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| Titel |
A joint geophysical investigation of the Cascadia subduction zone in central Washington using data from dense arrays of passive seismic and magnetotelluric stations |
| VerfasserIn |
Shane McGary, Stéphane Rondenay, Rob Evans, Geoffrey Abers, Philip Wannamaker, Chin-Wu Chen |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250049740
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| Zusammenfassung |
| Joint analyses that combine multiple geophysical methods can yield improved characterization of
subsurface structure over that achieved by single methods. Here, we investigate
the Cascadia subduction zone using dense seismic and magnetotelluric data sets
collected along an E-W profile running through western Washington State. We present
images generated by 2-D Generalized Radon Transform (GRT) inversion of scattered
teleseismic data recorded at 41 three-component broadband stations from the CAFÉ
experiment, the Earthscope Transportable Array, and the Pacific Northwest Seismic
Network over a period of roughly 26 months. The resulting profile clearly images the
subducted oceanic crust as a dipping low-velocity layer that persists to ~40-50 km
depth, and a disrupted continental Moho that may be weakened by serpentinization
of the underlying mantle wedge. We also present preliminary results from a 2-D
non-linear conjugate gradient inversion of magnetotelluric data recently acquired by 60
broadband and 21 long-period stations along a collocated profile. The resulting
model shows evidence for a subducted slab exhibiting higher electrical resistivity
than the surrounding mantle, and resistivity anomalies in the mantle wedge that
might be correlated to the distribution of fluids and melt. We consider how each
geophysical method informs us about the structure and dynamics of the system, and
explore how the two sets of results can be used to constrain one another. Finally,
we evaluate how these insights might be used to develop new techniques for joint
inversion of passive seismic and magnetotelluric data that would result in tighter
overall constraints on the key processes taking place in the subduction factory. |
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