Spatial Distribution of Landslides Triggered by the 2008 Wenchuan Earthquake: Implications for Landslide Fluvial Mobilization and Earthquake Source Mechanism

Assessing the spatial distribution of earthquake-induced landslides is important for quantifying the fluvial evacuation of landslide material [Hovius et al., 2011], for deriving information about earthquake sources [Meunier et al., 2013], and for understanding the role of earthquakes in shaping surface topography and in driving orogen evolution. The 2008 Mw 7.9 Wenchuan earthquake is characterized by large magnitude, widespread coseismic landsliding, typical mountainous ridge-and-valley topography of the region, and comprehensive geophysical observation. Previous work on landslides associated with the Wenchuan earthquake has focused on the occurrences of landslide-induced hazards and spatial relations between the landslide locations and the seismic features (i.e., the surface ruptures and the epicenter) [e.g., Dai et al., 2011; Gorum et al., 2011]. Little attention has been paid to how the landslide distribution determines the fluvial mobilization of landslide material or quantitative landslide-earthquake source mechanism inversion, even though the Wenchuan event provides an ideal case study to explore these problems for a larger magnitude earthquake than has yet been considered. We obtained a landslide inventory for the 2008 Wenchuan earthquake using high-resolution remote imagery and a semi-automated mapping algorithm. Here we report the results from spatial and statistical analysis of this landslide map using a digital elevation model (DEM) framework. We present the probability distribution of primary parameters (i.e., slope, aspect, elevation, and area density of all landslides) of the landslide inventory and discuss their relations to regional topographic features (i.e., river channels and mountain ridges). The landslide-river channel connectivity and landslide mobility were estimated using different hillslope-channel transition cutoffs. The landslide density and the probability of slope failure were calculated for all lithological units within the Longmen Shan range. The patterns of the derived landslide statistical parameters were compared to the fault slip distribution of the Wenchuan earthquake. This comparison allows the evaluation of the applicability of the inversion from landslide distribution to earthquake source mechanism for this high-magnitude earthquake. References Dai, F. C., C. Xu, X. Yao, L. Xu, X. B. Tu, and Q. M. Gong (2011), Spatial distribution of landslides triggered by the 2008 Ms 8.0 Wenchuan earthquake, China, Journal of Asian Earth Sciences, 40(4), 883-895. Gorum, T., X. M. Fan, C. J. van Westen, R. Q. Huang, Q. Xu, C. Tang, and G. H. Wang (2011), Distribution pattern of earthquake-induced landslides triggered by the 12 May 2008 Wenchuan earthquake, Geomorphology, 133(3-4), 152-167. Hovius, N., P. Meunier, L. Ching-Weei, C. Hongey, C. Yue-Gau, S. Dadson, H. Ming-Jame, and M. Lines (2011), Prolonged seismically induced erosion and the mass balance of a large earthquake, Earth and Planetary Science Letters, 304(3-4), 347-355. Meunier, P., T. Uchida, and N. Hovius (2013), Landslide patterns reveal the sources of large earthquakes, Earth and Planetary Science Letters, 363(0), 27-33.