Distribution of earthquake-triggered landslides across landscapes: Towards understanding erosional agency and cascading hazards

In mountainous regions, earthquake-triggered landslides are a critical geohazard, a major agent of erosion, and a powerful driver of the carbon cycle. How landslides are distributed across landscapes provides key information for hazard management and for better understanding of orogenic evolution and cycling of carbon. In this chapter, we study the distribution of landslides caused by the 2008 M_w7.9 Wenchuan earthquake at the eastern margin of the Tibetan Plateau in the context of recent advances in understanding landslide spatial patterns. We have previously produced a Wenchuan landslide inventory by mapping landslides from remote sensing images. Combining this landslide inventory map with analysis of digital topography, regional geology, and ground motion data, we explore the controlling factors of the Wenchuan earthquake-triggered landslides. We study the locations of the Wenchuan landslides relative to river networks to evaluate how and to what extent landslides supply sediment to rivers. We examine the hillslope aspects of landslides and discuss how the preferred facing directions reveal information about earthquake source, seismic ground motion, and rupture propagation. We evaluate the distribution of landslides from hillslope tops to bases and discuss the implications for long-term evolution of hillslope morphology. Assuming that the Wenchuan seismogenic fault was a linear energy source, we can successfully model the pattern of Wenchuan landslides by adapting a functional form of the law of seismic wave attenuation which accounts for both geometric spreading and quality decay. In conjunction with models predicting total volumes of earthquake-triggered landslides, this approach has promise for predicting the magnitude and pattern of landslides caused by earthquakes based on known characteristics of the seismogenic faults and the seismotectonic, topographic, and geological setting.