Lesson 08: Earthquakes in My Area





There were not any earthquakes extremely close to Rexburg, but there were a couple that were fairly close. Both earthquake hypocenters were fairly shallow, between 0-33 km deep. The first earthquake is to the northeast of Rexburg. This was east of West Yellowstone Montana, in Yellowstone National Park. This one did not surprise me at all because it is right near a hotspot where there is a lot of tectonic and seismic activity. 

The second earthquake that is pictured south of Rexburg was near Soda Springs Idaho. I honestly was surprised to see this one. I cannot think of any obvious reason why an earthquake would have occurred there. It is not very close to the hotspot, or a plate boundary which are places where earthquakes are frequent. However, the textbook said that an intraplate earthquake like this one could be caused by internal stress buildup due to the interaction of neighboring plates. 

Overall, I feel as safe as I did before starting this assignment. Other areas such as California, Oklahoma, Chile, and Japan experience a lot more frequent earthquakes. As far as earthquakes goes, Rexburg seems to be relatively safe. 

On another interesting note, 40 years ago yesterday, the Teton Dam, a short drive north of Rexburg, burst. Partially, this was due to where they decided to construct it. Not only were the underlying rocks (basalt and rhyolite) considered unfit to build a dam on because of their high permeability, the area was also seismically active. A US Geologic Survey was done on the area, and within the past five years, five earthquakes had occurred within 30 miles of the site. Two of those were of significant magnitude. Anyways, the builders basically ignored this information and built it anyways and before it was even completely filled, it failed. Not very many people died, but the property damage was extensive. These pictures show the dam before and after it failed. Long story short, the seismic history of an area is important! 



Images from https://en.wikipedia.org/wiki/Teton_Dam

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