June 30, 2008
- Earthquake prediction
- The scale of China’s May 12 quake
- Reservoir-induced seismicity and the role of China’s dams
- Quake lakes and dam failure
Li Yong, Geological Expert at the Chengdu University of Technology in Sichuan
This Chinese geological expert had raised the possibility of a dangerous earthquake in the area in 2007.
“The line of the middle fault is as clear as a string. It suggests continuous and strong movement. Such a long and clear lineament should trigger a big quake. Other scientists have had similar ideas….Many experts have provided their knowledge and suggestions, but how much of it became a reality in these towns and villages isn’t something that’s convenient for me to say.”
Liu Jingbo, Professor at the Construction Institute of Disaster Preparation and Relief at Tsinghua University in Beijing
A professor in disaster preparation comments on the failure of the Chinese government to heed the warnings of the scientific community.
“When I saw the footage of Beichuan City after the earthquake, I was stunned. How could a populous city be built in such a risky area, particularly right at the foot of mountains? When an earthquake occurs, it’s not just the collapse of buildings that buries people, but boulders and huge rocks and mud flows that follow on immediately.”
Peng Juan, Wenchuan County Government Official
This government official speaks to the lack of government preparedness.
“We had never been made aware of the earthquake risks. It had never happened before.”
Gao Jianguo, Researcher with the China Earthquake Administration in Beijing
This Chinese researcher speaks out about the failure of officials to listen to clear warnings of the potential for a devastating earthquake in the area.
“Chinese people have a saying that you learn a fence needs mending after the sheep have run away. In this case, people wouldn’t recognize the danger until the sheep actually died. We tried to lay out the reasons beforehand, but people wouldn’t listen….The earthquake administration didn’t warn the government enough.”[PDF]
Kwadwo Affram Asiedu, Chairman of the Eastern Regional Disaster Management Committee (ERDMT), Ghana
Chairman Asiedu sees the benefits of preparing for emergency disaster response, especially in the seismically-active region of Greater Accra where the Akosombo dam was built. [PDF]
The Scale of China’s May 12 Quake
Mario Chavez, Professor of Seismological Engineering at the National Autonomous University of Mexico in Mexico City.
Chavez’s preliminary results indicate how much, and in which direction, the ground moved throughout a vast region including the earthquake’s epicentre.
The seismic waves calculated by a computer model, and verified by ground-motion velocities measured during the earthquake and at Chinese seismological stations, may be of use in helping the Chinese target aid to the hardest hit of those areas… [and] may also help locate which of the hundreds of dams in the stricken region are the most at risk.
Chavez said that recorded displacements of at least 1.5 metres (5 feet) could readily explain the landslide that formed a fragile dam across the Jianhe River and forced the evacuation of approximately 160,000 people in the area.
Hong Hao, Civil Engineer at the University of Western Australia
Although the Global Hazard Seismic Assessment Program predicted that the Sichuan area had a 10% risk in 50 years of an earthquake with peak ground acceleration of 1.6 m/s squared, Hao says:
“This earthquake would have far exceeded that, perhaps by a factor of five. By some estimates at its epicenter, the energy released would have been equivalent to 300 to 400 Hiroshima atomic bombs….The seismic code for the area substantially underestimated the earthquake strength.”
Professor Yugi Yagi, Tsukuba University, Japan
The faults responsible for the Sichuan earthquake were about 250 kilometres to 300 kilometres long, and the focus was relatively shallow at a depth of about 10 kilometres to 20 kilometres.
“The fault possibly became that long because two faults slipped simultaneously,” said Prof. Yagi.
The shaking was said to have extended for some time as the faults shifted for about two minutes. The waves were felt by people as far away as Beijing and Shanghai – more than 1,500 kilometres from the epicentre.
Kevin McCue, Director of the Australian Seismological Centre in Canberra
“All around the world, buildings are designed to withstand ground motion that has a greater than 10% risk of occurring in 50 years…that’s considered too high a risk for dams and nuclear reactors.”
Leigh Royden, one of a team of geologists from Massachusett’s Institute of Technology researching in China
Having recently published a paper analyzing the causes of the quake in the July issue of the journal GSA Today, Royden confirms that:
“Nobody was thinking there would be a major seismological event in that area. This earthquake was quite unusual, and may have involved a simultaneous rupture of two separate but contiguous faults.”
Reservoir-induced seismicity and the role of China’s dams
Dr. Philip Williams of Philip Williams and Associates (Environmental Hydrology and Planning) points out the connection between reservoir-induced seismicity and the Zipingpu Dam, located a few kilometres from the earthquake’s epicentre.
Fan Xiao, Chief Engineer of the Regional Geology Investigation Team of the Sichuan Geology and Mineral Bureau
Fan Xiao expresses his concern about the earthquake and its potential link with the Zipingpu Dam reservoir.
“Even if the Zipingpu reservoir hadn’t been built, the quake would have occurred in this area, but not necessarily with a magnitude of 8…. Secondly, if Zipingpu hadn’t been built, the epicentre would not have been in the current position, so close to the reservoir, but possibly somewhere else. Thirdly, if Zipingpu hadn’t been built, the quake would likely have occurred 100 or even 200 years later, but not now.”
Jeff Freymueller and Shusun Li, Scientists at the UAF Geophysical Institute
“Because of the large distance (400 miles) between the [Three Gorges] dam and the [Sichuan] earthquake, it is unlikely that the dam and reservoir had a significant impact. The main cause (probably the only cause) of the earthquake is the eastward motion of the eastern Tibetan plateau relative to south China. This is ultimately driven by the collision of India with Eurasia.”
Dr. Christian Klose, Professor in the School of Engineering and Applied Sciences at Columbia University
Professor Klose has researched and published on the phenomena of man-made earthquakes. Read this article which refers to his work.
Dr. Christian Klose, Professor in the School of Engineering and Applied Sciences at Columbia University (interview)
What do you do at Think GeoHazards?
My research focuses on understanding natural hazards and their impacts on human security. We do research proposals and studies on the climate and help our clients manage their risks.
You study earthquakes caused by human actions. So are these still considered “natural” disasters?
It’s an event caused by the natural system, but triggered by human activities. I describe it as geohazards—hazards that can come from the earth. They can be triggered or induced by humans or by nature. Ninety-five percent of all earthquakes are of natural origin and occur in active regions, such as California, Japan, Turkey or the Pacific. Five percent occur in stable regions, and of that percent, you have a fraction that are human-triggered.
How should humans change our behavior to prevent these earthquakes?
I’m not going to come out and say you need to stop that [activity]. I’m saying you need to make an appropriate risk assessment. The goal is for people to understand the geology and understand the coupling of interactions between the human system and natural system. If we assume we can trigger an earthquake, there will be a risk. So to reduce the risk, you reduce the hazards. You decide not to build a dam, or you build a smaller dam, or we can decrease vulnerabilities. Don’t build close to where we can expect earthquakes.
Most of the time we have ignored those issues. When you look at the areas exposed to mining earthquakes—there’s an earthquake, and then afterward we will put some money into getting rid of the damages, but there’s no preemptive measure to make sure it doesn’t happen. Ignoring a problem until it happens is not the best way. I’ve shown this in the Newcastle, Australia earthquake [1989, Richter 5.6, 13 people killed, 160 injured]. This has been a coal-mining region for 200 years. If you do a cost-benefit analysis and look at the money you really make and compare this with the monetary amount of the damages, you end up at $3 billion in damages. These aren’t just little earthquakes and some damages. It can be detrimental.
What’s the difference between an induced earthquake and a triggered earthquake?
Induced earthquakes happen only when humans do engineering, such as when we excavate a mine. They would never happen under natural conditions. If you inject fluid into the rock for hydrocarbon production, you induce tiny earthquakes, and this is expected, for instance, when reservoirs are built. The only question is how big the earthquakes will be. But 40 years ago no one excepted the idea of this.
Triggered earthquakes are natural earthquakes that would have happened under natural conditions, but the question is, when do these natural conditions trigger earthquakes, and how much stress does it take to trigger them? You have to understand the geology to understand where the fault zones are and when was the last earthquake. Then you can come up with physical models that can tell you, for example, if you remove a huge amount of mass from mining, how it affects the earth’s crust. You will never be able to predict an earthquake—the uncertainties are too huge. But you can have a forecast.
Bill McGuire, Director of the Benfield Greig Hazard Research Centre in London, UK
“There’s no question that if you dig a big enough reservoir, you’re going to get earthquakes…. The Three Gorges Dam in China is going to be a big problem.”
Quake Lakes and Dam Failure
Dr. Martin Wieland, Chairman of the ICOLD Commission on Seismic Aspects of Dam Design
“Shortly after the devastating earthquake reports appeared of cracks on the concrete face of the 156m high Zipingpu concrete face rockfill dam (CFRD), which is located upstream of Dujiangyan City. [The reservoir’s] low level meant it was possible to detect these cracks – they would not have been visible if the reservoir were full. As modern CFRDs such as Zipingpu dam are designed to withstand severe leakages in the concrete face, and in view of the low water level in the reservoir, the dam can be considered stable and safe.”
“Around 400 dams were affected by the Sichaun earthquake. Most of these were small embankment dams and gaining access to these sites is difficult….Due to the large number of landslides it is expected that some smaller rivers will be blocked. The sudden failure of such ‘earthquake’ dams may have similar consequences as the failure of one of the damaged dams.”
E. Jingping, Deputy Minister of the Ministry of Water Resources
“Sixty-nine dams are in danger of collapse from the first quake,” and, “sixty-nine reservoirs are in ‘immediate’ danger of bursting.” This statement was made before the magnitude 6.4 aftershock hit Sichuan on May 25, 2008.
Yun Xiaosu, Vice Minister of Land and Resources & Liu Yuan, Engineer from the Chinese Environment Ministry
These government officials comment about the potential for danger caused by large scale flooding and backed-up rivers.
Yun Xiaosu said: “This can all cause new catastrophes. We must go to every village and we must go to all the sites of geological disturbances. This will take a long time.”
Liu Yuan added: “It is fair to say these lakes pose a very great danger.”
Liu Shukun, China Institute of Water Resources and Hydropower Research
Liu comments on the nearly 350 dams built along the Min River and its tributaries which were damaged during the earthquake.
“It is unwise to build so many dams in the Min River earthquake belt. The small hydropower plants do not have careful planning.”
Dr Hrishikesh Baruah teaches Geology at Arya Vidyapeeth College
In fact, the largest and most damaging earthquake (M = 6.3) triggered by a man-made reservoir occurred in 1967 in Koyna, India. India experienced two more such quakes due to failures in 1983 at Bhatsa in Maharashtra (M = 4.9) and 1993 at Killari or ‘Latur’ in SWIndia (M = 6.1).