Quantifying the effects of an extreme earthquake on a large river system

该项目将汇集第一张主要水系的主要化学和物理特征如何受到大地震极端扰动影响的综合图片，作为研究闽江或长江对2008年中国汶川8.0兆瓦地震的响应的基础。这次地震在闽江流域引发了大范围的滑坡，我们的初步数据表明，这些滑坡显著改变了河流携带的泥沙的数量和组成，以及河水的化学成分。在我们的研究中，我们将抓住这一罕见的自然实验带来的机遇，与来自英国、德国和中国的同事合作，结合(I)中国水文局水文数据的汇编和解释，(Ii)收集有代表性的样本的实地工作，以及(Iii)有针对性地探索河流携带物质中关键地球化学特征的新分析。我们的测量结果将与地震前收集的数据进行比较。我们尤其会探讨地震前后在(I)河流携带悬浮泥沙的数量；(Ii)河床沉积物中10Be的浓度；(Iii)河水中溶解的主要元素组成；以及(Iv)作为河流沉积物一部分输送的颗粒有机碳的浓度和通量方面的差异。在世界各地的河流中，沉积物浓度以及沉积物和河水的化学性质的测量通常被用来了解地球表面的一些最重要的过程，如1)构成广泛工程危害的物理侵蚀和泥沙动员，2)在全球碳循环中发挥核心作用的矿物风化和有机碳运输。人们通常认为，在河流上的任何一个时间点进行的测量都反映了在更长的一段时间内发生的事情。如果很少发生的非常大的骚乱呢？比如一场极端的地震？如果我们对这些测量参数有重大影响，那么我们对侵蚀、泥沙动员和全球碳循环等重要过程的定量理解可能是不完整的。2008年四川汶川地震，中国，提供了一个理想而难得的机会来探索是否是这样，因为大地震在长江源头引发山体滑坡具有如此显著的影响，因为我们可以利用地震前收集的关于长江的大量数据。我们的研究将抓住这一机会，建立一个国际合作，应用一系列方法来研究这一河流系统。

This project will assemble the first integrated picture of how key chemical and physical characteristics of a major river system are affected by extreme disturbance from a large earthquake, using as a basis for study the response of the Min Jiang, or Yangtze River, to the 2008 8.0 Mw earthquake in Wenchuan, China. This earthquake triggered widespread landslides in the Min Jiang catchment area, and our preliminary data indicate that these landslides significantly changed the amount and composition of sediment carried by the river, and the chemistry of the river water. In our research, which seizes the opportunity presented by this rare natural experiment, we will collaborate with colleagues from the UK, Germany, and China to combine (i) compilation and interpretation of hydrometric data from the Chinese Hydrologic Bureau, (ii) fieldwork to collect representative samples, and (iii) new analyses targeted to explore key geochemical signatures in material carried by the river. The results of our measurements will be compared to data collected before the earthquake. In particular, we will explore differences before and after the earthquake in (i) the amount of suspended sediment carried by the river; (ii) the 10Be concentration in riverbed sediments; (iii) the dissolved major element composition of river waters; and (iv) the concentration and flux of particulate organic carbon transported as part of river sediment. In rivers around the world, measurements of sediment concentrations, and of the chemical properties of sediment and river water, have been routinely used to understand some of the most important processes at the Earth?s surface such as 1) physical erosion and sediment mobilization that pose widespread engineering hazards and 2) mineral weathering and organic carbon transport that play central roles in the global carbon cycle. It is commonly assumed that measurements made at any one point in time on a river reflect what is going on over much longer periods of time. If very large disturbances that happen only very rarely ? such as an extreme earthquake ? have significant effects on these measured parameters, then our quantitative understanding of important processes like erosion, sediment mobilization, and the global carbon cycle may be incomplete. The 2008 Wenchuan earthquake in Sichuan, China, provides an ideal and rare opportunity to explore whether this is the case, because the large-magnitude earthquake had such a significant effect in triggering landslides in the headwaters of the Yangtze River, and because we can take advantage of extensive data that were collected on the Yangtze prior to the earthquake. Our research will seize this opportunity by building an international collaboration that will apply a range of approaches to studying this river system.