| dielectric permittivity aka dielectric constant aka relative permittivity is the property that has units of farads that relates how much electric potential leads to how much charge |
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Term
| if a material has a dielectric permittivity of one farad, what does that mean? |
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Definition
| if one volt (unit of electric potential) results in one columb (unit of charge) then a material has a dielectric permittivity of one farad |
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Term
| magnetic permittivity is a measure of what? |
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Definition
| magnetic permittivity is a measure of how much a material gets magnetized when it is placed in a magnetic field |
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Term
| what property of matierals has units of Henrey's? |
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Definition
| magnetic permittivity has units of Henreys |
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Term
| what are units of magnetic permittivity |
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Definition
| the units of magnetic permittivity are Henrey's |
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Term
| in a vaccum, radar waves move as fast as ____ |
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Definition
| in a vaccum, radar waves move as fast as the speed of light |
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Term
| what is the equation for radar wave velocity? |
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Definition
the equation for radar wave velocity is
V= c/(square root of (εr*μr))
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Term
| what is the skin depth equation? |
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Definition
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Term
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Definition
| skin depth is the depth that waves will travel in a given rock |
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Term
| the thing about GPR is that the _____ are much higher, so the ____ are much _____. |
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Definition
| the thing about GPR is that the velocities are much higher, so the wavelengths are much shorter |
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Term
I do GPR and acoustic surveys in a granite layer.
In Survey one, the wavelength for my waves is 50 meters.
In Survey two, the wavelengths for my waves is .6 meters.
Which survey is GPR, and which is acoustic? |
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Definition
GPR has shorter wavelengths
Acoustic has longer wavelengths
Survey 1 is acoustic
survey 2 is GPR |
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Term
| relationship between vertical resolution and wavelength |
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Definition
| the relationship between vertical resolution and wavelength is that vertical resolution is about a quarter of wavelength |
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Term
| as you use GPR to anaylze a system with an uneven boundary layer, what is an issue that will create more error? |
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Definition
| scattering and focussing are problems you run into when you use GPR to anaylze a system with an uneven boundary layer |
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Term
| what property of materials does an induced potential survey measure? |
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Definition
| an induced potential survey looks at the chargeability of materials |
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Term
| what electricity survey examines the chargeability of materials? |
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Definition
| induced potential surveys look at the chargeability of materials |
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Term
| what is the application of induced potential electrical survey? |
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Definition
| induced potential surveys are used for base metal exploration |
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Term
| how do you do an induced potential survey? |
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Definition
| an induced potential survey is done by applying an electric field to the ground, then turning it off. then you measure if the ground is still conducting electricity |
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Term
| in an induced potential survey, the time that rocks are still charged after you turn off the electric field is on the scale of _____ |
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Definition
| in an induced potential survey, rocks will be charged after you turn off the electric field on a scale of seconds |
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Term
| in an induced potential survey, the distance that the charge travels after you turn of the electric field is a function of _____ |
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Definition
| in an induced potential survey, you apply an electric field then turn it off. The distance that the charge travels through the ground afterwards is a function of frequency |
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Term
| why can't you use a standard resistivity array for a induced potential method? |
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Definition
| you need to record the charge of the ground for several seconds, which a standard resistivity array cannot do |
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Term
| what electrical technique do we use for base metal exploration? |
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Definition
| we use induced potential for base metal exploration |
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Term
| what does the spontaneous potential electrical survey look for? |
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Definition
| the spontaneous potential electric survey looks for an oxidizing/reducing boundary |
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Term
| what is the application of the spontaneous potential electric survey? |
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Definition
| the spontaneous potential electric survey is used for mineral exploration |
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Term
| what electric survey is used for mineral exploration? |
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Definition
| spontaneous potential is the electric survey used for mineral exploration |
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Term
| what signal does the magneto-telluric electrical method look at? |
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Definition
| the magneto-telluric electrical method is looks at electric flow caused by charged particles flowing from the ionosphere |
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Term
| the magneto-telluric method has what application? |
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Definition
| the magneto-telluric method is used to look at crustal/lithosphere scale studies. It is especially good at looking under basalts in sedimentary basins |
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Term
| what electrical method is used for crustal/lithosphere scale studies? |
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Definition
| the magneto-telluric method is used for crustal/lithosphere scale studies |
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Term
| with the magneto-telluric methods, you need a base station with _____ |
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Definition
| for the magneto-telluric method, you need a base station with two electrodes at 90° from one another. This is how you measure variations in voltage |
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Term
| for _____ surveys, you have a base station with electrodes at 90° to measure variations in voltage |
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Definition
| for magneto-telluric surveys, you have a base station with electrodes at 90º to measure voltage |
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Term
| definition of conductivity |
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Definition
| conductivity is defined as "the degree to which a material conducts electricity" |
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Term
| conductivity calculated as _______ |
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Definition
| conductivity is calculated as "the ratio of electric current density to the electric field that generated them" |
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Term
| this property is defined as "the ratio of current density to the electric field" |
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Definition
| conductivity is defined as "the ratio of current density to the electric field" |
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Term
| this property is the reciprocal of resistivity |
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Definition
| conductivity is the reciprocal of resisitvity |
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Term
| what is the difference between active and passive resistivity/electromagnetic surveys? |
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Definition
active surveys: you generate a current and measure how it travels through the subsurface
Passive surveys: you measure natural currents |
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Term
| what is induced polarization? |
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Definition
| induced polarization is when you apply a current to the ground and then make measurements |
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Term
| electromagnetic surveys all consist of what? |
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Definition
| all electromagnetic surveys involve generating a magnetic field, which generates an electric field which you measure with coils |
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Term
| ohm's law states that ____ |
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Definition
ohm's law states that the current flowing through a material is proportional to the potential applied to that material
V is proportional to i
V is voltage, a measure of potential
i is current flow |
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Term
which law states at V is proportional to i
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Definition
ohm's law states that V is proportional to i
V is voltage, a measure of potential
i is curent |
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Term
| what is the constant of proportionality between V and i? |
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Definition
the constant of proportionality between V and i is resistance, denoted as R. resistance has unit of ohms
V=R*i |
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Term
| resistance is related to potential and current how? |
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Definition
resistance is the proportionality constant between potential and current.
V=i*R |
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Term
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Definition
| units of resistance are Ohms |
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Term
| the law of cables states _____ |
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Definition
| the law of cables states that resistance is proportional to the length of cable it is running through (L) and inversely proportional to the cross-sectional area of the cable it is running through. |
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Term
| what is the constant of proportionality for resistance and length/area |
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Definition
the constant for proportionality of resistance and length/area is resistivity, denoted as ρ
ρ = (R*L)/A
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Term
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Definition
| units of resistivity are ohm-meters |
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Term
| resistivity is the constant of proportionality between ____ and ____ |
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Definition
| resistivity is the constant of proportionality between resistance and length/area |
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Term
| what is the connection between length of a current flow line and the time it takes the signal to be communicated? |
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Definition
| the longer the current flow line, the longer it takes the signal to be communicated |
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Term
| what kind of diagram could you look at to see how relatively long it takes different current paths to go from one point to another |
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Definition
| a current flow diagram shows current paths. the longer currents paths take longer to communicate signal compared to shorter ones |
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Term
| You are looking a current flow diagram. The current paths goes to a new layer and bends towards the vertical. What do we know about the lower layer? |
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Definition
| when a current enters a new layer and bends towards the vertical, the new layer is higher resisitivity |
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Term
| what is the change in resistivity data as electrodes are moved farther and farther away in a two layer system? |
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Definition
| as electrodes get farther and farther away, apparent resistivity gets closer and closer to the resisitivity of the lower layer |
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Term
| in a current flow diagram, path density is related to _____ |
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Definition
| in a current flow diagram, high path density means high current density |
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Term
| what is the biggest application of resistivity surveys |
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Definition
| the biggest application of resisitivity surveys is finding how much water is in different layers, which we can deduce permeability from |
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Term
| resistivity surveys don't give you distinct layers, they give you _____ |
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Definition
| resitivity survey's don't tell you what layers are present, they simply give you pseudosections |
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Term
| what kind of surveys always involve predictive modeling after you get information from the earth? |
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Definition
| Resistivity studies only give you apparent velocity and pseudosections, so you have to use predictive modeling to see what the information is actually telling you |
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Term
| after you get information from the earth from resisitivity surveys, this is the next step |
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Definition
| you always finish resisitivity surveys with predictive modeling |
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Term
| what is the difference between forward and reverse modeling? |
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Definition
forward modeling is making a model based on what you expect to see before you survey the earth.
inverse modeling is looking at the data from a survey and finding a model to match |
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Term
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Definition
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Term
| is spontaneous potential active or passive? |
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Definition
| spontaneous potential is passive |
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Term
| what do you need for spontaneous potential? |
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Definition
| the setup for spontaneous potential is simply two electrodes |
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