Collaborative Research: High Sample-Rate GPS: A New Tool for Earthquake Studies

合作研究：高采样率GPS：了解大地震中的断层破裂以及由此产生的地面运动，受到我们观测能力的限制。对非常大振幅地震波的观测，特别是对位移的直接测量，将在限制触发远程地震活动的动态应变的大小和揭示震源破裂过程的细节方面取得重大进展。例如，加速度计捕获震源附近强烈地面震动的细节，但很难将加速度测量值明确地转换为确定震源时间历史所需的位移。 宽频带地震仪更灵敏，对地面运动有更好的分辨率，但即使在距离大地震很远的地方，也经常会出现削波、饱和或非线性。 干涉合成孔径雷达（干涉合成孔径雷达）观测可以产生空间丰富的图像周围的地表位移的一些组件的破裂，但干涉合成孔径雷达在许多地区失败，并没有时间分辨率来解决动态现象。 全球定位系统（GPS）大地测量对于解决静态偏移具有重要意义，但其采样率通常很低，以致于无法解决破裂过程的细节问题，因此发展了一种利用GPS高采样率测量大地震地震波的新技术。该项目专门利用高速率GPS测量，以提高我们对2002年11月3日发生的MW 7.9 Denali断层地震的破裂过程的理解。 该项目的第一阶段评估与这些新的全球定位系统观测的可靠性和效用有关的技术问题。在第二阶段，所得到的数据被用来补充现有的地震数据：（1）更好地了解从德纳里地震，触发地震远程地面运动，（2）使用在远距离区域的表面波，以验证德纳里断层地震主震破裂模型。本文提出的研究有几个潜在的社会效益：（1）增加对触发地震所需应力水平的理解将有助于地震预测工作，这对公共安全具有长期效益;（2）GPS对强震位移的限制将通过增加可用数据量而对地震工程界产生重大影响，并解决了从加速度计恢复可靠的位移记录的非常有问题的方面。这将通过更好地了解建筑物反应和建筑物安全对公共安全产生影响;（3）高速率全球定位系统方法将通过提高高速率全球定位系统数据分析的准确性和效率，使更多的全球定位系统用户受益。研究结果还将影响研究和教育的基础设施，例如，影响国家科学基金会地球观测设施板块边界观测站组成部分内全球定位系统监测的设计和实施。

Collaborative Research: High Sample-Rate GPS: A New Tool for Earthquake StudiesUnderstanding fault rupture during major earthquakes, and the resulting ground motions, is limited by our observational capabilities. Observations of very large amplitude seismic waves, especially direct measurements of displacement, would make a significant improvement in constraining the size of dynamic strains that trigger remote seismicity and in revealing details of the source rupture process. For example, accelerometers capture the details of strong ground shaking near the source, but it is difficult to convert the acceleration measurements unambiguously to displacement which is required for determining the source time history. Broad-band seismometers are more sensitive, and have better resolution of ground motion, but frequently clip, saturate, or become non-linear even at great distances from a large earthquake. Interferometric Synthetic Aperture Radar (InSAR) observations can produce spatially rich images of some components of surface displacement surrounding a rupture, but InSAR fails in many regions and has no temporal resolution to resolve dynamic phenomena. Global Positioning System (GPS) geodetic measurements have been important for resolving static offsets, but are usually sampled at such a low rate that resolving details of the rupture process was not frequently attempted.A new technique has been developed for using high-rate measurements from GPS to measure seismic waves generated by large earthquakes. This project specifically exploits high-rate GPS measurements to improve our understanding of the rupture process of the Mw 7.9 Denali Fault earthquake of 3 November 2002. The first phase of this project assesses the technical issues relating to the reliability and utility of these new GPS observations. In the second phase, the resulting data are used to complement existing seismic data: (1) to better understand the ground motions from the Denali earthquake that triggered earthquakes remotely, and (2) to use the surface waves at far-regional distances to validate rupture models of the Denali Fault earthquake mainshock. The research proposed here has several potential societal benefits: (1) The increased understanding of stress levels required to trigger earthquakes will contribute to earthquake prediction efforts which has long term benefits to public safety; (2) GPS constraints on strong motion displacements will have a significant impact in the earthquake engineering community by increasing the amount of data available, and addressing the very problematic aspect of recovering reliable displacement records from accelerometers. This will have impacts on public safety through better understanding of building response and building safety; (3) The high-rate GPS methodology will benefit a larger community of GPS users by increasing the accuracy and efficiency of high-rate GPS data analysis. The results will also impact the infrastructure for research and education by influencing, for example, the design and implementation of GPS monitoring within the Plate Boundary Observatory component of the NSF Earthscope facility.