Damage caused by earthquake landslides

Damage caused by landslides during earthquakes : 

Damage caused by landslides during earthquakes David Petley Robert Parker, Nick Rosser, Alex Densmore Durham University, United Kingdom Huang Runqiu, Chengdu University of Technology, China Allahbuksh Kausar, Geological Survey of Pakistan Lin Jiun-Chuan, National Taiwan University http:daveslandslideblog.blogspot.com Google: “landslide blog”

Case study – Beichuan Town : 

Case study – Beichuan Town Beichuan town 2007

Slide 4: 

Beichuan Middle School landslide Location of school 700 people killed

Slide 5: 

1600 people killed Old Town Landslide (10 mins after main shock)

Post-seismic debris flows : 

Post-seismic debris flows

Fatal landslides: 2006, 2007 and 2008 : 

Fatal landslides: 2006, 2007 and 2008 NB does not include a strong El Nino event

Cumulative number of fatalities since September 2002 : 

Cumulative number of fatalities since September 2002 Kashmir earthquake-induced landslides Wenchuan earthquake-induced landslides Other disasters 2002-2009 (CRED database) Earthquake: 429,877 Flood: 37,860 Storm: 166,410 Volcano: 221

Aim of research : 

Aim of research To understand distributions of landsides triggered by earthquakes Ultimately: To be able to forecast earthquake-induced landslides To rapidly evaluate likely landslide impacts after earthquakes

Area affected by landslides vs earthquake magnitude : 

Area affected by landslides vs earthquake magnitude 2008 Wenchuan earthquake, China 1999 Chi-Chi earthquake, Taiwan After Keefer 1984 and others, updated with recent events 2005 Kashmir earthquake, Pakistan and India

Slide 12: 

Chi-Chi earthquake 21st September 1999, Mw = 7.6 Depth = 8 km

Chi-Chi landslides : 

Chi-Chi landslides >22,000 landslides in total 9,272 landslides > 625 m2 Total landslide area 128 km2

Distribution of landslides triggered by the earthquake : 

Distribution of landslides triggered by the earthquake Khazai and Sitar 2003

Slide 15: 

Kashmir earthquake 8th October 2005 Mw = 7.6 Depth = 10 km Map: GSP Deformation: GSI Japan

Hattian landslide : 

Hattian landslide

Slide 17: 

Kashmir landslides 2252 landslides > 625 m2 NB: Chi-Chi= 9272

Landslide map from SPOT imagery : 

Landslide map from SPOT imagery Balakot Muzaffarabad GSI Japan

Slide 19: 

0.8 g Ground accelerations: Ragukanth 2008 0.6 g 1.0 g 1.2 g 1.4 g 1.6 g 0.6 g 0.8 g 1.0 g 1.4 g 1.2 g Landslide distribution does not match modelled horizontal ground accelerations

Landslide distance from fault: Kashmir (data from Sato et al. 2007)Taiwan (data from Meunier et al. 2007) : 

Landslide distance from fault: Kashmir (data from Sato et al. 2007)Taiwan (data from Meunier et al. 2007) Number of landslides 600 500 400 300 200 100 0 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 Distance from fault rupture (km) 83% of landslides within 2 km of fault 90% on hanging wall Chelungpu Fault N-NW S-SE Number of landslides -10 0 10 20 30 40 50 Distance from fault rupture (km) 1200 800 400 0 -10 -20 Elevation (km) 3 2 1 0 Depth (km)

Kashmir and Taiwan earthquake landslides : 

Kashmir and Taiwan earthquake landslides

Precipitation data: average and 2005 : 

Precipitation data: average and 2005 2006

Observations from Taiwan and Kashmir earthquakes : 

Observations from Taiwan and Kashmir earthquakes Similar magnitudes and depths Similar mechanisms (reverse faults) (but see below) Very different landslide distributions Chi-Chi landslides cluster around point of maximum energy release Kashmir landslides cluster around surface trace of fault. Kashmir had a much greater strike-slip component Very strong hanging-wall / foot-wall effect Rainfall conditions before the earthquake may be a key factor in determining landslide outcome

Slide 27: 

2008 Wenchuan (Sichuan) earthquake, China 14:28 12th May 2008; Mw = 7.9; Depth = 19 km

Slide 28: 

Pengguan Beichuan Wenchuan

The Pengguan fault : 

The Pengguan fault

The Beichuan fault : 

The Beichuan fault

Hanging wall accelerations : 

Hanging wall accelerations

Slide 32: 

Foot wall accelerations

Slide 34: 

Landslides: before and after Landsat 5 18/09/2007 SPOT5 13/10/2008

Shallow rockslides : 

Shallow rockslides

Wenjiagou : 

Wenjiagou

Slide 37: 

Landslide occurrence along major rivers Barrier (“quake”) lakes Number of landslide lakes Distance from Beichuan fault (km)

Slide 40: 

Key findings from the Wenchuan earthquake Decay in landslide density with distance from the fault; Hanging wall – footwall effect; Large landslides and landslide dams occur close to the fault rupture; Strong lithological controls on landslide location; Landslide susceptibility significantly affected by aspect.

Slide 41: 

Fault Conclusion: where not to live! Close to the surface expression of the fault On a steep slope near the river On a slope that faces towards the fault On a susceptible rock type In an area that has just suffered heavy rainfall

Take home messages : 

Take home messages Presentation can be downloaded at: http:daveslandslideblog.blogspot.com Landslides are a major but under-appreciated problem in earthquakes in upland areas Hanging wall – foot wall effect; Relationship to seismic parameters is unclear Key factors are distance, lithology and weather

Slide 43: 

http:daveslandslideblog.blogspot.com Google search: “landslide blog”