ALBERT

Description / Table of Contents: PREFACE Following the economical and social development of the local communities, mountain regions of temperate climates are increasingly becoming the site of valuable infrastructures and important urban and industrial settlements. As the catastrophic events of last years in the European Alps have clearly shown, the vulnerability of these territories has correspondingly increased, in terms of both property damage and losses of human life. Until recently, the hydraulic scientific community has paid little attention to mountain watersheds, except perhaps during the period if the hydropower development. Nevertheless attention was then focused on problems and methodologies somewhat different from the issues of actual environmental concern. More recently, however, hydraulic engineers have joined their colleagues from forest and rural engineering, who have traditionally dealt with erosion control in mountain areas, to bring in their own methodology, already experienced in lowland rivers. At the same time, academic people focused an interest in some phenomena, like massive transport, which is typical of mountain environment. To bring together all these contributions and to make the state of the art of the mountain river science (oropotamology) and technology, an International Workshop was called at the University of Trent (Italy), on October 1989, under the sponsorship of Fluvial Hydraulic Section of the IAHR. Three main topics have been recognized as particularly relevant from the point of view of both research and professivnal people: a) Hydrodynamics of steep channels and local scale process; b) Sediment movement and sediment training, with special emphasis on massive transport; c) Particular features of sediment transport related to non-uniform grain-size. However, as it is the case in these circumstances, the contest of several contributions often spread over more than one topic. In the following Introduction to papers, the three topics were split into 11 Sections, each one devoted to a more particular aspect recurrently addressed during the discussion. The same paper, thus, may be mentioned in different Sections of the Introduction.

Description / Table of Contents: The subject of the book is an indepth description of the theory and mathematical models behind the application of the Global Positioning System in geodesy and geodynamics. The text has been prepared by leading experts in the field, contributing their particular points of view. Unlike a collection of disjoint papers, the text provides a continous flow of ideas and developments. The mathematical models for GPS measurements are developed in the first half of the book, followed by the description of GPS solutions for geodetic applications on local, regional and global scales.

Description / Table of Contents: PREFACE There are problems, when applying statistical inference to the analysis of data, which are not readily solved by the inferential methods of the standard statistical techniques. One example is the computation of confidence intervals for variance components or for functions of variance components. Another example is the statistical inference on the random parameters of the mixed model of the standard statistical techniques or the inference on parameters of nonlinear models. Bayesian analysis gives answers to these problems. The advantage of the Bayesian approach is its conceptual simplicity. It is based on Bayes' theorem only. In general, the posterior distribution for the unknown parameters following from Bayes' theorem can be readily written down. The statistical inference is then solved by this distribution. Often the posterior distribution cannot be integrated analytically. However, this is not a serious drawback, since efficient methods exist for the numerical integration. The results of the standard statistical techniques concerning the linear models can also be derived by the Bayesian inference. These techniques may therefore be considered as special cases of the Bayesian analysis. Thus, the Bayesian inference is more general. Linear models and models closely related to linear models will be assumed for the analysis of the observations which contain the information on the unknown parameters of the models. The models, which are presented, are well suited for a variety of tasks connected with the evaluation of data. When applications are considered, data will be analyzed which have been taken to solve problems of surveying engineering. This does not mean, of course, that the applications are restricted to geodesy. Bayesian statistics may be applied wherever data need to be evaluated, for instance in geophysics. After an introduction the basic concepts of Bayesian inference are presented in Chapter 2. Bayes' theorem is derived and the introduction of prior information for the unknown parameters is discussed. Estimates of the unknown parameters, of confidence regions and the testing of hypotheses are derived and the predictive analysis is treated. Finally techniques for the numerical integration of the integrals are presented which have to be solved for the statistical inference. Chapter 3 introduces models to analyze data for the statistical inference on the unknown parameters and deals with special applications. First the linear model is presented with noninformative and informative priors for the unknown parameters. The agreement with the results of the standard statistical techniques is pointed out. Furthermore, the prediction of data and the linear model not of full rank are discussed. A method for identifying a model is presented and a less sensitive hypothesis test for the standard statistical techniques is derived. The Kalman-Bucy filter for estimating unknown parameters of linear dynamic systems is also given. Nonlinear models are introduced and as an example the fit of a straight line is treated. The resulting posterior distribution for the unknown parameters is analytically not tractable, so that numerical methods have to be applied for the statistical inference. In contrast to the standard statistical techniques, the Bayesian analysis for mixed models does not discriminate between fixed and random parameters, it distinguishes the parameters according to their prior information. The Bayesian inference on the parameters, which correspond to the random parameters of the mixed model of the standard statistical techniques, is therefore readily accomplished. Noninformafive priors of the variance and covariance components are derived for the linear model with unknown variance and covariance components. In addition, informative priors are given. Again, the resulting posterior distributions are analytically not tractable, so that numerical methods have to be applied for the Bayesian inference. The problem of classification is solved by applying the Bayes rule, i.e. the posterior expected loss computed by the predictive density function of the observations is minimized. Robust estimates of the standard statistical techniques, which are maximum likelihood type estimates, the so-called M-estimates, may also be derived by Bayesian inference. But this approach not only leads to the M-estimates, but also any inferential problem for the parameters may be solved. Finally, the reconstruction of digital images is discussed. Numerous methods exist for the analysis of digital images. The Bayesian approach unites some of them and gives them a common theoretical foundation. This is due to the flexibility by which prior information for the unknown parameters can be introduced. It is assumed that the reader has a basic knowledge of the standard statistical techniques. Whenever these results are needed, for easy reference the appropriate page of the book "Parameter Estimation and Hypothesis Testing in Linear Models" by the author (Koch 1988a) is cited. Of course, any other textbook on statistical techniques can serve this purpose. To easily recognize the end of an example or a proof, it is marked by a A or a t~, respectively. I want to thank all colleagues and students who contributed to this book. In particular, I thank Mr. Andreas Busch, Dipl.-Ing., for his suggestions. I also convey my thanks to Mrs. Karin Bauer, who prepared the copy of the book. The assistance of the Springer- Verlag in checking the English text is gratefully acknowledged. The responsibility of errors, of course, remains with the author.

Description / Table of Contents: This volume contains the proceedings of a symposium held at Freiburg im Breisgau, October 7-11, 1990. The symposium was sponsored mainly by the Deutsche Forschungsgemeinschaft (DFG), by the Geological Institute of the University of Freiburg, and by the International Association of Mathematical Geology. We thank these and all other sponsors of the meeting. The symposium whose participants came from more then twenty countries was the first international meeting dedicated entirely to geological applications of threedimensional computer graphics, a rapidly growing field of scientific visualization in geology. The selection of papers in this volume covers a wide range of methods developed in the last decade.

Description / Table of Contents: Cellular growth is an important crystal growth process and offers an interesting example of natural pattern formation. The present work has been undertaken to study cellular growth, especially its pattern formation, both experimentally and numerically. In situ observations of faceted cellular growth clearly revealed cellular interactions in the array of cells. Cell tip splitting and loss of cells were observed to be the two main mechanisms for the adjustment of cell spacings during growth. For the first time, the true time-dependent faceted cellular growth has been modelled properly. The time evolution of faceted cellular growth has demonstrated the dynamical features of cellular growth processes. It was shown that the pattern formation was determined by cellular interactions in the array, either transient or persistent depending on the growth condition. The cellular structures were irregular when persistent interactions occurred, whereas relatively regular structures could be formed once the transient interactions had stopped. As a result of cellular interactions, a finite range of stable cell spacings was found under a given growth condition. Numerical experiments were carried out for k 〉 1 and k 〈 1 (where k is the solute partition coefficient), under a number of different growth conditions. It was found that these two cases were not symmetric as far as solute distribution is concerned; however the pattern formation behaviours were similar. For k 〉 1 shallow cells were retained, while for k 〈 1, the formation of liquid grooves along the cell boundary depended on the growth condition. The solute effect plays an important role in the cellular interactions in the array. The results were compared with experimental observations in thin film silicon single crystals. It is felt that a general behaviour of pattern formation is found and should be expected for other processes such as non-faceted cellular or eutectic growth. In addition, the solute flow in steady state cellular array growth was studied using the point source technique. Preliminary work was carried out to measure steady state non-faceted cell shapes. Heat flow in zone melting was studied numerically.

Description / Table of Contents: The present interest in sediments which are rich in organic matter results not only from their economic significance as potential oil and gas source rocks, but also from the fact that their deposition is the result of special environments. Subtle changes in the environmental conditions may result in great variations in the geochemical and petrographical characteristics of the organic matter. Therefore, the study of organic matter-rich sediments can provide a key to past sedimentary conditions. In addition, the elucidation of the depositional controls is of importance for oil and gas exploration strategies, for which the knowledge of source rock distribution and quality is critical. Furthermore, organic matter reacts extremely sensitive to changes in temperature during burial. The result of this sensitivity is the generation of volatile products such as carbon dioxide, water, nitrogen, oil and gas and a reorganization of the solid organic residue. Some of these changes are quantified as maturity parameters which can be used as calibration tools in basin modelling, i.e., in the modelling of temperature histories of sedimentary basins. The use of maturity parameters and other organic matter characteristics as indicators for diagenetic conditions and depositional processes is, however, restricted, if analyses are performed on outcrop samples, because weathering also affects organic matter.

Description / Table of Contents: PREFACE The aim of this volume is two-fold. At the more pragmatic level, it is to help answer the many questions about the structure of the Pacific continental margin of North America, which have arisen over the years as a result of continuing field mapping and geophysical surveys. The second objective is methodological - to illustrate the irreplaceable role of geological information among the various data sets used in earth-science studies. The need to address these issues became apparent to the author during the several years he spent taking part in geological and geophysical studies on the west coast of Canada. All too often, results of geologic field mapping disagreed with tectonic predictions from too-straightforward local applications of global plate reconstructions, which due to their generality do not always take a full account of specific character of particular regions. To be sure, the global approach has during the last q~/artercentury greatly expanded the vision of geoscientists, previously restricted to continental regions. However, a negative by-product of this expansion has been a decline of attention paid to local information, as tectonic studies have increasingly relied on simply fitting the development of a particular region into this or that prefabricated tectonic template. Direct geological observations have limitations of their own. The observer in most cases deals with products of geologic processes, rather than with the processes themselves. Field mapping provides local information, and many years of effort are needed before a regional overview becomes possible. Geologic mapping is restricted to the ground surface, and even the deepest drillholes cannot sample more than the outermost shell of the Earth. The factual side of geologic mapping is usually limited to determination of rock types and their relationships in areas of exposure. Conclusions about the three-dimensional structure of a region and its evolution are still mostly inferential. Broad incorporation into geological studies of geophysical data, assisted by ever-more-sophisticated modern computers, provides a huge volume of information unobtainable in other ways. Geophysical methods quickly afford regional coverage or images of the Earth's deep interior. Geophysical methods have prompted the application in geological sciences of methodologies borrowed from exact sciences, such as mathematics and physics. Particularly important has been quantitative modeling, which allows a scientist to use the known parameters of a system to predict others. But in taking this approach too far, one encounters a dangerous pitfall. A model is a simplified representation of a natural phenomenon. The quality of this or that representation is relative, and a representation is never perfect. To incorporate all characteristics of a geologic phenomenon, in a parametrized form, into a numerical or physical imitation is impossible. This requires one to rely on simplifying assumptions, and a model is no better than the assumptions at its base. Unrealistic assumptions lead to unrealistic models. When a disagreement arises between model predictions and observations - such as those from geologic field mapping - a modeler may be tempted to downplay the differences or the significance of the offending observations. It becomes tempting to underestimate the role of an experienced geologist as a principal arbiter of the realism of a model. But it is geological data and geological control that provide the ultimate means of testing abstract models. From this methodological position, the present study of the western North American continental margin is organized as follows: 1. Geological information, available from field mapping and drilling, is gathered and summarized. 2. Current geophysical models for this region are considered, with particular attention to their underlying assumptions. 3. The available data, geological and geophysical, are synthesized into an internally consistent geologic-evolution concept. 4. This concept is tested by comparison with direct geological observations from field mapping and drilling. Because most current data sets and models cover northwestern Washington and western British Columbia, particular attention was paid to these areas. Fortunately, these areas contain many keys that help understand the structure of the entire western North American continental margin, which has baffled scientists for decades. The author does not claim to have resolved all these problems, but he does believe he has made a useful contribution to understanding continental-oceanic plate interrelations at this continental margin. Rigidity of lithospheric plates is a critical assumption in current models of plate evolution. The lithophere of a plate is created at spreading centers manifested in the global system of mid-ocean ridges. It moves away from the place of its birth towards boundaries with other plates, with which it can interact in a variety of ways. Some interactions are of strike-slip type, with two plates simply sliding past each other. However, to compensate for the creation of new lithosphere at spreading centers, older lithosphere at some plate boundaries descends into the mantle as it is overriden by other plates. At such plate boundaries lie subduction zones. If both regimes occur along a single plate boundary, the transition between them must be abrupt. Unless it can be tied to a change in orientation of the boundary, it must be associated with a junction of not two, but three different plates. Such a template was used to interpret the structure and tectonic evolution of the western North American continental margin in the late 1960s and thereafter (Atwater, 1970; McManus et al., 1972; Barr and Chase, 1974; Riddihough and Hyndman, 1976). To satisfy the principles of rigid-plate tectonics, both regimes have to exist along this continental margin. Also needed in rigid-plate reconstructions is a plate triple junction somewhere between the areas of proven ongoing subduction (in Oregon and southern Washington) and transform plate motion (along the southeastern Alaska margin; Atwater, 1970; McManus et al., 1972). Such a triple junction has been placed off Queen Charlotte Sound offshore British Columbia (Keen and Hyndman, 1979; Riddihough et al., 1983), where a spreading center has been postulated between the Pacific and Explorer oceanic plates (Hyndman et al. 1979; Riddihough, 1984). Off northern Vancouver Island, a transform boundary between the Explorer and Juan de Fuca oceanic plates has been postulated, but both these plates are assumed to be subducting beneath Vancouver Island (Hyndman et al., 1979; Riddihough and Hyndman, 1989)o With the assumed universality of the rigid-plate model, "broad similarity" has been suggested between the geology of western Oregon and that of western British Columbia, and the Cascadia zone of active subduction has been extended as far north as the mouth of Queen Charlotte Sound (Riddihough, 1979, 1984). An accretionary sedimentary prism (Yorath, 1980) - or even an accretionary complex containing several exotic "terranes" (Davis and Hyndman, 1989) - has been postulated off Vancouver Island. Geological observations onshore and offshore (Shouldice, 1971; Tiffin et al., 1972) have come to be considered too "surficial" to be of major consequence for large-scale tectonic modeling (Yorath et al., 1985a,b; Yorath, 1987). Variants of the principal geophysical model for this area during the last decade (Clowes et al., 1987; Hyndman et alo, 1990; Spence et al. 1991; Yuan et al., 1992; Dehler and Clowes, 1992) have become increasingly distant from geological observations. As new model variants emerged, they were checked for internal consistency, compatibility with neighboring local models and fidelity to the overall assumed tectonic picture. However, detailed geological work continued, and many of its results proved incompatible with the conventional wisdom (Gehrels, 1990; Babcock et al., 1992, 1994; Allan et al., 1993; Lyatsky, 1993a). Importantly, questions arose about the applicability in this region of the conventional, simple rigid-plate assumption, as it was shown to be unable to account for all the geological and geophysical peculiarities in some areas (Carbotte et al., 1989; Allan et al., 1993; Davis and Currie, 1993). New solutions were made necessary by new findings and by rediscovery of forgotten old data (see Lyatsky et al., 1991; Lyatsky, 1993b). Without aiming to resolve all the outstanding debates, tectonic implications of the geologic mapping and drilling results in this region are considered in the following chapters. These results are integrated with geochemical and geophysical data. Interpretations of these data, made by this author and by other workers, are verified by geological observations and by geologically plausible extrapolations from these observations. In searching for solutions consistent with all the information, the author has restricted himself to analyzing continental-crust structures along this continental margin. He believes, however, that future models for the offshore regions of the northeastern Pacific should consider the results obtained herein.