Bulletin of Volcanology

, Volume 73, Issue 2, pp 143–153 | Cite as

Mechanism of the 1996–97 non-eruptive volcano-tectonic earthquake swarm at Iliamna Volcano, Alaska

Research Article


A significant number of volcano-tectonic (VT) earthquake swarms, some of which are accompanied by ground deformation and/or volcanic gas emissions, do not culminate in an eruption. These swarms are often thought to represent stalled intrusions of magma into the mid- or shallow-level crust. Real-time assessment of the likelihood that a VT swarm will culminate in an eruption is one of the key challenges of volcano monitoring, and retrospective analysis of non-eruptive swarms provides an important framework for future assessments. Here we explore models for a non-eruptive VT earthquake swarm located beneath Iliamna Volcano, Alaska, in May 1996–June 1997 through calculation and inversion of fault-plane solutions for swarm and background periods, and through Coulomb stress modeling of faulting types and hypocenter locations observed during the swarm. Through a comparison of models of deep and shallow intrusions to swarm observations, we aim to test the hypothesis that the 1996–97 swarm represented a shallow intrusion, or “failed” eruption. Observations of the 1996–97 swarm are found to be consistent with several scenarios including both shallow and deep intrusion, most likely involving a relatively small volume of intruded magma and/or a low degree of magma pressurization corresponding to a relatively low likelihood of eruption.


Iliamna Volcano VT earthquake Earthquake swarms Stress tensor inversion Fault-plane solutions 

Supplementary material

445_2010_439_Fig9_ESM.jpg (50 kb)
Online Resources 1

Lower-hemisphere projections of 13 FPS calculated for the background period. All FPS are shown with polarity data (+ compressional, o dilational) and P- and T-axes plotted on the focal sphere. The date (year, month, day, hour, minute) and location (latitude, longitude, and depth (BSL), where negative depths indicate earthquakes located above sea level) are also given above each FPS. (JPEG 50 kb)

445_2010_439_Fig10_ESM.jpg (197 kb)
Online Resources 2

Lower-hemisphere projections of 52 FPS calculated for the swarm period. All FPS are shown with polarity data (+ compressional, o dilational) and P- and T-axes plotted on the focal sphere. The date (year, month, day, hour, minute) and location (latitude, longitude, and depth (BSL), where negative depths indicate earthquakes located above sea level) are also given above each FPS. (JPEG 196 kb)


  1. Burton M, Allard P, Muré F, La Spina A (2007) Magmatic gas composition reveals the source depth of slug-driven Strombolian explosive activity. Science 317:227–230CrossRefGoogle Scholar
  2. Detterman RL, Hartsock JK (1966) Geology of the Iniskin-Tuxedni Region, Alaska. US Geol Surv Prof Pap 512:1–76Google Scholar
  3. Endo ET, Malone SD, Noson LL, Weaver CS (1981) Locations, magnitudes, and statistics of the March 20–May 18 earthquake sequence. In: Lipman PW, Mullineaux DR (eds) The 1980 Eruptions of Mount. St. Helens, Washington. US Geol Surv Prof Pap 1250:93–107Google Scholar
  4. Gephart JW (1990) FMSI—a fortran program for inverting fault slickenside and earthquake focal mechanism data to obtain the regional stress-tensor. Comput Geosci 16:953–989CrossRefGoogle Scholar
  5. Gephart JW, Forsyth DW (1984) An improved method for determining the regional stress tensor using earthquake focal mechanism data: application to the San Fernando earthquake sequence. J Geophys Res 89:9305–9320CrossRefGoogle Scholar
  6. Harlow DH, Power JA, Laguerta EP, Ambubuyog G, White RA, Hoblitt RP (1996) Precursory seismicity and forecasting of the June 15, 1991, eruption of Mount Pinatubo. In: Newhall CG, Punongbayan RS (eds) Fire and mud: Eruptions and Lahars of Mount Pinatubo, Philippines. Univ Washington Press, Seattle, pp 285–306Google Scholar
  7. Hirn A, Michel B (1979) Evidence of migration of main shocks during major seismo-volcanic crises of La Soufrière (Guadaloupe, Lesser Antilles) in 1976. J Volcanol Geotherm Res 6:295–304CrossRefGoogle Scholar
  8. Jolly AD, McNutt SR (1999) Seismicity at the volcanoes of Katmai National Park, Alaska: July 1995–December 1997. J Volcanol Geotherm Res 93:173–190CrossRefGoogle Scholar
  9. Jolly AD, Page RA, Power JA (1994) Seismicity and stress in the vicinity of Mount Spurr volcano, south central Alaska. J Geophys Res 99:15305–15318CrossRefGoogle Scholar
  10. Jolly AD, Stihler SD, Power JA, Lahr JC, Paskievitch J, Tytgat G, Estes S, Lockhart AB, Moran SC, McNutt SR, Hammond WR (2001) Catalog of earthquake hypocenters at Alaskan Volcanoes: January 1994 through December 31, 1999. US Geol Surv Open-File Rep 01–189Google Scholar
  11. Lehto HL, Roman DC, Moran SC (2010) Temporal changes in stress preceding the 2004–2008 eruption of Mount St. Helens, Washington. J Volcanol Geotherm Res 198:129–142CrossRefGoogle Scholar
  12. Lin J, Stein RS (2004) Stress triggering in thrust and subduction earthquakes and stress interaction between the southern San Andreas and nearby thrust and strike-slip faults. J Geophys Res 109:B02303. doi:10.1029/2003JB002607 CrossRefGoogle Scholar
  13. Lu Z, Dzurisin D (2010) Ground surface deformation patterns, magma supply, and magma storage at Okmok volcano, Alaska, from InSAR analysis: 2. Coeruptive deflation, July–August 2008. J Geophys Res 115:B00B03. doi:10.1029/2009JB006970 CrossRefGoogle Scholar
  14. Lu Z, Wicks C, Power JA, Dzurisin D (2000) Ground deformation associated with the March 1996 earthquake swarm at Akutan volcano, Alaska, revealed by satellite radar interferometry. J Geophys Res 105:21483–21495CrossRefGoogle Scholar
  15. Lu Z, Power JA, McConnell VS, Wicks C, Dzurisin D (2002) Preeruptive inflation and surface interferometric coherence characteristics by satellite radar interferomentry at Makushin volcano, Alaska: 1993–2000. J Geophys Res 107:2266. doi:10.1029/2001JB000970 CrossRefGoogle Scholar
  16. Moran SC, Newhall C, Roman DC (2010) Failed eruptions: when restlessness leads to quiescence. Bull Volcanol: this volumeGoogle Scholar
  17. Neal CA, McGimsey RG (1997) Volcanic activity in Alaska and Kamchatka: summary of events and response of the Alaska Volcano Observatory. US Geol Surv Open-File Rep 97–433Google Scholar
  18. Reasenberg P, Oppenheimer DH (1985) FPFIT, FPPLOT and FPPAGE; Fortran computer programs for calculating and displaying earthquake fault-plane solutions. US Geol Surv Open-File Rep 85–739Google Scholar
  19. Roman DC, Heron P (2007) Effect of regional tectonic setting on local fault response to episodes of volcanic activity. Geophys Res Lett 34:L 13310. doi:10.1029/2007GL030222 CrossRefGoogle Scholar
  20. Roman DC, Power JA, Moran SC, Cashman KV, Doukas MP, Neal CA, Gerlach TM (2004a) Evidence for dike emplacement beneath Iliamna Volcano, Alaska in 1996. J Volcanol Geotherm Res 130:265–284CrossRefGoogle Scholar
  21. Roman DC, Moran SC, Power JA, Cashman KV (2004b) Temporal and spatial variation of local stress fields before and after the 1992 eruptions of Crater Peak Vent, Mount Spurr Volcano, Alaska. Bull Seismol Soc Am 94:2366–2379CrossRefGoogle Scholar
  22. Rubin AM, Pollard DD (1988) Dike-induced faulting in rift zones of Iceland and Afar. Geology 16:413–417CrossRefGoogle Scholar
  23. Rubin AM, Gillard D, Got J-L (1998) A reinterpretation of seismicity associated with the 1983 dike intrusion at Kilauea Volcano, Hawaii. J Geophys Res 103:10003–10015CrossRefGoogle Scholar
  24. Scholz CH (2002) The mechanics of earthquakes and faulting, 2nd edn. Cambridge University Press, CambridgeGoogle Scholar
  25. Statz-Boyer P, Thurber C, Pesicek J, Prejean S (2009) High-precision relocation of earthquakes at Iliamna Volcano, Alaska. J Volcanol Geotherm Res 184:323–332CrossRefGoogle Scholar
  26. Taisne B, Tait S, Jaupart C (2010) Conditions for the arrest of a vertical propagating dyke. Bull Volcanol: this volumeGoogle Scholar
  27. Tanaka S, Hamaguchi H, Ueki S, Sato M, Nakamichi H (2002) Migration of seismic activity during the 1998 volcanic unrest at Iwate volcano, northeastern Japan, with reference to P and S wave velocity anomaly and crustal deformation. J Volcanol Geotherm Res 113:399–414CrossRefGoogle Scholar
  28. Toda S, Stein RS, Sagiya T (2002) Evidence from the AD 2000 Izu islands earthquake swarm that stressing rate governs seismicity. Nature 419:58–61CrossRefGoogle Scholar
  29. Toda S, Stein RS, Richards-Dinger K, Bozkurt S (2005) Forecasting the evolution of seismicity in southern California: animations built on earthquake stress transfer. J Geophys Res 110:B05S16. doi:10.1029/2004JB003415 CrossRefGoogle Scholar
  30. Ukawa M, Tsukahara H (1996) Earthquake swarms and dike intrusions off the east coast of Izu Peninsula, central Japan. Tectonophys 253:285–303CrossRefGoogle Scholar
  31. Umakoshi K, Shimizu H, Matsuwo N (2001) Volcano-tectonic seismicity at Unzen Volcano, Japan, 1985–1999. J Volcanol Geotherm Res 112:117–131CrossRefGoogle Scholar
  32. Vidale JE, Shearer PM (2006) A survey of 71 earthquake bursts across southern California: exploring the role of pore fluid pressure fluctuations and aseismic slip as drivers. J Geophys Res 111:B05312. doi:10.1029/2005JB004034 CrossRefGoogle Scholar
  33. Vidale JE, Boyle KL, Shearer PM (2006) Crustal earthquake bursts in California and Japan: their patterns and relation to volcanoes. Geophys Res Lett 33:L20313. doi:10.1029/2006GL027723 CrossRefGoogle Scholar
  34. Waythomas CF, Miller TP, Beget JE (2000) Record of Late Holocene debris avalanches and lahars at Iliamna Volcano, Alaska. J Volcanol Geotherm Res 104:97–130CrossRefGoogle Scholar

Copyright information

© Springer-Verlag 2011

Authors and Affiliations

  1. 1.Department of GeologyUniversity of South FloridaTampaUSA
  2. 2.Alaska Volcano ObservatoryUnited States Geological SurveyAnchorageUSA

Personalised recommendations