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Rob Parker (University of Cardiff) and Dave Petley
The Mw = 7.8 earthquake on Tuesday in Iran was the largest event in that country for about 50 years. Fortunately, the depth of the earthquake (82 km) and the low population density in the affected areas meant that loss of life was low for an event of this size. Indeed, reports suggest that only one person died in Iran, although there are reports of 40 deaths in Pakistan. This single fatality in Iran was the result of a landslide, and one of the images on the BBC reports about the earthquake also seems to show landslides:
Over the last three years or so, we have been working with our colleagues Alex Densmore and Nick Rosser, funded by the Willis Research Network, to develop a model that will allow us to make an initial assessment of landslide impacts in earthquakes. Rob recently submitted his PhD, and has now moved to a post-doctoral position at Cardiff. However, we thought that this event would be an interesting first application of the model, which has been produced through a statistical (logistic regression) analysis of spatial patterns of landslides (with areas larger than 11,000 square metres) triggered by four large earthquakes in the USA, New Zealand, Taiwan and China. The model provides a first-order prediction of the probability of hillslope failure across the region affected by seismic shaking, based on the strength of ground motions and the gradient of hillslopes. Areas likely to have experienced high levels of landslide activity are shown in red, and while areas we expect to be less affected by landslides are shown in green and then blue. Here, landslide probability has been estimated using preliminary ground motion data published by the USGS and hillslope gradients derived from the ASTER global elevation model. Read more
Professor Dave Petley presents how landslide hazards occur throughout the world, but especially in countries where people are most vulnerable such as China, India and Nepal. Prof Petley demonstrates the need for natural scientists, social scientists and social workers to work together to mitigate the risk of landslide hazards and increase resilience. This plenary talk was given at the 2012 Breaking the Mould Conference at Durham University.
Last year was the worst year on record for economic losses due to earthquakes especially in Japan and New Zealand, according to a report from the Center for Disaster Management and Risk Reduction Technology based on the CATDAT damaging earthquake database. In 2011, total damage caused by earthquakes and their secondary hazards, including tsunamis and landslides, cost 365 billion USD, most of which is from the Tohoku earthquake that hit Japan (335 billion USD) making it the costliest natural disaster on record. 19,300 people died and 450,000 lost their homes after the tsunami hit the northeast coast of Japan. The Christchurch earthquake in New Zealand caused a total of 20 billion USD in damages.
A total of 133 earthquakes were recorded for 2011 including major quakes in the US, Turkey, China and parts of India, Tibet and Nepal. 20,500 people died due to earthquakes in 2011 which statistically is actually lower than the past two years, but is not far from the annual average of 21,800. According to CATDAT, 2011 ’was the highest death toll year in developed nations versus developing nations’ over the past 111 years. While any large number of fatalities caused by earthquakes is staggering, it appears that deaths caused by earthquakes is actually lessening over time; perhaps showing that developing strategies to improve buildings to withstand earthquakes as well as emergency planning that can reduce loss of life is working.
Developed countries have a clear advantage in that they normally have the resources available to design and implement resilient infrastructure, but last year showed the world that in many cases wealthy nations are also vulnerable to large magnitude quakes. While people living in developing countries are likely more vulnerable overall when it comes to earthquake hazards there is still much that can be learned by nations as a whole to prepare for earthquakes taking into account the level of damage in Japan and New Zealand. Read more
The American Geophysical Union Meeting is an immense science conference, the largest of its kind in the world. Taking place in the multilevel citadel known as the Moscone Center in downtown San Francisco, it lies within the city’s technological landscape and seedy urban environment. I was fortunate enough to catch the first session of a press conference on the Tohoku earthquake that devastated Japan early this year, in particular its most destructive secondary hazard – the tsunami – that slammed into the east coast killing tens of thousands of people and causing catastrophic damage. Not surprisingly much attention is being given to the earthquake and tsunami at the conference. The first press conference on the disaster focused on technologies that were in place to track the tsunami, but also public risk perception of tsunami events in Japan, which needless to see seem alarming in regards to preparing for future tsunami events in Japan.
Prior to the tsunami in March of this year, there were four DART buoys in place along the coast of Japan. Three of them were owned by the US, while the other one was monitored by Russia. These buoys allowed researchers to see the tsunami 30 min after it first occurred and empirical observations matched modelling of the tsunami according to Dr Eddie Bernard from the Pacific Marine Environment Laboratory in Seattle, Washington. The buoys take measurements from the sea floor, detecting the changes in the weight of the water above it. Bernard thinks that solely reporting tsunami wave heights is insufficient for evacuating populations before a tsunami strikes, instead there should be ‘flood forecasts’ that can inform people about the levels of flooding that will likely occur, but this will vary depending on where people live along the coast line. Also, Bernard argues that flood forecasting cannot be done without the information available from DART. ‘An earthquake shakes the earth for four minutes and a tsunami crashes the Earth for 12 hours’, he said.
‘For the people who deal with this along the coastline for 12 hours, any additional information you can provide them as soon as possible, whether it’s five minutes, 40 minutes or 50 minutes, would have been very useful’. Read more
Sichuan still experiences mudslides and other secondary hazards from the 2008 Wenchuan earthquake with torrential rainfall during the monsoon season contributing to the ongoing problem. More efforts are needed to help people living in the Sichuan Province of China as it is in the midst of undergoing reconstruction since the 8.0 mag earthquake hit Wenchuan leaving 80,000 people dead or missing. A mining site that has opened in the epicentre of the earthquake has caused concern amongst some researchers in China who think that mining in the area could likely worsen the situation. Other than affecting local geology the mining and factory industries in the area could also increase pollution as businesses attempt to recover from the earthquake.
According to Yang Yung, a geologist who has undergone a series of independent investigations on the effects of the Wenchuan earthquake: ‘There is virtually no public participation in China’s environmental assessments. We urgently need more public participation and awareness of public participation. Environmental assessments ignore a whole range of interests, and there aren’t any mechanisms powerful enough to force the relevant companies to take responsibility’. Read more