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6 The Future: A National Seismic System Forecasting the future of regional seismic networks is facilitated because that future is severly circumscribed. The panel has reported on the follow- ing persistent themes, already well set, which will control the next one to two decades of observational seismology in the United States: · First, regional seismic networks, as currently configured and supported, do not have a long-term future; they will remain, at best, static in the western United States and will largely disappear in the East. . Second, the rationale for development of the USNSN is compelling. However, since design and implementation of the USNSN are already well under way and funding for the eastern portion has already been secured, this is largely an after-the-fact finding. . Third, the functions and data products of the USNSN are sufficiently different from those of the regional networks that the former cannot replace the latter. Even if completed nationwide, the USNSN will not eliminate the need for regional seismic networks. The above themes, which the panel considers are amply supported in Heaton et al. (1989) and in this report, prompt reconsideration of the central recommendation of the Panel on National, Regional, and Local Seismograph Networks (Committee on Seismology, 1980), which is quoted in the preface. Implementation of a "rationalized and integrated" system consisting of a partnership between the USNSN and a confederation of existing regional seismic networks is also the central recommendation of the current Panel on Regional Networks. But now, 10 years later, the needs cited by the 1980 38
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THE FUTURE: A NATIONAL SEISMIC SYSTEM 39 panel have become a crisis, the national network of "technologically ad- vanced observatories" is close to becoming a reality, and a detailed functional framework and specific funding requirements have been identified. The total concept is called the National Seismic System. ADVANTAGES OF A NATIONAL SEISMIC SYSTEM It is important to reemphasize that the USNSN will not meet the need for data that can be obtained only through the dense spacing of individual stations in the typical regional network. The resolution required for the definition of local active tectonic structures cannot be achieved by the pro- posed national effort. Variations in propagation and seismic wave amplifi- cation, important in the assessment of earthquake hazards on a regional and local scale, cannot be measured by the USNSN. And finally, the USNSN cannot replace the training facilities and intellectual focus for seismological education and research that the regional networks currently provide at many universities throughout the country. However, the USNSN will provide a uniform, national earthquake recording capability that currently does not exist. Indeed, the planned national network and existing regional networks would complement each other, and together if the former is developed and the latter continue to exist provide an unprecedented source of seismological data for public services, education, and basic and applied research. This combination of regional and national networks provides a unique opportunity to significantly advance seismic monitoring, data collection, data distribution, and seismological research in the United States within the next few years. This opportunity will be translated into reality only through close cooperation and coordination between the regional and national efforts and through the integration of certain aspects of their activities. The advantages that may be realized from a partnership of the regional and national network efforts include the following: . Use of USNSN facilities could reduce communications costs. Expen- sive, often unreliable, and capacity-limited ground line communication links used by the regional networks are not very suitable for the transmission of seismic data. The satellite-based seismic data communications system be- ing developed for the USNSN could revolutionize regional operations in that it will provide more reliable, more flexible, and less expensive commu- · . . neatens service. Regional networks could provide maintenance and facility support for national network stations located within the monitoring area of the regional network. The national network would benefit through reduced operational costs. The host regional network would benefit by having direct access to the communications links of the USNSN.
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40 ASSESSING THE NATION'S EARTHQUAKES The sharing of communication links and other facilities would force both the regional and the national networks to adhere to certain standards of data quality and format. · With such standards in effect, it would be easier to share and ex- change software used in routine data analysis at both national and regional data centers. The standardization of data formats and software would allow data to be shared between regional networks and give easy access to the data from the national network. · The national network could provide a framework or forum to draw the regional networks together to discuss and resolve common problems. The forum could prove to be an effective focus for the activities of the regional network operators and spur development of a body with a strong and uni- fied voice on behalf of the concerns of the regional networks. Thus, from both the state and the national perspective, there appears to be an opportunity for substantial benefit if the regional and national net- works work together closely. Finally, the panel examined the question of whether linkage with the USNSN is the only viable alternative for the regional networks and concluded that this is indeed the case. As has been shown, maintaining the status quo in network operations clearly is not an option. The most nearly related programs are the global network and portable array (PAS SCAL) of the Incorporated Research Institutions in Seismology (IRIS). However, these programs are complementary to a National Seismic System, and IRIS has specifically avoided involvement with permanent arrays, although modern- ized regional networks would contribute greatly to such PASSCAL goals as three-dimensional imaging of the earth's crust. These reasons, combined with the fact that planning and funding for the USNSN are already well advanced, make a National Seismic System the best and only logical choice for the future of regional seismic networks. As the U.S. Geological Survey has already been assigned the role of developing the USNSN, it would play a major part in implementing the proposed system. CURRENT AND PROJECTED COSTS OF A NATIONAL SEISMIC SYSTEM A National Seismic System cannot become a reality without the infusion of new funds. Currently, there are no new monies designated to (1) expand the USNSN to the western United States, (2) operate and maintain the USNSN beyond current NEIC resources, (3) replace the loss of $2 million in Nuclear Regulatory Commission regional network support, (4) replace and modernize aging and obsolete regional network instrumentation and equipment, or (5) provide for data links between the USNSN and the regional networks.
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THE FUTURE: A NATIONAL SEISMIC SYSTEM 4 1 Based on its survey of network operators (Appendix A), the survey of the Ad Hoc Committee on Regional Networks (ACORN, 1986), and discussions with federal agency officials, the panel estimated that the FY 1989 annual apportionment of federal seismic network funds is approximately as follows: $1.5 million (USGS external networks), $3.0 million (USGS internal networks), $1.0 million (NEIC), $2.0 million (Nuclear Regulatory Commission), $2.0 million (DOE), and about $0.2 million (U.S. Bureau of Reclamation), yield- ing a total of nearly $10 million. This estimate does not include support for global networks or the restricted-use seismic operations of the Department of Defense. This, then, represents the approximate current expenditure for operations that would come under the aegis of the proposed National Seismic System. The panel has not attempted a detailed analysis of projected costs for full implementation of a National Seismic System but has examined the question in sufficient depth to make firm recommendations in Chapter 7. For example, at least 65—and perhaps as many as 90- new stations will be required to complete the USNSN. At approximately $90,000 per station, the panel has conservatively estimated that 55 million will be needed for expanding the USNSN nationwide. Cost estimates for upgrading a typical regional network station range between $12,000 and $25,000, depending largely on whether broadband sensors are selected. If approximately one-third of the 1,500 regional network stations are modernized in the next five years, funding on the order of $10 million will be required for this element of a National Seismic System. These and other costs projected for full realization of a National Seismic System are included in Recommendation 6 of the next chapter.
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