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| Titel |
Attenuation and scattering tomography of the deep plumbing system of Mount St. Helens |
| VerfasserIn |
Luca De Siena, Greg Waite, Seth Moran, Stephan Klemme, Christine Thomas |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250090706
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| Publikation (Nr.) |
 EGU/EGU2014-4960.pdf |
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| Zusammenfassung |
| We present a combined 3D P-wave attenuation, 2D S-coda attenuation, and 3D
S-coda scattering tomography model of magmatic/fluid chambers, feeding systems,
and sediments below Mount St. Helens (MSH) volcano between depths of 0 and
18 km. High scattering and high attenuation shallow anomalies are indicative of
magma and fluid cumulates within and below the volcanic edifice down to 6 km
depth. These structures induce a combination of resonant-scattering and strong
attenuation on any seismic wave-field recorded north and east of the volcanic cone. North
of the cone between depths of 0 and 10 km a low-velocity, high-scattering, and
high-attenuation north-south trending trough is attributed to thick piles of Tertiary
marine sediments inferred to lie within the Saint Helens Seismic Zone (SHZ). A
laterally-extended 3D scattering contrast at depths of 10 to 14 km is related to the boundary
between upper and lower crust, and caused in our interpretation by the large scale
interaction of the Siletz terrane with the Cascade arc crust. This contrast presents a low
scattering, 4-6 km2 "hole" under the north-eastern flank of the volcano: we infer that
this section represents the main path of magma ascent from depths larger than 6
km at MSH. The images suggest a small north-east shift in the lower plumbing
system of the volcano as well as the absence of any large melt sill extending between
depths of 0 and 18 km. We conclude that combinations of different non-standard
tomographic methods, and particularly the application of full-waveform tomography
to highly heterogeneous media, represent the future of seismic volcano imaging. |
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