Collaborative Research: A community 3D seismic investigation of fault property controls on slow-slip along the Hikurangi megathrust

合作研究：断层属性控制 Hikurangi 巨型逆冲断层沿线慢滑移的社区 3D 地震调查

• 批准号: 1559298
• 负责人: Nathan Bangs
• 金额: $ 52.19万
• 依托单位: University of Texas at Austin
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-09-15 至 2021-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1559298&HistoricalAwards=false
• 关键词: Collaborative; Research; community; 3D; seismic

Subduction fault zones, where one of Earth's tectonic plates is forced beneath another plate, produce the most powerful and destructive earthquakes and tsunamis on the planet. What controls this fault slip behavior is virtually unknown and yet it is critical for understanding and assessing global seismic hazards. While these great subduction zone earthquakes release seismic energy in a matter of seconds to minutes, recent discoveries reveal another style of fault movement called slow slip earthquakes (SSEs) that take days, weeks or months to occur. While not as damaging as major earthquakes, these slow slip earthquakes are nonetheless thought to be a critical process in how strain builds up and is subsequently released on subduction zone fault systems. Slow slip earthquakes may also act as indicators of where, and possibly when, large damaging earthquakes might occur. The subduction zone along the east coast of the New Zealand North Island regularly (~ every 4 years) produces unusually shallow (4-5 km below the sea surface) slow slip earthquakes compared to the typical 20-50 km depths found in other areas such as the Cascadia and Alaska subduction zones on the west coast of the U.S. This project will conduct a 3D seismic survey that is designed to image the shallow slow slip region of the New Zealand subduction zone, map the fault systems, determine what conditions are associated with slow slip behavior and how they differ from conditions associated with subduction zones that generate great earthquakes. The project includes substantial international collaboration with New Zealand, Japanese and United Kingdom researchers on the seismic imaging as well as direct links with an international ocean drilling program designed to drill into the zone of slow slip. The project involves an early career scientist and several graduate students who will work on various aspects of the research for their thesis work. Additional students will be involved in the field data collection from all participating countries. Public outreach in the form of media coverage, news stories, public lectures and ship tours will be coordinated with New Zealand organizations and collaborators.Slip on plate boundary faults associated with recorded earthquakes typically fails to account for all of the expected plate motion predicted by geodetic methods or global models. Exciting advances in the last decade have recognized and documented transient slow slip earthquakes as another mode to accommodate plate convergence at subduction margins. This project addresses the mechanics of subduction thrusts and the conditions that lead to the wide variety of slip behaviors by carrying out the first-ever 3D seismic dataset acquired over a subduction thrust dominated by aseismic creep. The project will use the research vessel R/V Langseth to acquire an open-access 3D seismic reflection data set in a 15 x 60 km area offshore New Zealand's Hikurangi trench and forearc. These data will provide high-resolution images and seismic attributes of a transient-slip plate boundary megathrust identified by the research community as an important point of comparison to predominantly locked subduction thrusts such as Nankai, Tohoku, Cascadia, and Costa Rica. Seismic attributes linked to high fluid pressures are a promising indicator of conditions favorable for slow slip earthquakes and the Northern Hikurangi margin has well-documented slow slip earthquakes at 4-5 km depth - shallow enough for detailed seismic imaging and seismic attribute measurements. The 3D seismic images and attributes will allow for an accurate documentation of the structural, stratigraphic, and hydrogeologic conditions that lead to generation of slow slip earthquakes along a subduction megathrust. International collaborative experiments will record Langseth shots during 3D acquisition and develop the first ever high-resolution 3D velocity models across a subduction zone using 3D full-waveform inversion, which will overlap and extend beyond the 3D volume.

俯冲断层区（地球的一个构造板被迫在另一盘板下方），在地球上产生了最强大，最具破坏性的地震和海啸。 控制这种断层行为的是什么实际上是未知的，但对于理解和评估全球地震危害至关重要。尽管这些巨大的俯冲区地震在几秒钟到几分钟的时间内释放地震能量，但最近的发现揭示了另一种称为慢滑地震（SSE）的断层运动，这些变形运动需要数天，几周或几个月。尽管这些慢速地震不如主要地震那样破坏，但仍认为这些缓慢的地震是应变如何积聚并随后在俯冲带故障系统上释放的关键过程。慢滑地震也可能充当可能发生的大型破坏地震的指标。 与在卡斯卡迪亚（Cascadia）和阿拉斯加（Alaska）俯冲式的典型区域中发现的典型的20-50 km深度相比，新西兰北岛东海岸沿新西兰北岛东海岸（每4年）定期（每4年）产生异常浅的（4-5公里）的缓慢地震，而在其他区域（如Cascadia和Alaska俯冲式的动物园）中，该项目的新型see new se new Seect of Imploy Image Impact of Imploy Image Impact of Image Impact of Imploy Impact of Cascadia和Alaska俯冲式动物园，这是一个典型的20-50 km。俯冲区，绘制故障系统，确定哪些条件与缓慢的滑移行为相关，以及它们与与俯冲区有关的条件有何不同。 该项目包括与新西兰，日本和英国研究人员在地震成像方面进行的实质性国际合作，以及与旨在钻入慢速滑移区域的国际海洋钻井计划的直接联系。该项目涉及一位早期的职业科学家和几位研究生，他们将在研究工作的各个方面工作。其他学生将参与所有参与国家的现场数据收集。以媒体报道，新闻报道，公开演讲和船舶之旅的形式进行公共宣传，将与新西兰组织和合作者协调。与录制的地震相关的板边界故障的下滑，通常未能说明所有通过地球方法或全球模型预测的预期板运动。在过去的十年中，令人兴奋的进步已经识别并记录了瞬态慢滑地震，这是一种在俯冲边距下板收敛的另一种模式。该项目解决了俯冲推力的机制以及通过执行以俯冲推力以俯冲推力为主导的俯冲推力所获得的第一个3D地震数据集，从而导致了各种各样的滑移行为。 该项目将使用研究船R/V Langseth在15 x 60 x 60 km的新西兰海洋山丘沟和前齿中获得15 x 60 km地区的开放式3D地震反射数据集。这些数据将提供由研究界确定的瞬时滑移板边界大型象征的高分辨率图像和地震属性，这是与主要锁定的俯冲推力（如南卡伊，Tohoku，tohoku，cascadia和Costa rica）的重要比较点。与高流体压力相关的地震属性是有前途有利于慢滑地震的条件的有前途的指标，而北部的Hikurangi边缘在4-5 km的深度处有充分记录的慢速地震 - 足够浅，足以详细的地震成像和地震属性测量值。 3D地震图像和属性将允许对结构，地层和水文地质条件进行准确的文献，从而导致沿俯冲巨星沿着俯冲的慢速地震产生。国际协作实验将在3D获取期间记录Langseth的镜头，并使用3D Full-Waveform倒置开发俯冲带跨俯冲带的第一个高分辨率3D速度模型，这将重叠并延伸到3D体积之外。