HR: 0800h
AN: T41A-0364    [Abstracts]
TI: Character of the lower crust and upper mantle below the Baikal Rift Based on the Seismic Wave Field Pattern along Profile 1 from BEST Project
AU: * Perchuc, E
EM: per@igf.edu.pl
AF: Institute of Geophysics, Polish Academy of Science, Poland, Ksiecia Janusza 64, Warsaw, 01-452, Poland
AU: Gaczynski, E
EM: edek@igf.edu.pl
AF: Institute of Geophysics, Polish Academy of Science, Poland, Ksiecia Janusza 64, Warsaw, 01-452, Poland
AU: Malinowski, M
EM: michalm@igf.edu.pl
AF: Geological Survey of Canada, Seismology and Electromagnetism, Ottawa, ON, Canada, 601 Booth St., Ottava, ON K1A OE8, Canada
AB: The Baikal Rift Zone (BRZ) is located on the largest continental plate on the Earth, the Euro-Asiatic plate, between the Siberian platform to NE and the region of Paleozoic deformation belt to the SE. The BRZ is an active rift of late Cenozoic age. The aim of the BEST (Baikal Explosion Seismic Transects) project was to study the structure of the crust and upper mantle below Baikal Rift and surrounding areas. Experiment measurements were performed along two deep seismic profiles number 1 and 2. We concentrate on the profile 1 crossing BRZ from west to east direction. Along this profile 10 land shot points are located as well as air gun shots in the Baikal lake, recorded by the three arrays located in two sides of lake bank. Tectonically, the first 6 shot points of the profile 1 are located on the Siberian Craton and last 4 are on the Palaeozoic fold belt. Between these tectonic units is the BRZ (lake Baikal). We modeled the structure using different kinematics and dynamic programs based on raytracing and tomographic methods. We present velocity models across rift from NW to SE direction. We present optimal kinematic and dynamic model along the profile 1 with relation to recorded wave pattern. We discuss significant differences between tectonic units derived from variations of the wavefield pattern and character, studying in particular the arrivals from the transition between crust and upper mantle. For the understanding of the structure of the lower part of crust and upper mantle and differences between BRZ, Craton and Paleozoic fold belt, we present dynamic interpretation of wave pattern which suggest significant differences between the above-mentioned blocks. On the both sides of the BRZ, the Moho depth varies not so much and is located between 35 to 42 km with slight deepening towards the rift zone. Below the rift zone we localize reflection/refraction boundary on the depth 47-52 km with high velocity about 8.6 km/s (Pn^rift?). The character of the dynamic properties of the Moho reflections is significantly different for Siberian Craton and for Palaeozoic foredeep region.
DE: 7207 Core (1212, 1213, 8124)
DE: 7208 Mantle (1212, 1213, 8124)
DE: 7218 Lithosphere (1236)
DE: 8108 Continental tectonics: compressional
DE: 8120 Dynamics of lithosphere and mantle: general (1213)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting