第85回ジオダイナミクスセミナー
　 　Geodynamics　Seminar

要　旨
　The convergent plate boundary between the South American continent and the oceanic Nazca plate is characterized by several regions of flat-slab subduction. Here, the downgoing Nazca slab does not descend at a constant dip angle, but rather reaches some depth and then flattens, moving almost horizontally for hundreds of kilometers before resuming its descent into the mantle. These areas are spatially correlated with a cessation of arc volcanism and the existence of basement cored uplifts such as the Sierras Pampeanas. The 2000-2002 Chile Argentina Geophysical Experiment (CHARGE) was deployed above the southernmost region of flat-slab subduction in South America, between 30 and 36 degrees S. This deployment of 22 broadband seismometers recorded continuously for 18 months, and provides us with a unique look at the effects of flat-slab subduction on arc volcanism and crustal deformation. We use a number of broadband seismic techniques, including receiver functions, moment tensor inversions, and seismic tomography to better constrain the nature of the lithosphere overlying this unusual subduction zone.




　　　　　　　　問い合わせ先：山崎　大輔 　TEL　　　（089）927-8408
　　　 　　　　　　　　　　　　　　　　E-mail　　yamazaki@sci.ehime-u.ac.jp