Investigating Flat Slab Subduction and Plate Edge Tectonics in Northern South America

南美北部国家哥伦比亚和委内瑞拉的地震危险性很高。这些国家沿着走滑断层系统和俯冲带频繁发生大地震，其综合地震危险潜力与加利福尼亚州的圣安德烈亚斯系统以及俄勒冈州、华盛顿州和阿拉斯加州的俯冲带相同。最近的空间大地测量表明，沿哥伦比亚北部平坦的加勒比海俯冲带和马拉开波湖地区，南美洲西北部早该发生大地震(M8级)。虽然这两个国家都有现代化的地震监测和地震危险性评估机构，即西斯莫洛吉卡斯基金会(FUNVISIS)和哥伦比亚地质调查局(SGC)，但这两个国家的地震危险性都因糟糕的、不受监管的建筑做法和日益增长的城市贫困人口而加剧。这两个国家的总人口约为8000万，城市人口迅速增长。委内瑞拉和哥伦比亚的民用和石油基础设施都面临着大地震的风险。出于各种原因，包括毗邻，委内瑞拉和哥伦比亚对美国都具有战略意义。[例如，迈阿密和新奥尔良离波哥大和加拉加斯比离西雅图更近]。委内瑞拉具有国际重要性，其碳氢化合物储量超过沙特阿拉伯，并拥有广泛的碳氢化合物生产设施。委内瑞拉目前向美国供应约8%的石油进口，仅略低于从沙特阿拉伯的进口。美国是委内瑞拉最重要的贸易伙伴。美国与委内瑞拉和哥伦比亚之间的科学交流对于发展这些国家的科学能力以及培训他们的地球科学工作者非常重要。在其历史进程中，水稻地球科学系不断招收理科硕士。以及来自委内瑞拉和哥伦比亚的博士生。大约10%的现代俯冲带呈平板状，包括沿南美洲西部(SA)的3-4个。地质历史表明，SA西部边缘约70%的地区在新生代经历了平坦俯冲。板片的展平作用归因于板片浮力、地幔楔入性质和地幔流动动力学。从地震活动性、岩浆作用的类型和分布，以及在某些情况下的基底核隆起来看，平坦俯冲引起的覆盖板块的变形与正常俯冲引起的变形有很大的不同。现在人们认识到，加勒比海在南沙西北部以低角度俯冲，形成了圣玛尔塔、佩里哈和梅里达安第斯山脉的基底核心隆起。这些可能是美国西部中生代晚期-新生代早期拉莱米德基底隆起的现代类似物。与FUNVISIS和SGC合作，研究小组将安装一个大型宽带地震仪阵列，以成像俯冲带几何形状和测量南澳北部平板的板块耦合流变学，目的是了解基底隆起的地球动力学发展。他们的地震仪阵列记录的当地和地区地震将用于南美洲北部的地震危险性评估。

The northern South American countries of Colombia and Venezuela have high seismic hazard. These countries are subject to frequent large earthquakes along strike-slip fault systems and subduction zones with the same combined seismic hazard potential as California's San Andreas system, and Oregon, Washington, and Alaska's subduction zones. Recent space geodesy measurements suggest that northwestern South America is overdue for a great (M8) earthquake along the flat Caribbean subduction zone under northern Colombia and the Lake Maracaibo region. Although both countries have modern earthquake monitoring and seismic hazard assessment agencies, Fundación Venezolana de Investigaciones Sismológicas (FUNVISIS) and Servico Geológico Colombiano (SGC), seismic hazard in both nations is exacerbated by poor, unregulated construction practices and a growing population of urban poor. The two nations have a combined population of ~80 million, and rapidly growing urban populations. Both the Venezuelan and Colombian civil and petroleum infrastructures are at risk from large seismic events. For a variety of reasons, including proximity, both Venezuela and Colombia are of strategic significance to the U.S. [Miami and New Orleans are closer to Bogota and Caracas than they are to Seattle, for instance]. Venezuela is of international importance, with hydrocarbon reserves that exceed Saudi Arabia's and extensive hydrocarbon production facilities. Venezuela currently supplies the U.S. with ~ 8% of its oil imports, only slightly less than imports from Saudi Arabia. The U.S. is Venezuela's most important trading partner. Scientific exchange between the U.S. and Venezuela and Colombia is important for developing scientific capacity in these nations, and for training their earth science workforces. Over the course of its history, the Rice Earth Science department has continuously enrolled M.Sc. and Ph.D. students from Venezuela and Colombia. Roughly 10% of modern subduction zones exhibit flat slab segments, including 3-4 along western South American (SA). Geologic history suggests ~70% of the western SA margin experienced flat subduction in the Cenozoic. Slab flattening is attributed to slab buoyancy, mantle wedge properties, and mantle flow dynamics. Flat subduction causes deformation in the overriding plate substantially different than that caused by normal subduction, as seen in seismicity, type and distribution of magmatism, and in some cases, basement cored uplifts. It is now recognized that the Caribbean subducts at low angles under northwestern SA, forming the basement cored uplifts of the Santa Marta, Perija, and Merida Andes ranges. These may be modern analogs to the late Mesozoic-early Cenozoic Laramide basement uplifts of the western United States. With FUNVISIS and SGC, the investigator team will install a large broadband seismograph array to image the subduction zone geometry and measure plate coupling rheology of the northern SA flat slab, with a goal of understanding the geodynamic development of basement uplifts. The local and regional earthquakes recorded by their seismograph array will be used for seismic hazard assessment in northern South America.