Earthquake Engineering: Predicting Mother Nature
Earthquakes provide a complex challenge for engineers; they are difficult to predict, difficult to withstand and, subsequently, difficult to recover from. But that’s not all – as seen by the 2004 Indian Ocean and 2011 Tōhoku earthquakes, these events can also trigger unforeseen secondary disasters such as tsunamis and nuclear meltdowns, increasing the scale of the disaster several fold.
According to the United States Geological Survey, in an average year an estimated several million earthquakes occur around the world. Thankfully, most of these go undetected because they are in remote areas or are too small to register. However, 18 of these are typically major earthquakes that reach over magnitude 7 on the Richter scale. As a sense of scale, the 8.9 magnitude earthquake that hit Japan in 2011 was so intense that it altered the distribution of the Earth's mass. As a result, it caused the earth to rotate slightly faster and has fractionally shortened the length of each day.
While it was once a narrower discipline, earthquake engineering today combines several engineering fields with elements of sociology, political science, and finance in order to predict and mitigate the effects of these disasters.
In this episode of Create the Future, we speak with seismic expert Ziggy Lubkowski about the impact of earthquakes around the world, the origins of ‘flexible’ buildings, and how we can build more resilient structures in the future.
About the guest
Ziggy Lubkowski is an associate director and the leader for Arup’s seismic team based in London. He has over 30 years of experience in civil, geotechnical, and earthquake engineering, a varied career throughout which he has travelled around the world performing seismic design, analysis, and hazard assessments.
He is the Royal Academy of Engineering visiting professor in geotechnical earthquake engineering at University College London, and is the panel chair for the EPICentre group at University College London, a group working to provide guidance that will help to reduce losses from future earthquakes.
- Aceh had a major earthquake – magnitude 9.3, so a lot of buildings suffered damage. Some collapsed. The earthquake was some distance offshore, but then the big impact was the tsunami waves. When you walk along the coast along the north of Aceh province, there are areas where you can see the water levels were about ten meters above land so it just ripped the vegetation away. Any buildings within that region were just swept off their foundations, and you can see these villages and towns where the slate was wiped clean, literally.
- [On traditional Japanese architecture]: In Japan, some of the buildings were designed so each story – let's say, on a five or six story pagoda – slid on the roof of the previous story and had a large tree trunk running through the top to limit the amount of sliding. That created quite a flexible structure that was more resilient to shaking.
- What we've been trying to do is ensure that buildings are as flexible as possible. Think about the difference between something like a large oak tree and bamboo shoots: bamboo in wind moves quite a lot – the wind goes, it's back to standing upright. A large oak tree will sway in a large wind, but at a certain point it will crack and fall over. We want to ensure buildings are flexible, so they sway in the earthquake but, when the earthquake stops, they come back to where they were.
- When the earthquake occurred the [Fukushima Daiichi] plant survived very well. The motions were greater than it had been designed for, yet it performed adequately and was going through the shutdown process. Unfortunately, then the tsunami hit. The tsunami was much bigger than the local academics had predicted, and it inundated the plant. The plant was still was performing well, but then water got into the diesel tanks and diesel generators, which were being used as part of the shutdown process. Power was then cut to the plant, so it was the water getting into the diesel tanks that caused the meltdown.