25 August 2008

Presentation from New Zealand

Posted by Dave Petley

This week I am giving three presentations in New Zealand – first in Christchurch today, then Wellington tomorrow and Auckland on Thursday. The title of the presentation is Earthquake Induced Landslides – Lessons from Taiwan and Pakistan.

The talk is to the various branches of the New Zealand Geotechnical Society and the New Zealand Society of Earthquake Engineering.

I have uploaded the presentation to authorstream so that it can be downloaded (note that I have now given up using slideshare as I have found it too unreliable. The presentation can be found (and can be downloaded as a Powerpoint file from) here and should be viewable below:

Uploaded on authorSTREAM by Dr_Dave

Earthquake induced landslides – lessons from Taiwan and Pakistan

The recent Wenchuan earthquake in Sichuan Province of China has highlighted the impact of seismically-triggered landslides in mountain environments. In China, it is now estimated that approximately 28,000 fatalities, representing about 35% of the deaths in the earthquake, occurred as a result of burial by mass movements. In addition, the blockage of all of the mountain roads by landslides meant that rescue of buried victims in the so-called “golden” 24 hours was seriously impeded, and more than 150 rescuers were subsequent killed by slides triggered by aftershocks. This presentation seeks to examine the occurrence of landslides in two other major seismic events, namely the 1999 Chi-Chi earthquake in Taiwan and the 2005 Kashmir earthquake in Pakistan. Using field data from both sites, the occurrence of landslides induced by the earthquake is examined in both space and time. It is shown that the distributions of landslides are rather different in the two cases, even though they earthquakes themselves were of similar magnitudes. The reasons for this difference are explored, in particular in relation to topographic controls on the magnitude of earthquake accelerations on slopes.

In the second part of the presentation, the occurrence of landslides in the years following the earthquakes is explored. It is shown that there is a notable increase in the occurrence of landslides in the aftermath of the seismic event, and that these landslides release large volumes of sediment into the river system. This increase in landslide activity can have a major impact on the rehabilitation of earthquake-affected areas for long periods of time. Thus, there is a need to improve preparation for earthquakes in landslide-prone areas and to recognise that the impacts of such events are prolonged, rendering the recovery phase rather difficult from an engineering perspective.