Collaborative Research: Strain Rate and Moment Accumulation Rate along the San Andreas Fault System from InSAR and GPS

圣安德烈亚斯断层系统（SAFS）是研究沿主要大陆转换边界地震周期的物理性质的天然实验室。地震灾害评价的两个关键参数是地震矩积累率和应变积累率。板块边界观测站（PBO）的GPS组件提供沿SAFS间隔10至20公里的精确矢量速度（1毫米/年精度）。然而，在主要断层的20 km范围内，速度梯度（应变率）变化最快，因此仅靠GPS数据不能很好地解决应变率问题。雷达干涉测量（InSAR）提供了100米空间分辨率的变形图，尽管诸如时间去相关和大气路径误差等因素使得难以达到足够精确的全分辨率，以改进GPS测量。与之前的c波段任务相比，ALOS卫星（JAXA）提供的l波段数据在更长的时间间隔内保持相位相干性。这种改进与减少大气误差的叠加技术相结合，现在可以使用InSAR对整个SAFS进行成像，具有前所未有的空间覆盖和分辨率。本研究的重点是将PBO GPS高精度点测量数据与国内外SAR高空间分辨率InSAR测量数据相结合，构建高空间分辨率的矢量地表变形测量数据。该研究有四个主要目标：-利用EarthScope （PBO和WInSAR）提供的新的GPS和InSAR测量数据来解决长期板块边界变形。这涉及开发社区软件，对ALOS-2和Sentinel-1 InSAR卫星（2013年发射）提供的新数据流进行预处理；-使用GPS-4D模型- insar综合技术，更好地约束断层滑动率，并确定SAFS活动断层的锁定/爬行过渡深度；-生成高分辨率的应变率和地震矩率估计，沿主要断层；探索InSAR和GPS数据中常见的非构造形变的分离方法。加州为下一次大地震做好准备了吗？对主要断层（如圣安德烈亚斯断层系统（SAFS））沿线地震潜力的估计，用于开发情景地震、制定区域建筑规范和制定地震保险费率。虽然大地震的时间无法准确预测，但矩震级可以通过对现今地壳变形的大地测量来准确估计。目前在北美西部连续运行的700个GPS台站阵列由于平均台站间距太大，不能完全解决沿主要断层的地壳变形梯度（应变）。这项研究通过计算和模拟北美西部InSAR联盟（WInSAR）和阿拉斯加卫星设施存档的合成孔径雷达数据（SAR），来改进地壳变形测量。这涉及以近乎自动化的方式以0.5 km空间分辨率生成和存档大尺度（1000 km尺度）地壳形变网格。这笔资金用于支持SIO和UTEP（西班牙裔服务学院）的两名博士生，并用于进一步发展本科和研究生课程。这笔资金还将用于开发一种？InSAR是如何工作的？IRIS&#700；美国的“活跃地球”互动信息亭在全国各地展出。此外，正在使用资金将GMTSAR软件转移到GMT分发系统，使其可供全球15,000名用户使用。我们正在向科学界分发所有高分辨率矢量变形数据和地图，并将结果存档于联安援助团。

The San Andreas Fault System (SAFS) is a natural laboratory for investigating the physics of the earthquake cycle along a major continental transform boundary. Two of the key parameters that can be used for seismic hazard assessment are seismic moment accumulation rate and strain accumulation rate. The GPS component of the Plate Boundary Observatory (PBO) provides accurate vector velocities ( 1 mm/yr accuracy) at a spacing of 10 to 20 km along the SAFS. However, the velocity gradient (strain rate) varies most rapidly within 20 km of the major faults, so strain rate is not well resolved by the GPS data alone. Radar interferometry (InSAR) provides deformation maps at 100 m spatial resolution, although factors such as temporal decorrelation and atmospheric path errors have made it difficult to achieve this full resolution with sufficient precision to improve upon the GPS measurements. The L-band data provided by the ALOS satellite (JAXA) retains phase coherence over longer time intervals than the prior C-band missions. This improvement, combined with stacking techniques to reduce atmospheric errors, now makes it possible to image the entire SAFS using InSAR with unprecedented spatial coverage and resolution.The primary focus of this research is to construct high spatial resolution vector surface deformation measurements by combining the high accuracy point measurements provided by PBO GPS data with the high spatial resolution InSAR measurements available through WInSAR from foreign and domestic SAR missions. The research has four main objectives:- Resolve secular plate boundary deformation using new GPS and InSAR measurements provided by EarthScope (PBO and WInSAR). This involves the development of community software to preprocess the new data streams to be provided by the ALOS-2 and Sentinel-1 InSAR satellites (2013 launch);- Use an integrated GPS-4D model-InSAR technique to better constrain fault slip rates and determine the depth of the locked/creeping transition on active faults of the SAFS;- Generate high-resolution estimates of strain rate and seismic moment rate along major faults of the SAFS; and- Explore methods for isolating non-tectonic deformation contributions common in both InSAR and GPS data.Non-technical summaryIs California prepared for the next big earthquake? Estimates of earthquake potential along major faults, such as the San Andreas Fault System (SAFS), are used for developing scenario earthquakes, for setting regional building codes, and for setting earthquake insurance rates. While the timing of a major earthquake cannot be accurately predicted, the moment magnitude can be accurately estimated from geodetic measurements of present-day crustal deformation. The current array of 700 continuously operating GPS stations in western North America does not completely resolve the crustal deformation gradients (strain) along the major faults because the average station spacing is too large. This research is refining the crustal deformation measurements by computing and modeling the synthetic aperture radar data (SAR) archived at the Western North America InSAR consortium (WInSAR) and the Alaska Satellite Facility. This involves the generation and archive of large-scale (1000 km scale) crustal deformation grids at 0.5 km spatial resolution in a near-automatic fashion. Funding from this grant is supporting two Ph.D. students at SIO and UTEP (a Hispanic Serving Institute) and is being used for further development of undergraduate and graduate courses. This funding is also being used to develop a ?How InSAR Works? module for use in IRISʼs Active Earth interactive kiosks on display around the country. In addition, funding is being used to move the GMTSAR software into the GMT distribution system where it is available to 15,000 users worldwide. We are distributing all high-resolution vector deformation data and maps to the scientific community and archive the results at UNAVCO.