Nomenclature

The search for unambiguous nomenclature.

Angle domain, AVA

• AVA (amplitude vs angle) instead of AVO (amplitude vs offest). 'Offset' is ambiguous. — Agreed, but beware of acronyms. 'Pre-stack domain' is probably OK too. — Matt

Frequency domain, AVF

• I suggest we use the term, AVBw (amplitude versus bandwidth) instead of calling it a wavelet gather or a wavelet bank. AVF (amplitude versus frequency) is another option, but this might be confused with the concept of dispersion, or AVOF which isn't exactly what we are computing. — I like 'AVF'. It's not really 'bandwidth' — when we say '35 Hz' we mean 'a peak frequency of 35 Hz', not '35 Hz of bandwidth'. Bandwidth increases with peak frequency, but it's not the same thing. 'AVOF' is weird. — Matt

• Mark Chapman and others have used the term AVOF for "frequency dependent AVO", which isn't the same thing as the variations of seismic response as a function of wavelet bandwidth. AVOF has a notion of pre-stack incidence angle, whereas AVBw doesn't have a dependence on geometric angle, only twt.

• If we let, or select the dimensions to be x1 = two-way-time, x2 = incidence angle, and x3 = bandwidth, Using this notation, a x2, x3 plane gives the AVABw (amplitude as a function of angle and bandwidth). This is kind of like a "time-slice" with no spatial dimensions.

Spatial domain, AVS A seismic profile is can be defined as amplitude variations throughout (twt and) 3D space. I suppose we could use the term AVS (amplitude variations within the spatial geology dimension(s)) — Agree we should avoid 'offset' in general. I think 'AVS' is unnecessary and/or weird, and 'cross section' is probably the most obvious and descriptive language. Sidenote, when possible avoid terms like 'CDP'. 'Gather' is probably OK, as a general word for a non-spatial section, eg 'frequency gather'. — Matt

• two-way time (s or ms) positive increases downwards
• z (m) positive increases downwards
• x (m) Easting, y (m) Northing, or Distance (??)
• NB: avoid using the word "offset" for geo-spatial declarations

Other domains might include:

Pre-stack domains

Shot gather domain, A-V-?

• Offset (m) Source-receiver distances (Strictly speaking offset is a 3-dimensional vector between source and receiver)

Midpoint domain, AVO

• Use the word common midpoint (CMP) when talking about data sorted by surface geometries,
• Reserve the terms common-depth point (CDP) or common image point (CIP) for migration and imaging cases.

Azimuthal domain, AVAz

A so-called COCA cube could be generated by flattening the 3D array of AVA x AVAz x t into a 2D array.

Offset vector tile (OVT) an AVO gather filtered by source-receiver offset.

Notes by Matt When I think about projections of the data into a visualizable space (a 3D one), I think of the wedge, in the x–z cross-section, and ask 'what can we show on the y-axis?' I'd like to be able to show the x–z cross-section, the y–z cross-cross-section, and the x–y 'timeslice' for any 3 parameters. Could get weird! As you say, we could show entirely non-spatial volumes.

I quite like the idea of being able to slice into 'rock property space', or perhaps 'uncertainty space', where the rock properties vary systematically in the y-dimension (if we think of a wedge in the x–z plane). So I could define a different set of rocks at each end, for example, and interpolate between them. Or define a standard deviation, stochastically sample the distribution, and order them somehow. This way, I can explore the effects of uncertainty, or varying rock properties (Vp, porosity, fluid saturation, whatever). Maybe this is just part of a bigger 2D model-building effort, but I think the workflows are important.