Ambient noise tomography across Mount St. Helens using a dense seismic array

Yadong Wang, Fan-Chi Lin, Brandon Schmandt, Jamie Farrell

Research output: Contribution to journalArticlepeer-review

26 Scopus citations

Abstract

We investigated upper crustal structure with data from a dense seismic array deployed around Mount St. Helens for 2 weeks in the summer of 2014. Interstation cross correlations of ambient seismic noise data from the array were obtained, and clear fundamental mode Rayleigh waves were observed between 2.5 and 5 s periods. In addition, higher-mode signals were observed around 2 s period. Frequency-time analysis was applied to measure fundamental mode Rayleigh wave phase velocities, which were used to invert for 2-D phase velocity maps. An azimuth-dependent traveltime correction was implemented to mitigate potential biases introduced due to an inhomogeneous noise source distribution. Reliable phase velocity maps were only obtained between 3 and 4 s periods due to limitations imposed by the array aperture and higher-mode contamination. The phase velocity tomography results, which are sensitive to structure shallower than 6 km depth, reveal an ~10–15% low-velocity anomaly centered beneath the volcanic edifice and peripheral high-velocity anomalies that likely correspond to cooled igneous intrusions. We suggest that the low-velocity anomaly reflects the high-porosity mixture of lava and ash deposits near the surface of the edifice, a highly fractured magmatic conduit and hydrothermal system beneath the volcano, and possibly a small contribution from silicate melt.
Original languageEnglish (US)
Pages (from-to)4492-4508
Number of pages17
JournalJournal of Geophysical Research: Solid Earth
Volume122
Issue number6
DOIs
StatePublished - Jun 3 2017
Externally publishedYes

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