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AGU: Journal of Geophysical Research, Solid Earth

 

Index Terms

  • Seismology: Continental crust
  • Seismology: Seismicity and seismotectonics
  • Volcanology: Eruption monitoring
  • Volcanology: Hydrothermal systems
  • Tectonophysics: Earth's interior—composition and state
Abstract
Cited By (17)
 

Abstract

JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 108, 2147, 16 PP., 2003
doi:10.1029/2000JB000041

Three-dimensional crustal structure of Long Valley caldera, California, and evidence for the migration of CO2 under Mammoth Mountain

G. R. Foulger

Volcano Hazards Team, U.S. Geological Survey, Menlo Park, California, USA

B. R. Julian

Volcano Hazards Team, U.S. Geological Survey, Menlo Park, California, USA

A. M. Pitt

Volcano Hazards Team, U.S. Geological Survey, Menlo Park, California, USA

D. P. Hill

Volcano Hazards Team, U.S. Geological Survey, Menlo Park, California, USA

P. E. Malin

Division of Earth and Ocean Sciences, Nicholas School of the Environment, Duke University, Durham, North Carolina, USA

E. Shalev

Division of Earth and Ocean Sciences, Nicholas School of the Environment, Duke University, Durham, North Carolina, USA

A temporary network of 69 three-component seismic stations captured a major seismic sequence in Long Valley caldera in 1997. We performed a tomographic inversion for crustal structure beneath a 28 km × 16 km area encompassing part of the resurgent dome, the south moat, and Mammoth Mountain. Resolution of crustal structure beneath the center of the study volume was good down to ∼3 km below sea level (∼5 km below the surface). Relatively high wave speeds are associated with the Bishop Tuff and lower wave speeds characterize debris in the surrounding moat. A low-Vp/Vs anomaly extending from near the surface to ∼1 km below sea level beneath Mammoth Mountain may represent a CO2 reservoir that is supplying CO2-rich springs, venting at the surface, and killing trees. We investigated temporal variations in structure beneath Mammoth Mountain by differencing our results with tomographic images obtained using data from 1989/1990. Significant changes in both Vp and Vs were consistent with the migration of CO2 into the upper 2 km or so beneath Mammoth Mountain and its depletion in peripheral volumes that correlate with surface venting areas. Repeat tomography is capable of detecting the migration of gas beneath active silicic volcanoes and may thus provide a useful volcano monitoring tool.

Published 12 March 2003.

Citation: Foulger, G. R., B. R. Julian, A. M. Pitt, D. P. Hill, P. E. Malin, and E. Shalev (2003), Three-dimensional crustal structure of Long Valley caldera, California, and evidence for the migration of CO2 under Mammoth Mountain, J. Geophys. Res., 108(B3), 2147, doi:10.1029/2000JB000041.

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