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Geological Society, London, Engineering Geology Special Publications
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Geological Society, London, Engineering Geology Special Publications; 2002; v. 19; p. 111-126;
DOI: 10.1144/GSL.ENG.2002.019.01.06
© 2002 Geological Society of London

Data acquisition, processing and presentation

Geophysics involves the measurement of signals, which are subsequently processed and analysed prior to interpretation and presentation, in terms of a "geophysical" ground-model. Typically, a geophysical method concerns measurements that are in turn controlled by a "geophysical" mass property. For example, if the travel time of seismic waves were the measurement, the controlling ground property would be seismic velocity. Generally, geophysical mass properties are controlled by lithology and rock mass condition. It is important to select geophysical methods that give the greatest response to the variability of geophysical mass properties, of relevance to the civil engineering problem in hand.

Forward modelling

In the past, an estimate of the "likely" property distribution, typically a simple "layercake" ground-model, would be used to generate a synthetic dataset that would be compared to the measurement dataset acquired in the field. This property distribution would then be varied manually, until the synthetic and field measurement datasets agreed. This "forward modelling" approach, which can be laborious, requires knowledge of the number of layers present at a site and may be tractable for simple geology only (eg 1-D) (See Chapter 4).

Inverse modelling

Forward modelling has been largely superseded by automatic numerical inversion processing, that "inverts" measurements directly into a spatial property distribution (1-D, 2-D and 3-D) without manual intervention. Inversion is at the heart of modern geophysical data processing and interpretation. It is a significant advance on forward modelling methods, because it enables the spatial distribution of geophysical properties to be displayed "tomographically" as images (eg

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This 250-word extract was created in the absence of an abstract.