3D seismic investigation of upper plate deformation above a region of Slow Slip along the Hikurangi subduction margin of New Zealand

俯冲带是一个构造板块被压在另一个板块之下的地方。地质断层标志着两块板块之间的分界线。摩擦过程意味着沿着该断层的运动是不完美的，并可能导致应变的积累。这种压力的突然释放会引发地震。俯冲带是震级最大的地震的发源地，可能会伴随着海啸，使其具有特别的破坏性。然而，最近科学家们发现，这种毒株可能会以各种方式和在一系列时间范围内释放。其中一个例子是慢速地震，它的破裂时间是几周或几个月，而不是几秒钟。重要的是要了解是什么导致保证金以不同的方式释放压力，以便估计保证金的潜在危险。这项研究将集中在产生缓慢地震的条件上。之所以选择新西兰的Hikurangi边缘，是因为那里有异常浅的慢地震，可以使用地球物理仪器和钻探来成像。该项目为一名女研究生和一名夏威夷原住民本科生提供培训。该项目将促进更广泛地了解古代夏威夷圣歌和传说是如何受到地质事件(火山喷发、地震、海啸)影响的。该项目通过加强与新西兰、日本和英国的同事的联系，促进了国际合作和合作。该项目将以成功的社区项目为基础，调查新西兰Hikurangi俯冲边缘巨型逆冲带上的慢滑事件(SSE)的断层性质控制。2018年初进行的非常成功的地震采集巡航，采集了14.7x60公里的3D体积。该体经三维叠加、叠后时间偏移和深度转换等方法进行了初步处理，正在进行工业处理。对IODP探险372钻探的浅海沟斜坡盆地进行了初步解释，现在将使用商业处理的体积来扩展解释，以了解俯冲海山在SSE生成中的潜在作用。这项研究将集中于了解吐埃尼盆地的地质史，这是一个中坡盆地，形成于最初在俯冲带脚趾处聚积的海沟地层的逆冲包的顶部。调查人员将(1)追踪整个盆地的突出层位；(2)记录沿着切断这些层位的断层的偏移量；(3)将这些层位与IODP遗址联系起来，以确定它们的年龄和岩性。将在盆地内推断变形的时间和模式，以调查可能与俯冲海山相互作用的情况。与专注于俯冲系统更深部分的同事合作，将能够对海山俯冲对SSE产生的影响施加限制。该项目将为从根本上理解Hikurangi增积棱镜的前缘区域提供重要支持，该区域目前正处于浅部缓慢滑移的时期。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Subduction zones are the locations where one tectonic plate is forced beneath another. A geologic fault marks the boundary between the two plates. Frictional processes mean that motion along this fault is imperfect and may result in strain build-up. A sudden release in this strain build up causes earthquakes. Subduction zones are the locations of the greatest magnitude earthquakes and may be accompanied by tsunamis, making them particularly destructive. However, recently scientists have discovered that strain may be released in a variety of ways and over a range of time scales. One example of this is slow earthquakes, which rupture over weeks or months instead of seconds. It is important to understand what may cause a margin to release strain in different ways in order to estimate the hazard potential of the margin. This study will focus on the conditions that produce slow earthquakes. The Hikurangi Margin in New Zealand was chosen because it has unusually shallow slow earthquakes, which can be imaged using geophysical instruments and by drilling. This project provides training for a female graduate student and a Native Hawaiian undergraduate student. The project will promote a broader understanding of how ancient Hawaiian chants and legends were influenced by geologic events (volcanic eruptions, earthquakes, tsunamis). The project fosters international collaboration and cooperation by strengthening ties with colleagues in New Zealand, Japan and the U.K. This project will build upon the successful Community Project to investigate fault property controls on slow-slip events (SSEs) along megathrust of the Hikurangi subduction margin, New Zealand. The highly successful seismic acquisition cruise, carried out during early 2018, acquired a 3D volume of 14.7 x 60 km. The volume has undergone preliminary processing through 3D stack, post-stack time migration and depth conversion and is undergoing industry processing. Initial interpretation of the shallow trench slope basin that was drilled by IODP Expedition 372 was performed and now the commercially processed volume will be used to extend the interpretations in order to understand the potential role that subducting seamounts play in the generation of SSEs. The research will be concentrated on understanding the geologic history of Tuaheni Basin, a mid-slope basin that formed on top of thrust packages of trench strata that were originally accreted at the toe of the subduction zone. The investigators will (1) trace prominent horizons throughout the basin; (2) document offsets along faults that cut those horizons; and (3) tie the horizons to the IODP Site to determine their ages and lithologies. The timing and patterns of deformation will be inferred within the basin to investigate possible interactions with subducting seamounts. Collaboration with colleagues who are concentrating on the deeper parts of the subduction system will allow constraints to be placed on the effects of seamount subduction on SSE generation. This project will provide significant support for fundamental understanding of the frontal region of the Hikurangi accretionary prism, a region currently undergoing a period of slow slip in its shallow region.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.