Slab Geometry and Mountain Building Processes in the Southern Andes

这项研究利用阿根廷和智利的PASSCAL便携式宽带地震仪，研究了俯冲板块几何形状发生重大变化的中南部安第斯山脉下方的构造。这项研究将与智利、阿根廷、法国和德国的研究机构联合进行。在南纬约33.3度处，俯冲的纳斯卡斯拉布从北面没有任何活动性的水平板片几何形状转变为南面有活动性弧形的30度倾斜板。这种板块倾角的南北变化是全球瓦达蒂-贝尼奥夫大地测量法中最戏剧性的弯曲或翘曲之一。在南纬31度，扁平的板块向东延伸300公里，然后恢复下降到地幔。该段海拔高，构造缩短量大。将部署两条PASSCAL横断面：一条在水平板段上方南纬30.5度附近，另一条在南纬36度处。地震数据将从天然地震中收集并反演，以回答涉及跨越过渡的俯冲板块结构、周围地幔结构、山体建筑和地震孕育过程的问题。

This research involves the study, by means of PASSCAL portablebroadband seismometers in Argentina and Chile, of the structurebeneath the south central Andes where a major change in subductingslab geometry occurs. The research will be done in conjunctionwith research institutes from Chile, Argentina, France, andGermany. At approximately 33.3 degrees South, the subducting Nazcaslab changes from a horizontal slab geometry without any activevolcanism to the north, to a 30-degree dipping slab with an activevolcanic arc to the south. This north-south change in slab dip isone of the most dramatic bends or warps in a Wadati-Benioff zonegeometry anywhere globally. At 31 degrees South, the flattenedslab extends 300 km to the east before resuming its descent intothe mantle. This segment has high elevations and large amounts oftectonic shortening. Across the dipping slab segment, the elevation decreases, as does the amount of tectonic shortening.Two PASSCAL transects will be deployed: one near 30.5 degrees South above the horizontal slab segment and one at 36 degrees South above the dipping slab segment. The seismic data will be gathered from natural earthquakes and inverted to answer questions involving thestructure of the subducting slab across the transition, surroundingmantle structure, mountain building, and earthquake generationprocesses.