Earth, Planets and Space

, Volume 56, Issue 10, pp 29–32 | Cite as

Surface deformation caused by shallow magmatic activity at Okmok volcano, Alaska, detected by GPS campaigns 2000–2002

  • Yousuke Miyagi
  • Jeffrey T. Freymueller
  • Fumiaki Kimata
  • Toshiya Sato
  • Dörte Mann
Open Access


Annual GPS campaigns were carried out at Okmok volcano in the Aleutian Islands, Alaska, between 2000 and 2002. Surface deformation detected by these measurements reveals that Okmok volcano has been inflating over these 3 years at a variable inflation rate. The horizontal displacements show a radial outward pattern, and there has been significant uplift of the caldera center. The uplift of the caldera center relative to the caldera rim was ∼2.1 cm during 2000–2001, and ∼6.7 cm during 2001–2002. The latter rate is quite consistent with that deduced from InSAR measurements spanning 1997–2000, but the deformation rate during 2000–2001 was much slower than during the preceding and succeeding periods. Shallow pressure source was inferred at a depth of ∼3.1 km beneath the approximate center of the caldera. The location of the source, ∼5 km laterally from the active vent, is consistent with that inferred from InSAR data during 1997–1998. The total increase in volume during 2000–2002 of the inferred source is ∼0.44 × 107m3, which is 3–8% of the amount of volume erupted in 1997. The GPS and InSAR data show that magma accumulation beneath Okmok was steady in rate and location during 1997–2002, except for a pause at some time between 2000 and 2001.

Key words

Okmok GPS campaign significant inflation shallow magmatic activity 


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Copyright information

© The Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS); The Seismological Society of Japan; The Volcanological Society of Japan; The Geodetic Society of Japan; The Japanese Society for Planetary Sciences. 2004

Authors and Affiliations

  • Yousuke Miyagi
    • 1
  • Jeffrey T. Freymueller
    • 2
  • Fumiaki Kimata
    • 3
  • Toshiya Sato
    • 4
  • Dörte Mann
    • 5
  1. 1.Institute of Seismology and Volcanology, Graduate School of ScienceHokkaido UniversitySapporoJapan
  2. 2.Geophysical InstituteUniversity of AlaskaFairbanks, FairbanksUSA
  3. 3.Research Center for Seismology and Volcanology, Graduate School of Environmental StudiesNagoya UniversityNagoyaJapan
  4. 4.Research Center for Prediction of Earthquakes and Volcanic Eruptions, Graduate School of ScienceTohoku UniversityAoba-ku, SendaiJapan
  5. 5.Department of GeophysicsStanford UniversityStanfordUSA

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