Earthquakes and Buildings: A Rocky Relationship

I never traveled outside of the United States before. Therefore, I was never thrown into another culture. When we arrived in Santorini, I remember asking myself why the buildings looked so different. I found out that those buildings were just in the process of being built! It intrigued me to find out more about the buildings here. Where I am from, you often see complex structures made of wood, then insulation and dry wall. Before you know it, the homes are built!

Since we arrived in Santorini, we have been discussing the different hazards and geologic history on the island. As we’ve been talking about the hazards associated with the geologic history, I realized that both locals and tourists do not realize the dramatic affects that a high-magnitude earthquake can have on the towns. I will be discussing why earthquakes are common and how it will affect the buildings on the island of Santorini.

 

What Causes Earthquakes on Santorini?

As we have learned in class, an earthquake can be caused by tectonics or volcanoes. Volcanic earthquakes are caused by magma moving up beneath the surface and tectonic earthquakes are caused by plate tectonics and fault lines. Santorini has two major fault lines: the Kameni line and the Kolumbo line. The Kolumbo line runs through the northern part of Thera while the Kameni line runs through the southern part of Thera.

The Kolumbo line is one of the most active lines, which means that earthquakes are very common. Both sides of the fault are moving in opposite directions causing friction; when they get stuck and suddenly move, it creates seismic energy. The energy is carried and creates an earthquake. These tectonic earthquakes are usually higher in magnitude than volcanic induced earthquakes.

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Figure 1: The northern red line is the Kolumbo fault line. The southern red line is the Kameni fault line.

How are Buildings Made on Santorini?

Driving in Santorini is stressful, but at least we get to see amazing views and different architecture! Seeing many unfinished buildings allowed me to see the process of the how the homes are built. Each house we saw was in a different stage of being finished. They are made primarily of concrete followed by volcanic rocks. People depend on these materials because they are inexpensive. The picture below shows how homes are built on the island using concrete.

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Figure 2: This is the beginning stages of building
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Figure 3: Almost done building!

 

How did the Minoan Eruption Effect Buildings on Santorini?

Our hike down Cape Plaka (located on the caldera rim) showed us the different caldera forming eruptions through the layers. The last caldera forming eruption was the Minoan Eruption (1613 BC), which deposited 60 meters, or 200 feet, of ash and pumice onto the surface of Santorini. Pumice is a vesicular, light weight volcanic rock that is light in color. Locals built homes in the pumice deposits of this eruption.

Figure 4 shows what the popular city of Oia is built on. Oia is known for their architecture and where “Mamma Mia!” was filmed. Figure 5 was taken from the balcony of our apartments in Karterados, a town just outside of Fira.

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Figure 4: The city of Oia is built on the pumice showed above.
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Figure 5: Shows a house built into pumice.

The material shown is extremely unstable and can collapse at any time. During an earthquake, the pumice can become unstable, collapsing on homes built in the pumice and built on top of the pumice.

 

Why are Earthquakes a Hazard to the Buildings on Santorini?

Earthquakes are a hazard to buildings on Santorini because of the material they are built of and the material they are built on. Concrete buildings are rigid and will not be able to survive a major earthquake. They will have what is called a lateral collapse.

A lateral collapse is when each floor of the structure folds and collapses. Lateral collapse happens when the building is not able to move with the waves because of rigidity and stiffness.

The buildings built inside of the pumice will fall and collapse. Since they have pumice on top and on the bottom, they will fall and be crushed.

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Figure 6: This diagram shows the surface wave from an earthquake heading towards a building. The building will collapse because it can’t move with the wave.

 

We know that an earthquake will happen and cause significant damage due to the earthquake of 1956 that hit Oia. The city of Oia crumbled and was rebuilt afterwards. We could be looking at a repeat of history if another high magnitude earthquake were to hit the area. It will impact the buildings and homes all over the island. Buildings near both the Kameni and Kolumbo lines are at the most risk along with the buildings built in or on top of the volcanic pumice. I hope that Santorini can find a way to build stable buildings in stable locations.

5 thoughts on “Earthquakes and Buildings: A Rocky Relationship

  1. Hi Laura,

    While I understand the purpose for a geology course is to learn about our dynamic earth, you are certainly learning about discomforting facts. This post certainly captures “hazards associated with geologic history.” I wasn’t sure what you meant about the pumice until I read the caption under your drawing. Great combination. The fact that the pumice doesn’t move, who knew? Well, maybe Professor Skinner did. Remember to provide a brief follow up on any statements such as, “Driving in Santorini is stressful, but at least we get to see amazing views and different architecture!” Is the driving stressful because there are herds of cats moseying in front of cars? Because your new knowledge has everyone on edge and a bump on the road may be a tremor? Because the kids in the back of the van are asking “Are we there yet?” I’d like to see a video of Professor Skinner saying “Don’t make me stop this van.”

    The images that your provided help a great deal and now I’m feeling anxious for the Santorinians. Have you and your colleagues discussed projects that inform the locals of how best to live on an active volcano? Maybe an infographic on what it means to build homes with pumice and other details mentioned in this post?

    Such brainstorming works best with a Greek cookie:
    https://www.tripadvisor.com/Restaurant_Review-g635608-d8318692-Reviews-Santa_Irini_Bakery-Perissa_Santorini_Cyclades_South_Aegean.html

    For your next post, I am curious how you and your colleagues are managing learning this new information on hazards and dangers while enjoying the beaches (are you going to the beaches and hot springs?), and Greek island life.

    Perhaps you ought to sit down with Professor Skinner and discuss hopeful possibilities for your observations so that your family, friends, and faculty will feel better as we think about you and your group during our shopping in the Safeway, sadly looking over the bulk American version of Greek olives, near the fried chicken. So, your post did what you intended it to do. Explain how dynamic and unpredictable Earth can be. I’m left feeling a bit wary, so perhaps a balance of Earth and human possibilities for your next post? I need a cookie.
    I look forward to your next hopeful post.

    1. Thank you! It certainly scares/worries me now that I have researched this. Driving is stressful mainly due to the other drivers on the road. Although, I would love to see more cats, just not on the road! Professor Skinner has talked with us about how Greeks handle the different hazards. Geologists came to the island and identified red zones (where you can and cannot not build) but the Greek government does not do a good job regulating this. We spend a lot of time at the beach! It’s beautiful!

  2. Laura,

    I know we talked in depth about this post, and I think you did a good job integrating your photos with a post that flowed. Don’t forget that you can reference other students’ posts on this blog (like Tib’s on the 1956 earthquake) so readers have the opportunity to learn about more of our posts.

  3. Without repeating all that was said by Professor Barron, I only have to add that the Kameni line is drawn in the wrong location. It has the correct direction, but is more northerly running right through the Kameni Islands and Fira (please correct this). Also, it would be good to discuss how very porous, loose material amplifies seismic energy (like we learned in Geologic Disasters).

    I really enjoyed this post and I think it was organized very well.

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