a |
– abbreviation for acceleration |
acceleration |
– change in velocity in a given time |
aliasing |
– a result of improper measurement technique where effects appear at the wrong frequency |
ampere |
– a unit of electrical current |
amplitude |
– the displacement of an oscillation as in the extent of vertical motion of a water wave |
angle of incidence |
– the direction of wave travel as it approaches an interface |
angle of reflection |
– the direction of wave travel after it passes through an interface |
apparent resistivity |
– a volume-averaged resistivity |
attenuation |
– the loss of wave amplitude with travel distance |
average trace |
– a pervasive response in a ground penetrating radar measurement |
average trace removal |
– a procedure for removing unwanted ground penetrating radar responses |
backprojection |
– a procedure for creating images where it is assumed that waves travel along straight lines |
bandwidth |
– a continuous range of frequencies within some frequency interval |
c |
– abbreviation for wave speed |
center-frequency |
– the average value of a range of frequencies |
centrifugal force |
– an outward force associated with a change in direction |
chemical remnant magnetization |
– magnetism caused by the growth of certain crystals |
coefficient of reflection |
– a measure of the relative amount of wave energy reflected from a surface |
coil |
– numerous turns of a wire in a fixed shape such as a circle |
compass |
– a simple bar magnet used for navigation |
compression |
– pushing particles or molecules closer together |
conductivity |
– a measure of how easily electricity will flow in a material |
constructive interference |
– the interaction of multiple waves that results in wave growth |
contour plot |
– a means of displaying two-dimensional information where lines are drawn through points of constant value |
Coulomb’s Law |
– the relationship governing the forces acting between magnets |
coupling |
– a measure of the wave energy emitted by an antenna that enters the ground |
critical refraction |
– the limit to which a wave can change direction upon passing between two materials |
cross-borehole |
– a measurement geometry where wave sources are deployed in one borehole and receivers in a parallel borehole |
CT scanner |
– an x-ray device used for medical imaging |
current |
– the flow rate of electricity |
current density |
– the electrical current that flows through a unit cross-sectional area |
decay |
– the loss of wave energy as it travels |
density |
– the ratio of mass to volume |
depositional remnant magnetization |
– magnetization caused by the settling of magnetic particles in water |
destructive interference |
– the interaction of multiple waves that results in a loss of wave amplitude |
dielectric constant |
– a property that characterizes how easily a wave will travel through a material |
diffraction |
– the combined effects of reflection and refraction |
diffraction tomography |
– an imaging procedure that does not assume that waves travel in straight lines |
digital |
– number written as a sequence of 0’s and l’s |
dipole moment |
– a quantity that characterizes the strength of a magnet |
direct arrival |
– a measured feature associated with a wave traveling in a straight line |
Dynes |
– a unit of force |
electric field |
– the spatial variations of an imaginary force around an electrically charged particle |
eddy current |
– an electrical current that can flow in an object when it is exposed to a time-varying magnetic field |
electrical resistivity tomography |
– a technique where images are creating from the flow of electricity through a region |
electrodes |
– objects, usually metal stakes, that are used to introduce an electrical current into the ground |
electromagnet |
– a magnet created by exposing a ferromagnetic material to a magnetic field produced by a flow of electrical current |
electromagnetic induction |
– an effect that occurs when an electrically conductive object is exposed to a time-varying magnetic field |
electromagnetic waves |
– waves characterized by a time-varying electric field |
EMI |
– abbreviation for electromagnetic induction |
evanescent wave |
– a wave that rapidly loses amplitude as it travels |
expansion |
– pulling particles or molecules further apart |
external field |
– a magnetic field from a source outside of a study area |
f |
– the common abbreviation for frequency |
F |
– abbreviation for the force vector |
F |
– abbreviation for the magnitude of a force vector |
Fg |
– abbreviation for the vector force associated with gravity |
false-color plot |
– a means for displaying two-dimensional data by assigning colors to values |
ferromagnetic |
– a term pertaining to iron, nickel, or cobalt, the elements that can be magnetized |
focus |
– to render an image sharp |
forward modeling |
– synthesizing data |
frequency |
– the number of wave cycles that occurs within a certain period of time |
frequency sounding |
– a procedure for using a range of frequencies to extract depth information |
g |
– abbreviation for the gravitational acceleration vector |
g |
– abbreviation for the magnitude of the gravitational acceleration vector |
G |
– abbreviation for the universal gravitational constant |
gain |
– the multiplicative factor used to amplify a signal |
Gal |
– a unit of acceleration |
gamma |
– a unit of magnetic field strength |
geometric depth sounding |
inferring vertical structure by varying the electrode spacing in electrical resistivity measurements |
geometric spreading |
– the loss in wave amplitude as a result of the divergence of wave fronts |
geophysical diffraction tomography |
– a procedure for creating images where it is not assumed that waves travel along straight lines |
geotomography |
– the application of imaging procedures to geophysical data |
GPR |
– abbreviation for ground penetrating radar |
gradiometer |
– an instrument for measuring magnetic field strength at two nearby points |
gravitational acceleration |
– the acceleration produced by a gravitational force |
gravitational force |
– the force of mutual attraction between two masses |
gray-scale plot |
– a means for displaying two-dimensional data by assigning shades of gray to values |
grid |
– uniformly spaced measurement points in two dimensions |
ground penetrating radar |
– a radar wave-based geophysical technique |
gz |
– abbreviation for the vertical component of the gravitational acceleration vector |
H |
– abbreviation for the vector magnetic field |
H |
– abbreviation for the magnitude of the magnetic field |
H0 |
– abbreviation for the primary magnetic field vector in electromagnetic induction |
H1 |
– abbreviation for the secondary (induced) magnetic field vector in electromagnetic induction |
half-maximum distance |
– the distance between the position where a maximum response is observed and where half this value is measured |
half-maximum rule |
– a procedure for estimating depth from the half-maximum distance |
Hertz |
– a unit of frequency |
holographic lens |
– a mathematical equivalent to an optical lens that provides focus to images |
hyperbola |
– a ‘frown’ shape characteristic of small reflecting objects in ground penetrating radar data |
i |
– abbreviation for the current density vector |
i |
– abbreviation for the magnitude of the current density vector |
I |
– abbreviation for an electrical current vector |
I |
– abbreviation for the magnitude of a vector electrical current |
index of refraction |
– the relative change in wave speed between two materials |
induced current |
– the electrical current that can flow in an object when it is exposed to a time-varying magnetic field |
induced field |
– the magnetic field created when a time-varying induced electrical current flows through an object |
induced magnet |
– an object that remains a magnet only while exposed to a magnetic field |
in-phase |
– the component of an electromagnetic induction measurement associated with a short time response |
k |
– abbreviation for a spring constant |
k |
– abbreviation for magnetic susceptibility |
ka |
– abbreviation for apparent magnetic susceptibility |
line plot |
– a plot of one-dimensional data, a graph |
longitudinal wave |
– a wave characterized by oscillations in the direction of propagation |
m |
– abbreviation for the vector dipole moment |
m |
– abbreviation for the magnitude of the dipole moment vector |
m |
– abbreviation for mass |
magnetic field |
– imaginary forces that surround a magnet |
magnetometer |
– a geophysical instrument used in magnetometry |
magnetometry |
– a geophysical technique used to locate buried object that is based on measurements of magnetic force or magnetic fields |
mass |
– the quantity of matter |
mechanical waves |
– waves that result in the motion of matter such as water or sound waves |
mesh plot |
– a two-dimensional display of data where the measured value is plotted as elevation, the same as a surface plot |
microGal |
– a unit of gravitation acceleration equal to one-millionth of a Gal |
multipathing |
– waves originating at one point, following different paths, and arriving at the same point |
multiple |
– reflections of waves that result from multiple reflections of the same wave from an interface |
nanoTesla |
– a unit of magnetic field strength equal to one-billionth of a Tesla |
near-field |
– the area very close to a wave source or receiver |
Newton |
– a unit of force |
Newton’s Law |
– a fundamental law of physics that relates force, mass, and acceleration |
normal incidence |
– a wave traveling in a direction that is perpendicular to an interface |
ohm |
– a unit of resistance |
Ohm’s Law |
– the relationship between current, resistance, and voltage |
ohm-meter |
– a unit of resistivity |
orthogonal |
– perpendicular |
out-of-focus |
– a fuzzy image |
over sampling |
– making more than the necessary minimum measurements over space or time |
paleomagnetism |
– persistent induced magnetism that is associated with an object’s long-term exposure to a constant magnetic field |
partial image |
– an image reconstructed from a single direction of illumination |
period |
– the elapsed time between adjacent wave crests or troughs |
permanent magnet |
– an object that remain magnetized in the absence of some external magnetic field |
phase |
– relative time alignment of two waves |
pixel fill |
– a false-color or gray-scale plot of ground penetrating radar data |
plane wave |
– a wave having crests (and troughs) that are parallel |
polarization |
– the direction of a wave’s oscillations relative to its direction of propagation |
ppm |
– abbreviation for parts per million |
ppt |
– abbreviation for parts per thousand |
primary field |
– the source time-varying magnetic field used in electromagnetic induction |
propagate |
– the travel of a wave |
propagation |
– the general movement of a wave, for example, water waves propagate towards the shore |
pulse |
– a signal that persists only for an infinitesimally short time |
quadrature |
– the component of electromagnetic induction measurements associated with time-delayed response |
R |
– the abbreviation for resistance |
radargram |
– a display of ground penetrating radar data |
radio wave |
– a wave characterized by a time-varying electric field |
Radon transform |
– a mathematical procedure used in some types of imaging |
ray |
– an imaginary arrow that indicates the direction of wave propagation |
Rayleigh scattering |
– the scattering of a wave in all directions by particles or molecules |
reflection |
– the bouncing of a wave off an interface between materials of differing wave speed |
reflection coefficient |
– the same as coefficient of reflection |
refraction |
– the change in direction of a wave as it passes from one material to another |
remnant magnetization |
– magnetization of an object that persists for a long period of time |
resistance |
– a characterization of the extent to which a quantity of material impedes the flow of electricity |
resistivity |
– a property that defines how much a specific material impedes the flow of electricity |
resistor |
– an object designed to impede the flow of electricity |
resonance |
– a natural frequency of oscillation of an object |
S |
– symbol used to denote the shape factor in electromagnetic induction |
scalar |
– a quantity that is completely defined by a single number—for example,, distance is a scalar |
scattering |
– the redirection of wave travel direction as a result of its interaction with objects |
secondary field |
– in electromagnetic induction, the field produced by an induced current flowing in an object |
Seimen per meter |
– a unit of electrical conductivity |
seismic wave |
– a wave characterized by mechanical movements |
seismogram |
– a display of seismic wave data |
shielded |
– an antenna that is partially surrounded by a material that absorbs waves |
skin depth |
– a frequency-dependent characterization of the extent to which a time-varying magnetic field penetrates into a material |
Snell’s law |
– a relationship that describes refraction |
spectral response |
– the response of a material when it is exposed to waves or time-varying fields of various frequencies |
spectrum |
– a characterization of the relative frequency content of a wave or time-varying field |
speed of light |
– the speed at which electromagnetic (light or radio) waves propagate |
spring constant |
– characterizes the extent to which a spring resists movement |
standing wave |
– a special type of wave that does not propagate |
straight ray backprojection |
– the same as backprojection |
surface plot |
– the same as mesh plot |
surface-to-borehole |
– a measurement geometry where sources are deployed on the ground surface and receivers are emplaced in a borehole, or vice versa |
synthetic aperture lens |
– a mathematical procedure for synthesizing plane waves |
temporal |
– dealing with changes over time |
temporal sampling |
– characterizing how measurements are made over time |
Tesla |
– a unit of magnetic field strength |
thermoremnant magnetization |
– magnetization that results from the heating of certain types of materials |
time shadow |
– the change in arrival of a wave at various receiving locations |
time window |
– the elapsed time over which wave-based measurements are made |
tomographic imaging |
– a general procedure for creating spatial variations of material properties |
trace |
– a plot of measured response over time |
transmission |
– wave-based measurements that exploit waves that travel through objects |
transmission coefficient |
– the relative amount of wave energy that passes into an object, one minus the reflection coefficient |
transverse wave |
– a wave characterized by a direction of oscillation that is perpendicular to the direction of propagation |
trapped wave |
– a wave that undergoes repeated reflection with a layer or object |
under sampling |
– too few temporal or spatial measurements |
V |
– abbreviation for volume |
V |
– abbreviation for volt |
vector |
– a quantity characterized by a magnitude and a direction |
view |
– the direction in which an object is illuminated by a wave |
viscous remnant |
– magnetization induced when an object is exposed to a magnetic field for a |
magnetization |
long period of time |
volt |
– a measure of the effort required to cause electricity to flow a certain distance |
voltage |
– a measurement of the effort required to cause electricity to a flow a certain distance |
wave guide |
– a layer within which there are multiple wave reflections |
wavelength |
– the distance between adjacent wave crests or troughs |
wiggle trace |
– a means of displaying ground penetrating radar or seismic data as a sequence of line plots |
δ |
– the Greek letter delta used to abbreviate the skin depth |
∆x1/2 |
– abbreviation for the half-maximum distance used in depth estimation |
ɛ |
– the Greek letter epsilon used to abbreviate the dielectric constant |
η |
– the Greek letter eta used to abbreviate the shape factor in magnetic susceptibility |
k |
– the Greek letter kappa used to abbreviate the magnetic susceptibility per unit volume |
λ |
– the Greek letter lambda used to abbreviate the wavelength |
µ |
– the Greek letter mu used to abbreviate magnetic permeability |
µGal |
– abbreviation for microGal, a unit of gravitational acceleration equal to one-millionth of a Gal |
ø |
– the Greek letter phi used to abbreviate phase |
π |
– the Greek letter pi used to denote the constant ratio of the circumference of a circle to its diameter |
ρ |
– the Greek letter rho used to abbreviate density |
ρ |
– the Greek letter rho used to abbreviate resistivity |
σ |
– the Greek letter sigma used to abbreviate electrical conductivity |
τ |
– the Greek letter tau used to abbreviate the wave period |