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

高采样率GPS：地震研究的新工具在大地震中理解断层破裂，以及由此产生的地面运动，受到我们的观测能力的限制。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作出重大改进。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结果明确地转换为确定震源时程所需的位移。宽频带地震仪更敏感，对地面运动的分辨率也更高，但即使在距离大地震很远的地方，也经常出现夹波、饱和或非线性。干涉合成孔径雷达（InSAR）观测可以产生空间丰富的破裂周围地表位移分量图像，但InSAR在许多区域失效，并且没有时间分辨率来解决动态现象。全球定位系统（GPS）大地测量测量对于解决静态偏移非常重要，但通常采样率很低，因此不经常尝试解决破裂过程的细节。目前正在开发一种新技术，利用GPS的高速率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测量来提高对Denali、Parkfield、San Simeon、Tokachi-Oki和Sumatra地震破裂过程的理解。这项研究有几个潜在的社会效益：(1)增加对触发地震所需的应力水平的了解有助于地震预测工作，这对公共安全有长期的好处；(2) GPS对强震位移的约束在地震工程界具有重要影响，因为它增加了可用数据的数量，并解决了从加速度计中恢复可靠位移记录的非常困难的方面。通过更好地了解建筑反应和安全，这会影响公共安全；(3)高速率GPS方法通过提高高速率GPS数据分析的精度和效率，使更多的GPS用户受益。这将有助于震后研究和火山监测工作。研究结果还将影响研究和教育的基础设施，例如影响美国国家科学基金会Earthscope设施板块边界观测站组件内GPS监测的设计和实施。

High Sample-Rate GPS: A New Tool for Earthquake Studies Understanding 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 is being 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 the understanding of the rupture process of the Denali, Parkfield, San Simeon, Tokachi-Oki, and Sumatra earthquakes. This research has several potential societal benefits: (1) The increased understanding of stress levels required to trigger earthquakes contributes to earthquake prediction efforts which has long term benefits to public safety; (2) GPS constraints on strong motion displacements has 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 impacts public safety through better understanding of building response and safety; (3) The high-rate GPS methodology benefits a larger community of GPS users by increasing the accuracy and efficiency of high-rate GPS data analysis. This will be useful for postseismic studies and volcano monitoring efforts. 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.