New seismology research on Haiti, slow earthquakes and the southern San Andreas Fault

Please cite the Bulletin of the Seismological Society of America (BSSA) as the source of these papers. BSSA is published by the Seismological Society of America.

2010 Haiti quake possible start of new cycle of seismic activity, according to new study

The January 2010 quake that destroyed much of Port-au-Prince may have marked the start of a new cycle of active seismicity, putting Haiti and the Dominican Republic at high risk of future devastating earthquakes.

The island of Hispaniola, which is home to the two countries of Haiti and Dominican Republic, has a long seismic history, recorded by explorers, pirates and settlers from Spain, France, England and Holland. There are ample accounts of the physical condition of the island over the last 500 years that U.S. Geological Survey researchers used to evaluate the intensity of past earthquakes and estimate their location and magnitudes.

This article documents the seismic activity along the Enriquillo fault system, which reflects a period of significant earthquakes with intense aftershocks, followed by a long 240-year period of relative seismic quiescence. The island’s last intense period of seismic activity was from 1700 to 1770. Author William Bakun and his colleagues point to the similar seismic pattern in the San Francisco Bay Area, where the seismic cycle includes a period of significant earthquake activity followed by a period of relative quiescence.

While the January 2010 earthquake that struck Haiti was only magnitude 7.0, it caused great damage and loss of life due to poor planning and inadequate building practices. Bakun and his colleagues suggest planning for strong earthquakes based on the pattern of earthquakes that have occurred since 1500.

“Significant Earthquakes on the Enriquillo Fault System, Hispanioloa, 1500 – 2010: Implications for Seismic Hazard,” by William Bakun, Claudia Flores and Uri ten Brink of the U.S. Geological Survey.

Slow slip events vs. earthquakes

Slow slip events (SSE), or slow earthquakes, reflect a transient release of strain over days or weeks and have been documented worldwide, particularly in subduction zones where one tectonic plate lurches slowly under another plate. SSEs have also been documented along the San Andreas Fault and Hawaii, and the mechanics of slow slip events are not entirely understood.

In this paper, researchers from University of Rhode Island and University of Oregon explore the scaling relationships of various source parameters of SSEs and compare them to similar scaling laws for earthquakes. Source scaling similarities and differences between slow slip and earthquakes are presented and interpreted here.

Further study is needed, say the authors, to understand well the physical mechanisms of slow slip events, whose occurrence brings some new insights into our knowledge about fault mechanics. Whether occurrence of SSEs increases or decreases the potential probability of the next megathrust earthquakes in subduction zones is still enigmatic.

“Scaling Relationships of Source Parameters for Slow Slip Events,” by Haiying Gao at University of Rhode Island (formerly at University of Oregon) and David A. Schmidt and Ray J. Weldon II at University of Oregon, Eugene.

Newly defined “propeller-like” geometry of southern San Andreas Fault, implications for ground motion assessments

The San Andreas Fault (SAF) in Southern California may not be primarily vertical or steeply dipping, as is widely thought. A new study suggests a geometry that crudely resembles a propeller, which may require a re-thinking of the anticipated ground motions from future quakes.

By analyzing near surface and subsurface data from various studies, researchers at U.S. Geological Survey and UCLA constrained the direction of the dip of the SAF, which appears to change in a systematic way throughout the Transverse Ranges.

Since existing ground motion calculations for the southern San Andreas Fault assume a vertical fault in most places, the authors suggest new calculations be made based on the new interpretation of the fault’s geometry.

“A New Perspective o the Geometry of the San Andreas Fault in Southern California and its Relationship to Lithospheric Structure,” by Gary Fuis, Daniel Scheirer and Victoria Langenheim at the U.S. Geological Survey; and Monica D. Kohler at UCLA.

European Geosciences Union General Assembly, April 22-27, 2012, Vienna, Austria

Journalists, science writers, and public information officers can now register online to the 2012 General Assembly of the European Geosciences Union (EGU). The meeting brings together over 10,000 scientists from all over the world and covers all disciplines of the Earth, planetary, and space sciences.

EGU’s General Assembly is an opportunity for journalists and science writers to learn about recent developments in topics as diverse as shale gas and fracking, exoplanets, climate change, rare earth metals, natural disasters, energy and natural resources, among others. The preliminary programme for the meeting, the largest event of its kind in Europe, includes over 700 scientific sessions, described in detail at http://meetingorganizer.copernicus.org/egu2012/sessionprogramme.

The event will be held on 22-27 April 2012 at the Austria Center Vienna at Bruno-Kreisky-Platz 1, Vienna, Austria. Members of the media and public information officers are now invited to register online (free of charge) at http://media.egu2012.eu/registration.

Further information about media services at the General Assembly is available from http://media.egu2012.eu/. Closer to the date, this website will feature a full program of press conferences, which will also be announced in later media advisories.

Online (pre-)registration will be available until Friday 16 March. The advance registration assures that your badge will be waiting for you on your arrival to the Austria Center Vienna, giving you access to the press centre and other meeting rooms. You may also register onsite during the meeting.

For information on accommodation and travel, please refer to http://www.egu2012.eu/accommodation.html and http://www.egu2012.eu/venue.html, respectively.

Injecting sulfate particles into stratosphere won’t fully offset climate change

A polar bear walks along an expanse of open water at the edge of Hudson Bay near Churchill, Manitoba, in 2011.  The bears need pack ice to hunt for food, primarily seals, but climate change brings open water more often than it used to. Polar bears have been listed as a threatened species. -  Cecilia Bitz/U. of Washington
A polar bear walks along an expanse of open water at the edge of Hudson Bay near Churchill, Manitoba, in 2011. The bears need pack ice to hunt for food, primarily seals, but climate change brings open water more often than it used to. Polar bears have been listed as a threatened species. – Cecilia Bitz/U. of Washington

As the reality and the impact of climate warming have become clearer in the last decade, researchers have looked for possible engineering solutions – such as removing carbon dioxide from the atmosphere or directing the sun’s heat away from Earth – to help offset rising temperatures.

New University of Washington research demonstrates that one suggested method, injecting sulfate particles into the stratosphere, would likely achieve only part of the desired effect, and could carry serious, if unintended, consequences.

The lower atmosphere already contains tiny sulfate and sea salt particles, called aerosols, that reflect energy from the sun into space. Some have suggested injecting sulfate particles directly into the stratosphere to enhance the effect, and also to reduce the rate of future warming that would result from continued increases in atmospheric carbon dioxide.

But a UW modeling study shows that sulfate particles in the stratosphere will not necessarily offset all the effects of future increases in atmospheric carbon dioxide.

Additionally, there still is likely to be significant warming in regions where climate change impacts originally prompted a desire for geoengineered solutions, said Kelly McCusker, a UW doctoral student in atmospheric sciences.

The modeling study shows that significant changes would still occur because even increased aerosol levels cannot balance changes in atmospheric and oceanic circulation brought on by higher levels of atmospheric carbon dioxide.

“There is no way to keep the climate the way it is now. Later this century, you would not be able to recreate present-day Earth just by adding sulfate aerosols to the atmosphere,” McCusker said.

She is lead author of a paper detailing the findings published online in December in the Journal of Climate. Coauthors are UW atmospheric sciences faculty David Battisti and Cecilia Bitz.

Using the National Center for Atmospheric Research’s Community Climate System Model version 3 and working at the Texas Advanced Computing Center, the researchers found that there would, in fact, be less overall warming with a combination of increased atmospheric aerosols and increased carbon dioxide than there would be with just increased carbon dioxide.

They also found that injecting sulfate particles into the atmosphere might even suppress temperature increases in the tropics enough to prevent serious food shortages and limit negative impacts on tropical organisms in the coming decades.

But temperature changes in polar regions could still be significant. Increased winter surface temperatures in northern Eurasia could have serious ramifications for Arctic marine mammals not equipped to adapt quickly to climate change. In Antarctic winters, changes in surface winds would also bring changes in ocean circulation with potentially significant consequences for ice sheets in West Antarctica.

Even with geoengineering, there still could be climate emergencies – such as melting ice sheets or loss of polar bear habitat – in the polar regions, the scientists concluded. They added that the odds of a “climate surprise” would be high because the uncertainties about the effects of geoengineering would be added to existing uncertainties about climate change.

Scientists aboard Iberian coast ocean drilling expedition report early findings

Ending a successful expedition, the JOIDES Resolution arrives in Lisbon, Portugal. -  Fernando Barriga, ECORD Portugal
Ending a successful expedition, the JOIDES Resolution arrives in Lisbon, Portugal. – Fernando Barriga, ECORD Portugal

Mediterranean bottom currents and the sediment deposits they leave behind offer new insights into global climate change, the opening and closing of ocean circulation gateways and locations where hydrocarbon deposits may lie buried under the sea.

A team of 35 scientists from 14 countries recently returned from an expedition off the southwest coast of Iberia and the nearby Gulf of Cadiz. There the geologists collected core samples of sediments that contain a detailed record of the Mediterranean’s history. The scientists retrieved the samples by drilling into the ocean floor during an eight-week scientific expedition onboard the ship JOIDES Resolution.

The group–researchers participating in Integrated Ocean Drilling Program (IODP) Expedition 339: Mediterranean Outflow–is the first to retrieve sediment samples from deep below the seafloor in this region.

Much of the sediment in the cores is known as “contourite” because the currents that deposit it closely follow the contours of the ocean basin.

“The recovery of nearly four kilometers of contourite sediments deposited from deep underwater currents presents a superb opportunity to understand water flow from the Mediterranean Sea to the Atlantic Ocean,” says Jamie Allan, program director at the National Science Foundation (NSF), which co-funds IODP.

“Knowledge of this water flow is important for understanding Earth’s climate history in the last five million years.”

“We now have a much greater insight into the distinctive character of contourites, and have validated beyond doubt the existing paradigm for this type of sedimentation,” says Dorrik Stow of Heriot-Watt University in the United Kingdom and co-chief scientist for Expedition 339.

The world’s oceans are far from static. Large currents flow at various depths beneath the surface. These currents form a global conveyor belt that transfers heat energy and helps buffer Earth’s climate.

Critical gateways in the oceans affect circulation of these major currents.

The Strait of Gibraltar is one such gateway. It re-opened less than six million years ago.

Today, deep below the surface, there is a powerful cascade of Mediterranean water spilling out through the strait into the Atlantic Ocean.

Because this water is saltier than the Atlantic–and therefore heavier–it plunges more than 1,000 meters downslope, scouring the rocky seafloor, carving deep-sea canyons and building up mountains of mud on a little-known submarine landscape.

The sediments hold a record of climate change and tectonic activity that spans much of the past 5.3 million years.

The team found evidence for a “tectonic pulse” at the junction between the African and European tectonic plates, which is responsible for the rising and falling of key structures in and around the gateway.

This event also led to strong earthquakes and tsunamis that dumped large flows of debris and sand into the deep sea.

At four of the seven drill sites, there was also a major chunk of the geologic record missing from the sediment cores–evidence of a strong current that scoured the seafloor.

“We set out to understand how the Strait of Gibraltar acted first as a barrier and then a gateway over the past six million years,” says Javier Hernandez-Molina of the University of Vigo in Spain and co-chief scientist for Expedition 339. “We now have that understanding and a record of a deep, powerful Mediterranean outflow through the Gibraltar gateway.”

The first drill site, located on the west Portuguese margin, provided the most complete marine sediment record of climate change over the past 1.5 million years of Earth history.

The sediment cores cover at least four major ice ages and contain a new marine archive to compare against ice core records from Greenland and Antarctica, among other land-based records.

The team was surprised to find exactly the same climate signal in the mountains of contourite mud they drilled in the Gulf of Cádiz.

Because these muds were deposited much faster than the sediments at the Portuguese margin site, the record from these cores could prove to yield even richer, more detailed climate information.

“Cracking the climate code will be more difficult for contourites because they receive a mixed assortment of sediment from varying sources,” Hernandez-Molina says.

“But the potential story that unfolds may be even more significant. The oceans and climate are inextricably linked. It seems there is an irrepressible signal of this nexus in contourite sediments.”

The team also found more sand among the contourite sediments than expected.

The scientists found this sand filling the contourite channels, deposited as thick layers within mountains of mud, and in a single, vast sand sheet that spreads out nearly 100 kilometers from the Gibraltar gateway.

All testify to the strength, velocity and duration of the Mediterranean bottom currents. The finding could affect future oil and gas exploration, the researchers believe.

“The thickness, extent and properties of these sands make them an ideal target in places where they are buried deeply enough to allow for the trapping of hydrocarbons,” Stow explains.

The sands are deposited in a different manner in channels and terraces cut by bottom currents; in contrast, typical reservoirs form in sediments deposited by downslope “turbidity” currents.

“The sand is especially clean and well-sorted, and therefore very porous and permeable,” says Stow. “Our findings could herald a significant shift in future exploration targets.”

Waiting for Death Valley’s Big Bang

Death Valley's half-mile-wide Ubehebe Crater turns out to have been created 800 years ago -- far more recently than generally thought. -  Brent Goehring/Lamont-Doherty Earth Observatory
Death Valley’s half-mile-wide Ubehebe Crater turns out to have been created 800 years ago — far more recently than generally thought. – Brent Goehring/Lamont-Doherty Earth Observatory

In California’s Death Valley, death is looking just a bit closer. Geologists have determined that the half-mile-wide Ubehebe Crater, formed by a prehistoric volcanic explosion, was created far more recently than previously thought-and that conditions for a sequel may exist today.

Up to now, geologists were vague on the age of the 600-foot deep crater, which formed when a rising plume of magma hit a pocket of underground water, creating an explosion. The most common estimate was about 6,000 years, based partly on Native American artifacts found under debris. Now, a team based at Columbia University’s Lamont-Doherty Earth Observatory has used isotopes in rocks blown out of the crater to show that it formed just 800 years ago, around the year 1200. That geologic youth means it probably still has some vigor; moreover, the scientists think there is still enough groundwater and magma around for another eventual reaction. The study appears in the current issue of the journal Geophysical Research Letters.

Ubehebe (YOU-bee-HEE-bee) is the largest of a dozen such craters, or maars, clustered over about 3 square kilometers of Death Valley National Park. The violent mixing of magma and water, resulting in a so-called phreatomagmatic explosion, blew a hole in the overlying sedimentary rock, sending out superheated steam, volcanic ash and deadly gases such as sulfur dioxide. Study coauthor Brent Goehring, (now at Purdue University) says this would have created an atom-bomb-like mushroom cloud that collapsed on itself in a donut shape, then rushed outward along the ground at some 200 miles an hour, while rocks hailed down. Any creature within two miles or more would be fatally thrown, suffocated, burned and bombarded, though not necessarily in that order. “It would be fun to witness-but I’d want to be 10 miles away,” said Goehring of the explosion.

The team began its work after Goehring and Lamont-Doherty professor Nicholas Christie-Blick led students on a field trip to Death Valley. Noting that Ubehebe remained poorly studied, they got permission from the park to gather some 3- to 6-inch fragments of sandstone and quartzite, part of the sedimentary conglomerate rock that the explosion had torn out. In the lab, Goehring and Lamont-Doherty geochemist Joerg Schaefer applied recent advances in the analysis of beryllium isotopes, which change their weight when exposed to cosmic rays. The isotopes change at a predictable rate when exposed to the rays, so they could pinpoint when the stones were unearthed. An intern at Lamont-Doherty, Columbia College undergraduate Peri Sasnett, took a leading role in the analysis, and ended up as first author on the paper.

The dates clustered from 2,100 to 800 years ago; the scientists interpreted this as signaling a series of smaller explosions, culminating in the big one that created the main crater around 1200. A few other dates went back 3,000 to 5,000 years; these are thought to have come from earlier explosions at smaller nearby maars. Christie-Blick said the dates make it likely that magma is still lurking somewhere below. He pointed out that recent geophysical studies by other researchers have spotted what look like magma bodies under other parts of Death Valley. “Additional small bodies may exist in the region, even if they are sufficiently small not to show up geophysically,” he said. He added that the dates give a rough idea of eruption frequency: about every thousand years or less, which puts the current day within the realm of possibility. “There is no basis for thinking that Ubehebe is done,” he said.

Hydrological data points the same way. Phreatomagmatic explosions are thought to take place mainly in wet places, which would seem to exclude Death Valley–the hottest, driest place on the continent. Yet, as the researchers point out, Lamont-Doherty tree-ring researchers have already shown that the region was even hotter and drier during Medieval times, when the blowup took place. If there was sufficient water then, there is certainly enough now, they say. Observations of springs and modeling of groundwater levels suggests the modern water table starts about 500 feet below the crater floor. The researchers’ calculations suggest that it would take a spherical magma chamber as small as 300 feet across and an even smaller pocket of water to produce a Ubehebe-size incident.

Park officials are taking the study in stride. “We’ve typically viewed Ubehebe as a static feature, but of course we’re aware it could come back,” said geologist Stephanie Kyriazis, a park education specialist. “This certainly adds another dimension to what we tell the public.” (About a million people visit the park each year.) The scientists note that any reactivation of the crater would almost certainly be presaged by warning signs such as shallow earthquakes and opening of steam vents; this could go on for years before anything bigger happened.

For perspective, Yellowstone National Park, further east, is loaded with explosion craters made by related processes, plus the world’s largest concentration of volcanically driven hot springs, geysers and fumaroles. The U.S. Geological Survey expects an explosion big enough to create a 300-foot-wide crater in Yellowstone about every 200 years; there have already been at least 20 smaller blowouts in the past 130 years. Visitors sometimes are boiled alive in springs, but no one has yet been blown up. Death Valley’s own fatal dangers are mainly non-geological: single-vehicle car accidents, heat exhaustion and flash floods. Rock falls, rattlesnakes and scorpions provide extra hazards, said Kyriazis. The crater is not currently on the list. “Right now, we’re not planning to issue an orange alert or anything like that,” she said.

Acidification provides the thrust

Kimberlites are magmatic rocks that form deep in the Earth’s interior and are brought to the surface by volcanic eruptions. On their turbulent journey upwards magmas assimilate other types of minerals, collectively referred to as xenoliths (Greek for “foreign rocks”). The xenoliths found in kimberlite include diamonds, and the vast majority of the diamonds mined in the world today is found in kimberlite ores. Exactly how kimberlites acquire the necessary buoyancy for their long ascent through the Earth’s crust has, however, been something of a mystery. An international research team led by Professor Donald Dingwell, Director of the Department of Geo- and Environmental Sciences at LMU, has now demonstrated that assimilated rocks picked up along the way are responsible for the providing the required impetus. The primordial magma is basic, but the incorporation of silicate minerals encountered during its ascent makes the melt more acidic. This leads to the release of carbon dioxide in the form of bubbles, which reduce the density of the melt, essentially causing it to foam. The net result is an increase in the buoyancy of the magma, which facilitates its continued ascent. “Because our results enhance our understanding of the genesis of kimberlite, they will be useful in the search for new diamond-bearing ores and will facilitate the evaluation of existing sources,” says Dingwell. (Nature 18. January 2012)

Most known kimberlites formed in the period between 70 and 150 million years ago, but some are over 1200 million years old. Generally speaking, kimberlites are found only in cratons, the oldest surviving areas of continental crust, which form the nuclei of continental landmasses and have remained virtually unchanged since their formation eons ago. </P

Kimberlitic magmas form about 150 km below the Earth’s surface, i.e. at much greater depths than any other volcanic rocks. The temperatures and pressures at such depths are so high that carbon can crystallize in the form of diamonds. When kimberlitic magmas are forced through long chimneys of volcanic origin called pipes, like the water in a hose when the nozzle is narrowed, their velocity markedly increases and the emplaced diamonds are transported upwards as if they were in an elevator. This is why kimberlite pipes are the sites of most of the world’s diamond mines. But diamonds are not the only passengers. Kimberlites also carry many other types of rock with them on their long journey into the light.

In spite of this “extra load”, kimberlite magmas travel fast, and emerge onto the Earth’s surface in explosive eruptions. “It is generally assumed that volatile gases such as carbon dioxide and water vapour play an essential role in providing the necessary buoyancy to power the rapid rise of kimberlite magmas,” says Dingwell, “but it was not clear how these gases form in the magma.” With the help of laboratory experiments carried out at appropriately high temperatures, Dingwell’s team was able to show that the assimilated xenoliths play an important role in the process. The primordial magma deep in the Earth’s interior is referred to as basic because it mainly consists of carbonate-bearing components, which may also contain a high proportion of water. When the rising magma comes into contact with silicate-rich rocks, they are effectively dissolved in the molten phase, which acidifies the melt. As more silicates are incorporated, the saturation level of carbon dioxide dissolved in the melt progressively increases as carbon dioxide solubility decreases. When the melt becomes saturated, the excess carbon dioxide forms bubbles. “The result is a continuous foaming of the magma, which may reduce its viscosity and certainly imparts the buoyancy necessary to power its very vehement eruption onto the Earth’s surface,” as Dingwell explains. The faster the magma rises, the more silicates are entrained in the flow, and the greater the concentration of dissolved silicates – until finally the amounts of carbon dioxide and water vapor released thrust the hot melt upward with great force, like a rocket. The new findings also explain why kimberlites are found only in ancient continental nuclei. Only here is the crust sufficiently rich in silica-rich minerals to drive their ascent and, moreover, cratonic crust is exceptionally thick. This means that the journey to the surface is correspondingly longer, and the rising magma has plenty of opportunity to come into contact with silicate-rich minerals.

Rock stability research could make mining and construction safer

Pinnaduwa H. S. W. 'Kumar' Kulatilake, professor of geological engineering in the UA Department of Mining and Geological Engineering, is the sole principal investigator for a five-year project to develop new methods of assessing ground stability. -  University of Arizona College of Engineering
Pinnaduwa H. S. W. ‘Kumar’ Kulatilake, professor of geological engineering in the UA Department of Mining and Geological Engineering, is the sole principal investigator for a five-year project to develop new methods of assessing ground stability. – University of Arizona College of Engineering

A University of Arizona geotechnical engineer has been awarded $1.25 million to conduct research that could provide safer working conditions for miners and construction workers.

A University of Arizona College of Engineering research program looking at new methods of determining rock strength could reduce hazardous working conditions that currently cause thousands of deaths every year in mining and construction.

Pinnaduwa H. S. W. “Kumar” Kulatilake, professor of geological engineering in the UA Department of Mining and Geological Engineering, is the sole principal investigator for a five-year project to develop new methods of assessing ground stability. The National Institute for Occupational Safety and Health (NIOSH), which is part of the Centers for Disease Control and Prevention, is funding the research.

The true extent of mining fatalities globally is hard to gauge, but some estimates suggest that as many as 12,000 miners die every year in mine accidents. The primary cause of these fatalities is ground failure.

Ground failure is generally any significant movement of the ground, such as a landslide or underground excavation collapse, or when ground moves and flows like a liquid, which results when earthquakes or high water pressure cause soil to lose its strength.

Tunnel or underground cavern collapse and catastrophic failure of slopes, dams and foundations are examples of ground failure encountered in mining and civil engineering projects. Part of the problem is that current methods of rock assessment are simply not up to the task of providing a detailed picture of what engineers are truly getting into when they start blasting and tunneling.

During the five year project, Kulatilake will extend rock strength criteria he has developed to make them applicable in three-dimensions. He will be working with two mines in the U.S. and two mines in China to apply these new methodologies to underground and surface excavations to determine how well they work in the real world. China’s official mining death toll in 2010 was 2,631. It is the world’s largest coal producer and consumer, and employs 5.5 million coal miners.

Kulatilake points out that it is not only miners who will benefit from being able to evaluate rock masses for potentially hazardous working conditions. “This is not only for mining,” he said. “This work also relates to civil rock engineering projects such as tunnels, caverns, foundations, dams, and slopes.”

To develop new methods of ground stability analysis, Kulatilake will combine field investigations and extensive laboratory testing, such as CT scans and three-dimensional load testing, with three-dimensional numerical modeling, including new theoretical concepts and advanced statistical and probabilistic procedures to quantify variability and uncertainty.

His theoretical models will be made increasingly accurate over time as their predictions are validated using lab test results and field data. In essence, Kulatilake aims to bring more certainty to what is essentially educated guesswork when it comes to assessing ground stability. “We have been using very simple methodologies in practice to address very complicated problems,” he said.

EARTH: Setting off a supervolcano

Supervolcanoes are one of nature’s most destructive forces. In a matter of hours, an eruption from a supervolcano can force thousands of cubic meters of molten rock above ground, and scar landscapes with massive calderas and craters. These catastrophic eruptions have a global impact, and yet scientists still do not fully understand them. Today, a team of scientists studying Bolivia’s Uturuncu volcano is trying to shed some light on how supervolcanoes can become so powerful.

Uturuncu, nestled within one of the largest collections of supervolcano calderas on Earth, isn’t simply getting larger: it is the fastest growing volcano on the planet. Since monitoring began in the 1980s, the magma chamber has been steadily increasing at a rate of one centimeter per year. Could Uturuncu be the next supervolcano? And will any of us be alive to see this magnificent volcano come to a catastrophic end? Find out at http://www.earthmagazine.org/earth/article/5ef-7dc-1-11. </P

Drilling around the globe

On 15 January the International Continental Scientific Drilling Program ICDP heads into a new round. About a dozen proposals for drilling projects to explore our planet have been filed for the year 2012. The topics cover a wide range of research projects, ranging from earthquake research over paleao -climate research to the exploration of natural resources. The planned drill sites span the globe, from Iceland to South Africa.

New is also the Chairman of the Executive Committee, Professor Brian Horsfield of the GFZ German Research Centre for Geosciences, who now directs the evaluation of the proposals and the planning of the suggested research. New in the office but in business for a long time: Brian Horsfield heads the Center for Integrated Hydrocarbon Research at the GFZ, holds the Chair of Organic Geochemistry and Hydrocarbon Systems at the Technical University Berlin, and is a member of acatech, the National Academy of Science and Engineering. He has over 30 years of experience in the petroleum industry and research.

About his ideas concerning the importance of scientific research boreholes, he says: “Drilling the Earth’s crust is an indispensable tool for the geosciences and ICDP is the global leader in the effort to contribute to the understanding and sustainable use of our planet, be it the protection against natural disasters, serving an ever-growing population with natural resources or exploring the natural and anthropogenic processes of our dynamic earth.”

In December last year, Brian Horsfield took over the chair of the ICDP from Professor Rolf Emmermann, formerly the founding Director of the GFZ. It was Professor Emmerman who initiated the founding of the ICDP. In February 1996 in Tokyo, he encouraged China, the United States and Germany to sign an agreement establishing the International Continental Scientific Drilling Program, which serves the exploration of the active processes on the continents. The research topics cover the whole spectrum of Earth Sciences: Volcanoes are drilled, earthquake epicenters are pierced, sediments in lakes acting as climate archives are opened, geothermal energy and methane hydrates are examined as an energy source – there are very few geoscientific issues that are not examined by research drilling.

“The ICDP scientific drilling program has proved highly successful and has set new standards in the exploration of our planet,” explains Professor Reinhard Huettl, Chair of the Executive Board of the GFZ and Vice President of the Helmholtz Association. “Today, 24 states and UNESCO are members of and the ICDP. 29 drilling projects and 57 international workshops have already been conducted that have completely changed our view of Earth. In addition, this drilling program has the character of a role model for international cooperation. The achievement of Professor Emmermann against this background cannot be overstated.” After his retirement as the Chair of the Scientific Executive Board of the GFZ (1992 – 2007), Rolf Emmermann was the chairman of the ICDP governing board until December 2011.

Researchers to test ‘quad porosity simulation’ model for shale gas reservoirs

A University of Oklahoma interdisciplinary research team will field test a newly developed ‘quad porosity model’ for shale gas reservoirs in the next few months. The three-year, $1.5 million project was funded by the Research for Partnership to Secure Energy for America and a consortium of nine oil and gas producing companies.

“The challenge for the team at the outset was to understand shale gas reservoirs in order to develop a predictive tool for better forecasting and economics,” says Deepak Devegowda, professor and lead investigator in the Mewbourne School of Petroleum and Geological Engineering. “Shale gas reservoirs are complex systems unlike conventional reservoirs.”

Just a year into the project, the OU research team has made a number of discoveries, which has led to a greater understanding of gas and liquids transport in shale gas reservoirs and the development of the quad porosity model. A previous OU research effort led to the development of the quad porosity model by using scanning electron microscopy, which indicated that gas shales can be characterized by four porosity systems.

Notably, however, the key pore spaces influencing both storage and transport of fluids are the inorganic and organic pore space. “The texture, fabric and constituents of gas-bearing shale formations containing various pore types in the nanometer sizes are intriguingly complicated,” states Faruk Civan, OU professor and co-investigator on the project.

“Developing a realistic simulator is an exciting challenge,” he said. “Our work focuses on understanding and testing the theoretical description of mechanisms of gas storage and fluid (gas/liquid) transfer in such an intricate system of inorganic and organic pores and natural and induced fractures. OU is pioneering permeability measurement, which incorporates all flow regimes,” remarks Civan. “We can also determine properties of shale rock.”

The OU research team had to rethink the physics of fluid flow and storage, which are very different in these nanoporous inorganic and organic pores. Additional complexity arises due to adsorption of gas in the organics in a high-density layer adjacent to the pore walls. While current numerical reservoir simulators are sophisticated in terms of their gridding algorithms and computational efficiency, they are restricted to modeling viscous flow. Adapting these to model transport in nanoporous shale gas reservoirs, where up to four different flow regimes may be observed, is challenging.

The small pore size in shales has been shown to have considerable impact on gas and liquids transport. Pore proximity effects, which are negligible in conventional reservoirs, exert forces that lead to substantial enhancement in the ability of the rock to flow and modify the behavior of the molecules themselves.

Standard equations used to describe gas transport cannot be applied to the small pores in the organic material where a significant portion of the gas is stored. The OU research team has shown permeability enhancement effects of up to two orders of magnitude in very small pores and this, in part, explains how gas is produced from these extremely tight formations.

One of the key developments of the research team over the last year is predicting the phase behavior of gas condensates in nanopores. As development activity, spurred by low gas prices, is focusing on the liquids-rich regions of shale gas plays, a concern of immediate significance is how to model gas condensates in nanopores. In conventional reservoirs, at low pressures, a phenomenon called condensate dropout occurs, which restricts the available pore space for gas to flow, thereby impairing well performance.

The OU research team has been able to show that in very small organic and inorganic nanopores, the influence of pore walls on fluid behavior is such that gas condensates tend to behave as dry or wet gases leading to a considerable decrease in condensate dropout. This development further explains the prolific production of rich gas-condensate fluids from these extremely tight reservoirs while conventional knowledge tends to indicate higher well productivity impairment.

Not only do these nanopores favorably modify phase behavior and the permeability to gas, but the apparent viscosity and interfacial tension also change for the better under the influence of pore walls, causing Civan to remark, “Nanopores are our friends and OU is the first to model this phenomenon.”

One of the key advantages of their formulations to account for these diverse and complex phenomena in shale gas reservoirs is that they can easily be incorporated into commercial simulators. Ongoing research work is attempting to answer questions, such as the location and distribution of frac water following stimulation. The OU research team has already developed some flow models to answer these questions.

Future work will also include the effect of these mixed wettability systems where the organic material is predominantly gas wetting while the inorganics are water-wetting, thereby meriting new formulations for multiphase transport and relative permeability. For more project information and publications related to the development of the quad porosity simulation model for shale gas reservoirs, visit http://shale.ou.edu.