Enforcing scientific governance over seismic forecasts

Scholars called for the scientific management of seismic hazards at a symposium held recently by the Center for Policy Simulation under the CAS Institute of Policy and Management.

The seismic disaster management falls into four stages: pre-quake emergency plan formulation, emergency management at the outbreak of a seismic hazards, relief and rescue management during the disaster and post-quake management, according to CPS Director WANG Zheng.

He noted that the recent earthquake occurred in southwest China’s Sichuan Province showed that China’s organizational construction to deal with the disaster is primarily in good shape. However, traditional communication facilities such as the telegraph are overlooked because undue emphasis is put on advanced technology, resulting in a failure of rapid acquisition of related information.

At the same time, said Prof. Wang, efforts should be made to implement scientific governance over earthquake forecasts. He emphasized that, facing the outburst and devastating natural disasters such as an earthquake, Chinese seismologists should improve the earthquake forecasting and prediction reliability by making integrated applications of various techniques such as statistics, representation theory, and dynamic analysis. Efforts should also be made to combine special tasks with the mass line in the forecasting.

As to the emergency management at disaster outbreaks, he suggested that emergency scale classifications be made during earthquake forecasts in the same way as to those for hurricanes or typhoons. Governments at different levels will be responsible for releasing seismic warnings of various emergency scales, and for making relevant preventive preparations.

Regarding post-quake management, he proposed to establish a foundation for geological disaster-caused disabled persons so as to address their livelihood issues.

A sound public policy framework should be set up to improve China’s work on major disaster forecasting, urged Prof. ZHAO Zuoquan of the Center.

Fatal Mine Collapse Covered 50 Acres

This map shows the part of the Crandall Canyon Mine that was being mined in August, 2007, when a collapse occurred. A smaller collapse in March 2007 (red rectangle marked ‘March Damage’) forced coal miners out of the north barrier pillar. Mining later resumed in the south part of the mine. The solid red rectangle marked “Aug 6 Collapse” represents the Mine Safety and Health Administration’s original estimate of how much of the mine collapsed. A new study by University of Utah seismologists concludes the collapse covered an area four times larger, or 50 acres, represented by red-dashed rectangle. The new study also concludes the mine collapse’s ‘hypocenter’ — the underground point (red star) where a seismic event begins — was located very near where miners were working at the time of the collapse and near areas that had been mined during July and early August.

Seismology report: Disaster began near where miners worked

New calculations show that the deadly Crandall Canyon mine collapse – which registered as a magnitude-3.9 earthquake – began near where miners were excavating coal and quickly grew to a 50-acre cave-in, University of Utah seismologists say in a report on the tragedy.

The University of Utah Seismograph Stations estimated the size of the collapse is about four times larger than was thought shortly after the time of the Aug. 6, 2007, disaster that resulted in the deaths of six miners and, 10 days later, three rescuers.

The seismologists’ 53-page report has been submitted to the journal Seismological Research Letters and to federal Mine Safety and Health Administration (MSHA) investigators. Among the key findings:

  • Seismological and other data suggest the size of the area that collapsed in the nearly horizontal mine measured 920 meters (3,018 feet) from east to west – extending from about mine crosscut 143 to crosscut 120 – and measured 220 meters (722 feet) from north to south – a total of 50 acres. A crosscut is a north-south tunnel in this mine.
  • During the collapse, the space between the mine’s roof and floor decreased by an average of only 1 foot, but enough coal and rock exploded from the mine’s walls to fill much of the collapse area with rubble that likely prevented further collapse.
  • The collapse likely lasted only seconds – leaving no time for escape – and not for misery-prolonging minutes as some miners’ families have feared. The misconception arose from the fact seismic waves reverberate for much longer than the collapse or earthquake that generated them.
  • The mine collapse was followed in August by 37 measurable aftershocks, clustered near the east and inferred west ends of the collapse area, probably from post-collapse stress and from a vertical crack on the west end of the collapsed block of rock.
  • Seismologists recalculated the epicenter of the magnitude-3.9 mine collapse, and found it “was within the mine boundary and very close to where the miners were working,” says the study’s lead author, seismologist Jim Pechmann, a research associate professor of geology and geophysics at the University of Utah Seismograph Stations.

They did this “relocation” using new techniques, calibrated by data from five seismometers placed above and near the mine after the collapse and by the known location of the magnitude-1.6 coal “burst” on Aug. 16 that killed three rescuers and injured six others.

The epicenter is the point on the ground surface above a seismic event’s hypocenter, which is the underground point where the event begins.

The location of the preliminary epicenter calculated soon after the collapse was 0.4 miles outside the mine boundary and 0.6 miles to the west-southwest of the relocated epicenter. It was somewhat inaccurate partly because the nearest seismic station at the time of the collapse was 12 miles away, says seismologist Walter Arabasz, director of the University of Utah Seismograph Stations and a co-author of the new report. “That led some to conclude the seismic event was separate from the mine collapse.”

Arabasz and other seismologists insisted from the day of the collapse that available evidence indicated the magnitude-3.9 seismic event was the mine collapse itself. The mine’s owner argued it was a natural quake that triggered the collapse.

By showing the recalculated epicenter was within the mine boundary and near active mining, the new study adds strong evidence that the quake was the collapse itself.

“As seismologists, we’re as certain as we can be that the seismic event registered as a magnitude-3.9 shock was due to the collapse of the mine and not a naturally occurring earthquake,” Arabasz says.

Pechmann and Arabasz conducted the study with seismologists Kris Pankow and Relu Burlacu, both of the Seismograph Stations, and with Michael K. “Kim” McCarter, chair and professor of mining engineering at the University of Utah. The study was funded by the State of Utah and the U.S. Geological Survey.

Arabasz says all the information in the report has been given to MSHA investigators, but “we don’t have full access to their information, so we had to develop our interpretations, to a significant extent, independent of key information in the mine.”

Scientists usually don’t release studies until they are published in journals. But in this case, there have been numerous requests for the information, which is a matter of public interest, so researchers released the report now. They delayed the release a couple of weeks at MSHA’s request to give the agency time to inform disaster victims’ families.

Evidence of a Vertical Crack during the Mine Collapse

Soon after the Aug. 6 collapse, Utah seismologists gained support from University of California, Berkeley, and Lawrence Livermore National Laboratory seismologists, who said their analysis of the seismic recordings revealed implosive, downward movement – like a mine collapse and not like shearing motion along a fault.

The California seismologists also have submitted a report of their work to Seismological Research Letters. Pechmann says the new Berkeley paper shows that while seismic waves from the Aug. 6 mine collapse are incompatible with a natural earthquake, about 20 percent of the seismic energy released came from vertical shearing motion.

“The mostly likely explanation is a vertical, north-south crack in the roof of the mine that developed along the western edge of the collapse,” with the ground on the east side of the crack dropping downward, Pechmann says.

He emphasizes that seismic records show the shearing motion “did not occur at the start of collapse. It cannot be interpreted as an earthquake that triggered the collapse.”

Size of the Collapse

MSHA initially estimated the collapse extended 680 meters (2,231 feet) east to west – or from crosscut 137 to crosscut 120 – and at least 80 meters (262 feet) north to south, the study says, quoting an MSHA official. That is about 13 acres.

Pechmann says his team’s “model,” which shows a 50-acre collapse beginning at crosscut 143, is “based on seismological data, available underground observations, and constraints on how much collapse could occur given the amount of coal left in the pillars.

“It’s not the only possible scenario to describe the collapsed area, but it fits all the available data we have,” he adds. “The epicenter was near the western end of our proposed collapse area, suggesting the collapse started at the western end, and propagated mostly eastward” toward the mine entrance.

How did the calculated 1-foot roof collapse have such deadly consequences?

Pechmann says that within the collapsed area, only 37 percent of coal had been removed, and the rest was left behind in support pillars. “If those pillars shatter and covert to rubble – and if the coal increases 40 percent in volume when it shatters – then the closure you can get between the roof and the floor averages 0.3 meters [1 foot].” The roof can only collapse that far “because it gets stopped by the rubble,” he adds.

Collapse Began Near Where Miners Worked

The seismology report notes that the MSHA-approved 2007 amended mining plan called for removing coal from east-west tunnels called “entries” and from north-south tunnels, or crosscuts, leaving behind pillars about 110 feet long and 60 feet wide.

“The next phase of the plan was to mine coal in some of these pillars, working from west to east and allowing the roof around these pillars to collapse,” the report says.

The study shows the collapse hypocenter “was right at the edge of where miners were removing pillars in July and early August,” Pechmann says. The last known working location of the six miners was just east of where those pillars were removed.

How Long the Collapse Lasted

The report says: “Some people have interpreted a four-minute seismic signal duration reported for the Crandall Canyon main shock … as indicative of an extraordinarily long collapse duration. In reality, the duration of the collapse was probably only a few seconds, at most, as evidenced by reports that the surface building at the Crandall Canyon mine portal vibrated for a few seconds at the time.”

Seismologists could not directly measure how long the Aug. 6 collapse lasted, but note that seismic waves reverberate many times longer than an actual quake or collapse.

“The collapse probably happened within just a few seconds and was not a long, drawn-out affair,” Pechmann says. “There would have been no time for anybody to get out of the way. It would have happened too fast for that.”

He notes the deadly Aug. 16 “bump” that ended rescue efforts lasted a minute on seismographs, “but underground observers said it was essentially instantaneous.”

A History of Mine-Related Seismicity

Mining-induced seismicity is common in Utah’s Wasatch Plateau-Book Cliffs coal mining region, where more than 17,000 seismic events (most weaker than magnitude 3) were attributed to underground mining from 1978 through August 2007. Less than 2 percent of the area’s seismicity originates from natural earthquakes.

The researchers noted that from Jan. 1, 2007, until the Aug. 6 collapse and within 1.9 miles of it, there were 28 seismic events large enough to be detected and located. Of those, eight (all magnitude 1.9 or weaker) happened within 2.5 weeks before the collapse, and 15 (all 1.8 or less) happened in late February and early March.

“These events occurred primarily in areas where there was concurrent or recent mining activity,” the report states.

A large “bounce” on March 10, 2007, forced miners to abandon the north side of the active part of the mine due to damage in the event, and shift to the south side, where thicker pillars were left during mining but where the August tragedy occurred.

“We didn’t see any indication of accelerating seismic activity in the hours before the [Aug. 6] collapse,” Pechmann says. “We specifically looked for that.”

Afterward, many aftershocks likely were “continued failures of pillars supporting the roof due to stresses induced by the original collapse,” Pechmann says. “And some aftershocks may have been due to adjustments within the roof.”

The “Seismological Report on the 6 Aug. 2007 Crandall Canyon Mine Collapse in Utah” is available at: http://www.seis.utah.edu/

New geomorphological index created for studying the active tectonics of mountains

Map of relative tectonic activity in Sierra Nevada. - Credit: SINC/University of Granada
Map of relative tectonic activity in Sierra Nevada. – Credit: SINC/University of Granada

Active tectonics comprise the most up-to-date deformation processes that affect the Earth’s crust, resulting in earthquakes or recent deformations in the planet’s faults and folds. This phenomena is analysed in geology research carried out before commencing engineering works.

Depending on the type of project (nuclear power stations or power stations, radioactive storage, natural gas or CO2, large dams and tunnels, hydroelectricity projects…) and the type of earthquake (single or multiple), the time period for evaluating active tectonics varies between 10,000 and 100,000 years for studies prior to beginning construction work.

The study, which is now published in the magazine Geomorphology and is the result of the doctoral thesis of Rachid El Hamdouni, Professor of the Department of Civil Engineering at the University of Granada, defines a new geomorphological index called Relative Active Tectonics Index, which identifies four classes of active tectonics (from low to very high) and uses six geomorphological indicators.

“The main use of this new index is that it establishes a close relationship between this, the land forms, and direct evidence of active faults”, El Hamdouni explained to SINC.

According to José Chacón Montero, Director of the Department of Civil Engineering at the University of Granada and co-author of this research, in Sierra Nevada “areas with ‘high’ and ‘very high’ tectonic activity are areas with precipices, hanging valleys, deformed or hanging alluvial fans or deep and narrow gorges excavated near mountain fronts”.

A seismic map for southern Spain

The indices are calculated with the help of Geographical Information Systems and teledetection programs in large areas which identify geomorphological anomalies possibly related to active tectonics. “This is really useful in southern Spain where studies on active tectonics are not very widely distributed”, Chacón pointed out to SINC.

The study has focused on the Padul-Dúrcal fault and a series of associated fault structures on the edge of the Sierra Nevada, where over the last 30 years seismic activity has been recorded by the Observatory of the Andalusian Institute of Geophysics and Prevention of Seismic Disasters. Chacón explained that the map obtained with the new index depends exclusively on the land forms and divides the area studied into four parts, “of which two thirds of the total area is classed as having high or very high tectonic activity”.

The Sierra Nevada is an Alpine mountain chain “with variable active tectonic gradients caused by the collision of Africa with Europe which has given rise to anticlines aligned from east to west, as well as the transverse extension with variable vertical gradients around 0.5 mm/year in normal faults”, Chacón specified.

Researchers Uncover ‘Stirring’ Secrets of Deadly Supervolcanoes

Researchers from The University of British Columbia and McGill University have simulated in the lab the process that can turn ordinary volcanic eruptions into so-called “supervolcanoes.”

The study was conducted by Ben Kennedy and Mark Jellinek of UBC’s Dept. of Earth and Ocean Sciences, and John Stix of McGill’s Dept. of Earth and Planetary Sciences. Their results are published this week in the journal Nature Geoscience.

Supervolcanoes are orders of magnitude greater than any volcanic eruption in historic times. They are capable of causing long-lasting change to weather, threatening the extinction of species, and covering huge areas with lava and ash.

Using volcanic models made of Plexiglas filled with corn syrup, the researchers simulated how magma in a volcano’s magma chamber might behave if the roof of the chamber caved in during an eruption.

“The magma was being stirred by the roof falling into the magma chamber,” says Stix. “This causes lots of complicated flow effects that are unique to a supervolcano eruption.”

“There is currently no way to predict a supervolcano eruption,” says Kennedy, a post-doctoral fellow at UBC and lead author on the paper. “But this new information explains for the first time what happens inside a magma chamber as the roof caves in, and provides insights that could be useful when making hazard maps of such an eruption.”

The eruption of Mount Tambora in Indonesia in 1815 – the only known supervolcano eruption in modern history – was 10 times more powerful than Krakatoa and more than 100 times more powerful than Vesuvius or Mount St. Helens. It caused more than 100,000 deaths in Indonesia alone, and blew a column of ash about 70 kilometres into the atmosphere. The resulting disruptions of the planet’s climate led 1816 to be christened “the year without summer.”

“And this was a small supervolcano,” says Stix. “A really big one could create the equivalent of a global nuclear winter. There would be devastation for many hundreds of kilometres near the eruption and there would be would be global crop failures because of the ash falling from the sky, and even more important, because of the rapid cooling of the climate.”

There are potential supervolcano sites all over the world, most famously under Yellowstone National Park in Wyoming, the setting of the 2005 BBC / Discovery Channel docudrama Supervolcano, which imagined an almost-total collapse of the world economy following an eruption.

Bacteria ‘Feed’ on Earth’s Ocean-Bottom Crust

Scientists have found that rocks beneath the seafloor are teeming with microbial life. - Credit: Nicolle Rager-Fuller/National Science Foundation
Scientists have found that rocks beneath the seafloor are teeming with microbial life. – Credit: Nicolle Rager-Fuller/National Science Foundation

Rocks on and under seafloor offer feast for microbes

Seafloor bacteria on ocean-bottom rocks are more abundant and diverse than previously thought, appearing to “feed” on the planet’s oceanic crust, according to results of a study reported in this week’s issue of the journal Nature.

The findings pose intriguing questions about ocean chemistry and the co-evolution of Earth and life.

Once considered a barren plain dotted with hydrothermal vents, the seafloor’s rocky regions appear to be teeming with microbial life, say scientists from the Woods Hole Oceanographic Institution (WHOI) in Woods Hole, Mass., University of Southern California (USC) in Los Angeles, and other institutions.

While seafloor microbes have been detected before, this is the first time they have been quantified. Using genetic analyses, Cara Santelli of WHOI, Katrina Edwards of USC, and colleagues found three to four times more bacteria living on exposed rock than in the waters above.

“Initial research predicted that life could in fact exist in such a cold, dark, rocky environment,” said Santelli. “But we really didn’t expect to find it thriving at the levels we observed.”

Surprised by this diversity, the scientists tested more than one site and arrived at consistent results, making it likely, according to Santelli and Edwards, that rich microbial life extends across the ocean floor.

“This may represent the largest surface area on Earth for microbes to colonize,” said Edwards.

“These scientists used modern molecular methods to quantify the microbial biomass and estimate the diversity of microbes in deep-sea environments,” said David Garrison, director of the National Science Foundation (NSF)’s Biological Oceanography Program. NSF’s Ridge 2000 program funded the research. “We now know that this remote region is teeming with microbes, more so than anyone had guessed.”

Santelli and Edwards also found that the higher microbial diversity on ocean-bottom rocks compared favorably with other life-rich places in the oceans, such as hydrothermal vents.

These findings raise the question of where these bacteria find their energy, Santelli said.

“We scratched our heads about what was supporting this high level of growth,” Edwards said.

With evidence that the oceanic crust supports more bacteria than overlying water, the scientists hypothesized that reactions with the rocks themselves might offer fuel for life.

In the lab, they calculated how much biomass could be supported by chemical reactions with the rocky basalt. They then compared this figure to the actual biomass measured. “It was completely consistent,” Edwards said.

This discovery lends support to the idea that bacteria survive on energy from Earth’s crust, a process that could add to our knowledge about the deep-sea carbon cycle and the evolution of life.

Many scientists believe that shallow water, not deep water, is better suited for cradling the planet’s first life forms. Up until now, dark, carbon-poor ocean depths appeared to offer little energy, and rich environments like hydrothermal vents were thought to be relatively sparse.

But the newfound abundance of seafloor microbes makes it possible that early life thrived–and perhaps began–on the seafloor.

“If we can really nail down what’s going on, there are significant implications,” Edwards said. “I hope that people turn their heads and notice: there’s life down there.”

In addition to Santelli and Edwards, the paper’s co-authors are: Beth Orcutt of USC; Erin Banning of WHOI; Wolfgang Bach of WHOI and Universität Bremen; Craig Moyer of Western Washington University; Mitchell Sogin of the Marine Biological Laboratory; and Hubert Staudigel of the Scripps Institution of Oceanography.

The research was also funded by the NASA Astrobiology Institute and Western Washington University.