This blog is written by Zoë Mildon, a lecturer in Earth Sciences at the University of Plymouth. She has worked on earthquakes and geological hazards across the world, including Italy, Japan, Iceland and California. You can find her on Twitter @ZoeMildon
Humans have woven a rich history of myth and legend to explain why earthquakes happen, from a giant catfish called Ōnamazu 大鯰 (Japan), to gods such as Rūaumoko (Maori) and Poseidon (ancient Greece), to an Earth balanced on elephants, a turtle and a cobra (China and India).
Today, geologists understand that faults cause earthquakes. Faults are lines of weakness in the Earth’s crust that are most commonly found along the edges of tectonic plates. Earthquakes are almost always considered to be bad things, and many wonder why people choose to live in such dangerous places. The reason is often the most basic thing needed to sustain human life – water. In the deserts of the Middle East, water is scarce, so most settlements are located near springs. But the location of the springs is typically controlled by faults; cracks that let water from deep below the surface rise through the solid rock. In the Mediterranean, many ancient Greek settlements were located on or close to faults that provided a supply of water.
In more recent times, being near a spring is less of an issue given modern infrastructure, but earthquakes and faults have still controlled where towns and cities are built. In Japan, the land is either flat plains (great for building on) or steep rugged mountains (more difficult and with an increased risk of landslides). This can be seen really clearly in Google Earth. What controls where the flat plains are? – you guessed it – faults! But this comes with an added hazard. Flat plains are often made up of loose soil and rocks, which means that in an earthquake these areas often experience stronger shaking. This leads to more damage to buildings. So it’s really important to know where the faults are, and also what the ground is like under your city or building.
In the UK and western Europe, the threat of damaging earthquakes is relatively small. Whenever a small earthquake is felt in the UK, memes of ‘earthquake damage’ featuring toppled bins and deck chairs often pop up on social media. But that doesn’t mean that we don’t need to worry. In western Europe, there are a number of nuclear power stations, and these typically need to be built to withstand any possible size of earthquake for up to 10,000 years. But we know from the 2011 Tohoku earthquake and tsunami disaster, nuclear power plants and earthquakes don’t mix well!
So, where do geoscientists like me fit in? Geoscientists are able to hunt down where the faults that cause damaging earthquakes are located, so we can work out where earthquakes may happen in the future. This is because faults leave markers in the landscape, such as offset streams and uplifted hills. Geoscientists can also use a technique called “paleoseismology”, which looks at how different soil layers across a fault are offset, to work out when and where earthquakes have happened over the last few thousand years. Following a major earthquake, geoscientists survey the environmental damage, to look at how the ground moved as a result of movement along the fault or due to earthquake-triggered landslides.
I was involved in post-earthquake mapping after the 2016 Amatrice (Italy) and Kumamoto (Japan) earthquakes and found the work scientifically fascinating and exciting to be involved with. But it was an emotional experience to visit damaged areas while carrying out my work, particularly in Italy as I had visited the town before the earthquake and was familiar with the area.
Credit: Jenni Robertson
Studying geoscience has given me a greater appreciation how the natural world works and how our lives are interlinked closely with the environment. The world’s population is forecast to grow by 1 – 2 billion people in the next 20 years, so where are these people going to live? How can we ensure a growing population is safe from natural hazards like earthquakes? There are still many questions about why and when earthquakes happen that we don’t know the answers to yet, and there is a lot for future geoscientists to work on to better understand the earthquakes and faults that shape our natural environment.