Seismic Capability Research Articles

NSF considers recommendations for marine seismic reflection

As marine seismic reflection programs have become more complex, the number of active investigators has diminished because of the extensive technical expertise required. Establishing national facilities for at‐sea seismic acquisition is one way to shift much of the operational burden from individual scientists, enabling more scientists to use modern seismic methods and data. In addition, creating a seismic reflection data center would relieve accessibility issues and impediments to efficient multidisciplinary research and education.The U.S. National Science Foundation (NSF) funded a workshop to address marine seismic capabilities in the academic fleet, and the recommendations described above were part of the result. If implemented, the recommendations—which are now before NSF—would engage a broader segment of the scientific community in seismic acquisition and interpretive activities by simplifying fieldwork and access to data collected by other investigators. There are currently no official national facilities for seismic acquisition. The establishment of one or more NSF facilities would be a significant step, since many shortcomings could be addressed by consolidating management and incorporating coherent communitybased input at facilities operations.

Masonry in the seismic areas of the Americas, recent investigation and developments

Masonry, the oldest construction method, has become one of the major competing systems in modern construction. The great interest in its use around the world is due to its metamorphosis from a brittle and fragile material to one that can successfully withstand earthquake and wind forces while maintaining those features that in the past made masonry the preferred construction material. This paper reviews in general terms, the use of reinforced masonry in the construction of bearing wall buildings. It describes the different ways used to reinforce masonry walls to withstand earthquake forces. It discusses current issues of interest and areas of research, related in particular to the seismic resistance capabilities of the system. The paper also reviews the current situation in countries located in seismic areas of the Americas, with particular emphasis in Latin American countries.

Potential oil and gas resources of the arctic National Wildlife Refuge in Alaska: 1002 area

A geologist with extensive experience in the study of northern Alaska's petroleum resources provides an overview of the first comprehensive reassessment of the petroleum potential of section 1002 of the Arctic National Wildlife Refuge since the original study of 1987. The paper surveys the region's geology, and provides a description of the methods employed and assessment results. The current resource is compared with that estimated in the original study, and is considerably larger, given the availability of new geologic and geophysical data, improved seismic processing and interpretation capabilities, and changes in the economics of North Slope oil development.

Seismic capability evaluation of the prestressed/reinforced concrete containment, Yonggwang nuclear power plant Units 5 and 6

There are two methodologies to evaluate the seismic safety for a given structure; one is a seismic fragility method of analysis (SFA), and the other is a conservative deterministic failure margin method of analysis (CDFM). The former is a probabilistic approach, whereas the latter is a deterministic approach. In this paper, the containment structure of the Yonggwang Nuclear Power Plant Units 5 and 6 (YGN 5 and 6) is evaluated, using the two methods described above, to find the upper-shelf seismic capacity of the containment structure under the severe seismic loading exceeding the design basis earthquake. The YGN 5 and 6 containment structure is subjected to a design peak ground acceleration (PGA) of 0.2 g and a design pressure of 57 psig. The most critical failure mode is a diagonal shear failure of the cylindrical shell near the wall/base slab junction; the shear capacity of which was computed using a truss analogy theory. The two seismic capacities obtained from the SFA and CDFM approach are expressed as high capacity and low probability of failure (HCLPF) numbers and the evaluated final HCLPF numbers for YGN 5 and 6 are 1.20 and 1.34 g, in terms of PGA, respectively. A comparison of the two final numbers is then performed to obtain some insight over the two approaches, the ratio of which resulted in approximately 1.12. The ratio of 1.12 is judged to be reasonable based on similar studies in the U.S.

Experimental Data on Seismic Response of Piping Components

Experimental data from the EPRI Piping and Fitting Dynamic Reliability Program are evaluated. High-amplitude, seismic time history loads were applied to 32 piping components in a cantilevered configuration. Components included elbows, tees, reducers, a reinforced fabricated tee, a nozzle, and lugs. The test levels were about 2 to 8 times Level D. The seismic capability of elbows is shown to be remarkable. The seismic performance of lugs is judged to be poor. The tests demonstrate that collapse is a potential failure mode, particularly in low-frequency systems. The tests also demonstrate that a fatigue failure in a single, high-level, seismic event is possible. Of the 15 nonelbow tests that failed by fatigue, six (40 percent) failed during the first high-level seismic test. Design and fabrication details are crucial to seismic performance. Trends in the data need to be assessed to determine appropriate Section III stress limits for seismic loads. In particular, the impact of component frequency on seismic capability has to be quantified.

Seismic responses and resistance of age degraded structures and components

Nuclear power plants, as with many other structures, can experience aging degradation on a continuing basis. In some cases, the environmental or operating conditions, which they are subjected to, may be more severe than those affecting non-nuclear structures. This degradation needs to be understood and adequately managed for the continued safe operation of nuclear power plants. To date a limited number of nuclear power plants in the US have specific monitoring and inspection programs for structures. The evaluation for seismic loading is particularly important because the degraded structures or components could be more vulnerable to the seismic loads. From a seismic analysis point of view, the aging or degradation may affect dynamic properties, structural response, resistance or capacity, failure modes, and locations of failure initiation. Further, the NRC license renewal rule requires in part that the current licensing basis (CLB) be maintained throughout the period of extended operation. To meet this requirement, an assessment and timely maintenance of the degraded structures and components becomes necessary. An international cooperative program is being considered to pull together resources to tackle the issue of seismic effects on aged/degraded structures and components, and to augment existing databases by using experience of nuclear power plants worldwide. Based on the insights and lessons learned from this program, technical bases could be established for each participating country, as needed, to develop guidelines to address the seismic capability of aged/degraded structures and components for continued and extended service. The extent of the program will depend on the results of a scoping or bounding study to be performed in the initial phase.

Coupled wave-number integration approaches to range-dependent, seismoacoustic modeling

Wave-number integration (WI) approaches directly implement the ‘‘exact’’ spectral formulation for the seismoacoustic field in ocean waveguides. Therefore, these modeling approaches are inherently limited to range-independent, or horizontally stratified, environments. However, WI possesses a number of unique seismic capabilities, and various wave-field coupling approaches have recently been combined with WI to extend its applicability to two-way, seismoacoustic propagation in strongly range-dependent environments. These hybrid modeling approaches use a stepwise discretization of the environment similar to the one used in coupled-mode models. The spectral super-element approach [J. T. Goh and H. Schmidt, J. Acoust. Soc. Am. 100, 1409–1420 (1996)] then uses a Galerkin boundary-element formulation for the coupling between the range-independent sectors (super elements), while the virtual source approach [H. Schmidt, Proc. SWAC-97, Beijing (Apr. 1997)] uses an approximate, but highly efficient, local solution to the coupling problem. The performance of these new approaches has been demonstrated using a new class of two-way seismoacoustic benchmark problems with both weak and strong range dependence. Here, the new modeling approaches will be described, and their unique seismoacoustic capabilities will be discussed and illustrated by application to, e.g., the deep-ocean waveguide coupling of near-shore tomography sources, and analysis of potential seismoacoustic coupling mechanisms for oceanic T phases. [Work supported in part by the Office of Naval Research.]

Val Verde Basin: Thrusted Strawn (Pennsylvanian) Carbonate Reservoirs, Pakenham Field Area

An important target of recent exploration in the Val Verde basin of southwestern Texas has been thrusted Pennsylvanian (Desmoinesian) carbonates along the leading edge of the Ouachita front. These reservoirs produce gas and condensate at significant rates from fractured limestones, which were deposited in a variety of environments and later complexly juxtaposed during thrusting. Improvements in seismic imaging capabilities, particularly associated with the introduction of two-dimensional (2-D) swath and three-dimensional (3-D) surveys, have allowed accurate mapping of the thrust front and have resulted in revised interpretations of basin structure and history. These data highlight the existence of multiple reservoirs at separate structural levels. Strawn reservoirs are di cussed in relation to the Pakenham field area, northwestern Terrell County.

Soviet Efforts To Attract Foreign E and P Investment Through Joint Ventures

This paper reports that since 1987, Soviet efforts to attract Western E and P investment have been evolving through the framework provided by the 1987 Joint-Venture Law. While this law and dozen or so regular acts, decrees, and amendments have sought to stimulate interest, they have failed to address significant failings in the Soviet Union's institutional organization of the petroleum industry. While we anticipate that institutional authority will continue to devolve away from the All-Union central control in Moscow to the republican authorities, many obstacles to investors still have not been addressed by the joint-venture laws. Among these are the export regime, fiscal regime (which we expect will get stiffer), and the rules for joint-venture capitalization and valuation.

Piezocone penetrometer and its utilization in Australia : Simmons, J V Aust GeomechN18, Jan 1990, P19–24

There are many operators of cone penetration test (CPT) equipment in Australia, but only four operators of piezocones. The Vic Roads Geotechnical Group offers a heavy truck mounted CPT facility including standard 2 channel cones and a Fugro piezocone with a 5mm face mounted filter. An in house 3 channel piezocone design has reached prototype development stage. Associated with this equipment is several years' operating experience, a wide range of support facilities for geotechnical assessment and design. The recent addition of Dilatometer testing has enhanced the value of the CPT capabilities. Queensland Main Roads Department (QMRD) have for many years operated 2 channel cones from drilling rigs. The Hogentogler piezocone system has been used for a number of soft soil projects in coastal north Queensland since 1987. The equipment is maintained and operated by James Cook University of North Queensland (JCUNQ) except when required for QMRD work. The JCUNQ work is focussed on defining the field consolidation behaviour of soft sensitive mangrove muds, and will fully utilise the seismic capabilities of the equipment when additional facilities are acquired in 1989/90. The Water Authority of Western Australia (WAWA) operates a heavy truck mounted CPT facility. In 1988 WAWA purchased a Hogentogler seismic piezocone, and there are plans to fully implement the Hogentogler FCS during 1989. DJ Douglas and Partners have operated heavy truck mounted CPT equipment throughout Australia, and now offer Dilatometer testing services as well.

Hologene activity and tectonic setting of the Maacama fault zone, Mendocino County, California

The Maacama fault zone is a north-northwest trending, right-lateral zone of structural weakness in eastern Sonoma and Mendocino Counties, California, and fault-related landforms along its trace suggest that it may well have been active during Holocene time. Urbanization and dam construction in the vicinity of the zone have made it especially desirable to determine the extent and history of such geologically recent movements in order to better understand the seismic capability of faults within the zone. The Maacama fault zone is a segment of one of two north-northwest trending zones of right-lateral faulting that diverge as major branches from the easterly side of the San Andreas fault zone north of Hollister. These branches extend at least as far north as Eureka and may mark the eastern boundaries of slivers of a separate tectonic plate. This investigation was conducted to evaluate Holocene activity along the part of the Maacama fault zone in Mendocino County. The investigation shows that this zone comprises discontinuous, subparallel fault strands which extend from points south of the Sonoma—Mendocino county line to points north of Laytonville. Some fault segments are expressed by alignments of topographic features clearly caused by Holocene strike-slip movements. Other topographic features are less distinct and may well represent fault segments with pre-Holocene activity. The Maacama fault zone creeps at a current rate of possibly as high as 2 mm/yr. The total amounts of Holocene offset are unknown. Evidence obtained from exploratory trenches indicates that at least two surface rupture events have occurred within the past 16,200 years, that at least one has occurred within the past 8,310 years, and that there probably has been no surface rupturing within the past 1,140 years. I conclude that surface offsets have occurred along major portions of the Maacama fault zone during Holocene time, and that this fault zone should be regarded as capable of producing a moderate to strong future earthquake with accompanying surface rupture in Mendocino County.

A seismic margin assessment procedure

This paper presents recommendations for a seismic margin assessment program for operating nuclear power plants. The goals of such a program are stated, and an overview of two alternate approaches is presented. Brief guidance for performing a seismic capability walkdown (an integral part of such a margin program) is provided. One of the prime purposes of such a walkdown is to screen out from review those components which will not be significant contributors to seismic risk. As guidance, the dominant contributors to seismic risk as found from existing seismic probabilistic risk assessments are presented. Seismic capacity screening guidelines are also provided. Lastly, a conservative deterministic failure margin (CDFM) for estimating a high-confidence-low-probability-of-failure seismic margin level is summarized.

The dynamic response of multi-layers AGR core brick arrays

The graphite core of the Advanced Gas Cooled Reactor (AGR) core has been seismically qualified using a non-linear computer program AGRCOR. This complex three-dimensional code has been verified by comparing predicted responses with exact solution and also with AMP2D code. Using the contact input parameters derived from an extensive test program, the code was validated by comparing predicted responses with measurements of dynamic models of various complexity, one (36 bricks), two (63 bricks) and four (117 bricks) test assemblages. The impact loads generated in the key/keyway and between adjacent bricks due to postulated earthquake input were used to assess the seismic capability of the core by relating these loads to some form of cumulative damage criteria obtained from combined test and analysis.

A new airgun array for Conrad

The research vessel Robert D. Conrad, owned by the U.S. Navy and operated by Lamont‐Doherty Geological Observatory (LDGO) of Columbia University (Palisades, N.Y.), is a multi‐use ship that is principally employed for marine geology and geophysics surveys. For the last 10 years, the Conrad has had a multichannel seismic (MCS) capability, which is used to determine deep structure and velocity of the suboceanic crust around the world. While it is expected that the Conrad will be replaced by a new vessel sometime in the 1990s, the needs of current and future projects required that her MCS capability be upgraded and enhanced now. The National Oceanic Reflection Profiling Organization (NORPO) recommended in 1985 that up to $2 million be invested in the immediate upgrading of the MCS capability of the U.S. academic research fleet (see “Marine Multichannel Seismology Workshop ” in Eos, February 11, 1986, p. 70). This recommendation bore first fruit in late 1985, when The National Science Foundation (NSF) granted $425,000, matched by $ 100, 000 in Lamont‐Doherty institutional funds, for an upgrade to the seismic source system on the Conrad.

Addition of velocities

Not quite 20 years ago, Rudy Prince and I were dining with two Chevron geophysicists at a Los Angeles restaurant. The view was beautiful, the food delicious, and the conversation stimulating. All day Rudy had been telling Chevron about the latest seismic acquisition and processing capabilities of Digicon and I am sure that I was brought along to say something helpful at the right moment.

Dynamic response of multistoreyed brick buildings

AbstractThe paper presents the seismic response analysis of a typical multistoreyed brick building. A number of variables representing the physical properties of the structural system, namely, number of storeys from one to four, wall thickness in various storeys from one to one and a half brick thick and damping from 5 per cent to 15 per cent of critical value are considered. A shear beam type multi‐degree‐of‐freedom oscillator is taken to represent these buildings mathematically in which the masses of the floors and walls are assumed as lumped at the floor levels and the floors are assumed as rigid diaphragms. Koyna and El Centro earthquake accelerograms, representing two seismicity levels, are used for computing dynamic response of the buildings. Overturning and torsional effects have been included in the determination of timewise net stresses in the building elements and their seismic capabilities have been examined. From this study the critical sections for providing reinforcing have been identified and the minimum amount of necessary steel has been estimated.

Design development of the HTGR core and its support structure seismic considerations

This paper discusses the development of the core support structure design from that employed on Fort St Vrain to recently announced contracts by Philadelphia Electric, Delmarva Power and Light and Southern California Edison for the large HTGR. Particular emphasis is given to the seismic considerations in the design of the structure for the large HTGR. The overall configuration of each reactor type is critically compared. Although similar components are employed, the basic difference in layout configuration results in significant conceptual differences in the structural and mechanical requirements of the core support components. The configuration and major components for the large reactor are described in some detail. The essential features and function of components are discussed. The graphite components in the core support floor and permanent reflector are designed to form a tight array during reactor normal operating conditions. This composite structure resists compressive loading due to differential gas forces and concrete pressure vessel movement. This tight array concept has important advantageous effects on primary coolant flow distribution and seismic capability. The paper discusses the inherent requirements and methodology in developing a standard plant design for high seismic sites. A design suitable for 0.15 g operating basis earthquake and 0.25 g safe shutdown earthquake has been developed which is applicable for over 80% of the expected sites in the USA. The HTGR core and support structure consists of many thousand graphite elements. It behaves as an inelastic body having random response when subjected to seismic excitation. The paper describes simplified analytical models which have been developed to investigate this phenomenon. An overview of a test program to substantiate and correlate with the analytical models is provided. The program addresses the interelement collision forces and frequencies of elements within the core and the load/deflection at the boundary. Various one, two and three-dimensional scale models have been tested. A summary of the objectives of the program is provided.

Seismic Considerations in the Electrical Design of Nuclear Power Generating Stations

Meeting requirements for seismic capabilities in electric equipment installed in nuclearpower generating stations requires a working relationshipwith an esoteric and complex technology. This paper presents guidance to the electrical power engineer in understanding the considerations involved in the application of electric equipment that must meet seismic requirements. Basic requirements are explained, followed by more detailed discussions of methods of qualification and application of specific types of equipment.

Test Method to Demonstrate the Seismic Capabilities of Equipment

A study of random motion effects reveals that broadband seismic disturbances become filtered by mechanical soil-structure systems to produce narrow-band floor response motion under the equipment. The latter corresponds to quasi-resonance vibration buildup at one or more natural frequencies of the building.

SEISMIC STRATIGRAPHIC EXPLORATION—PART III

A review of seismic research and development shows there is available in 1971 an important new, mature, and sophisticated seismic technology. This technology, when added to the solid foundation of basic science and experience of the pre‐1963 model seismic stratigraphic exploration capability, produces a capability which can, in the future, discover stratigraphic oil. We suggest there are many ways of achieving seismic high resolution which are not now in widespread use. Applications of our high resolution concepts to stratigraphic exploration are illustrated, including the direct detection of hydrocarbon saturated sands. To illustrate types of situations where it seems reasonable to search for major undiscovered stratigraphic reserves, we analyze briefly the Gulf Coastal province. This province contains a huge carbonate basin and a colossal clastic basin which may have tremendous potential from a modern stratigraphic exploration viewpoint. It is again emphasized that the stratigraphic exploration process will have to be performed by fully integrated exploration teams composed of management, geologists, and geophysicists.