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1: School children cause Earthquake in Canberra, Australia.
2: Induced seismicity as a result of water filling large dams.
3: Reservoir induced seismicity in Australia.
4: Eartquake activity as a result of Oil and Gas extraction.
5: Induced seismicity due to Deep injection of fluid.
6: Mining and Quarrying Induced Seismicity.
7: Seismicity Induced by Nuclear Explosions.
Kids-induced earthquake at Parliament House. Canberra, Australia.
Scientists were in the right place at the right time today, witnessing a rare and unusual type of earthquake, estimated to occur in Australia only once per year at the most.
The epicentre is believed to be located on the lawn in front of Parliament House in Canberra, close to Canberra's well-known Deakin Fault.
Seismologists at Geoscience Australia say that this particular seismic event has a unique and unmistakable signature, which indicates that this earthquake is related to the exuberant jumping of some 200 young children.
Smaller aftershocks of the group's natural ebullience were also detected soon after the initial event, when the children began heading off to their tours of Parliament House. (Wednesday, 16 October 2002)
The children seemed to spontaneously congregate and jump for joy in celebration of international Earth Science Week, which started on Sunday this week and continues until October 19.
Preliminary estimates of the local magnitude are being calculated by seismologists at Geoscience Australia.
Source: http://www.ga.gov.au/about-us/news-media/media/releases/2002/16_Oct_2002_kidsquake.jsp
Seismic activity due
water filling large dams.
" Induced seismicity,
or seismic activity caused directly by human
involvement, has been recorded as a result of
water filling large dams, development
of mineral, geothermal and hydrocarbon
resources, waste injection, underground nuclear
explosions and large-scale construction projects.
That human activity can provoke
earthquakes is not a new discovery. Proposals
for impounding water in man-made lakes across
regions of southern California, USA, in the 1870s, were
rejected because of concerns that this might trigger
earthquakes.
The hundreds of small earthquakes
detected immediately after the 1936
filling of the Hoover Dam in Nevada and Arizona,
USA, provided the first definite evidence of such
an effect. Since then, more than 100 other cases
have been reported around the world.
In some
instances, the resulting seismic activity has been
severe.
Within four years of completing construction
in 1963, the reservoir area surrounding the
Koyna Dam near the west coast of India experienced
several significant earthquakes, the
largest being a major event of magnitude 7.0.
In
the nearby town of Koynanagar, masonry buildings
were destroyed and 200 people died. (1) "
Zipingpu dam in China.
An earthquake with a magnitude of 7.9 , that killed at least 80,000 people in Sichuan
in 2008 may have been triggered by an enormous dam just miles from the epicentre.
The 511ft-high Zipingpu dam holds 315 million tonnes of water and lies
just 550 yards from the fault line, and three miles from the epicentre,
of the Sichuan earthquake.
Scientists in China and the United States believe the weight of water,
and the effect of it penetrating into the rock, could have affected the pressure
on the fault line underneath, possibly unleashing a chain of ruptures that led to the quake.
Fan Xiao, the chief engineer of the Sichuan Geology and Mineral Bureau in Chengdu,
said it was "very likely" that the construction and filling of the reservoir in 2004 had led to the disaster.
Lei Xinglin, of the China Earthquake Administration, said that the Zipingpu reservoir
"clearly affected the local seismicity and it is worthwhile to study the role it played
in triggering the earthquake further".
Source: The Telegraph February 3, 2009
http://www.telegraph.co.uk/news/worldnews/asia/china/4434400/
Chinese-earthquake-may-have-been-man-made-say-scientists.html
RESERVOIR INDUCED SEISMICITY IN AUSTRALIA
Large new reservoirs can trigger earthquakes.
This is due to either a change in stress
because of the weight of water, or more commonly due to weakening of fractures and
faults under the reservoir by increased water pore pressure.
The energy released in a
reservoir induced earthquake is normal tectonic strain energy, released prematurely.
Reservoirs that have experienced reservoir induced seismicity.
Eucumbene Reservoir
The Eucumbene Reservoir began filling in 1958, with a capacity of 4.8 km3 and height of
116 m. An earthquake of magnitude ML 5.0 occurred about 10 kilometres south of the
dam on 1959 May 18.
Over 270 events occurred between Eucumbene Reservoir and
Jindabyne Reservoir over the next 40 years.
Warragamba Dam
The Warragamba Dam was completed in 1960, with a capacity of 2.06 km3 and height of
137 m. The dam is about 3 km west of the Lapstone Fault outcrop, and the reservoir
extends to about 30 km further west.
This is probably a reverse fault, dipping to the
west under the reservoir at about 35°.
On 1973 March 9, an earthquake of magnitude
ML 5.5 occurred at the south end of the reservoir, about 18 km west of the Lapstone
Fault at a poorly constrained depth possibly about 12 km. It was followed by over 300
aftershocks.
Talbingo Dam
The Talbingo Dam was completed in 1971 with a capacity of 0.92 km3 and depth of 162 m.
Over 200 small shallow events occurred under the reservoir over the next four years, the
largest of magnitude ML 3.5 in 1973.
Many of these were felt or heard in the town.
This is regarded as a classic example of a swarm of shallow induced earthquakes.
Lake Argyle
Lake Argyle in the north of Western Australia was completed in 1971. It has a capacity
of 5.72 km3 and a depth of 99 m.
To 1984, about 30 events occurred under or near the
reservoir from about ML 2.0 to ML 3.5, well above the activity of the surrounding area.
Seismograph coverage is poor, both before and since impounding. A seismograph
installed nearby from 1995 to 1996 recorded several small events under the reservoir.
Lake Gordon
Lake Gordon in Tasmania began filling in 1972.
This reservoir and Lake Pedder are
connected by a short canal, and have a total capacity of 13.5 km3 with a maximum
depth of 140 m at Gordon Dam.
A three to four-fold increase in earthquake activity
under the two lakes was detected from July 1974. The increased level of activity ended
about 1984 after some 120 events, the largest being only of magnitude ML 2.5.
Thomson Reservoir
The Thomson Reservoir began filling in July 1983, with a capacity of 1.1 km3 and depth of
166 m.
It is about 25 km northwest of the outcrop of the Yallourn Fault. A swarm of
very small events occurred at a depth of 11 km under the reservoir in November 1983.
There was no significant activity until February 1986, when a series of events began
under the reservoir at depths to about 3 km. For the next couple of years there were
about 2 to 5 events per week up to ML 2.5.
Activity from 1988 to 1996 spread away
from the reservoir, north, south and deeper, with maximum magnitude of ML 3.1, and at
a decreasing rate.
An earthquake of ML 5.0 occurred on the Yallourn Fault on 1996
September 25, with epicentre about 2 km from the dam, at a depth of 11 km, and at the
nearest slant distance from the reservoir to the fault.
Pindari Dam
Thw Pindari Dam in northeast NSW was built in 1969, doubled in height to 85 m in 1994,
and began to re-fill in early 1995.
In March 1995, a swarm of over 30 very shallow
earthquakes occurred under the reservoir. The largest was of magnitude ML 2.3 on
March 27, within 3 km of the seismograph at the dam, giving a peak acceleration of
0.09 g. None of these events was reported felt. Further activity occurred in the Pindari
area over the next two years.
Source: EARTHQUAKES AND DAMS IN AUSTRALIA
Gary Gibson
Seismology Research Centre, RMIT, Melbourne, Ausralia
Eartquakes due to Oil and Gas extraction.
Seismicity has also been associated
with production of oil, gas and geothermal energy. Extracting fluids can cause faults
which previously had been slipping aseismically to lock up for periods of time before
slipping seismically. Fluid extraction can also lead to compaction and underground
subsidence which can result in seismicity.
Some seismologists believe the three 7.0 magnitude Gazli, Uzbekistan (1976 & 1980)
earthquakes were also induced by gas extraction.
If this is true, these would be not
only the most damaging production-induced quakes known, but the largest magnitude
induced quakes of any kind.
In the early 1920s, geologists in south Texas
noted faulting, subsidence and earthquakes in
the vicinity of the Goose Creek oil field.
Houses
shook and faulting broke the earth’s surface.
A
direct relationship was proposed between oil
extraction and the onset of subsidence and seismic
activity.
At the time, subsidence associated
with hydrocarbon extraction was considered
rare, and this case was thought to be a unique
occurrence in geological literature.
Similar observations
were then reported for the Wilmington
oil field in Long Beach, California, USA, where six
small earthquakes occurred between 1947 and
1955, and surface subsidence reached 9 m [30 ft]
in 1966 after 30 years of oil production.(1)
The situation in regions of hydrocarbon recovery
is not always well understood: in some places,
extraction of fluid induces seismicity; in others,
injection induces seismicity.
In many areas where
the rock is not under large tectonic stresses, the
seismic energy released during induced events is
low—typically of magnitude 0 to 3 and not
even felt on the earth’s surface.
However, if the
rock mass is already under large tectonic
stresses, the energy added by man’s endeavors
can have a destabilizing influence.
Even minor
actions can trigger strong seismicity.
Long-term hydrocarbon exploitation can disturb
conditions around oil and gas reservoirs in
several ways, causing significant stress changes
in the reservoir and the surrounding rocks.
Injected fluid can propagate or filter into cracks
and cause increased fluid pressure in pores
and fractures, serving as a kind of lubricant in
fractured zones. Three types of forces help initiate
filtration-induced earthquakes as well as
other man-made and tectonic earthquakes by
causing motion of rock blocks along faults: First,
poroelastic forces can force displacement along
a fault in the surrounding rock mass. Second,
hydrostatic forces can transfer pore pressure
from an injection zone to a zone preparing for an
earthquake through a fault or other permeable
feature. Fluid migration in this case may be negligible.
Finally, pressure differences can cause
fluids to migrate from injection zones to zones of
earthquake incipience.(2)
Seismic activity
due to deep injection of fluid for waste disposal. (1)
Fluid injection for waste disposal or secondary recovery
of oil or gas can trigger earthquakes. Injecting fluids into deep wells increases
the pore pressure in the rocks in the injection zone and areas communicating with the
zone. This change in pore pressure can decrease the effective normal stress
across pre-existing faults making them more likely to slip, as well as
decrease the actual strength of the rock surfaces making them less resistant to slippage.
By the 1960s, it became clear that deep injection
of fluid could also cause seismicity. Early in
1962, waste-water by-products from the Rocky
Mountain Arsenal near Denver, Colorado, USA,
were injected into a disposal well in fractured
Precambrian rocks at a depth of about 12,000 ft
[3660 m]. Earthquakes up to magnitude 4.3 began
occurring one month later, and continued for the
three-year injection period. The frequency of
earthquake occurrence was clearly related to the
rate and pressure of fluid injection.
Mining and Quarrying
Induced Seismicity.
" Underground mining increases stress on surrounding rock and supporting columns when the
supporting mass is removed. This can cause failure of the columns, walls, ceiling or floor,
movement along pre-existing faults, or sometimes new faulting. Surface mining and
quarrying remove mass from above, decreasing the stress bearing down on lower layers of
rock. These lower layers of rock may then adjust to the change in stress by springing upward.
Up to 25% of all earthquakes recorded by the British Geological
Survey may be related to coal mining (Redmayne) and the Geological Survey of South Africa reports that,
" the bulk of the seismic events recorded by the regional network " are tremors resulting
from deep mining operations in the gold fields of Transvaal and the Orange Free State.
Strong correlations have been found between mining activity and seismicity. Seismicity slows when work
stops for a holiday or a miners' strike and eventually stops when all work on the mine ends.
The number of tremors also varies weekly and diurnally according to the rhythm of the work at the mine.
The frequency and severity of mining-induced seismicity tends to increase with increases in the
rate of extraction from the mine and depth of the mine.24 Many who study seismicity related to mining
believe that mining-induced seismicity and damaging rockbursts are increasing in number and severity
as the easier to reach minerals are mined out worldwide and new technology allows for deeper mines and
faster extraction. "
Source and referenced from: Colorado Law and Induced Seismicity Darlene A. Cypser 1996 (1)
Newcastle Earthquake 1989 - New South Wales, Australia.
The most damaging earthquake in Australia's history was caused by humans, new research says.
The magnitude-5.6 quake that struck Newcastle in New South Wales on December 28, 1989,
killed 13 people, injured 160, and caused 3.5 billion U.S. dollars worth of damage.
That quake was triggered by changes in tectonic forces caused by 200 years of
underground coal mining, according to a study by Christian D. Klose of Columbia University's
Lamont-Doherty Earth Observatory in Palisades, New York.
The removal of millions of tons of coal from the area caused much of the stress that triggered
the Newcastle quake, Klose said.
But even more significant was groundwater pumping needed to keep the mines from flooding.
"For each ton of coal produced, 4.3 times more water was extracted," Klose said.
Source: National Geographic News January 3, 2007 http://news.nationalgeographic.com/
Australian geoscientists deny Newcastle earthquake to coal mining.
Australian geoscientists and mining engineering experts are sceptical about Dr Klose's claims.
Geoscientist Professor Stephen Cox from the Department of Earth & Marine Sciences at the Australian National
University, said Dr Klose had drawn a “very long bow” in linking the earthquake with coal mining in the area.
Prof Cox, who specialises in the geology of mining and earthquakes, said while stress does occur
in the mining process, and can cause small earthquakes, it was unlikely to have occurred in the
Newcastle example.
“The stress change that's induced by mining commonly triggers very small earthquakes, fairly close to mining,
that is within two or three kilometres of mining,” he said.
“But this earthquake occurred at about 12 kilometres depth, and that would be very unusual to have
a mining induced earthquake at 12 kilometres deep.
“The historical records also show that there has been a number of substantial earthquakes in the
Hunter Valley of magnitudes up to four or five, going back two hundred years, and some predating mining.
“My gut feeling is that it is drawing a very long bow to say that the mining has induced the earthquake.
It may have, but it is unlikely.”
Bruce Hebblewhite, Professor of Mining Engineering at the University of NSW, labelled Dr Klose's
findings as “far-fetched”.
But he moderated his criticism, saying he had yet to read the original report.
“It sounds somewhat far fetched,” Prof Hebblewhite said.
“There is no doubt that any excavation in rock causes adjustments in stresses and adjustments in
structural geology.
We refer to it as mining-induced seismicity, which can cause very low level seismic activity, but we're not talking anywhere near the league of earthquakes.”
Professor Robert Melchers from Newcastle University, who sat on a taskforce set up by the state
government to investigate the earthquake and its aftermath, questioned the absolutism of Dr Klose claims.
“I think the problem I would have with the article as written is that it makes the claim that there is a definite link,” Prof Melchers, a professor of civil engineering, said.
“I would say it is one of many possible reasons why this could have occurred, but to say that this is definitely the cause or the triggering event is just a little far fetched.
“You can't make that conclusion at all.”
Source: The Australian January 09, 2007 http://www.theaustralian.news.com.au/
Seismicity Induced by Nuclear Explosions. (1)
Nuclear explosions at the Nevada test site and under Amchitka Island, Alaska have been followed
by large numbers of small earthquakes beginning just after detonation and continuing for some weeks.
Some tremors are located close to the shot chamber and are primarily due to the collapse of the underground
cavity created by the nuclear explosion. Other small earthquakes have been observed up to 10 km (6 miles) away.
These quakes may have been triggered by changes in stress caused by the opening of the cavity, changes in
pore pressure caused by a pressure wave created by the explosion, or other stress changes generated by
the explosion
In the late 1960's several large nuclear explosions at the Nevada Test site resulted in observable
displacements on nearby faults and numerous earthquakes. People became concerned that such an explosion
could trigger a large earthquake which would release as much seismic energy as the explosion itself or even more.
Source and Reference:
Seismicity in the Oil Field Vitaly V. Adushkin
Vladimir N. Rodionov
Sergey Turuntaev
Institute of Dynamics of Geospheres,
Russian Academy of Sciences
Moscow, Russia
Source: The Telegraph February 3, 2009
http://www.telegraph.co.uk/news/worldnews/asia/china/4434400/
Chinese-earthquake-may-have-been-man-made-say-scientists.html
Source: http://www.ga.gov.au/about-us/news-media/media/releases/2002/16_Oct_2002_kidsquake.jsp
Title Image Source:Seismicity in the Oil Field Institute of Dynamics of Geospheres,
Russian Academy of Sciences
Moscow, Russia
Source: National Geographic News January 3, 2007 http://news.nationalgeographic.com/
(1) Article source:Colorado Law and Induced Seismicity Darlene A. Cypser
http://www.darlenecypser.com/induceq/ColoradoLawandInducedSeismicity.html
(2) Seismicity in the Oil Field Institute of Dynamics of Geospheres,
Russian Academy of Sciences
Moscow, Russia.
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