b'Ted Tynes best of Exploration geophysicsFeaturedirect detection. A careful study of the rock properties and otherwas part of trials of the method, which was introduced into factors would be needed for successful application. BlackburnAustralia in late 1978. Pinchin et al., (1983) used both Mini-Sosie (1986b, 49) showed that Miocene channelling distorted time- and conventional explosive techniques in a high-resolution depth mapping in the Gippsland Basin; a linear velocity functionshallow seismic survey at the Wambo Colliery, Hunter Valley, method offered advantages over traditional methods in depthNSW. Doubt was cast on the existence of a postulated fault. It conversion. was found that both methods could be used in this area, and At the ASEG/SEG Conference in Adelaide, 1988 (Middleton,a choice of method for use in any area would depend on the ed., 1988), seismic papers presented included discussions ofparticular circumstances.deconvolution techniques, use of directed energy sources,Hatherly (1980, 303) described computer programs for estimation of velocity structure by tomography, analysis ofprocessing seismic refraction data. The generalised reciprocal amplitude variation with offset, improved methods for staticsmethod of Palmer was used for velocity and time-term corrections, shear waves and their relation to fractures, andanalysis, and a migrated depth section could then be vertical seismic profiling. plotted. Greenhalgh et al. (1980, 267) discussed the fitting of A 2D seismic modelling facility was developed at Flindersvarious mathematical functions to empirical refraction data University, SA for studies of elastic waves travelling throughwhere continuous velocity variation with depth is indicated. simulated geological structures (Pant et al., 1988). SignalsGreenhalgh and King (1980, 263) showed how to determine were recorded digitally from piezo-electric sensors, and bothvelocity-depth distributions from curvilinear refraction data.P and S waves could be processed and analysed by the usualBuchanan et al. (1981, 70) reviewed the use of channel waves procedures. Tests were carried out on models of a cavity, ain coal seams for predicting fault surfaces ahead of mining: horizontal linear target, a fault, and a basement mound. they quoted several cases from overseas. Greenhalgh and King Three-dimensional seismic work was well to the fore at the(1981, 264) developed theoretical dispersion curves for in-seam Melbourne 1989 Conference (Asten and Denham, eds, 1989),channel seismic waves.with discussions of isochronous models, velocity estimation,Use of an interactive computer system was described by Asten statics corrections, and amplitude-offset analysis, all applied to(1983, 23) to deal with the vast quantity of data collected from 30 situations. Other topics included interactive interpretationborehole logs during exploration. This approach combines using artificial intelligence, determination of porosity fromthe ability of the computer to undertake rapid calculations for seismic data, and F-K migration using variable velocities. mathematical correlations, with the intuitive judgement of the The problem of conversion of seismic time depths to trueearth scientist to recognise significant features visually and to depths away from control by well velocity surveys was tackledassess their structural and economic importance.by Megallaa (1989). The interval velocities derived by one ofHarman (1984, 300) reported on shallow reflection surveys the existing methods were checked by preparing a smooth,by BHP in the Cook Colliery, Bowen Basin, Queensland, which geologically representative map of normal move-out (NMO)showed complex faults. By comparison with borehole data, it velocity for each horizon; this was then used to prepare depthwas possible to trace coal seams and identify areas of splitting.maps from which depth-interval velocity functions could beHuber (1985, 336) reviewed the applicability of geophysical prepared. Deviations from original NMO and T Owere thenmethods to coal exploration, and concluded that seismic used to revise the models, and the process was repeated until(including high-resolution shallow reflection), and gravity convergence was reached. The method was applied to themethods could be used for direct detection, while magnetic and Snapper gas field in Bass Strait. electrical methods were useful indirect methods. Palmer (1985, 512) described the use of GRM in anisotropic situations.Coal ExplorationMason et al. (1985, 431) described experimental seismic in-seam Coal is one of Australias most important minerals, both forsurveys at West Wallsend Colliery, NSW. One seam transmitted local use and for export. It is not surprising therefore, thatleaky P, SH, and SV waves. Structures mapped were interpreted much attention has been devoted to the use of geophysics inas a dyke, and a sand channel. An old water-filled heading acted exploring for coal and for locating structural features whichas a barrier to SH waves, and transmitted P waves at 100 Hz. A could affect the planning of mining operations. The maincorridor of competent rock 75 m wide was mapped as having a method used was seismic refraction, but reflection techniques,width between 40 and 90 m.cross-hole seismics, and radar mapping have all come into use. At the Conference in Perth, 1987 (Middleton and Pridmore, Packham and Emerson (1975, 508) gave the results of a seismiceds, 1987) topics discussed included the use of vertical survey and eight-hole drilling program in the central partseismic profiling (VSP) to correlate well data with surface of the Sydney Basin. Two sedimentary units were identified:data, procedures for analysing cross-hole seismic data, and a lower unit with thin sandstones and dirty coals, and anthe development of a triaxial downhole geophone for use in upper unit with sandstones and conglomerates, and cleaneridentifying and separating different types of seismic waves.coals. Reflections from the upper measures tend to obscureSeveral papers were delivered on topics related to coal at the deeper reflections; White (1975, 704), using syntheticthe ASEG/SEG Conference, Adelaide, 1988 (Middleton, ed., seismograms, showed that better penetration of the upper1988). These included the effects of discontinuous seams on layers could be achieved by using lower frequencies. absorption of seismic waves, a comparison of the use of radio King (1979, 374) reported on an application of the Mini-SosieEM wave tomography with mine mapping, and cross-hole technique to shallow reflection mapping of coal seams andtomography, including a study of curved ray paths and the structural features in the Gloucester Basin, NSW. This surveyuse of damped least squares in interpretation. At the 7th ASEG FEBRUARY 2020 PREVIEW 40'