Collaborative Research: Improving models of interseismic locking and slow slip events in Cascadia and New Zealand

合作研究：改进卡斯卡迪亚和新西兰震间锁定和慢滑移事件的模型

• 批准号: 1905098
• 负责人: Noel Jackson
• 金额: $ 11.7万
• 依托单位: University of California-Berkeley
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-09-01 至 2020-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1905098&HistoricalAwards=false
• 关键词: Collaborative; Research; Improving; models; interseismic

This project will carry out new analyses of existing geophysical data with the complementary goals of advancing scientific understanding and improving upon future earthquake hazard forecasts. Subduction zones are where two tectonic plates collide and one sinks below the other. Subduction zones produce the largest earthquakes in the world, such as the magnitude 9.0 Tohoku earthquake of 2011 that caused widespread destruction in northern Japan. This project will focus on two subduction zone regions: Cascadia in the U.S. and Hikurangi in New Zealand. Onshore and offshore GPS data will be modeled to determine the amount of slip released as slow slip events, as steady creep, or where regions are locked and not slipping. Slow slip events refer to slip on a fault that is similar to what occurs during an earthquake, but occurs much more slowly and does not emit damaging seismic waves. Locked regions refer to areas of a fault in which friction prevents slip, allowing energy to build up for future release in an earthquake. In contrast to previous modeling work, this project will use realistic, three-dimensional elastic properties of the earth constrained by prior seismic studies. The products of this project will directly inform earthquake hazard forecasts for both the Cascadia and Hikurangi subduction zones, which have major cities nearby (Portland and Seattle in Cascadia; Wellington in Hikurangi). Important additional information will be obtained for an International Ocean Discovery Program project scheduled for the northern Hikurangi margin in 2018 that is targeting the slow slip region. The project will support and train an early career female scientist who will be mentored by a more established female scientist. The project also features public outreach through public talks in New Zealand and the U.S. and the incorporation of the results into lecture materials at two universities in the U.S.This project will generate new and improved catalogs of slow slip events and plate locking models for the Cascadia and Hikurangi (New Zealand) subduction zones. A Network Inversion Filter (NIF) technique will be used to process all available GPS data to identify slow slip events, and produce models of slip and slip-rate evolution over time. The NIF technique is based on a Kalman filter approach, which balances a physically reasonable but inaccurate model of steady slip with noisy data. Additionally, these NIF inversions will incorporate offshore ocean bottom pressure (OBP) data from the Hikurangi Ocean Bottom Investigation of Tremor and Slow Slip deployment during the mid-2014 to mid-2015 time period for the Hikurangi subduction zone. These OBP instruments recorded a large offshore slow slip event in late 2014. These models include, for the first time, realistic, three-dimensional earth structure and the effects topography and bathymetry. Long-term velocities of GPS stations will be modeled to obtain improved constraints on the plate interface locking region for each subduction zone. Plate locking indicates how much of the expected motion between tectonic plates is not occurring continuously at the boundary, and could therefore be released in earthquakes or slow slip events. GPS station velocities will be averaged in two ways: first only over times between slow slip events and second by averaging through slow slip events which will provide two locking models for each subduction zone. Products will include new realistic 3D locking models for the two regions, slow-slip event catalogs for both subduction zones and a full-slip budget with uncertainties for each subduction zone as a function of location over the time period of study.

该项目将对现有的地球物理数据进行新的分析，以促进科学理解和改进未来的地震危险预测。俯冲带是两个构造板块碰撞的地方，一个板块下沉到另一个板块下方。俯冲带产生了世界上最大的地震，例如2011年日本北部发生的9.0级东北地震，造成了广泛的破坏。该项目将专注于两个俯冲带地区：美国的卡斯卡迪亚和新西兰的希库兰吉。陆上和海上GPS数据将被建模，以确定释放的滑移量为慢滑事件、稳定蠕变或锁定区域而不滑动的区域。慢滑事件指的是断层上的滑动，类似于地震期间发生的滑动，但发生得慢得多，不会发出破坏性的地震波。锁定区域指的是断层上摩擦力阻止滑动的区域，使能量积累起来，以便在未来地震中释放。与以前的建模工作不同，该项目将使用受先前地震研究约束的地球的真实三维弹性特性。该项目的产品将直接为卡斯卡迪亚和希库兰吉俯冲区的地震危险预报提供信息，这两个地区附近有主要城市(卡斯卡迪亚的波特兰和西雅图；希库兰吉的惠灵顿)。将为计划于2018年在Hikurangi北部边缘实施的针对慢滑区域的国际海洋发现方案项目获得重要的补充信息。该项目将支持和培训一位职业生涯早期的女科学家，她将得到一位更成熟的女科学家的指导。该项目还包括通过在新西兰和美国的公开演讲进行公众宣传，并将结果纳入美国两所大学的讲座材料。该项目将为卡斯卡迪亚和希库兰吉(新西兰)俯冲带生成新的和改进的慢滑事件和板块锁定模型目录。将使用网络逆滤波(NIF)技术处理所有可用的GPS数据，以识别慢滑动事件，并产生滑动和滑动速率随时间演变的模型。NIF技术基于卡尔曼滤波方法，该方法将物理上合理但不准确的稳态滑移模型与噪声数据进行平衡。此外，这些NIF反演将纳入Hikurangi海底地震调查的近海海底压力(OBP)数据，并在2014年年中至2015年年中期间对Hikurangi俯冲区进行缓慢滑动部署。这些OBP仪器在2014年底记录了一次大规模的近海慢滑事件。这些模型首次包括逼真的三维地球结构以及地形和水深测量的影响。将对GPS站的长期速度进行模拟，以获得对每个俯冲区的板块界面锁定区域的改进约束。板块锁定表明构造板块之间的预期运动有多少不是在边界连续发生的，因此可能在地震或缓慢滑动事件中释放。GPS站的速度将以两种方式平均：第一，仅在慢滑事件之间的时间内进行平均；第二，通过慢滑事件进行平均，这将为每个俯冲带提供两种锁定模型。产品将包括两个区域的新的逼真3D锁定模型、两个俯冲区的慢滑事件目录以及作为研究时间段内位置函数的每个俯冲区的不确定性的全滑预算。