Post-Katrina re-survey of key geodetic benchmarks in coastal Louisiana

来自探索性研究（SGER）小额赠款的资金支持pi Tim Dixon（迈阿密- RSMAS）和Roy Dokka（路易斯安那州立大学）的合作努力，对新奥尔良地区现有的运动基准进行GPS勘测，并在该地区建立10个额外的连续运行和永久纪念碑GPS站。最近与2005年8月29日的卡特里娜飓风有关的路易斯安那州新奥尔良的悲剧性洪水强调了这个城市地区的危险环境。pi收集的初步GPS和水准数据表明，新奥尔良正在迅速下沉，因为它位于一个活跃的表面正断层系统（Michoud断层）的上壁上，该断层系统适应密西西比三角洲向南进入墨西哥湾的运动。在过去十年中，相对于北美稳定的内部，这一上地壳块体的平均南移速度为2.3±1.7毫米/年。平地数据表明，在最近的过去，运动的速度可能更高。相对于地球质心，位于三角洲的GPS站点的平均沉降率为5.2±2.3毫米/年，或相对于平均海平面约7毫米/年。地震反射活动成像显示，下伏的盐层似乎促进了表状断层上三角洲块体的运动。这些层位在低温下通过韧性流动容纳变形，因此很少或没有与断层有关的地震活动。拟议的额外GPS观测将有助于确认拟议的Michoud断层动力学，并测试卡特里娜相关水团加载后地面变形加速的可能性。该项目的数据将为指导新奥尔良重建期间的政策制定者提供关键的背景构造框架

0609768DokkaFunds from this Small Grant for Exploratory Research (SGER) support a collaborative effort by PIs Tim Dixon (Miami - RSMAS) and Roy Dokka (LSU) to conduct GPS resurveys of existing campaign benchmarks in the New Orleans area and to establish 10 additional continuously operated and permanently monumented GPS stations in the region. The recent tragic flooding of New Orleans, Louisiana, associated with Hurricane Katrina on August 29, 2005, emphasizes the hazardous setting of this urban area. Preliminary GPS and leveling data collected by the PIs suggest that New Orleans is subsiding rapidly because it is located in the hanging wall of an active listric normal fault system (the Michoud fault) that accommodates southward motion of the Mississippi delta into the Gulf of Mexico. Averaged over the last decade, southward motion of this upper crustal block relative to the stable interior of North America occurs at a rate of 2.3 plus or minus 1.7 mm/yr. Leveling data suggest that the rate of motion may have been higher in the recent past. The average subsidence rate for GPS sites located on the delta is 5.2 plus or minus 2.3 mm/yr relative to Earths's center of mass, or about 7 mm/yr relative to mean sea level. Movement of the delta block on the listric fault appear to be facilitated by underlying salt horizons that have been imaged by seismic reflection campaigns. These horizons accommodate deformation via ductile flow at low temperatures, hence there is little or no seismicity associated with faulting. The proposed additional GPS observations will help to confirm the proposed Michoud fault dynamics and to test the possibility that ground deformation accelerated following Katrina-related water mass loading. Data from this project will provide critical background tectonic framework to guide policy makers during the rebuilding of New Orleans.***