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迫压在另一个构造板块之下的地方。地质断层标志着两个板块之间的边界。地壳运动过程意味着沿该断层的运动沿着是不完全的，可能导致应变积累。这种应变的突然释放会引起地震。俯冲带是发生最大规模地震的地方，可能伴随着海啸，使其具有特别的破坏性。然而，最近科学家们发现，压力可能会以各种方式在一系列时间尺度上释放。其中一个例子是慢地震，它在几周或几个月内而不是几秒钟内破裂。重要的是要了解可能导致边缘以不同方式释放应变的原因，以便估计边缘的潜在危害。这项研究将集中在产生慢地震的条件。选择新西兰的希库朗吉边缘是因为它有异常浅的慢地震，可以使用地球物理仪器和钻井成像。该项目为一名女研究生和一名夏威夷土著本科生提供培训。 该项目将促进更广泛地了解古代夏威夷圣歌和传说如何受到地质事件（火山爆发、地震、海啸）的影响。该项目通过加强与新西兰、日本和英国同事的联系，促进国际协作与合作。该项目将建立在成功的社区项目的基础上，以调查新西兰Hikurangi俯冲边缘沿着巨型逆冲断层对慢滑事件（SSE）的断层属性控制。在2018年初进行的非常成功的地震采集巡航中，获得了14.7 x 60 km的3D体积。该体已通过三维叠加、叠后时间偏移和深度转换进行了初步处理，目前正在进行工业处理。对国际大洋钻探项目第372号考察队钻探的浅沟斜坡盆地进行了初步解释，现在将利用商业加工量来扩大解释范围，以了解俯冲海山在生成SSE方面的潜在作用。研究将集中于了解Tuaheni盆地的地质历史，Tuaheni盆地是一个中斜坡盆地，形成于最初在俯冲带趾部增生的沟槽地层的逆冲包顶部。调查人员将（1）追踪整个盆地的突出层位;（2）记录沿切断这些层位的断层的沿着偏移;（3）将层位与IODP现场联系起来，以确定其年龄和岩性。将在海盆内推断变形的时间和模式，以调查与俯冲海山的可能相互作用。与专注于俯冲系统更深部分的同事合作，将能够限制海山俯冲对SSE生成的影响。该项目将为基本了解Hikurangi增生棱镜的前沿区域提供重要支持，该区域目前正在其浅区缓慢滑动。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值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.