The Role of the 2008 Mw 7.9 Wenchuan Earthquake in Topographic Evolution: Seismically Induced Landslides and the Associated Isostatic Response. Issue 9 (1st September 2018) - Ren, Zhikun
Abstract: The widely held notion about the relationship between reverse‐faulting earthquakes and mountain building has been challenged by recent studies suggesting a net coseismic lowering of surface height due to the 2008 Mw 7.9 Wenchuan earthquake. We calculate the long‐term isostatic response to the removal of coseismic landslide mass produced by the 2008 Wenchuan earthquake, using re‐estimated coseismic landslide volumes. The total isostatic response volume is associated with the input landslide volumes and ranges from ~1.0 to 2.7 km 3, which did not change much with the varied input value of the effective elastic thickness ( Te ); however, the rebound distribution changes with Te . Consequently, the net uplift volume will be ~1.2–2.9 km 3, taking into account the total landslide volume of 2.8 + 0.9/−0.7 km 3 and the coseismic uplift of 2.6 ± 1.2 km 3 . The isostatic response due to Wenchuan earthquake is ~0.3 m but may vary from 0.15 to 0.6 m (input minimum and maximum landslide volumes from the combined scaling parameters, respectively) in the central Longmen Shan. We also find that the average net uplift is ~0.11–0.26 m, which resulted from the imbalance between earthquake‐caused uplift and the isostasy within the landslide region due to the Wenchuan earthquake. The total isostasy could reach ~550–1, 300 m during the past 10–15 Ma, in the corridor bounding the coseismic surface ruptures. Our findings reveal that the evolution of local topography in the Longmen Shan region is inevitably related to the repeated tectonic events, especially the strong earthquakes similar to the 2008 Wenchuan earthquake. Plain Language Summary: It has been almost 10 years after the occurrence of the 2008 Wenchuan earthquake. There has been numerous publications related to this earthquake in various aspects. Its role in topographic evolution is hotly debated. However, no detail reports about the isostatic rebound due to the removal of the landslide material caused by the Wenchuan earthquake can be found. In this study, we report the quantitative results of the isostatic reboud, its distribution character, and hence the role of the Wenchuan earthquake in local topographic evolution. Key Points: The seismical erosion and associated isostatic response to the Wenchuan earthquake are discussed The isostatic rebound contributes significantly to mountain peaks