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

0609768 DokkaFunds来自这一小笔探索性研究拨款(SGER)，用于支持PIS 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竞选基准进行GPS重新评估，并在该地区建立另外10个连续运行的永久纪念性GPS站。最近路易斯安那州新奥尔良与2005年8月29日卡特里娜飓风有关的悲惨洪水，突显了这一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，因为它位于一个活动的Listric正断层系统(Michoud断层)的上盘，该断层系统容纳了密西西比三角洲向南进入墨西哥湾的运动。在过去的十年中，这个地壳上部地块相对于北美稳定的内陆向南运动的速度为2.3加或减1.7毫米/年。平整数据表明，在最近的过去，运动速度可能更高。位于三角洲的GPS站点的平均下沉速率相对于地球质心为5.2正负2.3毫米/年，或相对于平均海平面约为7毫米/年。地震反射运动所显示的下伏盐层似乎促进了里斯特里克断层上三角洲地块的运动。这些层位适应了低温下韧性流动的变形，因此很少或根本没有与断层有关的地震活动。拟议的额外GPS观测将有助于确认所提出的米丘德断层动力学，并测试在卡特里娜飓风相关的水团加载后地面变形加速的可能性。该项目的数据将提供关键的背景结构框架，以指导新奥尔良重建期间的政策制定者。

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.***