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

合作研究：高采样率GPS：地震研究的新工具了解大地震期间的断层破裂及其引起的地面运动，受到我们的观测能力的限制。观测非常大的地震波，特别是直接测量位移，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做出重大改进。例如，加速度计捕捉震源附近强烈地面震动的细节，但很难明确地将加速度测量值转换为确定震源时间历史所需的位移。宽带地震仪更灵敏，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，也经常出现剪裁、饱和或变得非线性。干涉合成孔径雷达(InSAR)观测可以产生破裂周围地表位移的某些分量的空间丰富的图像，但InSAR在许多地区无法获得，并且没有时间分辨率来解析动态现象。全球定位系统(GPS)大地测量对于解决静态偏移量一直很重要，但通常采样速率很低，因此不经常尝试解析破裂过程的细节。开发了一种新技术，利用GPS的高速测量来测量大地震产生的地震波。该项目特别利用高速率GPS测量，以提高我们对2002年11月3日发生的MW7.9迪纳利断层地震破裂过程的了解。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实用性有关的技术问题。在第二阶段，产生的数据用于补充现有的地震数据：(1)更好地了解德纳利地震远程触发地震的地面运动，以及(2)使用遥远区域距离的面波来验证德纳利断层地震主震的破裂模型。这里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了解将有助于地震预测工作，这对公共安全具有长期好处；(2)GPS对强震位移的限制将通过增加可用的数据量和解决从加速度计恢复可靠的位移记录这一非常有问题的方面，在地震工程界产生重大影响。这将通过更好地了解建筑响应和建筑安全对公共安全产生影响；(3)高速GPS方法将通过提高高速GPS数据分析的准确性和效率而使更多的GPS用户受益。这些成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望远镜设施的板块边界观测站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.