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The sound of earthquakes

During the last days before christmas, our graduate program organized a public speaking workshop at the university. During these days we spent some time training interviews and we had some lectures on preparing for real interviews (like in this one). The rest of the time we were trained how to communicate our science to lay general public. To do so, we were supposed to create a short movie. The result you can see here:

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Co-seismic surface structures

In the first discussion with the local authorities and our guide, we also talked about the effects and damages of the El Galpón earthquake. The damages in the village were obvious and I wrote about them in the last post. But for us seismologists it is also interesting to see if there are damages in the landscape. Typical effects would be: cracks in the ground, landslides, water and sand fountains, a new step in the topography or changes in the ground water table. We call this stuff co-seismic effects, because they occur during the shaking of an earthquake. Some of these (i.e. changes in the ground water table) can occur before an event as pre-seismic or after an event as post-seismic events (e.g. landslides).
Luckily, the people understood what we were pointing at and they showed us pictures of big cracks in the ground. They found them directly after the earthquake, so they could be our co-seismic effects. On our last day of fieldwork we had some time left to have a look on these cracks in the ground. Read More…

The damages in El Galpón

During our fieldwork we had the chance to visit the village El Galpón, which was mainly affected by the earthquake in October 2015. To give a visible expression how much shaking can be generated by a 5.7 Mw earthquake watch this video of a security camera in the city of Metán, approximately 50 km away from the epicenter.

El Galpón is quite small and only has some hundreds inhabitants. When we first arrived we thought the people removed the damages really quick or nothing really happened. When we got closer to the center we investigated the latter was true. The newer buildings in the outer part had no obvious damage. But in the central part most of the buildings were stabilized by wooden planks.

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How a fault zone looks like

alternative: tectonics in the Santa María Basin

Although the fieldschool is mainly focussing on the development of the Geology and Stratigraphy of the intermontane basins in NW Argentina, I had several moments of happiness when we could observe some fault zones. Fault zones are planes along which earthquakes take place to release accumulated stresses. Big earthquakes occur mainly along the plate boundaries which are very big fault zones. But as explained in my first post, also far away from the plate boundaries we can have fault zones because the accumulated stresses due to plate tectonics influence regions on a much greater scales and bring mountains up in the air. The movement of rock masses and mountains is always related to a deformation of them. For example you can take a piece of plain paper and when you push both sides of the paper together you will end up with a deformation of the paper as it will become a convex bridge. But with respect to the table where the paper lays on, the paper will scratch and move along the table surface. This small area is then our fault zone when you apply this example in rocks.

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fieldwork in the jungle

The reason for the first visit of Argentina is the field-school organized within our StRATEGy program. This field trip is about 10 days only and we thought it would be a good idea to prolong the stay a few more days and get an impression of the area and search for possible sites for our seismographs. Hence, my second PI Gela and me left Germany 4 days earlier and teemed up with the Argentinian Professor Antonio and his student Ahmad to explore the Candelaria range 150km north of Tucumán.

Unfortunately, March is the end of the monsoon season; we got already surprised when we arrived in Tucumán by a typical convective rainstorm which lasted only 10-15 minutes, but enough time to flood all streets and sidewalks. Also the landscape responded to these weather conditions and I want to explain in this post how everything was affected.

I may should add that in this region you have 500-700 mm of precipitation during the year, but it will mainly happen in the summer monsoon. But due to El Niño this year, it is a lot more rainfall this summer. Read More…