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Detailed Reference Information |
Khazanehdari, J., Rutter, E.H. and Brodie, K.H. (2000). High-pressure–high-temperature seismic velocity structure of the midcrustal and lower crustal rocks of the Ivrea-verbano zone and Serie dei Laghi, NW Italy. Journal of Geophysical Research 105: doi: 10.1029/2000JB900025. issn: 0148-0227. |
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The Ivrea-Verbano zone and the adjacent Serie dei Laghi, in the inner arc of the western Alps (NW Italy), display an upended cross section through much of the thickness of the continental crust as it existed in that region in Triassic/Jurassic time. We collected a suite of oriented rock samples that represent most of the volume of the rocks of the region. P and S wave velocity measurements were made in three orthogonal directions, related to the mesoscopic fabric of the rocks, at room temperature and up to 550 MPa confining pressure. Combined high-temperature and high-pressure measurements were made up to 700 ¿C on a subset of the samples. The lithologic units were divided into 23 different principal rock types, and we present velocity data averaged in terms of these groups. Vertical and horizontal velocity and anisotropy sections are computed from the measured velocity data based on a restored geologic section. These show that Vp and Vs both increase and anisotropy decreases systematically with depth of burial, reflecting variations in rock type and metamorphic grade with depth. Vp and Vs anisotropy arises mainly because of crystallographic preferred orientation or mineralogical banding, with the slowest direction tending to be normal to the foliation or banding. The Vp velocity sections were used to compute synthetic seismic reflection profiles for the region when it lay at the bottom of the continental crust. These correspond well with contemporary deep reflection profiles for regions of comparable tectonic evolution. ¿ 2000 American Geophysical Union |
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Abstract |
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Keywords
Exploration Geophysics, Continental structures, Physical Properties of Rocks, Acoustic properties, Seismology, Continental crust, Tectonophysics, Continental tectonics—extensional |
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Publisher
American Geophysical Union 2000 Florida Avenue N.W. Washington, D.C. 20009-1277 USA 1-202-462-6900 1-202-328-0566 service@agu.org |
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