Competing Effects of Mountain Uplift and Landslide Erosion Over Earthquake Cycles
Competing Effects of Mountain Uplift and Landslide Erosion Over Earthquake Cycles
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DOI：
10.1029/2018jb016986
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发表时间：
2019-05-01
影响因子：
3.9
通讯作者：
Qiu, Hongrui
中科院分区：
文献类型：
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作者：
Li, Gen;West, A. Joshua;Qiu, Hongrui
大地震可以通过引起岩石隆起来构造山地地形，但也可以通过引起山体滑坡来侵蚀山脉。2008年汶川地震后的观测表明，在某些情况下，滑坡体积与地震引起的隆起相匹配，这就提出了关于单个地震的作用如何累积成地形的问题。在这里，我们模拟的二维地表位移场产生了一个完整的地震周期占同震变形，震后松弛，滑坡侵蚀，侵蚀引起的均衡补偿。我们探讨了不同地震构造和地形条件下的相关体积平衡，并在此背景下重新审视汶川案例。滑坡侵蚀和隆起之间的比值（Ω）对确定滑坡体积的参数（特别是地震震级M-W、地震能量源深度和失效敏感性，以及负责触发滑坡的地震因素）最为敏感，对岩石圈有效弹性厚度T-e也较为敏感。对于一个特定的震级，更侵蚀事件（较高的欧米茄）往往发生在较浅的深度，在厚的T-e岩石圈，在陡峭，更容易发生滑坡的景观。在一定的地形地貌和地震构造条件下，滑坡体和一级隆起体的体积均与M-w和地震矩M-o成正比。然而，较高的M-W地震产生较低的滑坡和隆起体积每单位M-O，这表明较低的效率，利用地震能量来驱动地形变化。用我们的模型计算了藏东地区长期平均地震体积平衡，发现该地区地震的净地形效应倾向于建设性而不是侵蚀性。总的来说，当考虑整个地震周期的过程时，破坏性事件是罕见的，尽管如果只考虑同震体积预算（如2008年汶川地震的情况，滑坡基本上抵消了同震隆起），它们更有可能发生。不考虑净预算，我们的研究结果表明，地震的侵蚀力在山区带的演变中起着重要的作用，包括通过影响结构和变形的空间模式，例如影响地形的波长。
Large earthquakes can construct mountainous topography by inducing rock uplift but also erode mountains by causing landslides. Observations following the 2008 Wenchuan earthquake show that landslide volumes in some cases match seismically induced uplift, raising questions about how the actions of individual earthquakes accumulate to build topography. Here we model the two-dimensional surface displacement field generated over a full earthquake cycle accounting for coseismic deformation, postseismic relaxation, landslide erosion, and erosion-induced isostatic compensation. We explore the related volume balance across different seismotectonic and topographic conditions and revisit the Wenchuan case in this context. The ratio (Omega) between landslide erosion and uplift is most sensitive to parameters determining landslide volumes (particularly earthquake magnitude M-w, seismic energy source depth, and failure susceptibility, as well as the seismological factor responsible for triggering landslides), and is moderately sensitive to the effective elastic thickness of lithosphere, T-e. For a specified magnitude, more erosive events (higher Omega) tend to occur at shallower depth, in thicker-T-e lithosphere, and in steeper, more landslide-prone landscapes. For given landscape and seismotectonic conditions, the volumes of both landslides and uplift to first order positively scale with M-w and seismic moment M-o. However, higher M-w earthquakes generate lower landslide and uplift volumes per unit M-o, suggesting lower efficiency in the use of seismic energy to drive topographic change. With our model, we calculate the long-term average seismic volume balance for the eastern Tibetan region and find that the net topographic effect of earthquakes in this region tends to be constructive rather than erosive. Overall, destructive events are rare when considering processes over the full earthquake cycle, although they are more likely if only considering the coseismic volume budget (as was the case for the 2008 Wenchuan earthquake where landsliding substantially offset coseismic uplift). Irrespective of the net budget, our results suggest that the erosive power of earthquakes plays an important role in mountain belt evolution, including by influencing structures and spatial patterns of deformation, for example affecting the wavelength of topography.