Appendix B

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