SEIDCAR: Seismic Investigation of Edge-Driven Convection Associated with the Rio Grande Rift

SIEDCAR旨在了解地幔中小规模的“边缘驱动”对流是否是一种重要的“现实世界”现象，如果是，则探索其对地表地质的影响。具体来说，研究人员希望确定沿b里约热内卢大裂谷东部边缘是否发生了地幔下流，以及它对南落基山脉的构造有什么影响。自白垩纪以来，美国西南部不同构造省的演化，包括大平原、科罗拉多高原和b里约热内卢大裂谷，都与法拉龙板块在大约80 Ma开始的平俯冲和随后在大约40 Ma开始的沉没有关。然而，在过去的10 Ma中，南落基山脉的构造活动（岩浆活动、伸展和可能的隆升）又出现了复苏。法拉龙板块的沉没发生在大约40 Ma，因此该事件与该地区目前的构造活动之间没有明确的联系。小规模的、边缘驱动的对流可能是这种新活动的一个解释。先前一项名为“拉里斯特拉”的研究结果表明，裂谷东侧下方有一股下流。然而，这个异常位于拉里斯特拉线的东南边缘附近，所以分辨率不是最佳的。此外，边缘驱动的对流，如果发生的话，应该沿着克拉通的边缘向南北延伸，但一维拉里斯特拉不能产生三维图像来描绘下流的边界或量化其特征。SIEDCAR的研究人员正在沿着大平原的西部边缘安装一个由75个宽带地震仪组成的二维阵列，以补充和增加USArray的可移动阵列站的密度，它将在2008-2009年穿越该地区。部署的目标是获得La Ristra观测到的特征的尺寸、几何形状、位置和密度对比的定量估计，并模拟其对表面变形的影响。

SIEDCAR: SEISMIC INVESTIGATION OF EDGE DRIVEN CONVECTION ASSOCIATED WITH THE RIO GRANDE RIFTSIEDCAR intends to learn whether small-scale, "edge driven" convection in the mantle is a significant, "real world" phenomenon and, if so, to explore its effects on surface geology. Specifically, the investigators wish to determine whether a mantle downwelling is occurring along the eastern edge of the Rio Grande Rift and what effect it has on the tectonics of the Southern Rockies. The evolution of distinct tectonic provinces in southwestern United States since the Cretaceous, including the Great Plains, the Colorado Plateau, and the Rio Grande Rift, has been linked to flat subduction of the Farallon plate beginning about 80 Ma and then its subsequent foundering beginning about 40 Ma. However, there has been a resurgence in tectonic activity (magmatism, extension, and possibly uplift) during the last 10 Ma in the Southern Rockies. The foundering of the Farallon slab occurred about 40 Ma, so there is not a clear connection between that event and present tectonic activity in the region. Small-scale, edge driven convection is a possible explanation for this renewed activity. Results from a previous study, called "La Ristra", indicate a downwelling under the eastern flank of the rift. However, this anomaly is located near the southeastern edge of the La Ristra line, so resolution less than optimal. Furthermore, edge driven convection, if it is occurring, should extend to the north and south along the margin of the craton, but the one-dimensional La Ristra could not produce a three-dimensional image to delineate the downwelling's boundaries or to quantify its characteristics. SIEDCAR's investigators are installing a two-dimensional array of 75 broadband seismographs along the western edge of the Great Plains to supplement and increase the density of USArray's Transportable Array stations, which will traverse the region in 2008-2009. The goal of the deployment will be to obtain quantitative estimates of the size, geometry, location, and density contrast of the feature observed by La Ristra and to model its effects on surface deformation.