Tomographic image of a seismically active volcano: Mammoth Mountain, California

Journal of Geophysical Research B: Solid Earth
By: , and 

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Abstract

High-resolution tomographic P wave, S wave, and VP/VS velocity structure models are derived for Mammoth Mountain, California, using phase data from the Northern California Seismic Network and a temporary deployment of broadband seismometers. An anomalous volume (5.1 × 109 to 5.9 × 1010m3) of low P and low S wave velocities is imaged beneath Mammoth Mountain, extending from near the surface to a depth of ∼2 km below sea level. We infer that the reduction in seismic wave velocities is due to the presence of CO2 distributed in oblate spheroid pores with mean aspect ratio α = 1.6 × 10−3 to 7.9 × 10−3 (crack-like pores) and mean gas volume fraction ϕ = 8.1 × 10−4 to 3.4 × 10−3. The pore density parameter κ = 3ϕ/(4πα) = na3=0.11, where n is the number of pores per cubic meter and a is the mean pore equatorial radius. The total mass of CO2 is estimated to be 4.6 × 109 to 1.9 × 1011 kg. The local geological structure indicates that the CO2 contained in the pores is delivered to the surface through fractures controlled by faults and remnant foliation of the bedrock beneath Mammoth Mountain. The total volume of CO2 contained in the reservoir suggests that given an emission rate of 500 tons day−1, the reservoir could supply the emission of CO2 for ∼25–1040 years before depletion. Continued supply of CO2 from an underlying magmatic system would significantly prolong the existence of the reservoir.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Tomographic image of a seismically active volcano: Mammoth Mountain, California
Series title Journal of Geophysical Research B: Solid Earth
DOI 10.1002/2015JB012537
Volume 121
Issue 1
Year Published 2016
Language English
Publisher American Geophysical Union
Contributing office(s) Volcano Science Center
Description 20 p.
First page 114
Last page 133
Country United States
State California
Other Geospatial Mammoth Mountain
Online Only (Y/N) N
Additional Online Files (Y/N) N