Earthquakes drive focused denudation along a tectonically active mountain front
Earthquakes drive focused denudation along a tectonically active mountain front
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DOI：
10.1016/j.epsl.2017.04.040
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发表时间：
2017-08
影响因子：
5.3
通讯作者：
Gen K. Li;A. West;A. Densmore;Zhangdong Jin;Fei Zhang;Jin Wang;M. Clark;Robert G. Hilton
中科院分区：
文献类型：
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作者：
Gen K. Li;A. West;A. Densmore;Zhangdong Jin;Fei Zhang;Jin Wang;M. Clark;Robert G. Hilton
地震引起大面积的滑坡，这可能会增加多年到几十年来观察到的侵蚀通量。然而，地震对剥蚀的影响，在较长的时间尺度有关的造山演化仍然难以捉摸。在这里，我们评估与地震引发的滑坡在龙门山山脉在青藏高原东缘的侵蚀。我们使用Mw 7.9 2008年汶川和Mw 6.6 2013年芦山地震来评估地震活动如何从短时间尺度（每年到十年，由沉积物通量记录）到长时间尺度（kyr到Myr，从宇宙成因核素和低温热年代学）对侵蚀预算做出贡献。在这个广泛的时间尺度范围内，龙门山最高的剥蚀率在空间上与汶川地震中最强烈的滑坡区域相吻合。在16个流域中，汶川地震后的泥沙剥蚀率与地震地面运动和汶川滑坡体积密切相关（r2> 0.6），与高强度径流事件的频率相关性较小（r2 = 0.36）。为了评估地震引起的滑坡是否能在较长的时间尺度上对剥蚀做出重要贡献，我们模拟了多个地震周期内不同震级地震引发的滑坡总量。我们将预测地震引发的滑坡量的联合收割机模型与地震震级-频率分布相结合，并根据汶川和芦山事件进行校准。长期滑坡持续的“地震侵蚀率”与区域长期剥蚀率（0.5-1毫米/年）的量级相似。相似的震级和空间重合性表明，地震触发的滑坡是龙门山前缘长期剥蚀的主要机制。我们认为，孕震断层的位置和强度有助于沿沿着高起伏高原边缘的集中剥蚀。
Earthquakes cause widespread landslides that can increase erosional fluxes observed over years to decades. However, the impact of earthquakes on denudation over the longer timescales relevant to orogenic evolution remains elusive. Here we assess erosion associated with earthquake-triggered landslides in the Longmen Shan range at the eastern margin of the Tibetan Plateau. We use the M w 7.9 2008 Wenchuan and M w 6.6 2013 Lushan earthquakes to evaluate how seismicity contributes to the erosional budget from short timescales (annual to decadal, as recorded by sediment fluxes) to long timescales (kyr to Myr, from cosmogenic nuclides and low temperature thermochronology). Over this wide range of timescales, the highest rates of denudation in the Longmen Shan coincide spatially with the region of most intense landsliding during the Wenchuan earthquake. Across sixteen gauged river catchments, sediment flux-derived denudation rates following the Wenchuan earthquake are closely correlated with seismic ground motion and the associated volume of Wenchuan-triggered landslides (r 2> 0.6), and to a lesser extent with the frequency of high intensity runoff events (r 2= 0.36). To assess whether earthquake-induced landsliding can contribute importantly to denudation over longer timescales, we model the total volume of landslides triggered by earthquakes of various magnitudes over multiple earthquake cycles. We combine models that predict the volumes of landslides triggered by earthquakes, calibrated against the Wenchuan and Lushan events, with an earthquake magnitude–frequency distribution. The long-term, landslide-sustained “seismic erosion rate” is similar in magnitude to regional long-term denudation rates (∼ 0.5–1 mm yr− 1). The similar magnitude and spatial coincidence suggest that earthquake-triggered landslides are a primary mechanism of long-term denudation in the frontal Longmen Shan. We propose that the location and intensity of seismogenic faulting can contribute to focused denudation along a high-relief plateau margin.