Volume 5, Issue 1, January - March 2016
CONTENT
- Chair's Foreword
- Human-induced Seismic Activity
- Earth Science Book Review
- Earth Science Events
- References and Selected reading
Chair's Foreword*
In
this
issue we consider the evidence in favour of human-induced seismic activity, which appears to have been growing in recent times.
It has long been known that local earthquakes can be caused by oil and gas extraction activities such as hydraulic fracturing2, which is being seriously considered by some African countries (for instance, South Africa, Algeria and perhaps also Morocco3) who are keen to exploit the resources in their backyard. Certainly, quakes occurring in the southern United states are thought to be related to such activities (among many other examples that may be given around the world).
The Southern Methodist University (SMU) published a peer reviewed study concluding that the pumping of millions of gallons of drilling and fracking wastewater into the earth was “the most likely cause” of minor earth quakes that have peppered the southern United States since 20134. However, the Texas Railroad Commission has published a document rebutting the claim by SMU and stating that oil and gas industry activities are not to blame5 . This report has to be seen in the context of the Railroad Commission’s conflict of interest in being the body charged with promoting the oil and gas industry.
It is worthy of note that the busy seismic activity occurring in the United States since 2013 is occurring within tectonically active regions on the edges of the pacific plate forming the famous “Ring of Fire”. The Ring of Fire, being the area encompassing the Pacific tectonic plate. The “Ring of Fire” is a string of volcanoes occurring along the boundary of the Pacific Plate, along the edges of the Pacific Ocean, where 90% of all the earth’s seismic activity occurs. The Ring of Fire is the result of plate tectonics. Tectonic plates are slabs of the Earth’s crust which sit on a layer of solid and molten rock called the mantle. The plates collide, rub against each other and also move apart. Earthquakes said to be the result of oil and gas activity have been seen to occur in Michigan, Texas, Mississippi, California, Idaho and Washington.
William Elsworth of the US Geological Survey, has published a paper in Science (2013)6 in which he appreciates the importance of the topic of human induced earthquakes, which he says has been a topic of both political and scientific discussion owing to the concerns these events may be responsible for widespread damage, loss of life and overall increase in seismic activity. What is not clear, and what might be regarded as a reason for the ongoing concern is the extent to which an increase in these minor seismic events might contribute to larger scale events.
Human Induced Seismic
Activity: To what extent are human actions to blame for modern earthquake activity?
Global seismic
activity records started in 1900 show that we have exceeded the long-term
average number of major earthquakes per year only 8 times in the past 116
years: in 1976, 1990, 1995, 1999, 2007, 2009, 2010, and 20111. So the average has been exceeded only in the last 40 years. This might suggest an increase in significant earth quakes in recent years. Without choosing to enter into the discussion on wether this seismic activity is on the increase, the current article is merely concerned with the recognition of human
induced seismic activity. It is not known to what extent this might contribute to greater seismic instability. Whilst global warming may form part of an explanation for any apparent
increase in seismicity, we should not discount the possibility that human
intrusions into the earth might also play a role in affecting the frequency of seismic events.
It has long been known that local earthquakes can be caused by oil and gas extraction activities such as hydraulic fracturing2, which is being seriously considered by some African countries (for instance, South Africa, Algeria and perhaps also Morocco3) who are keen to exploit the resources in their backyard. Certainly, quakes occurring in the southern United states are thought to be related to such activities (among many other examples that may be given around the world).
 | ||
| Hydraulic fracturing |
The Southern Methodist University (SMU) published a peer reviewed study concluding that the pumping of millions of gallons of drilling and fracking wastewater into the earth was “the most likely cause” of minor earth quakes that have peppered the southern United States since 20134. However, the Texas Railroad Commission has published a document rebutting the claim by SMU and stating that oil and gas industry activities are not to blame5 . This report has to be seen in the context of the Railroad Commission’s conflict of interest in being the body charged with promoting the oil and gas industry.
It is worthy of note that the busy seismic activity occurring in the United States since 2013 is occurring within tectonically active regions on the edges of the pacific plate forming the famous “Ring of Fire”. The Ring of Fire, being the area encompassing the Pacific tectonic plate. The “Ring of Fire” is a string of volcanoes occurring along the boundary of the Pacific Plate, along the edges of the Pacific Ocean, where 90% of all the earth’s seismic activity occurs. The Ring of Fire is the result of plate tectonics. Tectonic plates are slabs of the Earth’s crust which sit on a layer of solid and molten rock called the mantle. The plates collide, rub against each other and also move apart. Earthquakes said to be the result of oil and gas activity have been seen to occur in Michigan, Texas, Mississippi, California, Idaho and Washington.
William Elsworth of the US Geological Survey, has published a paper in Science (2013)6 in which he appreciates the importance of the topic of human induced earthquakes, which he says has been a topic of both political and scientific discussion owing to the concerns these events may be responsible for widespread damage, loss of life and overall increase in seismic activity. What is not clear, and what might be regarded as a reason for the ongoing concern is the extent to which an increase in these minor seismic events might contribute to larger scale events.
In his outlook, Elsworth considers
that injection induced earthquakes, like those concerned with hydraulic
fracturing clearly contribute to seismic hazard. Also, as he points out, the
oil and gas industry is surely in need of the guidance of operational requirements for safety
that have a solid scientific basis. Current regulatory frameworks in the US and
industrialised nations provide for the protection of groundwater against
contamination; but make no provision for actual seismic safety. Of course, the
great fear of introduction of fracking in Africa is the expectation that
even regulations designed to prevent
contamination of precious groundwater resources, will be flouted by
companies who have failed to be environmentally responsible in
their past African engagements. The fear is that even less
attention would be paid to the possibility of oil and gas extraction inducing seismic
instability in Africa, by companies (like Shell, for instance) with records of environmental recklessness.
In the mechanics of human induced
earth quakes, Ellsworth notes that earthquakes release stored up elastic strain energy when a fault
( a line of breakage between two tectonic plates)slips. The movement of the
fault (in tension under elastic strain energy) remains locked as long as the
applied shear stress is less than the strength of the contact. The failure
condition or threshold to initiate a rupture is expressed mathematically in
terms of the effective stress
Tau(crit) = mu (sigma(n) – P) + Tau(0)
................................(1)
Where Tau(crit)
= critical stress or effective stress; mu
= coefficient of friction; Sigma(n) =
applied normal stress; P = pore
pressure (water pressure). For most rocks, we have 0.6 < mu < 1.0, and the cohesive strength of the sliding
surface, Tau(0), is negligible under typical conditions within the Earth’s
crust. Any changes in these factors, including an increase in shear stress,
and/or raising the pore pressure can make the fault slip and fail, triggering
the start of an earthquake.
Rocks fail in tension when the
pore pressure exceeds the sum of the
least principal stress (sigma(3)). The industrial process of hydraulic
fracturing commonly involves both tensile and shear failure. Depending on local
stress states, hydraulically conducive fractures may be induced to fail in
shear before we reach the critical condition at failure
P = sigma(3)
..............................................(2)
Although it is not yet possible to
discriminate between man-made and natural tectonic earthquakes, earthquakes are
known to be induced by a wide variety of human activities that modify the
stress and/or pore pressure.
As well as human activity it has
been noticed by researchers that
rainwater may also play a role in triggering earthquakes, since altering
groundwater levels also can alter the pore pressure enough to trigger a failure
or slippage of a fault.
Dr Catriona Menzies of the
University of Southampton, Ocean and Earth Sciences department notes that:
“Large, continental-scale faults can cause catastrophic earthquakes, but the
trigger mechanisms are not well known.
Geologists have long suspected that deep ground waters may be important
for the initiation of earthquakes as these fluids can weaken the fault zones by
increasing pressures or through chemical reactions.
“Fluids are important in
controlling the evolution of faults between earthquake ruptures. Chemical
reactions may alter the strength and permeability of the rocks.”7
EARTH SCIENCE BOOK REVIEW
Gaia’s Body: Toward a Physiology
of Earth8
by
Tyler Volk
James Lovelock's Gaia Hypothesis or
theory has potentially revolutionised the earth sciences. Instead of seeing the
earth as an inanimate rock inhabited by
organisms, Gaia theory sees the organic and the inorganic working together
synergistically in a self-regulating system
in which organisms interact with their
inorganic surroundings to perpetuate the
survival of life on our planet.
Lovelock named this global
earth-system, Gaia, after the ancient Greek earth goddess. (Of course, there are
numerous African examples of earth godesses:
Ala (Igbo, eastern Nigeria); Asase Yaa (asante, Ghana); etc. denoting that the fundament of a Gaian conception of earth is already universally embedded in the belief systems and traditions of peoples all over the world ).
In Gaia theory, the earth is seen
as a singular living being, that
regulates itself to sustain the survival of its organisms as a whole (or the
balance between its organic and inorganic environment), it is natural to think
in globalistic terms about the health and wellbeing of our planet. Geophysiology,
is the study of the “physiology of the earth”, with interactions between living
organisms and their inorganic environment as if the earth were a single living
organism.
The foregoing describes the subject matter that Tyler Volk approaches in his work on geophysiology. Geophysiology, is a
logical progression from Gaia theory. Tyler Volk introduces the reader to this
emerging new science, explaining how all the major chemicals of the earth
are regulated by living processes, the interaction that takes place between
organisms and their environment. In an attractive and easily readable style of prose, Volk shows how complex cycles and material
transformations are driven by biological energy.
EARTH
SCIENCE EVENTS
Earth
Science Events
19-21 May
2016
International
Conference on Applied Geology & Environment
Venue: Mahdia,
Tunisia
VISION: Tunisian
association of applied geology has aimed since its creation, to continuously
hold
bi-annual meetings. Challenges arising from the implications of
economic development, progressive developments of all sectors are
threatening the whole ecosystem.
In this international conference on applied geology and the environment (iCAGE2016), we are going to deal with the Earth sciences, including the pressing naturally occurring problems and preservation of its natural resources. Our expectations are to bring together the experts and young researchers from all over the world to discuss the recent developments in fundamental and applied geology and to promote exchange of ideas in various applications of natural resources.
In this international conference on applied geology and the environment (iCAGE2016), we are going to deal with the Earth sciences, including the pressing naturally occurring problems and preservation of its natural resources. Our expectations are to bring together the experts and young researchers from all over the world to discuss the recent developments in fundamental and applied geology and to promote exchange of ideas in various applications of natural resources.
23-25 May
2016
International
Association of Sedimentology Meeting of Sedimentology
Venue: Marrakech,
Morocco
VISION: IAS
meeting and the Ibn Battuta Centre in collaboration with Cadi Ayyad University host international
meeting on sedimentology.
15-17
August 2016
International
Conference on Alternative and Renewable Energy Quest
Venue: Cairo,
Egypt
VISION: International
conference organised by IEREK. Promotional material includes the following:-
"The
world has a critical necessity to search for alternative and renewable
energy and the importance of its technologies have been growing
significantly.
For several important reasons, this is extremely important for the future of our society:
- Renewable energy still has a long way to go in order to replace fossil fuels and become a primary source of energy consumption but things have been lately definitely moving in the right direction.
- It would significantly decrease the current levels of greenhouse gas emissions, and this would have positive environmental impact for our entire planet.
IEREK
seeks to promote and disseminate knowledge of the various topics and
technologies of renewable and alternative energy resources through
organizing the international conference."
27 August
– 4 September 2016
International
Geological Congress
Venue: Cape
Town, South Africa
VISION: The
Council for Geosciences together with the Geological Society of South Africa
and other collaborators from academia and industry, currently lead the
preparations for the 35th IGC in South Africa.
1-7
October 2016
8th
Conference of the African Association of Women in the Geosciences
Venue:
Sibiu, Romania
VISION: The African Association
of Women in Geosciences (AAWG) is supporting the development of Earth
Scientists in Africa by providing opportunities for networking and promoting
the application of geosciences for sustainable development. To meet these
challenges, AAWG is organizing numerous activities in and out of the African
continent. Biannual International Conferences are being organized to address
various challenges that the African continent is facing and to which Earth
Sciences could make a contribution. In order to strengthen the collaboration
between our African and non-African members and also to increase the visibility
of the Association, the 8th AAWG Conference is being organized for the first
time out of the African continent. To meet these objectives, we choose as a
title for the 8th conference "Building bridges between Earth Scientists
Worldwide: A Way for Promoting Peace and Strengthening Integration". This
conference is organized locally by the Geological Society of Romania and is
hosted by Astra National Museum Complex, Sibiu.
31
October – 6 November 2016
African
Rift Geothermal Conference (ARGeo)
Venue: Asmara,
Eritrea
VISION: Sixth
Africa Rift Geothermal Conference in collaboration with United Nations
Environment Programme (UNEP) and other support partners…
2-4
December 2016
International
Conference on Improving Sustainability Concept in Developing Countries
Venue: Conrad
Cairo Hotel, Cairo, Egypt
VISION: International
conference…
References and Selected Reading
- Ellsworth, W., Injection-induced earthquakes, Science (341), 2013
- Hydraulic fracturing or "fracking" involves pumping millions of gallons of heated water mixed with rock and debris under pressure into the earth in order to force the release of natural (shale) gas. http://www.bloomberg.com/news/2012-09-07/south-africa-allows-exploration-of-shale-gas-resources.html
- Hornbach, M.J., et al. Causal factors for seismicity near Azle, Texas, Nature Communications 6, Article number: 6728; doi:10.1038/ncomms7728 (Southern Methodist University).
- https://stateimpact.npr.org/texas/2015/09/02/texas-railroad-commission-refutes-study-linking-quakes-to-oil-and-gas-industry/
- Ellsworth, W., Ibid.
- Catriona Menzie et al. The fluid budget of a continental plate boundary fault: Quantification from the Alpine Fault, New Zealand. Earth and Planetary Science Letters, April 2016 DOI: 10.1016/j.epsl.2016.03.046
- Volk, T., Gaia's Body: Toward a Phsiology of Earth, MIT Press, 2003.
- Jordan, et al (eds), Land & Power: Sustainable agriculture and African Americans - A collection of essays from the 2007 Black environmental thought conference. Sustainable Agriculture Research and Education (SARE), 2007.
- Gupta, S.K., Modern Hydrology and Sustainable Water Development, Wiley-Blackwell, West Sussex, 2011.
- A link on “Groundwater and Rural Water Supply in Africa”: http://www.iah.org/downloads/occpub/IAH_ruralwater.pdf
- Link to Journal of African Earth Sciences: http://www.journals.elsevier.com/journal-of-african-earth-sciences/
*Board of
the Society of African Earth Scientists: Dr Chukwunyere Kamalu (Chair -
Nigeria), Osmin Callis (Secretary - Guyana/Nigeria), Ndivhuwo Cecilia Mukosi
(South Africa), Mathada Humphrey (South Africa), Dr Enas Ahmed (Egypt).
