ALBERT

Description / Table of Contents: Chapter I. Air-Sea Exchange Processes and Flux --- Chemical composition of marine aerosols over the Central North Pacific—Results ftom the 1991 cruise of Hakurei Maru No. 2 / Uematsu, M., Kawamupa, K., Ibusuki, T. and Kimoto, T. / Biogeochemical Processes and Ocean Flux in the Western Pacific, / pp. 3-14 --- Estimation of mineral aerosol fluxes to the Pacific by using environmental plutonium as a tracer / Nakanishi, T., Shiba, Y., Muramatsu, M. and Haque, M. A. / Biogeochemical Processes and Ocean Flux in the Western Pacific, / pp. 15-30 --- Land-derived lipid class compounds in the deep-sea sediments and marine aerosols from the North Pacific / Kawamura, K. / Biogeochemical Processes and Ocean Flux in the Western Pacific, / pp. 31-51 --- Iron and manganese in the atmosphere and oceanic waters / Nakayama, E., Obata, H., Okamura, K., Isshiki, K., Karatani, H. and Kimoto, T. / Biogeochemical Processes and Ocean Flux in the Western Pacific, / pp. 53-68 --- Laboratory estimation of CO2 transfer velocity across the air-sea interface / Komom, S., Shimada, T. and Murakami, Y. / Biogeochemical Processes and Ocean Flux in the Western Pacific, / pp. 69-81 --- Dissolution of calcareous tests in the ocean and atmospheric carbon dioxide / Nozaki, Y. and Oba, T. / Biogeochemical Processes and Ocean Flux in the Western Pacific, / pp. 83-92 --- Calcium carbonate production and carbon dioxide flux on a coral reef, Okinawa / Ohde, S. / Biogeochemical Processes and Ocean Flux in the Western Pacific, / pp. 93-98 --- Chapter II. Geochemical Processes in Seawater --- Generations of carbonyl sulfide and hydrogen peroxide in the Seto Inland Sea—Photochemical reactions progressing in the coastal seawater / Fujiwara, K., Takeda, K. and Kumamoto, Y. / Biogeochemical Processes and Ocean Flux in the Western Pacific, / pp. 101-127 --- Speciation of organoarsenical compounds in the hydrosphere / Sohrin, Y., Hasegawa, H. and Matsui, M. / Biogeochemical Processes and Ocean Flux in the Western Pacific, / pp. 129-138 --- Chemical speciation of selenium in natural waters / Nakaguchi, Y., Koike, Y. and Hiraki, K. / Biogeochemical Processes and Ocean Flux in the Western Pacific, / pp. 139-158 --- The concentration distribution and chemical form of arsenic compounds in seawater / Tanaka, S. and Santosa, S. J. / Biogeochemical Processes and Ocean Flux in the Western Pacific, / pp. 159-170 --- The rare earth elements and yttrium in the coastal/offshore mixing zone of Tokyo Bay waters and the Kuroshio / Nozaki, Y. and Zhang, J. / Biogeochemical Processes and Ocean Flux in the Western Pacific, / pp. 171-184 --- The tetrad effect in seawater; a long dispute and an analytical approach to the confirmation of the effect / Akagi, T. and Masuda, A. / Biogeochemical Processes and Ocean Flux in the Western Pacific, / pp. 185-199 --- Detection, characterization and dynamics of dissolved organic ligands in oceanic waters / Tanoue, E. and Midorikawa, T. / Biogeochemical Processes and Ocean Flux in the Western Pacific, / pp. 201-224 --- Chapter III. Primary Production and Other Biological Processes --- Nitrate assimilation and new production in open ocean / Kanda, J. / Biogeochemical Processes and Ocean Flux in the Western Pacific, / pp. 227-238 --- Primary production and community respiration in the subarctic water of the western North Pacific / Odate, T. and Furuya, K. / Biogeochemical Processes and Ocean Flux in the Western Pacific, / pp. 239-253 --- Effects of a seamount on phytoplankton production in the western Pacific Ocean / Furuya, K., Odate, T. and Taguchi, K. / Biogeochemical Processes and Ocean Flux in the Western Pacific, / pp. 255-273 --- Marine colloids: Their roles in food webs and biogeochemical fluxes / Nagata, T. and Koike, I. / Biogeochemical Processes and Ocean Flux in the Western Pacific, / pp. 275-292 --- Regional and seasonal variations of biomass and bio-mediated materials in the North Pacific Ocean / Yanada, M. and Maita, Y. / Biogeochemical Processes and Ocean Flux in the Western Pacific, / pp. 293-306 --- Nitrogen and carbon stable isotopic ecology in the ocean: The transportation of organic materials through the food web / Sugisakj, H. and Tsuda, A. / Biogeochemical Processes and Ocean Flux in the Western Pacific, / pp. 307-317 --- The role of carnivorous zooplankton, particularly chaetognaths in ocean flux / Terazaki, M. / Biogeochemical Processes and Ocean Flux in the Western Pacific, / pp. 319-330 --- Seasonal changes in deep-sea benthic foraminiferal populations: Results of long-term observations at Sagami Bay, Japan / Kitazato, H. and Ohga, T. / Biogeochemical Processes and Ocean Flux in the Western Pacific, / pp. 331-342 --- Chapter IV. Particle Flux and Sediment Geochemistry --- Spatial variation of Al flux in the North Pacific observed with sediment trap / Noriki, S., Iwai, T., Shimamoto, A., Tsunogai, S. and Harada, K. / Biogeochemical Processes and Ocean Flux in the Western Pacific, / pp. 345-354 --- Spatial and temporal variation of δ515N in sinking particles in deep waters: Its implication for the origin and transport of particulate organic matter / Nakatsuka, T., Handa, N. and Imaizumi, S. / Biogeochemical Processes and Ocean Flux in the Western Pacific, / pp. 355-374 --- 230Th and 231Pa distributions in surface sediments off Enshunada, Japan / Taguchi, K. and Narita, H. / Biogeochemical Processes and Ocean Flux in the Western Pacific, / pp. 375-382 --- Remobilization of transition elements in pore water of continental slope sediments / Kato, Y., Tanase, M., Minami, H. and Okabe, S. / Biogeochemical Processes and Ocean Flux in the Western Pacific, / pp. 383-405 --- Geochemistry of pore waters from a bathyal Calyptogena community off Hatsushima Island, Sagami Bay, Japan / Masuzawa, T., Nakatsuka, T. and Handa, N. / Biogeochemical Processes and Ocean Flux in the Western Pacific, / pp. 407-421 --- Chapter V. Submarine Hydrothermal Processes --- Wide variation of chemical characteristics of submarine hydrothermal fluids due to secondary modification processes after high temperature water-rock interaction: a review / Gamo, T. / Biogeochemical Processes and Ocean Flux in the Western Pacific, / pp. 425-451 --- Geochemistry of phase-separated hydrothermal fluids of the North Fiji Basin, Southwest Pacific / Ishibashi, J. / Biogeochemical Processes and Ocean Flux in the Western Pacific, / pp. 453-467 --- Chemical modeling of seawater-rock interaction: Effect of rock-type on the fluid chemistry and mineral assemblage / Chiba, H. / Biogeochemical Processes and Ocean Flux in the Western Pacific, / pp. 469-486 --- Hydrothermal mineralization in the Mid-Okinawa Trough / Nakashima, K., Sakai, H., Yoshida, H., Chiba, H., Tanaka, Y., Gamo, T., Ishibashi, J. and Tsunogai, U. / Biogeochemical Processes and Ocean Flux in the Western Pacific, / pp. 487-508 --- Iron-rich smectite formation in the hydrothermal sediment of Iheya Basin, Okinawa Trough / Masuda, H. / Biogeochemical Processes and Ocean Flux in the Western Pacific, / pp. 509-521 --- Formation and alteration of organic compounds in simulated submarine hydrothermal vent environments / Kobayashi, K., Kohara, M., Gamo, T. and Yanagawa, H. / Biogeochemical Processes and Ocean Flux in the Western Pacific, / pp. 523-535 --- Localized heat flow anomalies in the middle Okinawa Trough associated with hydrothermal circulation / Kinoshita, M. / Biogeochemical Processes and Ocean Flux in the Western Pacific, / pp. 537-559 --- Chapter VI. Modeling and Physical Oceanography --- Material transport models from Tokyo Bay to the Pacific Ocean / Yanagi, T. / Biogeochemical Processes and Ocean Flux in the Western Pacific, / pp. 563-574 --- Climate and weather effects on the chlorophyll concentration in the northwestern North Pacific / Sugimoto, T., Tadokoro, K. and Furushima, Y. / Biogeochemical Processes and Ocean Flux in the Western Pacific, / pp. 575-592 --- Ecosystem models for the three regional problems in the Northern Pacific / Kishi, M. J. and Kawamiya, M. / Biogeochemical Processes and Ocean Flux in the Western Pacific, / pp. 593-611 --- A review on the subtropical mode water of the North Pacific (NPSTMW) / Hanawa, K. and Suga, T. / Biogeochemical Processes and Ocean Flux in the Western Pacific, / pp. 613-627 --- Flow distribution at 165°E in the Pacific Ocean / Kawabe, M. and Taira, K. / Biogeochemical Processes and Ocean Flux in the Western Pacific, / pp. 629-649 --- Determination of monthly mean sea surface temperature from 1981 to 1990 by the NOAA-AVHRR in the equatorial Pacific / Kishino, M. / Biogeochemical Processes and Ocean Flux in the Western Pacific, / pp. 651-659

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.

Description / Table of Contents: PREFACE The ocean has always been reluctant to reveal its secrets. Its size and the inaccessibility of its deeper regions have made their safeguard a reasonably simple matter with the result that significant misconceptions persisted for many years. Two of the most widespread of these concerned the featureless nature of the sea floor and the silence of the deep ocean. Underwater acoustics has played a key role in discrediting both and in so doing introduced new and exciting developments in oceanography and geophysics. In the years following World War II, echosounders and subbottom profilers based on new active sonar technology, revealed the true nature of the seafloor topography and led to the major advances represented by plate tectonics. Research driven by the requirements of passive sonar, on the other hand, was to demonstrate that the sea was not silent but was characterised by a complex noise spectrum. Many individual mechanisms and sources ranging from man-made, biological and geophysical activity to the intrinsic noise of the sea itself were found to contribute to this spectrum. A major component, which is the subject of this book, was to remain unrecognised to underwater acoustics until noise measurements could be made effectively at very low frequencies, although its presence had been indicated by seismology long before these measurements were possible. By virtue of its geographical isolation in the Southern Ocean, New Zealand has provided an ideal environment for long-range propagation and ambient noise investigations and numerous studies have been reported. Our interest in the subject of this book was aroused initially in the course of one such experiment in 1966. For the first time it had been possible to extend the recording bandwidth to 1 Hz and the improved performance of this new system was anticipated eagerly. However the main purpose of the experiment was nearly aborted by the appearance of a new and unsuspected noise component at frequencies below 10 Hz. Due primarily to technical limitations in the equipment then available, a subsequent programme, designed to identify the properties and origin of the source more clearly, was not productive and was soon abandoned. An opportunity to revisit the problem arose some 10 years later, when the University of Auckland became involved in a major environmental study in support of the development of an offshore gas field in Cook Strait. The technology then available provided an opportunity to examine afresh the relationship between sea state and the seismo-acoustic response generated. An initial trim demonstrated the potential of the site. Accordingly a long-term programme, involving the parallel measurement of the oceanwave field and acoustic response, was undertaken in a series of student research theses. The data so gathered were of sufficiently high quality to ultimately establish wave-wave interactions as the source of the acoustic effects observed and to identify many of its characteristics. This result was soon to be confirmed by other studies. As the noise data accumulated, however, it became apparent that certain refinements to the theories describing the mechanism were required. Our attempts to provide these refinements have been reported in a number of contributions in recent years. The accounts of these and similar contributions by others have unfortunately appeared in the literature in a somewhat disjointed manner, with the result that the evolution of the subject has not been easy to follow. This book attempts to present a more coherent account of the subject and its development. Most of the early experimental and theoretical results from our group have arisen from two key Ph.D. theses, due to Dr. K.C. Ewans and Dr. C.Y. Wu. The painstaking and careful instrumentation development and data analysis provided by Dr. Ewans were critical to the definitive correlation which we were able to establish between wind field, seastate and the acoustic response so generated. Dr. Wu's thesis presented the first phase of our attempt at the resolution of certain key theoretical issues, which were identified in the course of the experimental programme. Both studies owe much to the support of Shell BP Todd Oil Services Ltd., acting for Maui Development Ltd., and to the University of Auckland. The support of the Electricity Corporation of New Zealand Ltd. during a later experimental investigation of the Southern Ocean wave field is also acknowledged...

Description / Table of Contents: DEKORP, the German continental reflection seismic program, was the major focus of deep seismic research in Germany in the 1980s and 1990s. The seismic sections provided fundamental new insight into deep geological structure of the European continent and the dynamics of continental formation. They formed the basis for worldwide comparative studies of orogenic structure. The complicated signature of the reflections from the deep crust indicated that new processing and interpretation techniques must be considered to better image the crystalline crust. Results of these efforts, including pre-stack migration, 3-D imaging, shear waves and seismic anisotropy, are presented in this special volume. In part, the articles open the perspective to new and future research. In part, they document research activity triggered by technical and interpretational questions raised by DEKORP field work and profiling results. Many of the presented methods can find immediate application in industrial seismic prospecting.

Description / Table of Contents: This volume contains 18 papers from 8 countries dealing with different aspects of triggered and induced seismicity. In situ observations of the phenomenon include examples of seismicity due to reservoirs, hard-rock mines, coal mines, mine collapses, brine production caverns, fluid injections, and geothermal hot-dry-rock projects. High-frequency acoustic emission studies from laboratory experiments and hard-rock mines have also been reported. Besides providing case studies of previously unavailable observations of seismicity, the present volume contains investigations of the causes and source mechanism of seismic events, determination of source parameters, seismic hazard as related to the design of support systems for underground openings and procedures for closure of brine production caverns, and the use of seismic and non-destructive techniques in assessing rock damage, measuring dynamic elastic moduli and detecting discontinuities. This collection of papers provides an excellent indication of the state of the art, recent developments and outstanding challenges facing scientists and engineers in understanding the causes and alleviating the effects of induced seismicity.

Description / Table of Contents: This volume contains twenty-five research papers on seismicity patterns, their interpretation and their possible relevance to learning how to predict earthquakes. The interpretation of seismicity patterns has become somewhat controversial. Some researchers present case histories suggesting that earthquakes may be predicted by increased seismic moment release or seismic quiescence and, in general, by understanding the processes of self-organized criticality. Others deny these hypotheses. Although the problem of recognizing foreshocks in real time remains unsolved, new properties of microearthquakes as a function of time are coming to light. Computer modeling of seismicity also is advancing in sophistication and relevance. Surprisingly, b-values seem to hold substantial information about varying local conditions of earthquake generation.

Description / Table of Contents: Earthquakes in shallow subduction zones account for the greatest part of seismic energy release in the Earth and often cause significant damage; in some cases they are accompanied by devastating tsunamis. Understanding the physics of seismogenic and tsunamigenic processes in such zones continues to be a challenging focus of ongoing research. The seismologic and geodetic work reported in this volume highlights the recent advances made toward quantifying and understandig the role of shallow plate coupling in the earthquake generation process. The relation between regional seismotectonics, features in the downgoing plate, and the slip distribution in earthquakes are examined for recent and great historical events. In addition to papers reporting new results, review articles on tsunami and tsunamigenic earthquakes and depth dependent plate interface properties are presented. These observational results, along with complementary laboratory and theoretical studies, can assist in assessing the seismic potential of a given region.

Description / Table of Contents: Variations in seismic Q are sensitive to a much greater extent than are seismic velocity variations on factors such as temperature, fluid content, and the movement of solid state defects in the earth. For that reason an understanding of Q and its variation with position in the earth and with time should provide information in earth's tectonic evolution, as well as on aspects of its internal structure. Progress in understanding Q has suffered from difficulty in obtaining reliable amplitude data at global and temporary stations. Moreover, laboratory determinations of Q, until recently, were most often made at frequencies much higher than those measured by seismologists for waves propagating through the earth. Recent advances in seismic station distribution and quality, as well as in methodology at both high and low fequencies, have greatly improved the quality of observational data available to seismologists from global stations. Concurrent advances have been made in measuring Q using laboratory samples at frequencies that pertain to the earth and in theoretical understanding of seismic wave attenuation. Papers of this volume present new information on Q in the earth from several perspectives: methodology, results from global and regional observations of both body and surface waves, laboratory measurements, and theoretical understanding. The editors believe that we have reached a new threshold in Q studies and that advances in data quality and methodology will spur increased interest in this difficult, but interesting field.

Description / Table of Contents: The special issue contains contributions presented at the international workshop Seismic waves in laterally inhomo- geneous media IV, which was held at the Castle of Trest, Czech Republic, May 22-27, 1995. The workshop, which was attended by about 100 seismologists from more than 10 countries, was devoted mainly to the current state of theoretical and computational means of study of seismic wave propagation in complex structures. The special issue can be of interest for theoretical, global and explorational seismologists. The first part contains papers dealing with the study and the use of various methods of solving forward and inverse problems in complicated structures. Among other methods, discrete-wave number method, the finite-difference method, the edge-wave supperposition method and the ray method are studied and used. Most papers contained in the second part are related to the ray method. The most important topics are two-point ray tracing, grid calculations of travel times and amplitudes and seismic wave propagation in anisotropic media.

Description / Table of Contents: The 1993 Southwest Hokkaido Earthquake of Magnitude 7. 9 (July 12, 22: 17 JST) caused serious tsunami disasters in the southwestern part of Hokkaido, particularly on Okushiri Island (a tiny island off the southwest coast of Hokkaido with a population of about 4,500 at the time of earthquake). Of 230 casualties, including 28 missing, about 200 deaths are attributable to the tsunami. We have conducted detailed field surveys of tsunami disasters to learn lessons from this costly natural experiment for the future prevention of similar tsunami disasters. Our field work was conducted in four surveys totaling 39 days. During the first field survey (July 16 through July 21, 1994), we worked mostly on the estimation of the subsidence of Okushiri Island during the earthquake. Hence, our main work on tsunami disasters initiated from the second field survey (July 31 through Aug. 15, 1994). Several groups have conducted detailed surveys of the distribution of tsunami runup height as measured from the level of sea water (TsUJI et al. , 1 994a, b; MATSUTOMI and SHUTO, 1994; GOTO et al. , 1994). Such a precise runup height distribution is essential for characterizing tsunami, including its overall size. Indeed, the height distribution is the fundamental data for inferring earthquake source parameters through the simulation of tsunami generation (TAKAHASHI et al. , 1994; IMAMURA et al. , 1994; TSUJI et al. , 1994a; SATAKE and TANIOKA 1994; ABE, 1994; TANIOKA et al. , in review).