This bulletin marks the tenth anniversary of the May 18, 1980 eruption of Mount St. Helens by describing many of the monitoring techniques used since then to track the volcano's ongoing activity. All the chapters in this volume were written by technicians and scientists who are now or were at some time in the past 10 years members of the Cascades Volcano Observatory (CVO), which was established in Vancouver, Washington, in the summer of 1980 in response to the eruption of nearby Mount St. Helens. The chapters in the bulletin describe the techniques and strategies employed by CVO's staff to collect data used to monitor volcanic activity and predict eruptive activity at Mount St. Helens, as well as other volcanoes in the United states, Latin America, and New Zealand. The chapters focus on the methods for acquiring and managing data, not on the interpretations resulting from the data. We anticipate that the audience of the bulletin will be those scientists and technicians, particularly in developing countries, who themselves are, or will be, monitoring volcanoes. The bulletin is not intended to be a comprehensive text on volcano monitoring but instead a distillation of how CVO's staff responded both to the need to monitor an active composite volcano and to the dynamic technological developments during the 1980's. Further reading in volcano-monitoring techniques can be found in UNESCO (1972), Civetta and others (1974), Tazieff and Sabroux (1983) and Tilling (1989).
Much of the seismic monitoring of Mount St. Helens during the decade was conducted by S.D. Malone and associates in the University of Washington's Geophysics Program, not by CVO staff members. Techniques used by Malone's group are described in unpublished in-house manuals (Malone and Zollweg, 1985; Malone, 1989) available upon request from Malone (Geophysics Program AK-50, University of Washington, Seattle, WA 98195). The methods used by Malone's group are appropriate for large seismic networks that employ mainframe computers to acquire and process data. Examples of how these techniques are applied to interpret volcanic activity are papers by Malone and others (1981), Malone (1983), Malone and others (1983), Hofstetter and Malone (1986), and Swanson and others (1985).
Several of the methods used to monitor volcanoes have changed greatly since 1980 as a result of technological advances. Most important of these is the revolution in the field of electronics, particularly microcomputers. Smaller, more powerful electronic distance meters (EDM's), low-power digital telemetry, PC-based seismic-data acquisition and analysis systems, and laptop-computer controllers and interfaces are just some of the results of this revolution that have allowed us to improve established monitoring techniques or develop new ones.
When Mount St. Helens began showing signs of unrest in March 1980, most of the U.S. Geological Survey personnel dispatched to the volcano had previous experience monitoring Kilauea while stationed at the Hawaiian Volcano Observatory (HVO). Although most of the monitoring techniques used in 1980 were developed and (or) used at HVO, it became apparent that the different eruptive style of composite volcanoes in general, and of Mount St. Helens in particular, required modification of some of these monitoring practices. The chapters in this bulletin illustrate the degree to which modification was required.
The chapters fall into several logical groupings: telemetry, acquisition of seismic data, data management, ground deformation, geochemistry, and imaging. The first three groupings represent the areas in which the most marked technological progress has been made. Rapidly changing conditions prior to eruptive activity require that data be available to volcanologists in as close to real time as possible, in order to make reasonable assessments of the future and to aid in hazard-mitigation efforts. To be most effective, the data must be available in a format in which the different measured parameters can be easily compared and rapidly analyzed.
The real-time seismic-amplitude monitor (RSAM) (Murray and Endo, chapter 1 of this bulletin) allows seismic data to be quantified and utilized at the time such data are most needed -- when the seismic activity at a volcano is saturating all other seismic-data acquisition and analysis systems. Inexpensive, low-power, radio-telemetry systems (Murray, chapter 2; Lockhart and others, chapter 3) allow almost any sensor to send back data from the volcano in near real time. The microcomputer-based volcano-monitoring system using the program BOB (Murray, chapter 4) permits all data gathered by a monitoring team to be recorded, processed, and displayed on a common time base. Development of this system, together with that of the PC-AT and Sun workstation seismic systems (Endo and Smith, chapter 5), more than anything else represents the most dramatic new contribution to volcano-monitoring methods and techniques made by the CVO group. These PC-based systems are powerful, portable, and very inexpensive compared to what was only marginally available at the beginning of the 1980's.
Fully half of the chapters cover techniques for monitoring ground deformation, using both telemetered and nontelemetered methods. This emphasis in part reflects the success of the CVO staff in predicting eruptive activity at Mount St. Helens using these methods (Swanson and others, 1983, 1985). Four of the chapters deal directly with monitoring at Mount St. Helens itself and provide suggestions for field procedures gained from a decade of first-hand experience: those by Iwatsubo and Swanson (chapter 6), Dzurisin (chapter 7), Iwatsubo, Topinka, and Swanson (chapter 8), and Iwatsubo, Ewert, and Murray (chapter 9). Two of the chapters cover aspects of EDM techniques and strategies employed by CVO personnel at volcanoes other than Mount St. Helens (Iwatsubo and Swanson, chapter 10; Doukas and Ewert, chapter 11). The rest of the chapters on deformation cover various aspects of leveling, including geodetic leveling (Dzurisin, chapter 12; Yamashita and Kaiser, chapter 13), single-setup leveling using classical (Yamashita, chapter 14) and trigonometric (Ewert, chapter 15) methods, and lake leveling (Kleinman and Otway, chapter 16) that draws from experience gained in the United States and New Zealand.
In the chapters on leveling we introduce the term single-setup leveling to replace the widely used by inexpressive and slang term dry tilt. The new term also replaces tilt leveling, which mixes a method (leveling) with a goal (to determine tilt). Single-setup leveling implies that the techniques of leveling are used with only one instrument setup -- an implication that aptly describes the method. We hope that this more expressive term is used in the future by other workers.
The two chapters on geochemistry describe a technique for continuous monitoring of springs and lakes (McGee and others, chapter 17) and give an overview of an integrated approach to geochemical monitoring (Sutton and others, chapter 18). The geochemistry chapters reflect the perceived need of CVO's geochemists to obtain data in close to real time. Continuous geochemical monitoring of a variety of chemical species will no doubt provide important monitoring data that can be integrated with other monitoring data in the years to come.
The chapters on imaging describe the slow-scan-television surveillance system used to view the crater from 8.5 kilometers away (Furukawa and others, chapter 19) and the photodocumentation efforts (Topinka, chapter 20) used to trace the development of the eruption and the evolution of the crater, dome, and adjacent landscape. The bulletin's final chapter (21) by Swanson, points out the value of on-site observations and measurements in monitoring volcanoes, stresses that such techniques constitute important components of any monitoring program, and puts forth the view that monitoring should be done in as simple a way as is practical.
The progress in monitoring techniques displayed in this bulletin is notable on several counts. Available technology has been adapted to monitor active volcanoes by a very small group of dedicated and innovative people. Most of the development of new procedures, and the modification of old ones, was conducted with the guiding philosophy of keeping the techniques as inexpensive as practical using easily accessible technology. This philosophy results in systems that are both suitable for, and within the budgetary reach of, developing nations that have a need to evaluate, monitor, and mitigate volcanic hazards. In addition, personal, hard-won, trial-and-error experience gained from ten years of monitoring Mount St. Helens and other volcanoes contributes significantly to the improved procedures.
Most of the chapters were written by the technical personnel of CVO, who were largely responsible for the development and testing of the monitoring technologies. The new and improved capabilities resulted from the stimulating, give-and-take environment fostered by an observatory setting in which scientific and technical staff interact and learn with each other on a daily basis. This sort of environment encourages people to ask themselves "how can we do this better" and gives them the opportunity and freedom to try to do better. We believe that the chapters in this bulletin demonstrate the wisdom of promoting and maintaining such an environment.
Nothing is permanent except change. All of the techniques described in the bulletin can and will be improved with time. Certainly modifications will need to be made on a case-by-case basis for each volcano that requires monitoring. The chapters in the bulletin should provide well-grounded starting points for such improvements. We particularly hope that scientists and technicians in developing countries -- our primary audience -- will find the bulletin useful and will be able to adapt the methodologies to their particular problems.
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