Natural disasters are often not natural disasters, but are in fact human disasters. Discuss this statement in relation to seismic events.
The word ‘natural’ indicates that humans have not caused the disaster. However, human activity can certainly interfere with nature, which in turn may either cause a natural disaster or make its effects much worse. Earthquakes can affect people in many different ways in countries all over the world. They are a product of intense seismic activity where plates are interacting, at a destructive of transform faults, particularly leading to a build up of tension below the Earths surface. When this tension is released the buildings, bridges, pipes etc which lie in the line of the seismic waves can often not withstand the force and strain of the earthquakes and can potentially harm people. However is it the people’s fault that the earthquake occurred in the first place? Earthquakes induced by human activity have been documented in a few locations in the YSA, Japan and Canada.
The cause was injection of fluids into deep wells for waste disposal and secondary recovery of oil, and the use of reservoirs for water supplies. Most of these earthquakes however were minor. The largest and most widely known resulted from fluid injection at the Rocky Mountain Arsenal near Denver, Colorado. For decades scientists have been researching induced seismicity, or how human activity can cause earthquakes. Such a link gained attention in the early 1960s when hundreds of quakes were recorded in Colorado after the Army began injecting fluid into a disposal well. There are many ways human activity can trigger earthquakes. In the 1930s for example, the construction of Hoover Dam in Arizona unleashed a burst of seismic activity in the vicinity that reached a magnitude of 5 on the Richter scale. Geothermal- energy projects have been known to make the ground shake. This process involves pumping pressurised water a mile into the Earth, then sucking up the heated liquid to make steam and drive turbines to generate electricity. A dam cannot cause an earthquake by itself. The risk factors, specifically unstable fault lines, have to be there already.
With the right conditions in place, though, a dam can trigger the event earlier than would have happened naturally, and perhaps even increase its magnitude. ‘Human engineering has been triggering earthquakes for more than half a century’ says Leonardo Seeber, professor at Lamont- Doherty Earth Observatory, and manmade quakes may be more common than acknowledged. However Dr. Seeber says that ‘distinguishing natural from triggered earthquakes is generally difficult’ he said ‘Agents triggering the earthquake often refuse to admit responsibility and make it difficult to obtain the data that could prove it’. Even a smell stress increase can cause a fault to fail, Dr Seeber said: humans tend to do it in two ways. One is by changing the load on the crust, typically with artificial lakes, which increase the load, and with quarries and oil fields, which decrease the load. The other ways is increasing the pressure of the interstitial fluid.
This isn’t to say that all earthquakes are caused by humans. They are typically natural occurrences. They’re most often caused by the shifting of plates of rock under the surface od the earth. These plates move along fault lines, which are places where the otherwise solid rock of Earth’s crust has cracked. When the plates slide against each other, or away from each other, the Earth vibrates violently. Less often, earthquakes are caused by natural occurrences like volcanic eruptions. But vibrations felt at the surface of the Earth can also result from Earth-shaking, manmade events like underground bomb testing and mine collapses. In conclusion, my view is for the most part, the accumulating stress that creates the stress build up until it’s great enough to overcome that friction, at which point seismic energy is released violently as the blocks catch up on decade’s worth of motion in just a few seconds is much too large for human activities to make a difference.
We can, however, affect the friction that locks up the fault. Hydraulic fracturing, where fluids are pumped into the ground at extremely high pressures to crack rocks that release natural gas and oil, has been shown to do just that in certain situations. Increasing the fluid pressure inside the fault partially de-stabilises the friction-lock, lowering the stress threshold necessary to trigger an earthquake just enough for one to occur. Despite the obvious negative effects that humans have on prematurely causing an earthquake, the natural factors of the earthquake are fundamentally the reason they occur because without these then the earthquake wouldn’t happen. Human impacts speed up and may make the earthquake worse however they are in fact natural disasters with human elements thrown into the equation.