Collaborative Research: Nazca- South America Convergence and Continental Growth in the Central Andes via Global Positioning System (GPS) Measurements

尽管从达尔文开始进行了几个世纪的研究，但像安第斯山脉这样位于海洋-大陆交汇边缘的大型山带的起源仍然是个谜。人们提出了各种各样的假说来解释安第斯山脉，但就其本身而言，似乎没有一个假说能够解释这片隆起的、加厚的地壳的广大地区的形成。例如，研究人员的初步GPS数据表明，尽管中新世以来俯冲作用显著减缓，但安第斯山脉今天仍在以其长期平均速度增长，这对那些只认为快速俯冲作用形成安第斯山脉的模型来说是个问题。这个来自迈阿密大学和西北大学的合作团队提出了一系列的GPS测量，利用了1994年首次使用的网络，再加上相关的地震研究，旨在了解安第斯山脉带的形成过程。他们将把重点放在秘鲁和玻利维亚的安第斯山脉中部，那里是又高又宽的Altiplano高原最发达的地方，那里有一个活跃的褶皱和逆冲带，可以适应地壳的快速缩短。为了提高他们区分模式和节约资源的能力，测量将集中在跨越整个板块边界带的两个横断面上，即在平坦和正常俯冲的区域。新的测量将跨越总共四年的时间，以在新的地点获得足够的速度精度，以区分几个相互竞争的假设。

Dixon EAR-0003621SteinEAR-0004031The origin of large mountain belts like the Andes at ocean-continent convergent margins remains enigmatic despite centuries of study beginning with Darwin. Various hypotheses have been advanced to explain the Andes, but by themselves none seem capable of explaining the formation of this vast region of elevated, thickened crust. For example, the investigator's preliminary GPS data suggest that the Andes are growing today at roughly their long term average rate despite significant slowing of subduction since the Miocene, problematic for models that call on fast subduction alone to form the Andes. This collaborative team from the University of Miami and Northwestern University proposes a series of GPS measurements that exploit a network first occupied in 1994, coupled with related seismic studies, aimed at understanding the processes forming Andean mountain belts. They will focus on the Central Andes of Peru and Bolivia, where the high, wide Altiplano plateau is best developed, and where an active fold and thrust belt accommodates rapid crustal shortening. To enhance their ability to discriminate models and to conserve resources, the measurements will be densified in two transects that cross the entire plate boundary zone, in regions of flat and normal subduction. The new measurements will span a total of four years to obtain velocity accuracy at the new sites adequate to distinguish among several competing hypotheses.