Geotechnical Lessons From An Extreme Geo-disaster: Visit To The May 2008 Wenchuan Earthquake Zone, China

This paper summarises key geotechnical findings arising from studies by others and from a visit to the Wenchuan earthquake zone in China. The magnitude and scale of the May 2008 Wenchuan earthquake classifies this event as an extreme geo-disaster. Such events do not often attract the technical attention of the geotechnical profession due to their low probability-high magnitude nature which is outside the normal design codes and construction standards for engineering structures. However, study of these extreme events can provide valuable insight to the performance of natural and engineered systems under severe loading which can lead to improvements in geotechnical models and engineering design under normal loads.

The geology of the Wenchuan earthquake is described including the surface rupture and ground shaking features. Seismic damage to structures including buildings, dams and tunnels is discussed, highlighting the role of design codes and construction standards on damage control. Coseismal geohazards such as landslides, debris flows and landslide dams are summarised including mechanisms and impacts on life and property. Overall, the primary controls on the extensive devastation suffered include the high magnitude, shallow depth and long duration nature of the seismic event, the strong vertical component of movement due to the imbricated thrust tectonic control on movement and the fact that deformation was not constrained to the main rupture plane but also occurred along secondary structures between bounding faults within a structural zone some 50-70 km wide and 500 km long.