January 31, 2017 Environmental Issues Written by Greentumble
Human causes of earthquakes
From volcanoes, tsunamis, hurricanes, drought,

tornadoes to earthquakes, natural hazards are everywhere. When one thinks about these hazards, they are destructive, unpredictable acts of nature that come without warning.

Many of these these events are caused by natural processes within the atmosphere or within earth’s crust, however, humans can actually influence or induce some natural disasters themselves. One example are earthquakes triggered by our actions [1]

The most common human causes of earthquakes

#1 Hydraulic fracturing (fracking) or injection wells

Hydraulic fracturing is a process used to extract natural gas or other fossil fuels from within the earth. To extract the fossil fuel, workers drill into the crust and inject chemicals in order to disturb and fracture the ground, releasing the natural gas, which is then captured for future use.

However, this can cause earthquakes [2] because the chemicals stay underground and make their way to faults, adding lubrication that may lead to an earthquake [1].

An example of this can be seen in the state of Oklahoma in the United States. As fracking became more frequent in 2011, so did the number of earthquakes. In fact, in 2008 there were only about 12 earthquakes reported. In 2011, this number increased to more than 1,000 earthquakes just in one year [1].

#2 Dams and reservoirs

Dams and reservoirs can be found all over the world. Their main purpose is to store water for future use and generate electricity. Some dams are mega structures that hold large quantities of water. This water is extremely heavy, powerful and contains a massive amount of potential energy concentrated all in one area. Given the right conditions, the power of water can induce an earthquake [1,2].

The 2008 earthquake in Sichuan, China left over 70,000 dead and is believed to have been caused by the construction of the nearby Zipingpu Dam. This dam is located only a third of a mile away from a plate tectonic fault line and geologists believe this added mass of the water caused the fault to slip sooner that it naturally would have [1].

#3 Groundwater extraction

In many places around the world, water can be found underground in soil, cracks and pockets below the surface.  Groundwater extraction, such as a well, is common and safe, however, it can be dangerous if extraction is done at a quicker rate than the underground reservoir can be recharged [3]. In fact, if the water table drops too quickly near a fault, it could cause an earthquake.

For example, in 2011, there was a 5.1 magnitude earthquake in Lorca, Spain that is believed to be caused by excessive groundwater extraction. The epicenter of this earthquake was close to the surface leading scientists to believe it was due to the groundwater extraction nearby [1].

#4 Geothermal power plants

It is also thought that earthquakes can be caused from geothermal power plants. Geothermal power plants make electricity by powering a generator from hot, pressurized water extracted from deep within the crust.

When these plants are near a fault, such as in the Salton Sea, seismic activity has been seen to increase forming numerous small earthquakes [1]. If this happens near a smaller fault, it is alarming to think of this happening in a place with a larger fault.

#5 Construction

It is certainly hard to believe that certain buildings can possibly inflict earthquakes. In Taiwan, the Taipei 101 tower was built in 2002 to be able to withstand earthquakes and typhoons. The building is sitting on soft sedimentary rock and the materials used to fortify this building for withstanding earthquakes are very heavy.

Ironically, geologists believe this building has been causing earthquakes in the area [1,2]. In fact, there was one earthquake at the site during construction, two large earthquakes with their epicenter directly below the building, and two smaller earthquakes in the area [1].

Overall, there are different ways that humans can cause earthquakes and it is important to keep in mind the effect humans can have on the environment. Surprisingly, it has been seen that seismic activity increased due to a sporting event. Although only a magnitude 1 or 2, an earthquake was registered when the crowd was cheering at a Seattle Seahawks game.

The seismometer that registered this earthquake was just a block away, however, even this is a testament to how influential humans are to the environment [1].



[1] http://gizmodo.com/5-ways-humans-can-cause-earthquakes-1480705519
[2] http://www.livescience.com/32932-can-humans-cause-earthquakes.html
[3] https://water.usgs.gov/edu/gwdepletion.html