Integrating Geologic, Geodetic, and Coastal Tide Gauge Observations with 100-year Vertical Deformation Models of California Earthquake History

本项目利用海岸潮汐计、大地测量和太平洋-北美板块边界的地质数据综合研究地震引起的垂直变形。虽然该地区不断增长的空间大地测量数据档案提供了高度空间覆盖的精确变形测量，但这些数据仅提供了15年的地壳运动记录，因此对地壳运动的时间依赖性约束较弱。地质数据提供了1000年的平均变形记录，然而这些数据往往分布稀疏，具有很大的不确定性。另外，在过去的50-100年里，沿着加利福尼亚海岸线的几个潮汐测量站连续记录了海平面的变化。这些站点提供了海平面变化的时间记录，海平面变化通常归因于冰川后的反弹和海洋气候现象。然而，地质过程，包括大地震的位移，也被证明会产生海平面变化，因为垂直的地震间应变积累可以促进1-3毫米/年的上升和下沉速率。利用海岸潮汐计时间序列数据，该项目正在探索海平面变化与三维地震周期变形模型产生的垂直位移估计之间的相关性，该模型受地质滑动率、大地测量速度和圣安德烈亚斯断层系统历史地震数据的限制。由地质和大地测量约束模型得出的一阶垂直变形估计与长期海平面趋势高度兼容，但需要进一步分析，以彻底探索模型参数空间，并调查不拟合和未建模现象的来源。该项目将整合100年的海岸潮汐测量数据（平均海平面永久服务），过去15年的大地测量数据（地球范围板块边界观测站连续GPS和InSAR），以及一个新的地质数据库（南加州地震中心地质垂直运动图）。本研究调查了过去100年来加利福尼亚海岸线上记录的构造变形对海平面变化的长期作用。通过这样做，这些研究活动有助于实现NSF的目标。通过进一步提高我们对断层系统地壳动力学、地震危险性和数据综合的理解，我们的地球范围倡议。这次调查产生的数据和模型产品将为教育和公众对加州过去和现在地震危害的认识提供加强的基础设施。此外，由于加利福尼亚大地震有可能造成巨大的经济和人员损失，因此依赖于加利福尼亚构造运动准确特征的定量地震危险性估计对地震科学的进步至关重要。

This project investigates earthquake-induced vertical deformation using a synthesis of coastal tide gauge, geodetic, and geologic data of the Pacific-North American plate boundary. While the growing archive of space geodetic data in this region provides precise deformation measurements with a high degree of spatial coverage, these data supply only a 15-year record of crustal motions and therefore only weakly constrain time-dependence of crustal motions. Geologic data provide a 1000-year averaged record of deformation, however these data are often sparsely located and can have large uncertainties. Alternatively, sea level change has been continuously recorded along the California coastline at several tide gauge stations for over the past 50-100 years. These stations provide a temporal record of sea level change, generally attributed to post-glacial rebound and ocean climate phenomena. However, geologic processes, including displacements from large earthquakes, have also been shown to produce sea level variations, as vertical interseismic strain accumulation can contribute uplift and subsidence rates of 1-3 mm/yr. Using coastal tide gauge time series data, this project is exploring the correlation between sea level variations and estimates of vertical displacements produced by a three-dimensional earthquake cycle deformation model that is constrained by geologic slip rates, geodetic velocities, and historical seismic data along the San Andreas fault system. First order vertical deformation estimates derived from geologically and geodetically constrained models are highly compatible with long-term sea level trends, however further analysis is needed to thoroughly explore model parameter space and investigate sources of misfit and unmodeled phonomena. The project will integrate 100-year coastal tide gauge data (Permanent Service for Mean Sea Level), geodetic data (EarthScope Plate Boundary Observatory continuous GPS and InSAR) spanning the last 15 years, and a new geologic database (Southern California Earthquake Center Geologic Vertical Motion Map).This study investigates the long-term role of tectonic deformation on sea level change recorded over the past 100 years along the California coastline. In doing so, these research activities contribute to the objectives of NSF?s EarthScope Initiative by further advancing our understanding of fault system crustal dynamics, earthquake hazards, and data synthesis. The data and model products generated by this investigation will provide an enhanced infrastructure for education and public awareness of both past and present earthquake hazards in California. Furthermore, because a major California earthquake has the potential for massive economic and human loss, quantitative seismic hazard estimates, which rely on an accurate characterization of tectonic motions in California, are critical to the advancement of earthquake science.