Glossary

anomalies    Unusually high or low values or patterns.

chirp seismic    A seismic system that transmits a linearly swept signal (from low to high), wide band frequency modulated (FM) pulse in the water. When the reflections are received they are processed to remove the FM carrier signal.

conductivity    The ability of a material or mixture to carry an electrical current.

dipole    A pair of positive and negative charges separated by a small distance.

draft   A nautical term describing the depth of an object on a ship below the water surface, often the bottom or keel of the ship.

eutrophication    An increase in the concentration of dissolved nutrients in a water body that increases growth or algae, often to a harmful degree, and often caused by human influences.

geophysical   Relating to the application of surface or borehole measurements, often using sound or electrical energy, to determine or infer the subsurface properties of land and water bodies.

groundwater    Water located beneath the ground surface or sediment surface in pore spaces and fractures.

interpolated   Interpreted conditions between locations of measured data.

inversion    The process of working backwards from measured properties, such as electrical resistivity, to reconstruct the actual conditions that yielded the measurements.

Julian day    Day of the year measured from January 1, without regard to months.

linearized    Converted from an irregular or curved path into a straight line to simplify computations.

paleochannels    Depression cut by rivers into underlying material during periods of lower sea level, and now submerged by rising sea level and often partially or fully buried by sediments.

peat   Organic-rich sediment deposited beneath wetlands.

potential    The property of electrical potential energy divided by electrical charge, usually measured in volts.

profile    A cross-section produced from geophysical data.

pseudosection     An image plotting apparent electrical resistivity data against position along a traverse line; this image is produced as an intermediate step to reconstructing the true electrical properties and geometry of a measured transect.

resistivity    A measure of how strongly a material or mixture opposes the flow of electric current through it.

saline    At or near the saltiness of seawater.

SEG-Y    An open standard file format developed by the Society of Exploration Geophysicists for storing geophysical data.

seismic reflection    A geophysical technique that uses sound waves to detect variations in geologic properties below the Earth's surface.

shapefile    A data format commonly used for geographic information systems files.

starboard    A nautical term for the right side of a ship when facing toward the front (bow).

streamer    A cable towed behind a ship that contains electrodes or acoustic sensors.

surface water    Water occurring in the form of a stream, river, lake, estuary, or ocean.

trackline    An individual segment of a larger marine geophysical survey, often assigned a sequential number that corresponds to the order in which that interval of data was collected.

voltage    The driving force that moves an electrical current between two points, measured in units of volts.