It takes seismic force to make the ground give up its secrets. Through the years, those searching for oil and gas have used varied methods to send sound energy into the ground and to record the waves reflected by the geological features beneath the surface.

Modern methods include large vibrator trucks and many thousands of surface sensors called geophones, all precisely located to obtain the most useful information with which to explore for hydrocarbons. Today, seismic surveys planned with satellites are yielding clearer, deeper subterranean views at reduced cost.

Often carried out in the remotest parts of the planet, these surveys are almost military in scale and expense; a seismic crew exploring a 500-square-kilometre area can require 400 people with up to 50 small and 15 large vehicles working with up to 600,000 geophones, and carrying out 600 seismic ’shots’ daily.

Seismic surveyor WesternGeco, has been working with ESA for the last three years to integrate satellite data into its working practices. What Earth Observation can provide is a detailed preview of a region’s topography and geology, valuable for assessing areas that will produce the best and worst seismic quality - meaning the sending and receiving of vibration signals - far in advance of commencing the survey.

“Working on the surface, we deliver imaging and structural characterisation of the subsurface, down to 6000 metres or deeper,” says Andreas Laake of WesternGeco. “Technology has moved on since the days of heavy explosives, but the principle remains the same.”

Elastic waves are excited at the surface and propagate through the subsurface, partly transmitting, partly reflecting, and partly scattering. The reflected waves are then detected on the surface by a pre-planned array of geophones. Sophisticated processing of these sensor data creates a three-dimensional picture of the underlying geology of the survey area.

“The modern vibroseis technique has spatial resolution sufficient not just to identify oil and gas reservoirs, but also to show internal details such as their fracture geometry,” Laake adds. “This is vital, because our customers do not make money for the amount of hydrocarbons theoretically in the ground, but what they actually recover.�

“The vibroseis method uses trucks with heavy masses and baseplates that vibrate the ground to provide a far more controlled source,” Laake explains. “Depending on the target, the trucks can be tuned to work across a pre-defined frequency spectrum, providing ‘multicoloured’ views in terms of elastic waves.”

To achieve high-fidelity reservoir characterisation, the surveyors aim to exclude as many variables as possible. Around 80% of acoustic signal distortion comes from propagating through the top 100 metres of ground, with the most problems encountered nearest the surface.

“For satisfactory results, we must achieve very good coupling of both the vibration source and the receivers with the ground,” Laake recounts. “The mechanical energy generated by a vibrator truck is only useful if it gets converted into elastic energy in the ground. And elastic energy coming back out of the ground must be converted into electrical signal in order to be measured, so here we must have good coupling of the geophones with the ground as well.

“Very hard rock has poor coupling with the baseplate, and the returning signal is low-quality because receivers cannot be placed satisfactorily. Coupling cannot take place on uneven ground. And with soft ground, the baseplate may just sink, or the soft ground may just absorb high frequencies at the receiver end to reduce the potential image resolution.

“But, until we started using satellite imagery, we could only guess at the coupling and data quality in advance of an actual survey. Space-derived topographic information is also important because rises or falls in the landscape delay signal arrival time, and if they are not compensated for, they cause blurring of imagery.

“These two variables set the scene for a broad range of information we require. For example, we must know if there is anywhere we can’t go due to steepness and roughness of terrain. Also, we need to know if there are any rivers to cross or infrastructure to avoid such as oil wells or pipelines whose activities may interfere with our signal.”

No single space-borne instrument can supply all the data required. Instead, data from a variety of different satellites are collected and combined within a geographic information system to yield information on accessibility, data quality, and source and receiver coupling.

The process begins with a digital elevation model, available from many sources including space shuttle mapping and ESA’s ERS-tandem mission. This provides topographic and gradient information for logistics and safety planning. Next comes radar imagery - from spacecraft such as Envisat and ERS - to measure surface roughness, forming the basis of a map of coupling potential.

Visible light images provide infrastructure and land use information that help determine accessibility for vehicles and people. Also, surface vegetation detected in this imagery may indicate sediment-buried water channels that weaken signal propagation.

The ground reflects short-wave infrared (SWIR) light immediately, revealing the spectral characteristics of minerals at the surface. SWIR imagery, obtained from hyperspectral satellite sensors, is particularly sensitive to carbonates such as limestone and basalt and occurrences of softer materials such as gypsum or quartzite gravel.

Advancing further into the infrared spectra permits surveyors to peer deeper beneath the surface. Thermal infrared (TIR), or heat radiation from the surface, is a delayed response to incoming solar radiation, coming from the top half-metre of subsurface.

“It is important to characterise this area, as this is where most of that 80% of data distortion comes from,” says Laake. “In particular, TIR is useful for identifying underlying layers of basalt, which radiate strongly in thermal energy, so much so that we can interpret its presence indirectly from well below a half a metre.

“Basalt is a massive reflector, functioning like a shield between the surface and the hydrocarbon reservoirs. We can’t work on surface basalt - the baseplate simply jumps back - but there are optimal design geometries we can use for buried basalt layers using selected angles of incidence for the seismic waves to ensure that not all the signal is reflected and that some goes through.”

WesternGeco has so far used remote sensing data for sites in Algeria and Argentina. “We have started with desert areas because they are a relatively simple case with unchanging landscapes,” Laake concludes. “But, the technology we are developing here can fully apply to other locations.

“What Earth Observation represents for us is a means of carrying out seismic survey feasibility studies prior to defining survey programmes for our clients, and ensuring enhanced data quality for even the most challenging environments.”

UK-based Infoterra and WesternGeco have jointly developed a seismic-quality mapping service as part of an ESA Earth Observation Market Development (EOMD) project. EOMD is a programme aimed at strengthening the European and Canadian capacity to provide geoinformation services based mainly on Earth Observation data, with a particular emphasis on addressing the needs of small value-adding companies.

Original press release: Views from space help oil prospectors see deep underground (ESA)

Japan’s 45th expedition weathers extreme conditions to unlock secrets of the Earth’s ancient past. `It’s (Dome Fuji Station) like a dark empty ice cave.’ FUMIO KIUCHI Expedition team member

SYOWA STATION, Antarctica–There is vast frontier far more formidable than even this remote outpost.

Perched 3,810 meters above sea level, and 1,000 kilometers inland from Syowa Station where the average temperature is 40 degrees warmer, is Dome Fuji Station.

It is the highest facility operating in Antarctica and one of the Earth’s last great frontiers.

Complete article: Frigid Frontier: Locked in ice (Asahi Shimbun)

Research to reduce sheeps’ production of methane - one of the most potent greenhouse gases - received a boost recently with the installation of four new methane chambers at CSIRO Livestock Industries’ facilities in Perth.

Shaped like cubicles, the see-through chambers enable researchers to accurately measure the continuous volume of methane produced by sheep over a 24-hour period.

They have been operating efficiently for more than four months in a trial to measure the response of sheep to products designed to reduce methane gas emissions.

Anti-methanogen project leader, Dr Andre-Denis Wright, says the new chambers are a significant improvement on the previous method of measuring sheep emissions - tanks attached to the animal’s backs - and will complement the cattle respiration chambers at the CSIRO’s facilities in Rockhampton, Queensland.

“The chambers have an open-air system that allows uninterrupted, real-time measurements, making it considerably more accurate and more time and cost efficient,” Dr Wright says.

“The sheep can also see each other and the researchers while in the cubicles, making them less stressed, so they behave naturally and their feed consumption is not affected.”

Designed and developed by CSIRO Livestock Industries, the new chambers will be available for use for other research projects both within and outside CSIRO.

“Given that livestock account for 12 per cent of Australia’s man-made greenhouse gases, it is important that we develop strategies to mitigate methane emissions,” Dr Wright says.

“CSIRO will be addressing this via other projects to examine plant and feed additives, as well as strategies to manipulate methane-producing microbes in the guts of livestock animals.”

Original press release: New methane chambers to help reduce global warming (CSIRO)

Greenhouse gases could cause global temperatures to rise by more than double the maximum warming so far considered likely by the Inter-Governmental Panel on Climate Change (IPCC), according to results from the world’s largest climate prediction experiment, published in the journal Nature this week.

The first results from climateprediction.net, a global experiment using computing time donated by the general public, show that average temperatures could eventually rise by up to 11C - even if carbon dioxide levels in the atmosphere are limited to twice those found before the industrial revolution. Such levels are expected to be reached around the middle of this century unless deep cuts are made in greenhouse gas emissions.

Chief Scientist for climateprediction.net, David Stainforth, from Oxford University said: “Our experiment shows that increased levels of greenhouse gases could have a much greater impact on climate than previously thought.”

Climateprediction.net project coordinator, Dr. David Frame, said: “the possibility of such high responses has profound implications. If the real world response were anywhere near the upper end of our range, even today’s levels of greenhouse gases could already be dangerously high.”

An assessment of the climate response and impacts associated with different greenhouse gas levels is the aim of Stabilisation 2005, next week’s international conference proposed by Tony Blair.

The project, funded by the Natural Environment Research Council, is ongoing and involves more than 95,000 people from 150 countries. Schools, businesses and individuals across the globe can download the free climateprediction.net software which incorporates the Met Office’s climate model and runs in the background when their computers lie idle.

The programme runs through a climate scenario over the course of a few days or weeks, before automatically reporting results back to climate researchers at Oxford University and collaborating institutions worldwide, via the internet.

Participants have simulated over four million model years and donated over 8,000 years of computing time, making climateprediction.net easily the world’s largest climate modelling experiment, comfortably exceeding the processing capacity of the world’s largest supercomputers. This allows the project to explore a wide range of uncertainties, picking up previously unidentified high-impact possibilities.

“Using the technique of distributed computing and the generous support of many thousands of individuals we have been able to carry out an experiment which would otherwise have been impossible,” explained Dr. Andrew Martin of the Oxford e-Science Centre.

Scientists at Oxford are urging more people to become involved. Mr. Stainforth said, “Having found that these extreme responses are a realistic possibility, we need people’s support more than ever to pin down the risk of such strong warming and understand its regional impacts.”

“This ongoing project allows anyone to participate in science that affects us all,” he added.

Professor Bob Spicer of the Open University, has developed extensive web-based educational materials around the project. He said, “Schools can run the software and build the experiment into science, geography and maths lessons with help from our new teaching materials. And everyone can take part in the lively debates on our internet discussion forum that has attracted more than 5,000 people.”

In May the Open University will start a distance-learning course based on the project. Anyone can register and learn even more about simulating and predicting climate change.

Original press release (pdf): Bleak first results from the world�s largest climate change experiment (ClimatePrediction.net)

Other related stories: Alarm at new climate warning (BBC News)

As chair of the G8, the Prime Minister should seek agreement to create a G8-Plus Climate Group to engage the US and major developing countries in action to reduce greenhouse gas emissions, according to a high-level taskforce established by the Institute for Public Policy Research (IPPR), the Centre for American Progress and the Australia Institute.

In its report out tomorrow (Tuesday), the International Climate Change Taskforce concludes such a group would provide a way for G8 countries and other major economies - including India and China - to take action that would lead to large-scale reductions in emissions. The G8-Plus Climate Group would pursue partnerships to achieve immediate deployment of existing low-carbon energy technologies, including agreements to shift agricultural subsidies from food crops to biofuels and promote sales of highly efficient cars.

The report also argues that all G8 countries should set a lead by adopting national targets to generate at least 25 per cent of electricity from renewable energy sources by 2025 and mandatory cap-and-trade schemes for emissions, like the EU scheme. In the US, this could happen through the Climate Stewardship Act, proposed by Republican Senator John McCain and Democratic Senator Joseph Lieberman, and could provide a path for US re-entry into a global climate change agreement after the Kyoto Protocol’s first phase ends in 2012.

The Taskforce also calls on governments to agree to a long-term objective of preventing global temperature from rising by more than 2 C above pre-industrial levels. Other key recommendations include:

• The need for a step-change in financial and technical assistance for developing countries to adapt to climate change.
• The creation of a leadership coalition of countries to move ahead with reforms to boost investment in climate-friendly energy technologies worldwide.

Rt Hon Stephen Byers MP, co-chair of the Taskforce with US Republican Senator Olympia Snowe, said:

“Our planet is at risk. With climate change, there is an ecological time-bomb ticking away, and people are becoming increasingly concerned by the changes and extreme weather events they are already seeing. Urgent action is required if we are to win the battle against this problem. That can only happen with strong political leadership.

“I appreciate that tackling climate change is politically difficult. First, there is a mismatch between the potentially unpopular decisions that need to be taken now and the benefits that will come in the medium and long term. Secondly, no country acting on its own can resolve the issue. Strong international action is vital.

“The Taskforce with its diverse membership has been able to find common ground. Our recommendations are practical, realistic but also challenging. World leaders need to recognise that climate change is the single most important long term issue that the planet faces and to discharge their responsibilities to the people they represent by agreeing to concerted international action to tackle climate change.”

Key recommendations of the Taskforce include:

• The G8 and other major economies, including from the developing world, form a G8+ Climate Group, to pursue technology agreements and related initiatives that will lead to large emissions reductions.
• The G8-Plus Climate Group agree to shift their agricultural subsidies from food crops to biofuels, especially those derived from cellulosic materials, while implementing appropriate safeguards to ensure sustainable farming methods are encouraged, culturally and ecologically sensitive land preserved, and biodiversity protected.
• G8 governments establish national renewable portfolio standards to generate at least 25% of electricity from renewable energy sources by 2025, with higher targets needed for some G8 governments.
• G8 governments increase their spending on research, development, and demonstration of advanced technologies for energy-efficiency and low- and zero-carbon energy supply by two-fold or more by 2010, at the same time as adopting strategies for the large-scale deployment of existing low- and zero-carbon technologies.
• All industrialised countries introduce national mandatory cap-and-trade systems for carbon emissions, and construct them to allow for their future integration into a single global market.
• A global framework be adopted that builds on the United Nations Framework Convention on Climate Change (UNFCCC) and the Kyoto Protocol, and enables all countries to be part of concerted action on climate change at the global level in the post-2012 period, on the basis of equity and common but differentiated responsibilities.
• A long-term objective be established of preventing global average temperature from rising more than 2 C (3.6 F) above the pre-industrial level, to limit the extent and magnitude of climate-change impacts.
• Governments remove barriers to and increase investment in renewable energy and energy efficient technologies and practices by taking steps including the phase-out of fossil fuel subsidies and requiring Export Credit Agencies and Multilateral Development Banks to adopt minimum efficiency or carbon intensity standards for projects they support.
• Developed countries honour existing commitments to provide greater financial and technical assistance to help vulnerable countries adapt to climate change, including the commitments made at the seventh conference of the parties to the UNFCCC in 2001, and pursue the establishment of an international compensation fund to support disaster mitigation and preparedness.
• Governments committed to action on climate change raise public awareness of the problem and build public support for climate policies by pledging to provide substantial long-term investment in effective climate communication activities.

All of the Taskforce’s recommendations are designed to build on the UNFCCC and the Kyoto Protocol to help ensure that climate change is addressed effectively over the long term.

Jonathon Porritt Taskforce member and Chair of the Sustainable Development Commission said:

“As the news about climate change goes on getting worse, political inertia all around the world remains the biggest barrier to finalising an appropriate response. It’s now critically important to inject some creative new thinking into today’s climate change negotiations, and the Taskforce has an important contribution to make to that process.”

Original press release: G8-Plus Group needed to tackle climate change (IPPR)

Mission controllers cross their fingers whenever the Sun is stormy and their spacecraft have to fly over the South Atlantic. There, even satellites in low orbits suffer many hits by atomic bullets from the Sun. Troublesome faults occur in electronic systems and astronauts see flashes in their eyes. The Earth’s magnetic field, which shields our planet against charged atomic particles coming from outer space, is curiously weak in that region.

The South Atlantic Anomaly, as the experts call it, is one pressing reason why they are intensifying their exploration of the Earth’s magnetism. Denmark’s Oersted satellite, launched in 1999, is dedicated to magnetic research, whilst Germany’s CHAMP mission (2000) measures both magnetism and gravity. These satellites show that the danger zone for satellites over Brazil and the South Atlantic is growing wider towards the southern Indian Ocean.

The Earth’s magnetic field is becoming generally weaker at an astonishing rate. When a French-Danish team compared Oersted’s results for 2000 with those from an American satellite, Magsat, 20 years earlier, the decline in the field’s strength suggested that it might disappear completely in a thousand years or so. The experts wonder if our planet is preparing to swap its north and south magnetic poles around, as it has often done before during the Earth’s long history.

Swarm constellation

These and other mysteries about our magnetic planet will get the closer attention they deserve, in ESA’s forthcoming Swarm project. Three satellites will work together to measure the magnetic field and its variations far more accurately than ever before. The Swarm mission was proposed to ESA by Eigil Friis-Christensen (Copenhagen), Hermann Luhr (Potsdam) and Gauthier Hulot (Paris) with support from scientists in seven European countries and the USA. ESA selected the project in 2004 as an ‘opportunity mission’ in its Earth Explorer programme. All being well, Swarm will be operational by 2009.

After climbing into space on a single launcher, the satellites will adopt orbits passing over the Earth’s poles. Swarm A and B will fly side by side, simultaneously measuring the magnetic field from positions up to 150 kilometres apart in the east-west direction near the equator. Their orbits will at first be 450 kilometres above the surface, but by the end of the mission they will come as low as 300 kilometres, for more accurate measurements of magnetism originating from the Earth’s crust.

Swarm C will always fly higher, remaining at more than 500 kilometres altitude throughout the mission. Compared with its sisters, Swarm C will give simultaneous snapshots of the magnetic field over quite different regions of the Earth, and impressions of the same region at different times of day.

The Earth’s self-sustaining dynamo

Ordinary magnetic compasses obey the main magnetic field, produced by electric currents in the Earth’s core of molten iron. But in magnetic storms, compass needles wander. Since the 19th Century scientists have linked these storms to eruptions on the Sun. Many space ventures, recently including the ESA-NASA SOHO spacecraft and ESA’s four-satellite Cluster mission, have helped to clarify the solar connection.

We live in a protective bubble in space called the magnetosphere. At its boundary, gusts in a non-stop solar wind of atomic particles battle with the Earth’s magnetism. As a result, events in outer space make a continual but highly variable contribution to the magnetic field. So do electric currents in the ionosphere, the zone of free electrons and charged air molecules high in the atmosphere that’s best known for reflecting radio signals.

Other, much weaker patterns are overlaid on the global picture. In the Earth’s crust, many rocks have built-in magnetism that remembers the direction of the main magnetic field when they formed. This affects the field measured locally. By its subtle east-west comparisons Swarm will picture the magnetic field of the crust with unprecedented clarity. And even ocean water generates electric currents as it move in the main field, so that the ebb and flow of the tides have a slight magnetic effect.

As gauged by the satellites, the main field is roughly 6,000 times stronger than the rock magnetism of the ocean floor, and 30,000 times greater than the influence of the oceanic tides. Only with delicate measurements by satellite constellations, supported by ground stations, ships and aircraft carrying magnetic instruments, can scientists sort out all the patterns of magnetism from the different sources.

Swarm

The most careful analyses reveal yet another effect. Magnetic variations drive electric currents in the mantle, the main region between the core and the crust. These in turn cause further magnetic changes, from which scientists can estimate the electrical conductivity of the mantle. This provides a check on the temperature of the material hidden deep in the Earth’s interior.

“What excites us is the huge scope of what we can study even with quite small satellites,” comments Nils Olsen of the Danish National Space Center in Copenhagen, who analyses Oersted’s results while he helps to plan Swarm. “By making magnetic measurements in space we get new information about the Earth, from the molten core deep under our feet, through the mantle, to the crust on which we live. And then we go on upwards into the upper atmosphere, through the planet’s local space environment, and all the way to the Sun itself, which is the source of daily magnetic disturbances.”

Practical benefits

Solar storms can be fatal for satellites, and not only on account of radiation damage. The atmosphere inflates and low-orbiting spacecraft run into unexpected air resistance. Experts used to think it was just a matter of the air being heated by particles and electric currents in the regions around the poles, where auroras occur. Now a sensitive French-built accelerometer on the German CHAMP satellite has revealed heating by intense currents where the solar wind pushes towards the magnetic poles in daytime. The three Swarm satellites will investigate this new effect with accelerometers of their own.

Swarm’s operational lifetime, 2009-13, will coincide with the next expected peak of storminess on the Sun. Immediate practical benefits will centre on Swarm�s general monitoring of space weather, and the solar events affecting not just spacecraft and astronauts but technological systems on the ground as well. Magnetic storms can damage power systems and pipelines, whilst the changes in the magnetic field can mislead any navigational systems that use magnetic compasses. These include compasses operating underground to guide the drills used to find and recover oil.

For scientists, the biggest benefit of Swarm is that high-quality magnetic measurements provide a new way of ‘x-raying’ the hidden interior of planet. Earthquake waves and variations in the strength of gravity already provide a picture of the hot core, the rocky mantle that surrounds it, and the ever-active crust. But the picture is not yet clear enough for scientists to agree how the internal machinery of the planet really works.

“Magnetic measurements give a fresh point of view on the Earth’s interior,” says Roger Haagmans, who is responsible for solid-Earth science in ESA’s Earth Observation programme. “And Swarm will also investigate the puzzling changes in the Earth’s core that are responsible for the present weakening of the magnetic field. That’s already a matter of practical concern for many satellite operators. With a better idea of the reasons, we may know what to expect in the busy decades of spaceflight that we have ahead of us.”

Original press release: Focus on our magnetic planet (ESA)