Collaborative Research: Superior Province Rifting Earthscope Experiment (SPREE)

这些研究人员与研究生和本科生一起，正在安装来自EarthScope柔性阵列池的83个宽带地震站，以探索中大陆裂谷系统（MCRS）的深层结构。MCRS是中元古代一次大规模裂谷事件的化石遗迹，该事件未能分裂北美。这一事件留下了大量致密的玄武岩，并伴有强烈的地球物理异常。通过对裂谷下面的深层结构进行成像，这个地震实验研究了这些裂谷是如何形成和消亡的，而不是发展成海洋扩张中心的。地震台站位于从明尼苏达州-爱荷华州边界到加拿大苏必利尔湖的断裂周围，横跨和沿着断裂。利用接收函数偏移、环境噪声分析、远震表面波色散分析、区域S波和表面波序列拟合、远震到达时间层析成像、现有地震反射和折射数据再分析、sks分裂分析等方法对MCRS中心部分的深部地震结构进行成像。这些分析结果结合成一幅多分辨率、各向同性和各向异性地壳和地幔结构的三维图像。这些分析结果将阐明地幔在裂陷过程及其开始和停止中的作用。研究结果也将增强我们对中大陆地震的认识。该研究项目雇用至少三名研究生，也包括本科生，并促进加拿大和美国研究人员之间的合作。

These investigators, along with graduate and undergraduate students, are installing 83 broadband seismic stations from the EarthScope Flexible Array pool to explore the deep structure of the Mid-Continent Rift System (MCRS). The MCRS is the fossil remnant of an extensive rifting event that failed to split North America during the Middle-Proterozoic era. This event left a large volume of dense basalts and associated strong geophysical anomalies. By imaging the deep structure beneath the rift, this seismic experiment investigates how such rifts form and then die, rather than developing into oceanic spreading centers. The seismic stations are located around, across, and along the failed rift, from the Minnesota-Iowa border into Canada by Lake Superior. Imaging the deep seismic structure of a central part of the MCRS will be undertaken with receiver function migration, ambient noise analysis, teleseismic surface wave dispersion analysis, regional S- and surface wave-train fitting, teleseismic arrival time tomography, re-analysis of existing seismic reflection & refraction data, and SKS-splitting analysis. These analyses are combined into a multi-resolution, three-dimensional image of the isotropic and anisotropic structure of the crust and mantle beneath the MCRS and its surroundings. Results of these analyses will illuminate the role of the mantle in the rifting process and its initiation and cessation. The results will also enhance our understanding of mid-continental earthquakes. This research project employs at least three graduate students, also involves undergraduate students, and fosters collaboration between researchers from Canada and the USA.