Collaborative Research: GEMT: Bridging Multiple Time Scales of Erosion and Rock Uplift in Taiwan

该奖项的全部或部分资金来自《2021年美国救援计划法案》(公法117-2)。在不经意的观察者看来，山脉似乎是静止的，但在许多地方，它们正在积极向上生长，以回应板块构造，而它们的形状、高度和宽度则因气候驱动的侵蚀而改变。山脉改变海拔的速度取决于观察它们的时间尺度和位置。在地震中，山脉可以在几秒钟内移动数米，但当地震运动平均为数百万年时，再加上地震之间可能发生的断层的缓慢运动，山脉移动的速度要慢得多。这些缓慢但持续的运动如何与短暂的高震级事件相结合，形成数百万年来山区的地形，这是一个需要回答的重要问题，以了解地震、山体滑坡和洪水等短期危险事件是如何长期整合在一起，形成壮观的山脉景观的。在这项拟议的工作中，台湾是一个自然的、持续的实验，如何在一系列时间尺度上整合抬升和侵蚀，以建立山脉。研究人员将研究十年、千年和百万年时间尺度上的隆起和侵蚀，以记录测量的速率变化，并建立一个框架，以了解不同方法之间的差异。该项目将把美国和台湾不同职业水平和学科的科学家聚集在一起，解决构造学的这一基础研究问题。在第二年，美国和台湾的研究生将一起参加为期一个月的跨学科建模研讨会。此外，该项目将通过一门创新课程支持STEM的招聘，该课程包括一年级本科生，他们将探索台湾的大地测量和地貌数据。该项目是美国和台湾研究人员在NSF/GEO/EAR-MOST-TOST-台湾(GEMT)合作研究机会的支持下进行的合作努力。该项目将建立一个新的框架，通过建立一套将变形过程和侵蚀过程联系起来的模型，将跨大地测量的变形速率与地质时间尺度联系起来。活跃的台湾山脉地带是检验假设的绝佳地点，这些假说包括弹性地震周期、河流切割和身体挖掘等短期过程如何聚集在一起形成造山带和演变地形。台湾被广泛引用为侵蚀或地形稳定状态下的山脉带的案例研究，然而，许多观察结果挑战了这一经典观点。对不同时间间隔得出的剥蚀率和切削率的高度不同的估计，引发了关于稳定状态造山概念在台湾相关的时间段的问题。此外，今天的大地测量抬升速率也不容易与千年和更长时间尺度的侵蚀速率相协调。这些令人困惑的观察表明，造山的机制在很大程度上，特别是在台湾，还没有完全被理解，关于形变、构造抬升和侵蚀在广泛的时间尺度上的关系的基本问题仍然没有得到回答。我们将建立一系列运动学模型，模拟潜在的断层几何和演化，并评估断层活动和几何演化的历史是否与热年代学约束的0.5 Ma折返历史、侵蚀和切割数据约束的地貌推断的千年速率以及大地测量约束的现今岩石隆升速率一致。我们的综合方法将确保决定变形运动学的断层几何模型和滑动速率，以及它们对驱动河流切割和折返的隆起场的影响，在不同的时间尺度上是兼容的。为了实现这一集成，我们提出了一个由五部分组成的研究计划：(1)建立受地质和热年代学约束的10万至100万年的运动造山模型；(2)利用河流切割率数据、流域范围的CRN和河道形态建立千年时间尺度的侵蚀模型；(3)构建更新的大地垂直速度场；(4)构建现代形变的地震周期模型；(5)通过模型集成来构建桥梁时间尺度。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。

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2). Mountains appear static to the casual observer, yet in many locations they are actively growing upward in response to plate tectonics, while their shape, height and width is altered by climate-driven erosion. How fast mountains change elevation depends on the timescale and locations in which one observes them. During an earthquake, mountains can move many meters in a matter of seconds, yet when earthquake motions are averaged over millions of years, and combined with the slow motion of faults that may happen between earthquakes, the rate that mountains move is much slower. How these slow, but continuous motions combine with short high-magnitude events to build topography of mountainous regions over millions of years is an important question to answer to understand how short-term, hazardous events like earthquakes, landslides, and floods integrate over long periods to build the spectacular scenery of mountain systems. In this proposed work, Taiwan is a natural, ongoing experiment of how uplift and erosion is integrated over a range of timescales to build the mountain range. The investigators will examine uplift and erosion over decadal, millennial, and million-year timescales to document changes in measured rates and build a framework for understanding discrepancies among the different approaches. The project will bring together US and Taiwanese scientists across career levels and disciplines to address this fundamental research question in tectonics. In year 2, U.S. and Taiwanese graduate students will come together for a month-long cross-disciplinary modeling workshop. Additionally, the project will support recruitment to STEM through an innovative course involving 1st year undergraduates who will be exploring geodetic and geomorphic data of Taiwan. This project is a collaborative effort between U.S. and Taiwanese researchers under the aegis of the NSF/GEO/EAR - MOST-Taiwan (GEMT) Collaborative Research opportunity. This project will build a new framework for bridging measurements of deformation rates across geodetic to geologic timescales, by building a suite of models that link deformational and erosional processes. The active Taiwan mountain belt is an excellent location to test hypotheses of how short-term processes such as the elastic earthquake cycle, river incision, and exhumation aggregate to build orogens and evolve topography. Taiwan is widely invoked as a case study for mountain belts in erosional or topographic steady-state, however, a number of observations challenge this classical view. Highly variable estimates of denudation and incision rates inferred over disparate time intervals raises questions about the time periods over which the concepts of steady-state mountain building are relevant in Taiwan. In addition, present-day uplift rates from geodesy are also not easily reconciled with the millennial and longer time-scale erosion rates. These confounding observations suggest that the mechanisms of mountain building broadly, and in Taiwan specifically, are not fully understood and fundamental questions remain unanswered about the relationship of deformation, tectonic uplift, and erosion over a wide range of time scales. We will build a series of kinematic models that simulate potential fault geometry and evolution and evaluate if the history of fault activity and geometric evolution is consistent with 0.5 Ma exhumation history constrained by thermochronology, geomorphically inferred millennial rates constrained by erosion and incision data, and present-day rock uplift rates constrained by geodesy. Our integrated approach will ensure that the model fault geometry and slip rates that dictate deformation kinematics, and their influence on the uplift field that drives river incision and exhumation, be compatible across time scales. To accomplish this integration, we propose a five-part research plan: (1) Build hundred-thousand to million-year kinematic orogenic models constrained by geology and thermochronology; (2) Build a millennial time-scale erosion model using river incision rate data, basin-wide CRN, and channel morphology; (3) Construct an updated geodetic vertical velocity field; (4) Construct earthquake cycle models of present day deformation; (5) Bridge time scales through model integration.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.