Evaluation of full wave sonic (FWS) data for rock properties such as fractures and dipping boundaries often requires qualitative analysis of visually distinct wave patterns. Conventional waveform plots do not reveal all the information available from FWS data. With the application of an analytical method called "Instantaneous Waveform Characteristics" (IWC) analysis and with the use of color encoded displays called "colorgrams", additional FWS characteristics, helpful to formation description, can be observed and interrelated.The characteristics used in the IWC analysis are the instantaneous phase, the instantaneous frequency, and the complex waveform magnitude called "sonic transmissivity".Changes in these characteristics as observed in the colorgrams are excellent qualitative, locally sensitive, indicators of variations in rock properties. The transmissivity indicates formation attenuation, especially in fractured intervals. The instantaneous phase enhances the reflections from fractures and boundaries, and reveals their presence and dip. The instantaneous frequency shows the effects of dispersion due to abrupt changes within the formation.The application of the IWC analytical method is demonstrated with several examples. The IWC colorgrams from three different wells are displayed and analysed: a test well with core information. a References and iIIustratons at end of paper. naturally fractured well, and a cased hole before and after hydraulic fracturing. All these examples illustrate how the IWC method, enhanced with colo rg rams, broadens our analytical understanding of FWS well log data, provides new fracture and dip indicators, and assists in geological interpretation.

Evaluation of full wave sonic (FWS) data for rock properties such as fractures and dipping boundaries often requires qualitative analysis of visually distinct wave patterns. Conventional waveform plots do not reveal all the information available from FWS data. With the application of an analytical method called "Instantaneous Waveform Characteristics" (IWC) analysis and with the use of color encoded displays called "colorgrams", additional FWS characteristics, helpful to formation description, can be observed and interrelated.The characteristics used in the IWC analysis are the instantaneous phase, the instantaneous frequency, and the complex waveform magnitude called "sonic transmissivity".Changes in these characteristics as observed in the colorgrams are excellent qualitative, locally sensitive, indicators of variations in rock properties. The transmissivity indicates formation attenuation, especially in fractured intervals. The instantaneous phase enhances the reflections from fractures and boundaries, and reveals their presence and dip. The instantaneous frequency shows the effects of dispersion due to abrupt changes within the formation.The application of the IWC analytical method is demonstrated with several examples. The IWC colorgrams from three different wells are displayed and analysed: a test well with core information. a References and iIIustratons at end of paper. naturally fractured well, and a cased hole before and after hydraulic fracturing. All these examples illustrate how the IWC method, enhanced with colo rg rams, broadens our analytical understanding of FWS well log data, provides new fracture and dip indicators, and assists in geological interpretation.

A marine seismic system for recording near-vertical incidence to wide-angle reflected waves and refracted waves has been used to obtain detailed crustal structure off Canada's west coast. Profiles about 20 km in length were recorded in three regions: the Hudson '70 survey area near 51 °N, 133 °W; west of Queen Charlotte Sound; and in northern Cascadia basin, west of central Vancouver Island. In the first area, the interpretation was completely consistent with the Hudson '70 study, but more detail was provided for the upper crust. About 0.6 km of sediments with velocity 2.4 km/s overly layers 2A and 2B with velocities of 4.0 and 5.5 km/s and thicknesses of 1.1 and 1.5 km respectively. The oceanic layer has a velocity of 6.8 km/s. Off Queen Charlotte Sound, the sediments vary in thickness from 3–3.5 km and are divided into an upper sequence with low velocities (2.1 and 2.8 km/s) and a lower sequence with higher velocities (about 4.2 km/s). Basaltic basement beneath the sediments has a velocity of 5.85 km/s. The seismic data indicate that sediment deposition has been complex, possibly interspersed with thin basalt sills derived from a nearby spreading centre. On the basis of these and other data, Winona basin is proposed to extend northwestward as far as an imaginary line drawn landward from the trough between the Dellwood Knolls. In order to test this proposal and delineate in detail the total sedimentary section, high resolution reflection studies with greater than 2 s of subbottom penetration are required. In Cascadia basin, reflection and refraction interpretations gave consistent results. The entire sedimentary sequence has low velocity values (≤2.6 km/s) and is about 1.8 km thick. A thin layer (0.4–0.7 km) of basaltic basement with velocity ~5.1 km/s lies below the sediments, and in turn is underlain by a 2 km layer with velocity ~6.1 km/s. A near-vertical incidence profile recorded in this study and a stacked record section provided by an oil company show reflections to subbottom depths of ~4.5 km, corresponding to the top of layer 3. The latter is laterally variable and poorly defined. Reflections from within layer 2 are recorded and some may be related to flows of basalt during crustal formation.

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