摘要:

No one had foreseen that a shock as large asMs6.7 could strike at the eastern edge of the California Coast Ranges near the town of Coalinga. No faults of any age cut the gently folded sediments at the earthquake focus, and equally astonishing, no ground breakage accompanied the earthquake. A month would pass before surface rupture did occur, in a sequence of large aftershocks (see cover: large blue circles west of the yellow main shock) on a minor adjacent fault.The May 2, 1983, earthquake, which caused $31 million in damage and took one life, alerted the seismological community to the earthquake potential of active folds. Leveling surveys demonstrated that Anticline Ridge (whose fold axis plunges southeast through the main shock) uplifted 0.5 m during the event, while adjacent Pleasant Valley (see cover: red and white squares immediately southwest of the aftershocks) subsided half that amount. The surface deformation is best explained by a fault that slipped over a depth of 4–12 km but does not reach the surface. Identification of earthquake risk has proceeded almost exclusively on the premise that faults capable of generating large shocks must extend to the surface. Surface faults that do not cut young deposits are not deemed active, even if the faults displace older beds at greater depth. At Coalinga, on the other hand, the fault, the seismic slip, and the aftershocks are confined to deeper and therefore older strata. The fault is invisible on seismic reflection profiles, but it is indisputably active. The surface fold which built Anticline Ridge appears to have formed as a consequence of repeated slip events at depth. From the pattern of earthquake deformation, R. Stein and G. King have argued that many folds mask subsurface thrust faults and that these folds may largely deform elastically in jumps, rather than through steady and aseismic ductile deformation. In retrospect, a number of large thrust earthquakes over the last 30 years have uplifted anticlines, dropped synclines, and produced little or no ground rupture, such as the 1964Ms7.5 Niigata shock in Japan. Thus, despite the paucity of bounding faults, the folded eastern margin of the California Coast Ranges must now be regarded as a possible target for large thrust events. The uplift rate of the folds should guide judgments of relative activity. Ominously, the Kettleman Hills anticline, which abuts the Coalinga aftershocks to the southeast, is rising at twice the rate of Anticline Ridge. (These processes will be discussed at the AGU Fall Meeting in the Tectonophysics session entitled “Mechanics of Large‐Scale Faulting and Earthquakes,” scheduled for Friday morning, December 7; see abstracts in this issue for more infor

ISSN:0002-8606    

DOI:10.1029/EO065i045p00794-01

年代:1984

数据来源: WILEY

摘要:

A National Research Council (NRC) panel has endorsed a plan for a proposed underground military nuclear waste disposal facility located on a site near Carlsbad, N.M. The Department of Energy (DOE) asked NRC to evaluate the geologic suitability of the site.The NRC panel, chaired by Frank L. Parker of Vanderbilt University, concluded in its final report that “the important issues about the geology of the site have been resolved…” Those issues include the purity and volume of salt, the absence of brine pockets at the repository horizon in the areas excavated, the absence of breccia pipes and of toxic gases, and the nearly horizontal bedding of the salt. Thick underground salt beds have long been considered prime candidates for nuclear waste repositories. The existence of salt beds is believed to indicate long‐term stability. In addition, the salt is flexible and will seal cracks and discontinuities ov

ISSN:0002-8606    

DOI:10.1029/EO065i045p00795-01

年代:1984

数据来源: WILEY

摘要:

It has long been recognized that the fossil record is characterized by a number of major extinction episodes, but the cause of these remains a controversy. Among the many suggested factors, a correlation with major rifting events has often been postulated [e.g.,Hallam, 1984;Valentine and Moores, 1970], and we feel that the implication of this deserves much greater attention. The widespread volcanism, both submarine and subaerial, associated with such mega‐tectonic events with energy much greater than 1030ergs, offers a natural explanation for several of the features that have been linked with extinction crises. The occurrence of widespread submarine volcanism is likely to have been especially important in promoting massive marine extinctions through chemical and biologic mechanisms. Of the numerous extinction events cited in the literature, there are five major episodes for which there is widespread agreement, and several minor ones (Figure 1). Significantly, each of these can be correlated with an important volcanic event, and the correlation is especially strong for the three more recent major crises for which data is available (Table 1). These are the ones occurring at the ends of the Permian, Triassic, and Cretaceous period

ISSN:0002-8606    

DOI:10.1029/EO065i045p00796

年代:1984

数据来源: WILEY

摘要:

The National Oceanic and Atmospheric Administration (NOAA), acting as the lead agency in the United States for the Tropical Ocean and Global Atmosphere (TOGA) program of the World Climate Research Program, has negotiated an agreement with its counterpart, the National Bureau of Oceanography (NBO) of the People's Republic of China (PRC) for jointly carrying out a TOGA‐related air‐sea interaction study of the western Pacific region near 165°E. This study was originated under the U.S.‐PRC Protocol on Cooperation in the Field of Marine and Fishery Science and Technology as a contribution to the TOGA Pacific program. In addition to NOAA and NBO the Academia Sinica, the State Meteorological Administration of China, and the National Science Foundation (NSF) of the United States are all active participating agencies. Participation of scientists from other agencies and from the scientific communities of both countries is welcome and encouraged in any part of the cooperative air‐sea study

ISSN:0002-8606    

DOI:10.1029/EO065i045p00800

年代:1984

数据来源: WILEY

摘要:

The International Court of Justice has resolved the long‐term conflict between the United States and Canada over claims to mineral and living resources lying along the countries' common Atlantic maritime border. On October 12, in a 4–1 decision, the World Court rejected the United States' claim to the entire Georges Bank area, a region of the Continental Shelf off Massachusetts and Nova Scotia that is a prime fishing ground and is believed to have good potential for oil and gas deposits as well. The disputed area is roughly the top third of the Georges Bank area. The court awarded each country approximately half of this disputed area. No appeals are allowed under this decis

ISSN:0002-8606    

DOI:10.1029/EO065i045p00801

年代:1984

数据来源: WILEY

摘要:

A transpacific section across the subpolar gyre near latitude 47°N is planned for September–October 1985. This complements the 24.5°N section planned for March–May 1985. The purpose of the expedition is to determine the western boundary current structure, to determine the meridional flow in the region of the Emperor Seamounts, to measure the transport of heat by ocean currents, to determine the net transport of water masses and estimate the meridional general circulation of the north Pacific, and to improve the mapping of tracer distributions in the deep north Pacific.Approximately 110 surface‐to‐bottom conductivity, temperature, and depth (CTD) rosette stations across the width of the ocean will be occupied, with maximum station spacing of 80 km over abyssal plains, closing to 30–50 km over rough topography and boundaries. Water samples will be collected and analyzed on board for salinity, oxygen, an

ISSN:0002-8606    

DOI:10.1029/EO065i045p00802-01

年代:1984

数据来源: WILEY

摘要:

A Conference on the Tropical Oceans and Global Atmosphere (TOGA) Scientific Program was held in Paris during September 17–21, 1984. The purposes of the conference were to assess present knowledge about ocean‐atmosphere interactions in the tropics, particularly exemplified by the 1982–1983 El Niño‐Southern Oscillation (ENSO) event, to present and discuss a draft scientific plan for the TOGA program, and to inform scientists and science managers about TOGA opportunities.The TOGA program is a specific project within the World Climate Research Program, and its principal aim is the study of the coupled system constituted by the tropical oceans and the global atmosphere. The motivation for TOGA arises from the evident connection between global‐scale variability of atmospheric circulation and sea surface temperature anomalies and from the growing evidence that this connection can be simulated and ultimately predicted on time scales of month

ISSN:0002-8606    

DOI:10.1029/EO065i045p00804

年代:1984

数据来源: WILEY

摘要:

Preparation of a good introductory textbook on groundwater contamination is a challenge, since it requires treating a complex topic in a scientifically rigorous way while maintaining an introductory level. Of necessity, tradeoffs must be made to achieve this objective and brevity as well. Another difficulty arises because research into the fate of chemicals in the subsurface is a relatively new and evolving area. The authors of this book note that, “In the investigation and analysis of a groundwater pollution problem involving hazardous wastes, there is no established method or procedure.” Despite this handicap, the authors do succeed in demonstrating that although any given case of contamination is unique, it is possible to identify common attributes and outline a general framework for monitoring and remedial act

ISSN:0002-8606    

DOI:10.1029/EO065i045p00806-01

年代:1984

数据来源: WILEY

ISSN:0002-8606    

DOI:10.1029/EO065i045p00831

年代:1984

数据来源: WILEY