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REGIONAL NETWORKS REVIEW Regional networks are those that have been installed to study seismological problems on a geographic scale of l00 to l000 km. Such networks have been established widely in recent years, and today there are approximately 50 regional networks in the United States, each consisting of tens to hundreds of individual seismographic stations. These networks are supported by a number of different groups (e.g., USGS, U.S. Nuclear Regulatory Commission (USNRC), DOD, DOE, and other federal, state, and local agencies) for a number of different reasons. The role of regional networks is, in general, to delineate the time and space distribution of earthquakes on a fine enough scale to contribute to our scientific understanding of earthquake occurrence and related tectonic processes and to provide important baseline data for engineering investigations (e.g., earthquake prediction and hazard assessment). Figure 2 shows the earthquake occurrences in California for l980. U.S. regional networks date from the l887 installation of the University of California seismographic stations. The first telemetered network in the U.S was that of the USGS in Hawaii. Developed during the mid-l950s, the network had four original stations around the summit of Kilauea Volcano with the information telemetered to the Hawaiian Volcano Observatory. By July l958 this local network had expanded to about l5 km across. An early U.S. regional network of seismographic stations that was connected by FM telemetry to a central site was installed by the University of California at Berkeley in l960 to monitor and study seismicity in central California. Regional networks with increased l7

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l8 FIGURE 2 California seismicity for l980 from data of three regional networks - Caltech, Univ. of Nevada, and USGS. station density were installed by the USGS in the late l960s to study in greater detail the San Andreas Fault in California, within a very short time, well-defined spatial patterns of earthquakes were delineated, providing a clearer fine-scale picture of the spatial distribution of earthquakes. Given this initial success, throughout the next decade, regional networks were extended in California and established in other states with ongoing seismicity.

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l9 Only since l970 or later have the major seismological problem areas of the United States been consistently monitored at high sensitivity by regional networks. The increase in data flow resulting from this large number of seismographic stations has, in part, been managed by the introduction of automatic detection and digital data processing. The acquired data have been used for engineering planning, disaster mitigation, and fundamental scientific investigations. In many cases the results of a network installation and operation transcend the original purpose of its installation. Some relatively small networks have contributed important scientific results on topics ranging from plate tectonics to the mechanics of crustal deformation and from induced seismicity to the prediction of volcanic eruptions. The proliferation of regional networks, usually funded initially by various mission-oriented agencies for very specific purposes, has resulted in some problems. Coordination of the establishment, distribution, and shutdown of local and regional networks has proved to be a difficult task. An increasingly acute problem for the USGS is its role in continuing the operation of networks that have lost support from their original funding agency, and the impact upon other USGS programs if financial support is provided. The prime reason for this workshop was a perceived need to assess the future of regional networks in terms of federal agency funding constraints in late l98l. The particular trigger was the threatened budget cuts in the fall of l98l that could have decimated this vital data base. Important decisions are being made now on the l983-l984 network funds. This report marks the first time that the activities and problems of regional networks have been examined inclusively. The basic background data were obtained from a thorough questionnaire used by the committee to obtain data and opinions from the responsible operators of some 45 regional networks. The collected information helped in the assessment of the problems and the formation of the recommendations that follow. ASSESSMENT OF PROBLEMS Given that there are more than l600 U.S. seismographic stations grouped functionally and operationally into 50-odd independently managed networks, with funding

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20 coming from about l0 different federal agencies, an equal number of states, some cities, utilities, and even private universities, it is not surprising that there are problems in regional network seismology. Mixed with this basic diversity of purpose and support are the particular goals of the operators, usually established research scientists with their own perception of purpose for the network they manage. The committee, in considering agency questions and operators' comments, has defined a number of problems facing the regional networks. They fall into three separable categories: functional definition, funding difficulties, and operational problems. A functional definition, that is, a clear statement of network goals and a realistic estimate of its planned lifetime, must always be provided. Funding difficulties are of two types: a lack of stability on a year-to-year basis and the vulnerability of research funding being decreased to keep networks operating in times of fiscal stress when research funding is mixed with basic operational costs of the network. Operational problems are seen in a lack of coordination among networks, the need for a more standardized data base management system, and a growing obsolescence of network equipment. These problems are interrelated and difficult to order in importance. A robust funding environment would go far toward solving most of them. Unfortunately, such is not the present situation. We consider these problems now in turn. A significant part of the overall problems of regional networks is the difficulty of designating a realistic design lifetime of a particular network. It is a well- recognized fact that some networks are operated to provide a specific data base and that when that data base has been collected the network is expendable to the supporting agency. There are a number of support agencies that are mission-oriented, serving either a regulatory or a service function for the government as contrasted to a research function. In addition, there are agencies that represent a gradation between functions. The USNRC and the U.S. Army Corps of Engineers might be taken as examples of the former, whereas the USGS is an example of an agency in the middle ground, serving both a service and a research function. The particular mission of the support agency has a definite controlling influence on the design lifetime of a network. While it may seem appropriate to operate a

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2l small regional network in the immediate vicinity of a proposed critical facility to obtain seismological data for design purposes, any such window of data must be recognized as a very short-time sample of natural phenomena that occur infrequently. Furthermore, the facility itself may alter the seismological character- istics of the site, as in the impoundment of a large reservoir. Some regional networks such as those in California supported by the USGS or those in the Northeast and Southeast supported by the USNRC are intended to provide seismological data over a very broad region—not specifically for a particular site. Such regional networks may require a minimum of l5 to 20 years to obtain a representative sampling of seismicity. Clearly, an initial understanding of design lifetime is important, as well as a regular evaluation of the initial plan in light of the results of operating the network. Perhaps the most significant problem perceived by networks is the lack of a rational approach to stable network funding. Many operators attribute this situation to a lack of realization at high levels in support agencies that many of the applied and basic research problems addressed by regional networks require long and continuous data bases. Operators see vagaries in funding as a result of this situation. Separation of the research activities from the operation of regional networks appeared as a common theme in the non-USGS operators' responses to the questionnaire and leads to our identifying the following problem: for funding purposes the operation of a network (all steps through bulletin preparation) is often lumped together with research (the scientific analyses of the network data). In times of financial stringencies, we thus see elimination of research funds, since operational costs are fixed and subject to inflation. When the scientist in charge can cut only research funds in combined budgets, he assumes more and more the role of a technician providing services. Research and network operation are usually not evaluated by different standards, but they should be. For the former the standard is scientific merit, whereas for the latter it should be stability, quality, and service. A related but specialized difficulty is seen in maintaining a balance of support for operations and network development between funding agency and funded

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22 operator when there is a joint responsibility for that network. Lack of coordination appears as a generic problem that emerges in one fashion or another in the majority of the problems that confront the regional seismographic networks. Effects of a lack of coordination show up in the areas of data exchange, network boundaries, software compatability, data archives, and duplication of efforts in a number of technical developments, including both software and hardware. The net result has been to reduce the effectiveness of the regional network operations as a whole. A class of problems involves the lack of standardized methods for data base management. This problem involves a number of elements, including data management, data centers, software portability, and manpower usage. Network operators customarily face two conflicting objectives. On the one hand, they contribute to an archive of data that can be used long-term, together with other geophysical data (perhaps including other seismic networks) for an overall synthesis. On the other hand, the scientist-operator must undertake (usually on a more short-term basis) scientific research objectives specific to the immediate field area, and drawing heavily on the data set. There exists a need to achieve a standard set of regional seismographic network data that can be easily accessed by general users for both service and research purposes. We anticipate that the archive that is supplied by the aggregate of networks will constitute a major scientific resource for understanding seismicity patterns on a regional and national scale. With respect to present scientific and technologic capabilities, regional networks suffer from obsolete equipment. The existing regional networks of seismic stations, including more than l600 stations, almost universally employ short-period, vertical seismometers. Most of the signals from these instruments are trans- mitted by narrow bandwidth, low-dynamic range FM telemetry that was first employed more than 20 years ago. The seismograms obtained from these networks have proven to be an economical and effective scientific tool for solving problems of earthquake location and, to a limited degree, for defining their source mechanisms. However, these data are inadequate for analysis by many powerful seismological methods developed during the past decade, and the data consequently do not provide

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23 critically needed new information on earthquake source properties and the structure of the earth's crust. The problem is particularly acute in the regional networks located outside of California, where network station spacing is large, and in areas where there are few high-quality instruments of other types operating within the short-period vertical networks. The lack of higher- quality data not only affects the basic research capabilities of the networks, but also may compromise their potential for answering mission-oriented questions posed by funding agencies. Within California, for example, it may be argued that present coverage, with hundreds of obsolete short-period stations, could be replaced to economic and scientific advantage by fewer modern instruments. RECOMMENDATIONS There are no easy answers to the problems summarized above. It is probably not possible to assign rationally a priori a design lifetime to any but the most local, site-specific networks. On the other hand, initial guidelines must be set by funding agencies when a limited duration is planned. Problems of regional seismicity will not be "solved" in a three- or a five-year period. Rather, it will normally require lifetimes of decades to obtain a representative sampling of the seismicity. Nevertheless, networks of planned, limited lifetime should be reviewed on a three- to five-year basis so that the state of knowledge gained by operation can be weighed against the network purpose. There exists a disturbing range of quality among regional network operations. Different networks currently operate to quite different standards. While some operators can produce on demand a bulletin updated to within a few days prior to a request for information, others have essentially no bulletin. Some produce seismicity maps with accurate information on magnitudes and focal mechanisms, but others have been operated with ignorance of instrument gain or polarities. The periodic review should involve the supporting agency or agencies and address a network's intended purpose and performance, considering all specific mission-oriented goals. A network should also be reviewed with respect to alter- native approaches that implement new technology to achieve equal or better performance at comparable or

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24 lower cost. We believe also that all regional networks, regardless of size or funding source, should be reviewed by the same review panel. There is, of course, no way to guarantee stable funding of regional networks. However, an irrational slashing of networks can be alleviated by an increased understanding of the broader role of regional networks by the funding agencies and by increased coordination of network operations at the national and local levels. Further- more, the above review procedure can result in a firm commitment to support (or terminate) until the next three- to five- year review. Agencies have the responsibility to decide when a network has satisfied their needs and to arrange for an orderly closure. Since networks often involve other users (who probably are not sharing in support), these "shadow" users should be informed early of decisions to terminate. Exhibit 3 in Appendix B gives examples of the wide variety of such users for four networks. The mission-oriented support agencies should also recognize and carefully evaluate their role and responsibility to support a national network independent of their current needs. We recommend that the network funding agencies admit to a realization that for most operators the main purpose of a regional network is to provide data fundamental to research on seismotectonic processes and earthquake occurrence in the region. This simple acknowledgment will allow open and rational discussion of the separate costs of routine operation versus research. A good faith effort must be made to remove the serious vulnerability of research support in the packaged funding practice. It will go far in eliminating different opinions between operators and funding agencies on true operational costs. We believe that it is time to emphasize the archival function of regional networks. Minimum desired archived data include earthquake summaries, phase lists, and digital seismograms at some minimum magnitude cutoff. Network specifications, including station parameters and response characteristics, are necessary. This function can be used as the major distinguishing feature separating what we call a network from a portable array. Of the 45 U.S. regional networks responding to the questionnaire, there are ll that operate dedicated computer-based recording centers. Many of these centers were established with direct support from the USGS. These regional centers provide the beginning of a skeleton framework for a recommended system of U.S. Regional

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25 Network Data Centers that should operate with standardized data formats that provide easily transportable data and that are well documented. A specific effort should be made to provide easy access via telephone terminal or equivalent to the developing Regional Network Data Centers. Coordination is not easy, but the above initiatives will in effect force a semblance of coordination and cooperation onto the regional network scene. We con- templated a recommendation for a regional coordinator who would work toward a greater integration of operations in a given area. It seems best, however, to hope than an evolution toward Regional Network Data Centers will provide a natural focus for coordination among operators, users, and support agencies. Seismologists throughout the United States are working on a variety of theoretical and operational software—at a great investment of manpower and money. Through an effective coordination among networks, duplication can be minimized and significant developments can be made available to the rest of the community on a timely basis. Throughout the history of seismology in the United States, technical, theoretical, and observational problems have been tackled by seismologists. With the rapid expansion in seismological efforts and with advances in modern electronics, computation capabilities, numerical modeling, etc., it is cost effective to use experts in these fields to help solve seismological problems, and to disseminate the solutions, as a means of allowing seismologists time to pursue their own research. There exists within the broad seismological community considerable expertise and experience in data collection systems other than those in common network usage. Such systems employ broadband sensors and wide dynamic range digital telemetry and recording. The opportunities presented by this technology are in many respects com- parable to those apparent in l960 when specifications were set for the worldwide standard seismograph network first proposed in l959 by the Berkner panel. Several groups are proposing new generations of instruments, for various applications. It is important that input comes also from the regional networks on standardization and the type of recording and data collection systems to be used. It is recommended that a standing working group be established by the Committee on Seismology (the same group that represents the seismological community on the

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26 problem of a national network—a problem that is closely interrelated) to evaluate continually the overall health and status of regional networks. This working group would provide all the review functions recommended for regional networks in this section. It would work closely with the network operators and with agencies that fund the network and provide advice on related matters. Most such agencies were represented at this workshop, and their representatives indicated a need for ongoing review of the type recommended here.