Collaborative Research: Using GPS to Unravel the Long-Term Kinematics and Dynamics of the American Southwest from an Ever-Changing Deformation Field

合作研究：利用 GPS 从不断变化的变形场中揭示美国西南部的长期运动学和动力学

• 批准号: 1615253
• 负责人: Cornelis Kreemer
• 金额: $ 24.65万
• 依托单位: Board of Regents, NSHE, obo University of Nevada, Reno
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-06-01 至 2020-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1615253&HistoricalAwards=false
• 关键词: Collaborative; Research; Using; GPS; Unravel

Using GPS to Unravel the Long-Term Kinematics and Dynamics of the American Southwest from an Ever-Changing Deformation FieldThis project aims to improve our understanding of the long-term crustal kinematics and dynamics of the American Southwest, and the underlying Earth structure, by developing a dynamic model that explains both geodetic and other geophysical data. The American Southwest (here defined as Arizona, southern Utah, and southern Nevada) appears to be mostly inactive tectonically. However, there is evidence that large earthquakes have occurred here in recent geologic times. We explore the possibility that the amount of crustal deformation in this area (and thus can generate (large) earthquakes) varies with time and is modulated by large earthquakes in southern California and Gulf of California. We have seen evidence for this by using GPS observations of the deformation pattern before and after the 2010 El Mayor-Cucapah earthquake (M7.2). We will combine ongoing GPS measurements with different modeling tools to characterize and model the source of the time-variable and long-term deformation, which we aim to separate. The time-variable deformation can be understood as visco-elastic deformation in the lithosphere following large (far-field) earthquakes. The long-term deformation can likely be modeled by considering the proper ratio of the far-field stresses imposed by Pacific plate motion and stresses due to lateral variation in crustal thickness and density in our study area. This is a follow-on proposal that extends our current EarthScope project on the Colorado Plateau area. Over the last five years, the long-term kinematics as measured by GPS are obscured by postseismic deformation from the 2010 El Mayor-Cucapah earthquake, which occurred 3 months before we installed a new 34-station continuous network. As a result, important questions on the role of Gravitational Potential Energy (GPE) variations in driving deformation, the reasons for the dearth of active faults and seismicity in southern Arizona, and the reach of plate motion stresses remain unanswered. In order to address these questions, and simultaneously further our understanding of the postseismic process, we propose a three-tiered approach: 1) extend existing GPS time-series to improve characterization of transient deformation, 2) use those data to explore the crustal and mantle viscosities required to match the GPS time-series data, and 3) create physical models of the long-term expected deformation, that includes the latest GPE estimates, to explain the residual motions after correction for postseismic effects. We will also leverage GPS data from other NSF funded projects, as well as seismic data products obtained by USArray that have helped to constrain crustal and lithospheric thickness structure and stress orientations. Geodetic strain rates could potentially be used as an independent constraint on the regional seismic hazard, but only after we have corrected it for all post-seismic effects, and assessed the long-term drivers of crustal motion. We will employ a female graduate student at UNR to work on the project. We will also engage a RESESS undergraduate intern during the summer of the second year. The goal of the RESESS program is to increase diversity in the Geosciences work force. We will recruit one student from the UA Disability Resource Center (DRC) to conduct a small research project associated with the larger goals of the overall project. We will also lead an accessible field trip to the Grand Canyon for students registered at the DRC in a program that we developed and implemented in September 2015. The goal of these activities is to draw attention to the numerous research opportunities made available by the large volume of data in NSF and other national data archives, available to a wide range of individuals. Finally, we plan to give outreach talks at the area's parks and monuments.

利用GP从不断变化的变形现场揭示美国西南部的长期运动学和动力学，旨在通过发展我们对美国西南部的长期地壳运动和动态的理解，并通过发展地球结构来发展一个解释地球物理数据和其他地球物理数据的动态模型。美国西南部（这里定义为亚利桑那州，犹他州南部和内华达州南部）似乎在构造上几乎是不活跃的。但是，有证据表明，最近地质时期发生了大地震。我们探讨了该地区的地壳变形量（因此可以产生（大）地震）随时间而变化，并且受到南加州和加利福尼亚海湾的大地震调节的可能性。我们已经通过使用GPS观察到2010年El Cucapah地震之前和之后的变形模式（M7.2），看到了这一点的证据。我们将将正在进行的GPS测量与不同的建模工具相结合，以表征和建模时间变化和长期变形的来源，我们旨在分开。在大型（远场）地震后，岩石圈中的粘膜弹性变形可以理解为粘弹性变形。长期变形可以通过考虑太平洋板运动施加的远场应力的适当比率以及由于我们的研究区域的地壳厚度和密度的横向变化而建模的。这是一个后续提案，扩展了我们当前在科罗拉多高原地区的Earthscope项目。在过去的五年中，由GPS衡量的长期运动学因2010年El Mayer-Cucapah地震的后视性变形而掩盖了，该地震发生在我们安装新的34个站连续网络之前3个月。 结果，关于重力势能（GPE）在驱动变形中的作用（GPE）的作用的重要问题，亚利桑那州南部的活跃断层和地震性的原因以及板运动应力的触及范围尚未得到解答。 为了解决这些问题，并同时进一步理解后的震荡过程，我们提出了一种三层方法：1）扩展现有的GPS时间序列以改善瞬态变形的特征，2）使用这些数据探索外壳和地壳和匹配GPS时间序列数据所需的地幔粘度，以及3）创建长期预期变形的物理模型，其中包括最新的GPE估计值，以解释校正后视力效应后的剩余运动。我们还将利用来自其他NSF资助的项目的GPS数据，以及由USArray获得的地震数据产品，这些数据有助于限制地壳和岩石圈厚度的结构和压力取向。测量应变率可能可能用作对区域地震危害的独立限制，但只有在我们对所有后抗性作用进行纠正并评估了地壳运动的长期驱动因素之后。我们将雇用一名女性研究生在UNR上从事该项目。我们还将在第二年的夏季与一名经验丰富的本科实习生。 Resess计划的目标是增加地球科学劳动力的多样性。我们将从UA残疾资源中心（DRC）招募一名学生，以进行与整个项目更大目标相关的小型研究项目。我们还将在我们在2015年9月开发和实施的计划中在刚果民主共和国注册的学生进行一次可访问的实地考察。 NSF和其他国家数据档案中的数据，可用于广泛的个人。最后，我们计划在该地区的公园和纪念碑上进行外展会谈。