Hazards from the Sichuan Earthquake

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Presentation made at Philip Allen "Hazards Day" for AS/A2 students on the Wenchuan (Sichuan) earthquake

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Hazards from the Sichuan earthquake : 

Hazards from the Sichuan earthquake David Petley Durham University Powerpoint file on my blog – Google: “Petley landslide blog”

Plan for the next 30 minutes : 

Plan for the next 30 minutes Why was there are earthquake? What happened on the day? What was the damage? What were the short term hazards? What happens next?

5 minutes of intense shaking, 8 minutes in total : 

5 minutes of intense shaking, 8 minutes in total

Area of shaking : 

Area of shaking 300 km Moderate damage to well-constructed buildings; difficult to stand Most buildings collapse

Impacts of the earthquake : 

Impacts of the earthquake Mw = 7.9; depth = 19 km >87,000 thought to have died >69,000 confirmed killed >18,000 “missing “ 374,000 injured >4.8 million homeless (up to 11 million?) Rebuild costs = c.£100 billion

Schools performed very poorly : 

Schools performed very poorly 7000 classrooms collapsed killing at least 19,000 children

But hospitals and government buildings performed quite well : 

But hospitals and government buildings performed quite well

Response: destruction to communication structures and roads was a major problem : 

Response: destruction to communication structures and roads was a major problem

Major challenge – quickly assessing damage and being able to deliver help when roads are blocked : 

Major challenge – quickly assessing damage and being able to deliver help when roads are blocked

Technology would seem to be the answer, but never delivers in earthquake zones : 

Technology would seem to be the answer, but never delivers in earthquake zones

Experience of the 1980 Italian Earthquake : 

Experience of the 1980 Italian Earthquake 94% of survivors were rescued in first 24 hours 35% of people found were still alive 8% of people found were still alive Rescuers need to be on site within a few hours In Italy 90% of rescuers came from the same village as the victim

Immediate key issue 1: Multiple building collapses : 

Immediate key issue 1: Multiple building collapses People killed or injured People trapped Loss of space to live, eat and sleep

Key issue 2: Large numbers of injured people : 

Key issue 2: Large numbers of injured people 374,000 injured Arranging medical care proved to be very difficult Need to provide long term care for both physical and psychological injuries

Key issue 3: Water and power : 

Key issue 3: Water and power Infrastructure for delivering water extensively damaged Electricity generating and transmission capability also greatly damaged

Key issue 4: landslides during and after the earthquake : 

Key issue 4: landslides during and after the earthquake Huge numbers of landslides occurred Landslide activity continued after the earthquake during aftershocks and in heavy rain

The cost of landslides : 

The cost of landslides It is estimated that 35% of people killed were buried in landslides In addition, 15% of people who survived the earthquake could not be rescued because landslides blocked roads

Case study: Qushan, Beichuan : 

Case study: Qushan, Beichuan Town of 40,000 people Regional centre for 160,000 people

Beichuan after the earthquake : 

Beichuan after the earthquake 13,000 (out of 40,000) people killed

Slide 22: 

13,000 (out of 40,000) people killed

What happened? : 

What happened? Landslide 1 Landslide 2 Damage from shaking Air blast

Why so bad? : 

Why so bad? But the landslide behind the school was known about and had been “fixed”

But there were monsters in the hills… : 

But there were monsters in the hills…

1786 Dadu River : 

1786 Dadu River 1st June 1786 Magnitude = 7.75 earthquake 10th June 1786 landslide dam collapsed Flood wave killed 100,000 people downstream

The landslide dams : 

The landslide dams 45 landslide dams blocked rivers All had to be cleared by building new channels Very difficult to access Very difficult to control flow >1 million people evacuated Tangjiashan, upstream from Beichuan, was the worst

Drained! : 

Drained!

Draining of lakes was successful, but problems remain : 

Draining of lakes was successful, but problems remain

What happens next? : 

What happens next? Three major challenges: The winter The landslides Rebuilding