INTRODUCTION

Since the Consortium for Continental Reflection Profiling (COCORP) began profiling the Canadian lithosphere in 1975, deep seismic reflection studies have enjoyed a rapid global expansion. In the past, the greatest focus was upon simply acquiring as many datasets from as diverse a set of geological terranes as possible, rather than upon developing and applying advanced acquisition and processing technologies. This approach provided many undreamt of insights into the inner Earth. With the basic skills in hand, deep seismic profiling is now progressing to a new level. The exploration industries have begun realizing that tectonic-scale structures are often important controls upon economically significant features such as intra-basin structures and mineralizing zones. In turn, expensive high-resolution deep seismic studies are being funded for the first time. Both LITHOPROBE (Canada) and the Australian Geological Survey Organisation (AGSO) are developing cooperative programs with the exploration industry. Such ventures apply acquisition and processing technologies most similar to those employed in conventional hydrocarbon exploration; close source and receiver spacings, high data redundancy (fold), and a pursuit of high frequency information.

It is my opinion however, that for some time yet, deep seismic studies will continue to operate as two separate thrusts; gross-scale academic studies and studies with a more commercial motive. The flux of technology demanded by the high-resolution studies, to the more regional studies, will therefore be slow and erratic. It is true that a great deal of uncertainties and ambiguities remain in our understanding of the Earth, and thus the academic community have many broad problems to address. In recent times, academics have been organizing symposiums and discussion groups in an attempt to address these unanswered questions. It is apparent that the resulting call will not be for better technology; rather, the call will be for the input of workers outside the seismic domain. Another reason for there being no urgency to speed along the input of newer technology into regional studies is derived from the history of deep seismic profiling, which I briefly discuss below. Practice has shown that the gross-scale features of the outer Earth are best tackled with simplistic processing approaches and novel or unconventional methodologies.

For those that place more emphasis upon doing research more precisely and powerfully, than scouting around simply acquiring more data, it is the commercially-driven surveys that will be the torchbearer for the application of more advanced acquisition and processing techniques to deep seismic studies. I suggest that once several high-resolution, deep seismic datasets have been acquired (and exploration surveys already are regularly recording their data for 8 to 12 s TWT), a significant contribution will then have been made to the general science of ``crustal studies''. Perhaps then, the academic studies will be more inclined to play catch-up. In the remainder of this paper I briefly discuss, with examples, how deep seismic profiling studies have commonly only required simplistic processing sequences, hence the lack of urgency in applying approaches better known in the exploration community. To place the science of reflection-seismic-based studies in a historical context, I then summarize the most nagging unresolved geological problems. Rather than dwell upon the superior nature of high-resolution commercial datasets, I then discuss how the application of rock physics principles in particular are being used to obtain more useful information from even the most coarsely-sampled data. As these efforts develop in popularity and success, I suggest that the application of other approaches such as 3D acquisition will be better appreciated for the contribution they can make to seismic studies, on any scale.