GEOPHYSICS

1. adj. [Geophysics] Pertaining to traces that have a different source but share a receiver. See: trace

common receiver

1. n. [Geophysics] A display of seismic traces that share a receiver. Alternate Form: CRG See: seismic trace,  trace

common receiver gather

1. n. [Geophysics] In multichannel seismic acquisition, the common midpoint on a reflector, or the halfway point when a wave travels from a source to a reflector to a receiver that is shared by numerous locations if the reflector is flat-lying. Like common depth point, this term is commonly misused, because in the case of dipping layers, common reflection points do not exist. See: channel,  dipping bed,  fold

common reflection point

1. adj. [Geophysics] Pertaining to traces that have a different receiver but share a source. See: trace

common source

1. n. [Geophysics] A display of seismic traces that share a source. Alternate Form: CSG See: seismic trace,  trace

common source gather

1. adj. [Geophysics] Pertaining to traces that have the same offset, or distance between source and receiver. See: trace

common-offset

1. adj. [Geophysics] Pertaining to traces that have a different source but share a receiver. See: trace

common-receiver

1. n. [Geophysics] A display of seismic traces that share a receiver. Alternate Form: CRG See: seismic trace,  trace

common-receiver gather

1. adj. [Geophysics] Pertaining to traces that have a different receiver but share a source. See: trace

common-source

1. n. [Geophysics] A display of seismic traces that share a source. Alternate Form: CSG See: seismic trace,  trace

common-source gather

1. n. [Geophysics] A change made to porosity measurements, such as those from sonic logs, to compensate for the lack of compaction, or the predicted loss of pore space as sediments are buried by overburden. Compaction corrections are commonly performed in uncompacted sediments. See: compaction,  porosity,  sonic log

compaction correction

1. n. [Geophysics] A mathematical method to determine seismic attributes, including reflection strength and instantaneous frequency, by using the Hilbert transform, a special form of the Fourier transform, and the quadrature trace, or the component of the signal that is 90 degrees out of phase. The Fourier transform a(t) = h(t) + jx(t), where h(t) = seismic trace x(t) = quadrature trace can be used to determine reflection strength by combining h and x: r(t) = [h(t)2 + x(t)2]1/2, and to determine instantaneous phase: θ(t) = tan−1[x(t)/h(t)]. See: attribute

complex trace analysis

1. n. [Geophysics] An elastic body wave or sound wave in which particles oscillate in the direction the wave propagates. P-waves are the waves studied in conventional seismic data. P-waves incident on an interface at other than normal incidence can produce reflected and transmitted S-waves, in that case known as converted waves. Synonyms: acoustic wave,  dilatational wave,  P-wave See: amplitude variation with offset,  body wave,  dilatation,  four-component seismic data,  Poisson's ratio,  rarefaction,  S-wave,  shadow zone

compressional wave

1. n. [Geophysics] The product of conductivity and thickness, typically measured in units of siemens (S). In the inversion of electrical and electromagnetic measurements, the conductance of a layer or zone is usually much better determined than either the conductivity or thickness individually.

conductance

1. n. [Geology] The movement of tectonic plates toward each other, generating compressional forces and ultimately resulting in collision, and in some cases subduction, of tectonic plates. The boundary where tectonic plates converge is called a convergent margin. See: lithosphere,  plate tectonics,  transpression,  turbidity current

convergence

1. adj. [Geology] Pertaining to the movement of tectonic plates toward each other, generating compressional forces and ultimately resulting in collision, and in some cases subduction, of tectonic plates. The boundary where tectonic plates converge is called a convergent margin. See: lithosphere,  plate tectonics,  transpression,  turbidity current

convergent

1. n. [Geophysics] A seismic wave that changes from a P-wave to an S-wave, or vice versa, when it encounters an interface. See: amplitude variation with offset,  attenuation,  reflection,  refraction,  SH-wave,  SV-wave

converted wave

1. n. [Geophysics] A mathematical operation on two functions that is the most general representation of the process of linear (invariant) filtering. Convolution can be applied to any two functions of time or space (or other variables) to yield a third function, the output of the convolution. Although the mathematical definition is symmetric with respect to the two input functions, it is common in signal processing to say that one of the functions is a filter acting on the other function. The response of many physical systems can be represented mathematically by a convolution. For example, a convolution can be used to model the filtering of seismic energy by the various rock layers in the Earth; deconvolution is used extensively in seismic processing to counteract that filtering. The mathematical form of the convolution of two functions, a filter f(t) and a time-series x(t), is y(t) = ∫ f(t−τ)x(τ)dτ, where y(t) is the output of the convolution. In the frequency domain, convolution is simply the product of the Fourier transforms (FT) of the two functions: Y(ω) = F(ω)*X(ω), where X(ω) = FT of the time series x(t) F(ω) = FT of the filter f(t) Y(ω) = FT of the output y(t) ω = angular frequency. See: embedded wavelet,  synthetic seismogram,  wavelet

convolution

1. vb. [Geophysics] To perform a convolution, which is a mathematical operation on two functions that is the most general representation of the process of linear (invariant) filtering. Convolution can be applied to any two functions of time or space (or other variables) to yield a third function, the output of the convolution. Although the mathematical definition is symmetric with respect to the two input functions, it is common in signal processing to say that one of the functions is a filter acting on the other function. The response of many physical systems can be represented mathematically by a convolution. For example, a convolution can be used to model the filtering of seismic energy by the various rock layers in the Earth; deconvolution is used extensively in seismic processing to counteract that filtering. See: embedded wavelet,  synthetic seismogram,  wavelet

convolve

1. n. [Geology] A connection of points from well to well in which the data suggest that the points were deposited at the same time (chronostratigraphic) or have similar and related characteristics. Alternate Form: correlate See: chronostratigraphy,  geomagnetic polarity reversal,  paleontology,  sequence,  sequence stratigraphy

correlation