Collaborative Research: Revealing the Environment of Shallow Slow Slip

合作研究：揭示浅层慢滑移环境

• 批准号: 1551683
• 负责人: Susan Schwartz
• 金额: $ 14.17万
• 依托单位: University of California-Santa Cruz
• 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: 2016-05-15 至 2021-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1551683&HistoricalAwards=false
• 关键词: Collaborative; Research; Revealing; Environment; Shallow

Subduction zones, where one tectonic plate bends down beneath another tectonic plate, are important in the evolution of Earth's surface as well as being a major earthquake and tsunami hazard for society. In the last 15 years, dense Global Positioning System (GPS) and earthquake observations made at subduction zones have revealed a new style of fault slip. In addition to continuous slip and sudden earthquake motion, many faults experience slow slip. In some instances, a relationship between slow slip and damaging large earthquakes has been observed. Most observations of slow slip occur at 20-40 km depth below the seafloor. At the Hikurangi margin offshore of New Zealand, slow slip also occurs at shallow depths, but detailed investigation of shallow slow slip has been hampered by the lack of suitable seafloor observations. Understanding the extent, distribution, and range of physical conditions for shallow slow slip events is important, especially since the shallow fault interface is where tsunamis are generated by earthquakes. This project uses recently collected ocean bottom seismic and absolute pressure gauge data from the Hikurangi margin to investigate the relationship between earthquake and slow slip and the physical conditions that favor them. Results of this research will be incorporated into an earthquake science course for the California State Summer School for Mathematics and Science program for high school students at the University of California-Santa Cruz. This project involves the mentoring and training of three graduate students and two to four undergraduate interns, including at least one from an underrepresented group in the Earth Sciences. All students will benefit by receiving training from researchers at different institutions.A large shallow slow slip event occurred in October 2014, directly beneath the Hikurangi Ocean Bottom Investigation of Tremor and Slow Slip instrument array, a major U.S. led international experiment with Japanese and New Zealand researchers. The experiment was designed to investigate the physical environment that hosts shallow slow slip and its relationship to destructive, seismic slip on the Hikurangi subduction thrust. This project will build on the initial data analysis from this experiment to tackle four main objectives: 1) to improve initial tremor and earthquake detection and location using the PageRank technique and matched filtering cross correlation, 2) to investigate changes in coulomb failure stress imparted on the megathrust from the 2014 slow slip event and compare it to earthquake and tremor locations to test whether static stress changes can explain their location, 3) to determine earthquake source parameters and explore their spatial and temporal relationships with slow slip, geodetic coupling and physical properties of the plate interface and 4) to improve images of seismic velocity and attenuation structure using body wave velocity and attenuation tomography and ambient noise surface wave tomography. This project will complement similar efforts in Cascadia and Japan, allowing comparison of the properties and environment of shallow and deep slow slip and build a detailed picture of the relationship between seismic and aseismic slip and its dependence on the velocity and attenuation structure.

俯冲带是一个构造板块弯曲到另一个构造板块之下的地方，在地球表面的演变中非常重要，也是社会的主要地震和海啸危险。 在过去的15年里，在俯冲带进行的密集全球定位系统（GPS）和地震观测揭示了一种新的断层滑动方式。 除了连续滑动和突然的地震运动，许多断层经历缓慢滑动。在某些情况下，已经观察到缓慢滑动和破坏性大地震之间的关系。大多数慢滑观测发生在海底以下20-40公里深处。 在新西兰近海的Hikurangi边缘，在浅水处也发生缓慢滑动，但由于缺乏适当的海底观测，对浅水缓慢滑动的详细调查受到阻碍。了解浅层缓慢滑动事件的物理条件的程度、分布和范围是重要的，特别是因为浅层断层界面是地震产生海啸的地方。该项目使用最近从希库朗吉边缘收集的海底地震和绝对压力计数据，调查地震和缓慢滑动之间的关系以及有利于它们的物理条件。这项研究的结果将被纳入一个地震科学课程的加州国家暑期学校的数学和科学计划的高中生在加州大学圣克鲁斯分校。 该项目涉及指导和培训三名研究生和两至四名本科生实习生，其中至少有一名来自地球科学领域代表性不足的群体。所有学生将受益于接受来自不同机构的研究人员的培训。2014年10月，在Hikurangi海底震颤和慢滑仪器阵列调查的正下方发生了一次大型浅层慢滑事件，这是一项由美国领导的与日本和新西兰研究人员进行的重大国际实验。 实验的目的是调查物理环境，主机浅缓慢滑动和它的关系，破坏性，地震滑动Hikurangi俯冲逆冲断层。 该项目将建立在该实验的初步数据分析的基础上，以解决四个主要目标：1）使用PageRank技术和匹配滤波互相关来改进初始震颤和地震检测和定位，（二）调查2014年慢滑事件中对巨型逆冲断层施加的库仑破坏应力的变化，并将其与地震和震颤位置进行比较，以测试静态应力是否发生变化可以解释它们的位置; 3）确定震源参数并探索它们与慢滑动、大地耦合和板块界面物理性质的空间和时间关系; 4）使用体波速度和衰减层析成像以及环境噪声面波层析成像来改进地震速度和衰减结构的图像。 该项目将补充卡斯卡迪亚和日本的类似努力，从而能够比较浅和深缓慢滑动的性质和环境，并详细了解地震和地震滑动之间的关系及其对速度和衰减结构的依赖性。