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~2 Problems and Constraints Regional seismic networks have been faced with numerous funding and operational challenges virtually since their inception. Many of these were documented in the report of a 1982 National Research Council workshop (Committee on Seismology, 1983~. The problems have become more acute as the network instruments age and as funding drops. The principal prob- lems arise from three causes: (1) obsolete, aged, and narrow-focus instru- mentation; (2) difficulties in handling large volumes of network data; and (3) labor-intensive operations with significant capitalization requirements. OBSOLETE INSTRUMENTATION Obsolete instrumentation is a major problem facing the regional seismic networks. Many powerful new analytical techniques, developed over the last 10-20 years, require higher-quality data than current regional networks can supply. An overwhelming majority of the more than 1,500 stations in existing regional seismic networks consist of short-period, vertical seis- mometers that were developed and installed one to two decades ago. The FM radio telemetry system used to transmit nearly all the data was developed over 25 years ago; the resulting signals have a narrow frequency band (~1- 20 Hz) and low dynamic range (often only 40 dB). This type of system produces seismic signals with clear P-wave arrivals, well suited to the task of locating and determining first-motion focal mechanisms of local earth- quakes in a relatively effective manner. (Focal mechanism determination is a technique by which the orientation (strike and dip) of a fault and the 17

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18 ASSESSING THE NATION'S EARTHQUAKES direction of slip on that fault are determined from the radiation pattern of seismic waves generated by the earthquake and recorded at numerous seis- mic stations.) The response and sensitivity typical of a regional network seismograph, relative to representative levels of earth noise and earthquake ground accelerations, are illustrated in Figure 3. The typical station producing one-component, narrow-band, low-dynamic-range data is inadequate for studies of moderate to strong ground motion, teleseismic earthquakes, or rigorous waveform analysis; and most importantly, the signals are usually "clipped" (i.e., the recording system is overdriven) for local earthquakes of magnitude 4, regional events of magnitude 5, and teleseisms of magnitude 6-7. Even for the purpose of earthquake monitoring, for which many of the regional seismic networks were installed, existing instrumentation is inad- equate for some routine earthquake cataloging tasks. Determination of magnitudes over the normally recorded range (1.0 ~ M < 6.5) is often impossible be- cause of the limited dynamic range of the sensing-recording system. The accuracy of depth determinations of earthquakes is greatly improved if S-wave arrivals are included, but they are poorly recorded by vertical seismometers, which are the only sensor component deployed at the great majority of stations. Thus, the instrumentation of regional seismic networks, while 'relatively inexpensive in initial cost per station, ultimately has penalized regional networks in terms of missed research opportunities. Unfortunately, the relatively unsophisticated instrumentation has served to isolate regional network operations from the forefront of the seismological community, which relies on the advanced technology of relatively few stations for state-of-the- art analyses. DATA-HANDLING DIFFICULTIES Handling large volumes of network data poses additional problems. The large number of stations and low-magnitude threshold of regional networks lead to such a large quantity of seismic data that only computer-based stor- age and manipulation of the data are feasible. Although the use of comput- ers for the acquisition, processing, and storage of data has become standard for regional networks, the computer systems and software used have not. Different individually developed and generally undocumented systems are in use at different networks, which makes internetwork data exchange difficult. It is obviously inefficient for each individual network operation to develop its own software for data analysis. Because written documentation for the systems is commonly lacking, use of the data by visiting scientists often demands significant time from the network operator or data analyst to ex- plain the local system. This difficulty in accessing data has restricted the usefulness of regional networks. In most cases, the fundamental raison

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PROBLEMS AND CONSTRAINTS 1o1 10-, 10 a) 10~ . ~ - z o 6 ~ 10-7 UJ LL C) 10 - 1 0-1 1 10-13 10-2 10-1 19 . "' '- ~ . ~ ., w~ `~ ,, JO / ' '~5 Earth noise Surface wave at 3,000 km. P-wave at 3,000 km. Shear wave at 10 km. Shear wave at 100 km. l ~ - 10 FREQUENCY (Hz) 100 Figure 3. Dynamic range versus frequency for a typical station of a regional seismic network and a typical strong motion compared with the expected levels of ground motion (acceleration) for seismic waves from earthquakes of differing size and dis- tance (from Heaton et al., 1989~. For the ground acceleration, the units have been approximated to 1 g = m/s2. Mw is seismic moment magnitude and may be taken as equivalent to the generic magnitudes used in the text. (From Heaton et al., 1989.)

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20 ASSESSING THE NATION'S EARTHQUAKES d'etre of the regional network is the generation of a local earthquake cata- log, and this objective is almost always fulfilled. However, the scientific objective of furthering the understanding of local seismotectonic structure and earthquake hazards requires an in-depth analysis by scientists with a variety of backgrounds. In the worst case, data inaccessibility means that such worthwhile studies are never undertaken. OPERATIONAL DIFFICULTIES The operation of regional networks is especially time-consuming both for scientists managing the operation of the network and for analysts pro- cessing the data. The close involvement of research seismologists with the operation of a regional network is essential to maintain the integrity and usefulness of the network as a scientific tool. For the seismologists, however, this represents a drain on time that usually detracts from research time. Although the situation has improved with the use of computers, the process- ing of earthquake data requires much meticulous, albeit repetitive, work by data analysts. During times of budget constraint, these manpower requirements are sometimes not met, forcing strict economy measures, which in the worst case can lead to unprocessed, or even lost, data. ARE REGIONAL NETWORKS COST-EFFECTIVE? Another problem faced by operators of regional seismic networks is the perception that the costs of their network operations are highat least com- pared to budgets typically prepared by academic seismologists for competitive research funding. What are these costs? Can they be reduced significantly? Are large networks more economical than small ones, and are university- operated networks more costly than federally operated ones? Care has to be taken in addressing these questions because there are evident pitfalls, espe- cially in comparing costs reported for individual networks. Available sur- veys of cost informationincluding the one conducted for this report (see Appendix A) do not contain uniform or complete information. Seismolo- gists are not experienced accountants, and hidden expenses such as the cost of facilities, complete personnel costs, benefits, and separately paid telemetry or computer maintenance charges may be unintentionally neglected. Despite their recognized shortcomings, surveys of network operators re- main the best source of information about true costs at the individual network level. Figure 4 shows the annual operating costs reported to the panel by the operators of 43 regional (and local) seismic networks in the United States versus the number of stations in the network. Operators were asked to report "total number of stations" and "total current annual funding for network operations alone, exclusive of research." There may be a differ-

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PROBLEMS AND CONSTRAINTS 1 500 1400 1 300 1 200 1100 i, 1000 0 900 ~ 800 o v 6 z z 70G 600 500 400 Z 300 C" 200 100 o 21 _ i I I I I I I ~ I I T T I I ' I ' I ' 1/ 1 ' I _ ~ /b ~XX ~ -ant it,, ~ X /5~ - ' X ,, 1, . . . ~~- .~$ -0~; - - 1 00 1 50 200 250 ' ' ~ 1 NUMBER OF STATIONS Figure 4. Apparent annual cost versus number of stations for 43 regional (and local) seismic networks in the United States. X's indicate university-operated networks; O's, nonuniversity networks. Tie lines give the range where the number of stations operated by a network (the smaller number) differs from the number of stations recorded. The information comes from a survey conducted for this report in late 1988 by the panel. Trend lines for cost per station relate to a report on seismic networks by the Committee on Seismology (1983; see text). The values of $7.1K per station and $4.7K per station are adjustments to 1988 dollars from originally re- ported values of $6K per station and $4K per station, respectively. ence between the number of stations recorded (in all cases less than or equal to the total number of channels recorded) and the number of stations actually maintained and operated by a unit. Where a network operator has distinguished between the numbers of stations operated and recorded, Fig- ure 4 shows both data points connected with a tie line. The two largest regional seismic networks in the United States are CALNET, a network of 327 stations operated by the USGS in central California (operational costs

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22 ASSESSING THE NATION'S EARTHQUAKES for CALNET were not provided to the panel), and the Southern California Seismic Network of more than 200 stations, jointly operated by the USGS and the California Institute of Technology. In a 1982 survey made for the Committee on Seismology (Committee on Seismology, 1983), trend lines for cost per station of $4,000 and $6,000 enveloped average survey results. These trend lines, adjusted to 1988 dol- lars, are superimposed on Figure 4 because the dollar estimates still tend to be cited in debates about network costs, although as is apparent in Figure 4, the relation of operational costs to number of network stations is not simply linear. The data summarized in Figure 4 show that the annual operational cost for a seismic network that is truly regional in character is on the order of hundreds of thousands of dollars and exceeds a million dollars for the larg- est networks. The scatter evident for annual operational costs as a function of network size is remarkable and is partly explainable by factors already described. Despite the scatter, the information provides some useful in- sights. First, the large California networks that have more than 200 stations should probably be considered in a category by themselves, with distinctive costs and economies of scale. At the other end of the scale, Figure 4 shows a distinctive grouping of 22 networks (close to half the survey sample) having 21 or fewer stations and an annual reported cost of $110,000 or less. This group appears chiefly to include small networks surviving on minimal funding and solidly established networks whose true total costs, arguably, may not have been completely accounted for. Except for two networks whose apparent annual cost is $600,000 or more, the remaining 18 networks characterized in Figure 4 seem to define a pattern marked by annual opera- tional costs of approximately $200,000 to $400,000despite having numbers of stations ranging from less than 20 to 123. Because capital costs for station hardware are not included in this analysis, the $200,000 to $400,000 cost range appears to reflect a fundamental threshold of operational costs for regional networks of moderate size. Are these operational costs (exclusive of research) excessive? A simple analysis, using for convenience the federal pay scale for FY 1989 as a reasonable index of salaries, may suggest an answer. A generic regional network of, say, 50 stations might conservatively require the following: one quarter-time equivalent for management by a Ph.D.-level seismologist with three years' experience (GS-13 or equiva- lent); one full-time, M.S.-level seismologist (GS-10~; one full-time field technician (GS-8~; one full-time seismic analyst (GS-S); and one full-time secretary (GS-51. The resulting total for annual salaries would be $117,000. (The GS-ratings used for this analysis were intentionally pegged low for the sake of argument. In some networks, such as in the eastern United States,

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PROBLEMS AND CONSTRAINTS 23 where seismicity is relatively low, student assistants commonly replace the seismic analyst.) A complete cost profile for a hypothetical, relatively low-cost network might be as follows: Item Salaries Employee benefits (at 30%) Telemetry Computer-related costs Supplies Field travel Indirect costs (25%) Total Annual Cost $1 17,000 35,000 25,000 20,000 15,000 10,000 55,000 $277,000 The telemetry costs in this example would be for telephone and/or micro- wave charges. (Actual telemetry costs for some moderate-sized networks in the eastern United States approach $100,000 per year.) Computer-related costs are chiefly for maintenance contracts. Indirect costs arbitrarily have been assigned at the low level of 25% of the total direct costs. (This is roughly half the typical federally approved rate for a university, but the number may be realistic if only a part of the total operational costs comes from federal awards or if some of the costs are paid directly by a federal agency.) The example above readily shows why annual operational costs for a regional seismic network amount to hundreds of thousands of dollars- whether or not those costs are fully identified. Realistically higher salary levels, greater telemetry costs, greater costs for network maintenance in environments harsher than those in California, and other justifiable factors easily escalate the total costs. Personnel costs for minimal core staffing indicate much about why an average cost per station will be predictably nonlinear for most moderate-sized networks. Finally, Figure 4 shows that university-operated networks do not tend to be more costly than nonuniversity networks. The panel emphasizes that this example includes no funding for perma- nent equipment. For most networks, meeting unavoidable operational costs in the face of inflation-eroded, level federal funding has allowed only mini- mal spending for permanent equipment in the last five years. The modern- ization of existing seismic networks will involve costs on the order of tens of thousands of dollars per individual seismic station, and a few hundreds of thousands of dollars for the computer-recording-and-analysis laboratories

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24 ASSESSING THE NATION'S EARTHQUAKES of individual networks. (Survey results summarized in Table Al, Appendix A, highlight the problem of aging computers.) The panel has estimated the cost to modernize the recording centers and a subset of stations of the regional networks and included these estimates as Recommendation 6 in Chapter 7. In sum, the operation of regional seismic networks involves unavoid- able inherent costs that require sustained support. Regional seismic net- works are fundamentally wide-area communication networks requiring complex electronics, all-weather remote field installations, telemetry systems for continuous data transmission, elaborate central-recording laboratories with dedicated computers and peripherals for recording and data processing, and well- trained scientists, technicians, and data analysts for efficient and productive operation. The returns for such an investment of manpower and resources have been amply demonstrated in Chapters 1 and 2, and additional benefits to science and society are explored in Chapter 4. The panel strongly be- lieves that when the costs and benefits of regional networks are assessed comprehensively, the latter clearly outweigh the former. The panel thus concludes that regional seismic networks are a cost-effective investment for the nation.