| 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 |