Airborne Gradiometer Survey For The Proposed San Andreas Fault Drill Site

对拟议的圣安德烈亚斯断层钻探地点进行机载梯度计测量

• 批准号: 0132137
• 负责人: Manik Talwani
• 金额: --
• 依托单位: William Marsh Rice University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-09-01 至 2005-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0132137&HistoricalAwards=false
• 关键词: Airborne; Gradiometer; Survey; Proposed; San

0132137TalwaniAirborne gravity gradiometry is a technology that has only recently been developed, but which has enormous potential. It is capable of making absolute gravity gradient measurements of great precision very rapidly over almost any kind of terrain, and at a relatively modest cost. It could well revolutionize measurements involving gravity for various types of studies focused on the shallow crust, and because the instrument determines absolute values, for time lapse studies as well. The former could include, for example, studies involving the detection of blind faults, determination of the thickness of sedimentary fill or of basalt flows and lithologic contacts in densely vegetated areas as well as environmental and mineral exploration related problems. The latter could help trace fluid flow in the shallow crust or magma movement in volcanoes, as well as other movements of material within the shallow crust on the human time scale.Only two airborne gradiometers are actually operational today. Both are based on Lockheed Martin's GGI gradiometer and have been adapted for airborne work jointly by Lockheed Martin and BHP. It is clear that this technology is in its infancy and some preliminary experimentation is necessary in order to test its suitability for crustal work. This project involves an aerial gradiometer survey of the proposed drill site for the San Andreas Fault Observatory at Depth (SAFOD), a component of EAR's Earthscope Initiative. SAFOD will involve drilling a 4 km deep hole which will intersect the San Andreas Fault near Parkfield, CA. In addition to helping determine the deep structure at the proposed drill site, the fact that the gradiometer makes absolute measurements can be put to another use. It is quite possible that in a time lapse experiment, that is by making two measuremenbts over the identical space separated in time, changes in the subsurface can be monitored. These changes could be the motion of fluids or changes associated with an earthquake. For the latter experiment, it is obviously important to establish a base line measurement before the earthquake. If a number of measurements are made it may be also possible to see if fluid motions in the shallow subsurface are reliable precursors to earthquakes.***

0132137 Talwani航空重力梯度测量是一项最近才开发的技术，但具有巨大的潜力。 它能够在几乎任何类型的地形上非常迅速地进行高精度的绝对重力梯度测量，并且成本相对较低。 它可以彻底改变涉及重力的测量，用于各种类型的研究，重点是浅地壳，因为该仪器确定绝对值，也用于时间推移研究。 例如，前者可包括涉及探测盲断层、确定沉积填充物或玄武岩流的厚度和植被密集地区的岩性接触以及环境和矿物勘探相关问题的研究。 后者可以帮助追踪地壳浅层的流体流动或火山的岩浆运动，以及人类时间尺度上地壳浅层内物质的其他运动。 两者都是基于洛克希德·马丁公司的GGI梯度仪，并已被洛克希德·马丁公司和必和必拓公司联合改装用于机载工作。 显然，这项技术尚处于初级阶段，需要进行一些初步试验，以检验其是否适用于地壳工作。 该项目涉及对拟议的圣安德烈亚斯断层深度观测站钻井地点进行航空梯度仪测量，这是地球观测局地球观测计划的一个组成部分。SAFOD将涉及钻一个4公里深的孔，该孔将与加州帕克菲尔德附近的圣安德烈亚斯断层相交。 除了帮助确定拟议钻探地点的深部结构外，梯度仪进行绝对测量的事实还可以用于另一种用途。 在时间推移实验中，也就是在时间上分开的同一空间内进行两次测量，很可能可以监测到地下的变化。 这些变化可能是流体的运动或与地震有关的变化。 对于后一个实验，显然重要的是在地震前建立基线测量。 如果进行了大量的测量，也有可能看到浅层地下的流体运动是否是地震的可靠前兆。