CIFALPS seismic experiment reveals high-resolution characteristics of continental subduction channel beneath western Alps, Europe
Abstract
Plate subduction is the primary engine that shapes up our planet, and the study of subduction geodynamics remains a hot research topic in geosciences for decades. Especially, the dynamics of continental subduction is largely controlled by the rheological properties of rocks involved along the subduction channel. As a special type, we focus on the continent-continent subduction channel in the Western Alps, where the first conclusive evidence in support of burial (and exhumation) of the continental crust to depths >90 km.
Aiming to provide high-resolution seismic images of the western Alps subduction system, the China-Italy-France Alps Seismic survey (CIFALPS) was the first passive seismic transect that cross-cuts the entire orogen across the Dora Maira massif. Fifty-five temporary broadband seismic stations were deployed along a linear WSW-ENE transect during 2011 to 2012. Using the data from permanent and portable seismic stations, applying methods of receiver function, waveform modeling, body wave and surface wave tomography, shear wave splitting measurements, we reveal high-resolution characteristics of the subduction channel beneath western Alps. The highlights of the new results with respect to the subduction channel are summarized as below. Seismic image of subducted continental lithosphere with a crust-mantle boundary at 75 km in depth provides decisive proof of the concept of continental subduction. European slab, shown as 3D continuous high velocity anomaly, extends from the surface to the mantle transition zone. Along the plate interface, a prominent low-velocity zone extends down to at least 60 km depth, and spatially links to the surface exhumed UHP rocks. The previously observed continuous trend of anisotropy fast axes near-parallel to the western Alpine arc is confirmed, this arc-parallel trend of fast axes is located in correspondence to a low velocity anomaly in the European upper mantle. Our findings here may provide key clues for better understanding of continent-continent subduction systems likely not only in the western Alps but also global continental subduction zones, and may be of interest not only to seismologists, but also to any geoscientist who study plate tectonics.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.T31H0304Z
- Keywords:
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- 8110 Continental tectonics: general;
- TECTONOPHYSICS;
- 8124 Earth's interior: composition and state;
- TECTONOPHYSICS;
- 8177 Tectonics and climatic interactions;
- TECTONOPHYSICS