Bulletin of Volcanology

, Volume 53, Issue 7, pp 533–545 | Cite as

Real-time Seismic Amplitude Measurement (RSAM): a volcano monitoring and prediction tool

  • Elliot T Endo
  • Tom Murray


Seismicity is one of the most commonly monitored phenomena used to determine the state of a volcano and for the prediction of volcanic eruptions. Although several real-time earthquake-detection and data acquisition systems exist, few continuously measure seismic amplitude in circumstances where individual events are difficult to recognize or where volcanic tremor is prevalent. Analog seismic records provide a quick visual overview of activity; however, continuous rapid quantitative analysis to define the intensity of seismic activity for the purpose of predicing volcanic eruptions is not always possible because of clipping that results from the limited dynamic range of analog recorders. At the Cascades Volcano Observatory, an inexpensive 8-bit analog-to-digital system controlled by a laptop computer is used to provide 1-min average-amplitude information from eight telemetered seismic stations. The absolute voltage level for each station is digitized, averaged, and appended in near real-time to a data file on a multiuser computer system. Raw realtime seismic amplitude measurement (RSAM) data or transformed RSAM data are then plotted on a common time base with other available volcano-monitoring information such as tilt. Changes in earthquake activity associated with dome-building episodes, weather, and instrumental difficulties are recognized as distinct patterns in the RSAM data set. RSAM data for domebuilding episodes gradually develop into exponential increases that terminate just before the time of magma extrusion. Mount St. Helens crater earthquakes show up as isolated spikes on amplitude plots for crater seismic stations but seldom for more distant stations. Weather-related noise shows up as low-level, long-term disturbances on all seismic stations, regardless of distance from the volcano. Implemented in mid-1985, the RSAM system has proved valuable in providing up-to-date information on seismic activity for three Mount St. Helens eruptive episodes from 1985 to 1986 (May 1985, May 1986, and October 1986). Tiltmeter data, the only other telemetered geophysical information that was available for the three dome-building episodes, is compared to RSAM data to show that the increase in RSAM data was related to the transport of magma to the surface. Thus, if tiltmeter data is not available, RSAM data can be used to predict future magmatic eruptions at Mount St. Helens. We also recognize the limitations of RSAm data. Two examples of RSAM data associated with phreatic or shallow phreatomagmatic explosions were not preceded by the same increases in RSAM data or changes in tilt associated with the three dome-building eruptions.


Volcanic Eruption Seismic Station Volcanic Tremor Eruptive Episode Limited Dynamic Range 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. Aki K, Richards PG (1980) Quantitative seismology, theory and methods. WH Freeman, San Francisco, Calif, 932 pGoogle Scholar
  2. Alaska Volcano Observatory Staff (1990) The 1989–1990 Eruption of Redoubt volcano. EOS: 71:265272–273275Google Scholar
  3. Decker RW (1973) State-of-the-art in volcano forecasting. Bull Volcanol 37:372–393Google Scholar
  4. Decker RW (1986) Forecasting volcanic eruptions. Ann Rev Earth Planet Sci 14:267–291Google Scholar
  5. Endo ET, Dzurisin D, Murray T, Syverson K (1987) The rate of magma ascent during dome building at Mount St Helens (abstract). Abstract volume Hawaii Symposium on How Volcanoes Work, Hilo, Hawaii, p 64Google Scholar
  6. Gutenberg B, Richter CF (1956) Magnitude and energy of earthquakes. Estratto da Annali di Geofisica 9:1–15Google Scholar
  7. Hurst AW (1985) A volcanic tremor monitoring system. J Volcanol Geotherm Res 26:181–187Google Scholar
  8. Kieffer SW (1984) Seismicity at Old Faithful Geyser: an isolated source of geothermal noise and possible analogue of volcanic seismicity. J Volcanol Geotherm Res 22:59–95Google Scholar
  9. Korneff T (1966) Introduction to electronics. Academic Press, NY, 545 pGoogle Scholar
  10. Koyanagi RY, Meagher K, Klein FW, Okamura AT (1975) Hawaiian Volcano Observatory Symmary 75, 117 pGoogle Scholar
  11. Lee WHK, Stewart SW (1981) Principles and applications of microearthquake networks. In: Advances in Geophysics, Supplement 2. Academic Press, NY, 293 pGoogle Scholar
  12. Malone SD, Boyko C, Weaver CS (1983) Seismic precursors to the Mount St Helens eruptions in 1981 and 1982. Science 221:1376–1378Google Scholar
  13. Minakami T (1960) Fundamental research for predicting volcanic eruptions, pt. 1. Bull Earthquake Res Inst 38:497–544Google Scholar
  14. Minakami T (1974) Prediction of volcanic eruptions. In: Civetta L, Gasparini P, Luongo G, Rapolla A, (eds) Physical volcanology. Amsterdam, Elsevier, pp 313–333Google Scholar
  15. Minakami T, Hiraga S, Miyazaki T, Uchibori S (1969) Fundamental research for predicting volcanic eruptions, pt. 2. Bull Earthquake Res Inst 47:893–949Google Scholar
  16. Murray TL, Endo ET (1986) BOB, a computer graphics tool for real-time integrated volcano monitoring. EOS 67:397Google Scholar
  17. Nakamura Y (1977) Detection and analysis of acoustic emission signal. In: HR Hardy Jr, FW Leighton (eds) Proceedings First Conference on Acoustic Emission/Microseismic Activity in Geologic Structures and Materials 2:445–457Google Scholar
  18. Nishi K (1987) Automatic data processing system for volcanic earthquakes and tremors, Annuals Disaster Prevention Res. Inst Kyoto Univ 30B-1:1–18Google Scholar
  19. Norwack R, Aki K (1984) The two-dimensional gaussian beam synthetic method:testing and application. J Geophysical Res 89:7797–7819Google Scholar
  20. Richter CF (1958) Elementary Seismology. WH Freeman and Company, San Francisco, 768 pGoogle Scholar
  21. Sassa K (1936) Micro-Seismometric study on eruptions of the Volcano Aso (Part II of the Geophysical studies on the Volcano Aso). Memoirs of the College of Science, Kyoto Imperial University, vol XIX, 1:11–56Google Scholar
  22. Scandone R, Malone SD (1985) Magma supply, magma discharge and readjustment of the feeding system of Mount St Helens during 1980. J Volcanol Geotherm Res 23:239–262Google Scholar
  23. Schick R (1988) Volcanic tremor-source mechanisms and correlation with eruptive activity. Natural Hazards 1:125–144Google Scholar
  24. Schick R, Lombardo G, Patane G (1982) Volcanic tremors and shocks associated with eruptions at Etna (Sicily), September 1980. J Volcanol Geotherm Res 14:261–79Google Scholar
  25. Swanson DA, Holcomb RT (1989) Regularities in growth of the Mount St Helens dacite dome 1980–1986. In: Fink J (ed) Lava flows and domes. Springer, Berlin Heidelberg New York 24 pGoogle Scholar
  26. Swanson DA, Casadevall TJ, Dzurisin D, Holcomb RT, Newhall CG, Malone SD, Weaver CS (1985) Forecasts and predictions of eruptive activity at Mount St Helens, USA: 1975–1984. J Geodynamics 3:397–423Google Scholar

Copyright information

© Springer-Verlag 1991

Authors and Affiliations

  • Elliot T Endo
    • 1
  • Tom Murray
    • 2
  1. 1.U.S. Geological SurveyAPONew YorkUSA
  2. 2.Cascades Volcano ObservatoryVancouverUSA

Personalised recommendations