Collaborative Research: The Peru Subduction Experiment (PeruSE), a Seismic Investigation of the Role of Water in the Lithospheric Dynamics of Subduction Zones

正如印度尼西亚、中国、海地和智利最近的地震史所表明的那样，俯冲带会产生最大的地震。 地震发生在岩石易碎且应力高到足以克服摩擦力的地方。 摩擦力取决于岩石的性质和含水量，以及水是自由地施加孔隙压力，还是在变质岩中被结晶束缚。 释放出来的水会导致火山爆发。了解地震力和地震机制对于估计灾害是很重要的。特别是，我们寻求使用地震和跨学科的数据来了解如何脱水发生在秘鲁俯冲带，其摩擦，流变学和火山作用的影响。 这项工作对估计该区域主要城市的地震和火山危险以及了解过去的构造和导致大陆构造和成矿作用的过程都很重要，秘鲁是研究水、地震、地震耦合和火山活动的路径之间关系的一个很好的地方。 特别是在秘鲁南部，板块有一个陡峭的倾角，在板块达到约100公里深度的地方，火山就出现在板块上方。 相比之下，更北的板块倾角较浅，没有火山，但深地震发生在600公里的深度，一些是世界上最深的。地震台阵测深是推断地球深部性质的主要方法。目标是调查地壳和地幔的属性的对比，以及从非火山平板向火山陡板俯冲过渡的地震活动的对比，并推断水的路径。 水对摩擦力、地震速度、Q值、变质变化、熔融和地震的产生有重要影响。地震层析成像和地震活动性将被用来绘制这些影响的三维图。 我们的地震台阵实验涉及秘鲁的宽带网络，由4个线性网络组成。1号线由50个车站组成，从阿雷基帕附近的海岸穿过陡峭的石板到的的喀喀湖。 3号线是平行的，但在更北的地方穿过库斯科，在平板地区上方。 2号线和4号线分别沿着安第斯山脉和海岸线。这四条线路形成了一个由125个车站组成的箱形网络。 每条线路由25至50个宽频带地震台站组成，间隔6至12公里，将记录一至两年，以提供该地区结构和地震活动的前所未有的覆盖范围。 我们希望回答有关俯冲的力学和矿化作用的基本问题。我们的实验涉及许多秘鲁人，包括大学和研究所的专业人员以及我们台站的普通民众。 秘鲁受到大地震的威胁，例如最近的皮斯科2007年毁灭性地震和2001年的地震。海啸也是一种威胁。当地人口受教育程度越高，准备就越充分。我们将通过IRIS向社区提供数据。该项目由国际科学与工程办公室的地球物理计划和美洲计划资助。

As the recent history of earthquakes in Indonesia, China, Haiti and Chile has demonstrated, subduction zones generate the largest earthquakes. Earthquakes occur where the rock is brittle and stresses are high enough to overcome friction. The friction depends on the properties of the rock and water content, and whether the water is free to exert pore pressure, or is crystallographically bound in metamorphic rocks. Released water causes explosive volcanism. Understanding the forces and earthquake mechanisms is important for estimating hazard. In particular, we seek to use seismic and interdisciplinary data to understand how dehydration takes place in the Peru subduction zone, its effect on friction, rheology and volcanism. The work is important both to estimate the earthquake and volcanic hazard of major cities in the region as well as understanding past tectonics, and the processes that led to the tectonic structure and the mineralization of continents.Peru is an excellent place to study the relationship between the pathways of water, earthquakes, seismic coupling and volcanism. In particular, in southern Peru the slab has a steep dip and volcanoes occur above it where the slab reaches depths of about 100 km. In contrast, further north the slab dip is shallow and there are no volcanoes, but deep earthquakes occur at depths of ~600 km, some of the deepest in the world. Seismic array deep-sounding is the premier method to infer properties deep in the Earth. The goals are to investigate the contrasts in the properties of the crust and mantle, and contrasts in earthquake activity across the transition from non-volcanic flat-slab to volcanic steep-slab subduction and to infer the water pathways. Water has a major effect on friction, seismic velocities, Q, metamorphic changes, melting, and the generation of earthquakes. Seismic tomography and seismicity will be used to map these effects in 3D. Our seismic array experiment involves a broadband network in Peru comprised of 4 linear networks. Line 1 consists if 50 stations that run from the coast near Arequipa to Lake Titicaca across the steep slab. Line 3 is parallel but runs further north through Cusco above the flat-slab region. Lines 2 and 4 are connecting lines along the Andes and the coast respectively. The four lines form a box-shaped network of 125 stations spanning the transition. Each line is comprised of twenty five to fifty broadband seismic stations at 6-12 km spacing and will record for one to two years to give an unprecedented coverage of the structures and seismicity of the region. We would like to answer fundamental questions on the mechanics and mineralization of subduction.Our experiment involves many Peruvians both professionally in universities and institutes and the general population who host our stations. Peru is threatened by large earthquakes, such as the recent Pisco 2007 devastating earthquake and the 2001 event demonstrated. Tsunamis are also a threat. The more educated are the local population the better prepared. We will make the data available to the community through IRIS.This project is funded by the Geophysics Program and the Americas Program of the Office of International Science and Engineering.