1. SPATIAL DISTRIBUTION OF LANDSLIDES TRIGGERED BY THE WENCHUAN EARTHQUAKE, SICHUAN PROVINCE, CHINA Tolga Görüm & Cees J. Van Westen

2. OVERVIEW Global significance of seismically triggered landslides Introduction to the 12 th May 2008 Wenchuan Earthquake Landslide Mapping & Spatial Distribution of Landslides Key findings from the Wenchuan earthquake

3. EARTHQUAKE TRIGGERED LANDSLIDES Fatal landslides 2008 International Landslide Centre: Landslide Database D. N. Petley Some notable events: 1.1994 North Ridge Earthquake, California (M=6.7) over 10 000 landslides 1.2005 Kashmir Earthquake, Pakistan (M = 7.6) over 20 000 landslides

4. RESEARCH ON EARTHQUAKE-INDUCED LANDSLIDES & FINDINGS The main underlying assertion in most research on regional patterns of coseismic landslides is that the landslides cluster in parts of the landscape can reflect the properties of their triggers, and a considerable amount of these studies has focused on the relationship between the seismic parameters (i.e. epicenter, coseismic fault or ground motion) and landslides, generally addressing the correlation of landslide intensity with the distance from or to the seismic source parameters.

5. WENCHUAN EARTHQUAKE ThrustOblique 30 million people affected 70,000 dead 375,000 injured Direct losses to buildings and infrastructure of over US$150 billion 35% of people killed were buried by landslides 15% of survivors could not be rescued because landslides blocked roads (M w 7.9)

6. PRE- AND POST-EARTHQUAKE SATELLITE IMAGE COVERAGE

7. METHODOLOGY

9. The tone, defined as the relative brightness in a black/white image, or the colour in the false colour composite allowed to differentiate unvegetated areas that are most indicative for recent landslides. Texture relates to the frequency of tonal change. Shape or form refers to the geometric aspects of the object in the image Pattern refers to the spatial arrangement of features and implies a characteristic repetition of certain forms or relationships.

10. LANDSLIDE INVENTORY

11. Dai et al., 2011

12. WENCHUAN LANDSLIDES Deep-seated bedrock avalanches & slides 700 1600

13. WENCHUAN LANDSLIDES Deep-seated bedrock avalanches & slides Pre-earthquakePost-earthquake

14. WENCHUAN LANDSLIDES

19. 17 June 18 Nov Aggradation of >10 m in Beichuan in 5 months, due to landslide remobilization Post-earthquake sedimentation – Beichuan

20. EPICENTER Distribution of landslides as a function of distance

21. Waves traveling through the rocks are both reflect and refract across boundaries between different lithologies and at Earth’s surface due to different response of materials. This may cause the increasing the intensity of shaking which is known as ground amplification. On the other hand, propagation direction of fault ruptures can affect the seismic waves, and tend to focus earthquake energy in that direction (McGuire et al., 2002; Ben‐Zion and Shi, 2005; Minster et al., 2006; Dor et al., 2008). (Khazai and Sitar, 2003) (Keefer, 2000) EPICENTER

22. PROPAGATION DIRECTION Relationship between landslide concentration (LC) and directional distance from the epicenter in different buffer zones

23. WHERE NOT TO LIVE!

24. WHERE TO LIVE!

25. Thanks… 謝謝