The New Geophysics

New Geophysics of critically microcracked rock is a new understanding of fluid‐rock deformation that matches much of the behaviour of in situ rock observed throughout the Earth's crust and uppermost mantle. The behaviour of rock in New Geophysics: is self‐similar; can be monitored, calculated, predicted, even in principle controlled; prevails in almost all rocks; and has ‘butterfly‐effect’ sensitivity. All of these remarkable features (except controllability) have been observed, in some cases many times. However, New Geophysics is innovative, controversial, and currently “ridiculed” and “violently opposed” (Schopenhauer Stages 1 and 2), and is difficult to get published via consensus‐driven peer‐review. Consequently, in the last 10 years, various aspects of New Geophysics have been published in some 20 different journals and conference proceedings making it difficult to access by the general reader. This review presents a synopsis of what is believed to be a fundamental advance in solid Earth geoscience.     

Geophysics of proposed proterozoic sutures in Canada

Sutures have been identified or proposed at several sites in the Canadian Shield. Although many authors have suggested that some form of primitive plate tectonic processes have played a major role in the formation of the Archean crust of the Superior structural province, Proterozoic sutures, resembling Phanerozoic examples, have been proposed only within the younger Churchill and Grenville provinces, and at or near the boundaries between the older Superior and Slave provinces and the younger provinces. Gravity, magnetic, seismic and paleomagnetic data related to three proposed sutures in the latter category have been interpreted and generally support the view that the Shield comprises a mosaic of once separated, but now joined cratonic blocks. The sutures vary in complexity from wide zones, containing distinctive rocks formed at ancient accreting and consuming plate margins, to cryptic sutures marked only by abrupt changes in metamorphism and zones of cataclasis. Paired negative and positive gravity anomalies associated with these sutures have been interpreted in terms of juxtaposed crustal blocks of different density and thickness. Magnetic anomaly patterns change abruptly at structural province boundaries. Available seismic results support the concept of thickened crust in the younger province as derived from gravity modelling. Most authors prefer interpretation of Proterozoic pole positions in terms of one-plate models, but in some cases the interpretation of paleomagnetic data is equivocal and two-plate models have been proposed.     

Geophysics of the Quebec Appalachians

This paper deals with a synthesis of the geophysics of the Quebec Appalachians. An emphasis is given to the regional geophysical surveys for the final geological interpretation. Regional, residual and downward continued aeromagnetic (AM) data yield information on the tectonic history of the region. The main features are pattern recognition of folded and particularly faulted structures and the boundaries of the tectonic domains. Three main fault systems have been identified and classified using AM information. In addition, depths to the crystallise basement and to the Cambro-Ordovician magnetic layers were obtained for sectors of the Gulf of St. Lawrence-Gaspé region. Nine main geological features are extracted from the processed AM data. Detailed geological modelling of some of the identified structures (e.g. nappes) are presented.Five main geological features are recognized from the gravity data. These features are correlated with the ones obtained from AM data whenever possible. Geological models based on information from surface geology, rock density contrasts and occasional contraints from regional seismic reflection data are presented. The boomerang shape of the Sutton-Bennett anticlinorium and the planar or curved slab-like shape of the obducted ophiolite bodies (upper mantle proto-oceanic floor) may be considered as the significant features.Regional reflection seismic data give a clear geological picture of three (out of four) distinguishable zones of the Quebec Appalachians, that is: autochthonous, parautochthonous, and transition zone: parautochthonous-allochthonous(corresponding approximately to the external domain). The pattern recognition of the allochthonous (approximate internal domain) is somewhat more difficult to decipher from the reflection seismic data. Intraplate seismicity and seismotectonics indicate the presence of four zones of high seismicity in southern Quebec. In almost all zones, the seismotectonic history goes back to Late Precambrian (Hadrynian) times.The scarce and scattered paleomagnetic data of geological formations located on the platform and the external domain of the Quebec Appalachians and in the internal domain are compared with those belonging to the stable North American plate. The paleomagnetic results indicate that the angular difference between the poles from the platform and external domain is large at Cambrian times (40°) and small at Devonian times (5°-10°). This suggests a fast rate of motion and accretion of the internal domain relative to the North American Plate in the Cambrian—Lower Devonian time span (550→-385 Ma).     

海洋地球物理技术的发展

海洋地球物理的海底探测技术在20世纪里的迅猛发展推动了地球科学的进展。高精度的导航定位技术是实现海底高精度探测的基础。高精度的导航定位包括水面船只和水下探测系统的精确定位。现代水面船只定位依赖以全球卫星定位技术为主的导航定位系统；水下定位系统主要发展有超短基线定位系统(USBL)、短基线定位系统(SBL)和长基线定位系统(LBL)等。海洋重力测量系统的主体技术得到改进，陀螺稳定平台广泛采用光纤陀螺技术，开发出改正交又耦合效应的新技术，系统实现数字化控制，卫星测高技术引入海洋重力测量领域。海洋地磁测量发展出光泵式测量技术、多分量测量技术和梯度测量技术，近数十年快速发展起来的海底声学探测技术有多波束测深技术、声纳侧扫技术和浅层剖面测量技术等，这些技术已经在当代海底科学研究、海底资源勘查、海洋工程和海洋开发等方面发挥出极其重要的作用。在新的世纪里，海洋地球物理仍然保持着前沿科学的地住。