Man made earthquakes.

sjastro

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An article appeared in Science magazine speculating the 2008 magnitude 8 Sichuan earthquake in China that killed over 68,000 people may have been caused by the filling of the Zipingpu dam.
While there is no general consensus on this claim there seems to be little doubt the 1967 magnitude 6.5 Koynanagar earthquake in India that killed over 1500 people was caused by the filling of the Koyna dam.

The mechanism is explained as follows.
earthquake1.jpg

Water behind the dam is pressing down on and infiltrating the rock underneath.
The weight of the water (small) arrows combined with seepage into fractures effectively lubricates the fractures and reduces the basement rocks frictional strength.
This induces slippage (large arrow) along the fault.

On a smaller scale the US army's Rocky Mountain arsenal near Denver Colorado was considered to be in a geologically stable region until the early 1960s.
Then for no apparent reason from 1962-1965 there were over 1000 earthquakes some of which were as high as magnitude 4.6.
An investigation revealed the arsenal generated large amount of liquid toxic waste.
To dispose of this contaminated water the army drilled a well five and a half inches in diameter and over 2 miles deep.
In March 1962 they started pumping the effluent into the well under pressure and at a rate of 300 gallons per minute.
After a month the tremors began; when pumping ceased in 1966 so did the earthquakes.

earthquake2.jpg
 

Aaron_Bethlhm

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When earthquakes increase, there will be a larger number of them.

*like the weather: we are predicting clouds in some places, and wind is possible. Sunshine also will happen in some places , during the day, and as evening passes into night, more darkness is expected.

:)
 
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keith99

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There is a huge difference between triggerd and caused!

The cause in all the cases presented wound be unballanced tactonic stress. The quakes coiuld have very well been triggered by the manmade events given. BUT that triggering would mean that the stress was released earlier and almost surely in a less devastating event or series of events.

That is especially the case in the Fracking in Oklahoma.
 
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Occams Barber

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An article appeared in Science magazine speculating the 2008 magnitude 8 Sichuan earthquake in China that killed over 68,000 people may have been caused by the filling of the Zipingpu dam.
While there is no general consensus on this claim there seems to be little doubt the 1967 magnitude 6.5 Koynanagar earthquake in India that killed over 1500 people was caused by the filling of the Koyna dam.

The mechanism is explained as follows.
earthquake1.jpg

Water behind the dam is pressing down on and infiltrating the rock underneath.
The weight of the water (small) arrows combined with seepage into fractures effectively lubricates the fractures and reduces the basement rocks frictional strength.
This induces slippage (large arrow) along the fault.

On a smaller scale the US army's Rocky Mountain arsenal near Denver Colorado was considered to be in a geologically stable region until the early 1960s.
Then for no apparent reason from 1962-1965 there were over 1000 earthquakes some of which were as high as magnitude 4.6.
An investigation revealed the arsenal generated large amount of liquid toxic waste.
To dispose of this contaminated water the army drilled a well five and a half inches in diameter and over 2 miles deep.
In March 1962 they started pumping the effluent into the well under pressure and at a rate of 300 gallons per minute.
After a month the tremors began; when pumping ceased in 1966 so did the earthquakes.

earthquake2.jpg

This article from the Seismology Research Centre explains things in a little more detail.
Dams & Earthquakes – Seismology Research Centre (src.com.au)

@keith99 has it right. Dams are usually constructed to enclose reservoirs in valleys. Valleys are typically the product of tectonic activity so are naturally prone to earthquakes. Quakes are usually triggered as a result of the filling process. There can be long term effects as the water seeps down to deeper levels.

Basically dams/reservoirs can activate an existing potential for quakes.

OB
Dams & Earthquakes – Seismology Research Centre (src.com.au)
 
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sjastro

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The quakes coiuld have very well been triggered by the manmade events given. BUT that triggering would mean that the stress was released earlier and almost surely in a less devastating event or series of events.
This is one of the myths about earthquakes that smaller magnitude earthquakes release enough stress to prevent a larger more devastating earthquake.
It was this form of reasoning that got one of the scientists charged with involuntary manslaughter over the L'Aqulia earthquake as described in this post.
He assured the locals they were reasonably safe as the large number of small tremors in the region had released enough energy to make a major quake highly unlikely which history has shown was a serious error.

The magnitude of an earthquake is on a logarithmic scale and the energy released for every unit increase in magnitude increases by a factor of 30.
Hence it would take a 1000 earthquakes of magnitude 4 to release all the energy of a single magnitude 6 earthquake.
 
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sjastro

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This article from the Seismology Research Centre explains things in a little more detail.
Dams & Earthquakes – Seismology Research Centre (src.com.au)

@keith99 has it right. Dams are usually constructed to enclose reservoirs in valleys. Valleys are typically the product of tectonic activity so are naturally prone to earthquakes. Quakes are usually triggered as a result of the filling process. There can be long term effects as the water seeps down to deeper levels.

Basically dams/reservoirs can activate an existing potential for quakes.

OB
Dams & Earthquakes – Seismology Research Centre (src.com.au)
There is no disagreement here; human involvement changes earthquake frequency or earthquakes occur sooner than later.
The human induced earthquake database (HiQuake) based on 1196 events gives the following breakdown for causes.
quakes.jpg
 
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stevevw

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An article appeared in Science magazine speculating the 2008 magnitude 8 Sichuan earthquake in China that killed over 68,000 people may have been caused by the filling of the Zipingpu dam.
While there is no general consensus on this claim there seems to be little doubt the 1967 magnitude 6.5 Koynanagar earthquake in India that killed over 1500 people was caused by the filling of the Koyna dam.

The mechanism is explained as follows.
earthquake1.jpg

Water behind the dam is pressing down on and infiltrating the rock underneath.
The weight of the water (small) arrows combined with seepage into fractures effectively lubricates the fractures and reduces the basement rocks frictional strength.
This induces slippage (large arrow) along the fault.

On a smaller scale the US army's Rocky Mountain arsenal near Denver Colorado was considered to be in a geologically stable region until the early 1960s.
Then for no apparent reason from 1962-1965 there were over 1000 earthquakes some of which were as high as magnitude 4.6.
An investigation revealed the arsenal generated large amount of liquid toxic waste.
To dispose of this contaminated water the army drilled a well five and a half inches in diameter and over 2 miles deep.
In March 1962 they started pumping the effluent into the well under pressure and at a rate of 300 gallons per minute.
After a month the tremors began; when pumping ceased in 1966 so did the earthquakes.

earthquake2.jpg
The eqation is simple. Take the earth crust at an average of 15 kilometres thick and drill, mine and frack the life out of it and your bound to destablize it.

How Humans Are Causing Deadly Earthquakes
 
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Ophiolite

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Take the earth crust at an average of 15 kilometres thick
Slightly misleading since that is an average of two radically different crustal types, oceanic versus continental.

Oceanic crust: 5km - 10 km
Continental: 30km - 50 km

Since all of the mining and practically all of the drilling take place in the continental crust, the 30-50 km would be the more meaningful numbers to use. It doesn't alter your argument, but your 15 km was just to simplified for this geologist to remain silent over.
 
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stevevw

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Slightly misleading since that is an average of two radically different crustal types, oceanic versus continental.

Oceanic crust: 5km - 10 km
Continental: 30km - 50 km

Since all of the mining and practically all of the drilling take place in the continental crust, the 30-50 km would be the more meaningful numbers to use. It doesn't alter your argument, but your 15 km was just to simplified for this geologist to remain silent over.
Ok fair enough. I was just going by a quick google search on the thickness of the earths crust which gave this reference.

The average thickness of the crust is about 15 km (10 mi) to 20 km (10 mi).
Earth's crust - Wikipedia.

But that may not be a good measure.
 
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Ophiolite

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Ok fair enough. I was just going by a quick google search on the thickness of the earths crust which gave this reference.

The average thickness of the crust is about 15 km (10 mi) to 20 km (10 mi).
Earth's crust - Wikipedia.

But that may not be a good measure.
As I said, it's not a problem for the point you are making, but from the broader geological perspective it is misleading. The distribution of crustal thicknesses is bimodal because of the distinct differences between continental and oceanic crust.

Oceanic crust is comparatively thin and very simply organised (superficial sediments/basaltic pillow lavas and sheeted dykes overlying layered basic and ultrabasic rocks). It forms at mid-ocean ridges and is consumed at subduction zones (or occasionally thrust onto continental margins where they form ophiolite complexes). No oceanic crust has been found older than 200 million years.

In contrast continental crust is thick and very complex (Stable cratons of intensely folded and deformed metamorphic rock, sometimes overlain by thick near horizontal sedimentary deposits and unstable orogenic zones with extensive mixtures of sedimentary, igneous and metamorphic rocks.) Continental crust forms from igneous activity based upon partial melting of upper mantle and of descending slabs of oceanic crust. Some continental crust dates back to almost 4 billion years (and individual crystals to almost 4.4 bya)
 
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stevevw

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As I said, it's not a problem for the point you are making, but from the broader geological perspective it is misleading. The distribution of crustal thicknesses is bimodal because of the distinct differences between continental and oceanic crust.

Oceanic crust is comparatively thin and very simply organised (superficial sediments/basaltic pillow lavas and sheeted dykes overlying layered basic and ultrabasic rocks). It forms at mid-ocean ridges and is consumed at subduction zones (or occasionally thrust onto continental margins where they form ophiolite complexes). No oceanic crust has been found older than 200 million years.

In contrast continental crust is thick and very complex (Stable cratons of intensely folded and deformed metamorphic rock, sometimes overlain by thick near horizontal sedimentary deposits and unstable orogenic zones with extensive mixtures of sedimentary, igneous and metamorphic rocks.) Continental crust forms from igneous activity based upon partial melting of upper mantle and of descending slabs of oceanic crust. Some continental crust dates back to almost 4 billion years (and individual crystals to almost 4.4 bya)
Very interesting. I found an interesting article in my search where they are trying to drill through the earths crust to the mantle. Though this is an old article so they probably have done that by now. They have discovered that the earths composition is more copmplex than thought and this is changing what we know about the earths evolution.
Hole Drilled to Bottom of Earth's Crust, Breakthrough to Mantle Looms | Live Science
 
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