RAPID: Observations of Vertical Deformation From Tidal Time Series for the 2010 Slow Slip Event in Cascadia

该项目将利用密集的潮汐计网络测量的隆起来描述卡斯卡迪亚俯冲带界面上的下一次慢滑地震。12个临时潮汐计被部署在华盛顿的奥林匹克半岛，卡斯卡迪亚俯冲带的一部分预计将在2010年8月经历里氏6.5级的慢滑地震。由于在俯冲带的这部分缓慢滑动的复发间隔为~14个月，海洋在夏季安静一个数量级，2010年8月的事件提供了一个机会，可以在一年中最平静的时间捕捉到至少7年不会再发生的事件。来自这个临时网络和NOAA现有的稀疏的潮汐测量网络的数据提供了与2010年事件相关的垂直变形的详细图像，而GPS或地震技术用于研究最近12次此类事件的分辨率很差。垂直变形，结合GPS的水平变形和地震学的震源位置和时间信息，使我们能够准确地确定俯冲界面上的滑动分布和应变释放。对深俯冲带界面滑动的进一步认识将为建立更好的模型提供必要的数据，这些模型将沿俯冲带的应变随时间释放联系起来，包括在卡斯卡迪亚俯冲带平均300-500年发生一次的M~9特大逆冲地震的破裂时间和程度。据推测，未来的慢滑地震将引发下一次大型逆冲地震和海啸，因此了解这些事件以及它们与破坏性发震地震的关系至关重要。来自美国国家科学基金会UCORE项目的本科生正在俄勒冈大学参加一个夏季研究，他们正在进行大部分的仪器部署。UCORE项目将社区大学生带到俄勒冈大学，通过积极参与正在进行的项目来学习开展科学研究。UCORE的学生们正在安装和校准潮汐计，下载和解释数据，并将在项目结束时以正式的海报形式展示他们的工作结果。除了描述2010年慢滑地震的主要目标外，我们的部署使我们能够计算每个站点的长期相对海平面变化，因为我们的大多数站点在过去的一个世纪中都是间歇性的。这意味着我们可以将长期抬升率与个别慢滑地震相关的抬升率进行比较，从而确定板块构造提供的应变中有多少可用于大型逆冲断裂和永久性景观发展。最后，我们的项目使我们能够改进我们在潮汐记录中发现构造瞬变的方法，并有可能应用这种方法来生成该地区延伸至100年前的慢滑事件目录。

This project will characterize the next slow slip earthquake on the Cascadia Subduction zone interface using uplift measured by a dense network of tide gauges. 12 temporary tide gauges are being deployed on the Olympic Peninsula of Washington, the portion of the Cascadia subduction zone expected to experience a M ~6.5 slow slip earthquake in ~August of 2010. Because the recurrence interval of slow slip on this part of the subduction zone is ~14 months and the ocean is an order of magnitude quieter during the summer, the ~August 2010 event provides an opportunity to catch an event at the calmest time of year that will not recur for at least 7 years. Data from this temporary network and the existing sparse NOAA network of tide gauges are providing a detailed image of the vertical deformation associated with the 2010 event, which is poorly resolved by GPS or seismic techniques that have been used to study the last 12 of these events. The vertical deformation, combined with horizontal deformation from GPS and source location and timing information from seismology, allows us to accurately determine the distribution of slip and the release of strain on the subduction interface. This improved understanding of slip on the deep subduction zone interface will provide the necessary data to build better models that link the time-dependent release of strain along the subduction zone, including the timing and extent of rupture of M~9 megathrust earthquakes that occur on average 300-500 years on the Cascadia subduction zone. It has been speculated that a future slow slip earthquake will trigger the next megathrust earthquake and tsunami, so it is critically important to understand these events and how they relate to damaging seismogenic earthquakes.Undergraduate students from NSF's UCORE program, who are participating in a summer research at the University of Oregon, are carrying out most of the instrument deployments. The UCORE program brings community college students to the University of Oregon to learn to carry out scientific research by actively participating in ongoing projects. The UCORE students are installing and calibrating the tide gauges, downloading and interpreting the data, and will present the results of their work in a formal poster session at the end of the program.In addition to the primary goal of characterizing the 2010 slow slip earthquake, our deployment allows us to calculate the long-term relative sea level change at each site, because most of our sites have been occupied intermittently over the past century. This means we can compare the long term uplift rate to the uplift associated with individual slow slip earthquakes and thus determine how much of the strain provided by plate tectonics is available for megathrust rupture and permanent landscape development. Finally, our project is allowing us to improve our methodology for finding tectonic transients in tidal records, and potentially to apply this method to generate a catalog of slow slip events that extends back ~100 years in this area.