The next cascadia slab model
| Autor: | Bloch, Wasja, Bostock, Michael, Audet, Pascal |
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| Jazyk: | angličtina |
| Rok vydání: | 2023 |
| Zdroj: | XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG) |
| Popis: | Detailed knowledge about the location and properties of the structures that host the megathrust is required to predict ground motions, model tsunami hazards and better understand subduction zone processes in Cascadia. Here we present our efforts to bring forward a new, detailed slab model based on azimuthally variable receiver functions from almost 300 on-shore 3-component broadband seismic stations.We observe a characteristic succession of a negative top-, a positive central- and the positive oceanic Moho-conversion, where either the top or central conversion may be absent. We interpret it as the subducting oceanic crust that is at places overlain by, or contained within, a low-velocity zone. Inverse modeling of synthetic receiver functions allows us to resolve the strike and dip of this structure, the interface depths and seismic velocities of the intervening material along the fore-arc.The top conversion exhibits a progressive landward evolution displaying (i) a weak contrast with overriding crust near the coast, (ii) full expression with the development of an upper low-velocity zone downdip, and (iii) disappearance in advance into the fore-arc, where the oceanic crust is inferred to turn to eclogite.The thickness of the entire structure frequently exceeds the thickness of the oceanic crust offshore. At depth, the location of the central converter approximately correlates with the location of low-frequency earthquakes. These observations suggest that the subduction megathrust either continues downdip, a few kilometers below the top conversion, or widens into a distributed shear zone that includes upper plate material. The 28th IUGG General Assembly (IUGG2023) (Berlin 2023) |
| Databáze: | OpenAIRE |
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