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

对不经意的观察者来说，山脉似乎是静止的，但在许多地方，它们正在积极地向上生长，以应对板块构造，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人们观察它们的时间尺度和地点。在地震中，山脉可以在几秒钟内移动数米，但当地震运动是数百万年来的平均值时，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。这些缓慢但连续的运动如何与短时间的高震级事件联合收割机结合，在数百万年的时间里形成山区地形，这是一个重要的问题，要理解地震、山体滑坡和洪水等短期危险事件如何在长时间内整合，形成壮观的山脉景观。在这项拟议的工作中，台湾是一个自然的，正在进行的实验，如何隆起和侵蚀是在一系列的时间尺度整合，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，以记录测量速率的变化，并建立一个框架来理解不同方法之间的差异。该项目将汇集美国和台湾不同职业水平和学科的科学家，以解决构造学中的这一基本研究问题。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，该课程涉及将探索台湾大地测量和地貌数据的一年级本科生。本计画是美国与台湾研究人员在NSF/GEO/GEMT合作研究机会下的合作成果，透过建立一套连结变形与侵蚀过程的模型，建立一个新的架构，以跨大地测量与地质时间尺度的变形速率测量。活动台湾山带是一个很好的位置来测试的假设，如何短期过程，如弹性地震周期，河流切割，折返聚合，以建立造山带和地形演变。 台湾被广泛援引为侵蚀或地形稳定状态的山区带的案例研究，然而，一些观察挑战这一经典的观点。高度可变的估计剥蚀和切割率推断在不同的时间间隔提出了问题的时间段内，稳态造山的概念是相关的在台湾。此外，目前的隆起率从大地测量也不容易与千年和更长的时间尺度的侵蚀率。这些令人困惑的观察结果表明，广泛的山地建设的机制，特别是在台湾，还没有完全理解和基本的问题仍然没有答案的关系变形，构造隆起，侵蚀在很宽的时间尺度。我们将建立一系列运动学模型，模拟潜在的断层几何形状和演变，并评估断层活动和几何演变的历史是否与0.5马折返历史的热年代学约束，地貌推断的侵蚀和切割数据约束的千年率，以及现今的岩石隆起率由大地测量约束的一致。我们的综合方法将确保模型断层的几何形状和滑动速率，决定变形运动学，以及它们对隆升场的影响，驱动河流切割和折返，是跨时间尺度兼容。为实现这一整合，我们提出了一个五部分的研究计划：（1）建立十万年到百万年的运动学造山模型，（2）建立一个千年的时间尺度侵蚀模型，利用河流切割率数据，全流域CRN和河道形态，（3）建立一个更新的大地垂直速度场，（4）建立一个新的地球物理模型。（4）构建现今变形的地震周期模型;（5）通过模型集成桥接时间尺度。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估而被认为值得支持。

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.