Investigation of Cascadia segmentation with ambient noise tomography
نویسنده
چکیده
Several lines of evidence suggest that simple subduction with one downgoing and one overriding plate is an insufficient model of the Cascadia Subduction Zone. Instead, the subduction zone and arc are segmented, exhibiting variations in multiple characteristics along strike. One line of evidence comes from the analysis of seismicity. The subduction zone is atypical everywhere in that the Wadati-Benioff zone is sparsely defined and shallow. There are a few subduction interface events deeper than the continental crust at the northern and southern ends of the subduction zone in Washington and California, but only to 75km depth. However, there are almost no sub-crustal (>30km depth) earthquakes beneath Oregon. In contrast, Episodic Tremor and Slip (ETS) events have been mapped throughout the subduction zone (Brudzinski and Allen, 2007). The recurrence rate of ETS, consisting of many non-volcanic (or tectonic) tremors at the same time as geodetically measured backslip, varies along strike with similar segment boundaries as observed by the variation in seismicity and topography. Other evidence for segmentation along the arc comes from the composition of arc volcanism. Detailed analysis of primitive basalt families in the main volcanic arc reveals variable mantle domains and melting regimes attributed to the effects of the slab window to the south, impingement of the Basin and Range terrain, and interaction with the Siletzia Terrane (Schmidt et al., 2008). In addition, measurements of total heat production from volcanic fumaroles, thermal springs, and slightly thermal springs (Ingebritsen and Mariner, 2010) show significantly higher total heat production in the southern part of the arc where Basin and Range extension is thought to create permeable zones in the crust (Ingebritsen and Mariner, 2010).
منابع مشابه
Upper mantle structure of the Cascades from full-wave ambient noise tomography: Evidence for 3D mantle upwelling in the back-arc
a r t i c l e i n f o a b s t r a c t Keywords: full-wave ambient noise tomography the Cascadia subduction zone low-velocity anomaly decompressional melting Melt generation and volcanism at subduction zones may result from several possible processes: hydration of the mantle wedge by fluid released from the slab, subduction-induced mantle upwelling beneath the back-arc, and heating of downgoing ...
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