Sensors that improve rail transport safety

Cloud-supported sensor network for the condition-based maintenance of rail vehicles.
Credit: © Fraunhofer IZM

A new kind of human-machine communication is to make it possible to detect damage to rail vehicles before it's too late and service trains only when they need it -- all thanks to a cloud-supported, wireless network of sensors.

A train running on damaged wheels could easily be heading for serious trouble. This is why German national rail corporation Deutsche Bahn continuously monitors the wheelsets of its intercity express trains -- a process that costs a considerable amount of time and money. 

Researchers at the Berlin-based Fraunhofer Institute for Reliability and Microintegration IZM are collaborating with industry partners to develop a solution that ensures a great safety while reducing effort and cost. "We want to root out any damage early on and move away from maintenance at set intervals in favor of condition-based maintenance," explains Dr. Michael Niedermayer, microsystems engineer and head of the IZM's Technology-Oriented Design Methods working group. He is also project coordinator for "Mobile Sensor Systems for Condition-Based Maintenance," or MoSe for short.

Seamless monitoring

It's all based on a cloud-supported, wireless network of sensors. Every axle and undercarriage on a train is fitted with small radio sensors, which collect data on the condition of wearing parts. These data are then transferred to the online maintenance cloud, where the measurement and analysis data are encrypted and stored ready for use. The sensors can detect even the tiniest scratch on a ball bearing. As Niedermayer says, "Here we have sensor nodes that can capture even the slightest variations in vibration. We call this in-depth diagnosis." As a result, repairs can be made before anything works its way loose and causes damage.

"What's remarkable about this approach is that it allows everything to be monitored with the train in service, rather than having to inspect it at the rail yard. And in any case, visual checks are not 100 percent reliable," says Manfred Deutzer from project partner Deutzer Technische Kohle GmbH. Although there are wired sensors out there that can be used to examine rail vehicle chassis for wear and tear, these fail to match the high diagnostic quality standards the MoSe developers are striving for.

Using the new method, it is possible to get precise data on, say, whether an axle bearing will have to be replaced three months down the line, which avoids the need to replace it prematurely just in case. The latter is just as uneconomical as the custom of overhauling wheels at preset intervals with a view to resolving any wheel flats that could damage rails. 

"Wheels can tolerate such repairs no more than three times before they have to be scrapped," Deutzer reports. "It would make more sense and cost less to grind only those wheels we know actually turn poorly. The problem is that there has never been a suitable way of checking for wheel flats." MoSe is to change all that and much more besides.

"Not only do we intend to improve diagnostics, a top priority is also to process the data collected in as detailed and tailored a manner as possible," says Niedermayer. The idea is to provide train drivers with all relevant data (for instance about critical wheel damage), diagnostic technicians with detailed measurement data so they can assess how fast gear damage is progressing, and designers with measurement statistics covering wear to all parts, enabling them to improve the technical design of the next product generation. Making sure everyone involved receives the data they need in a form they can work with right away involves developing some clever diagnostic algorithms. "Yet another advantage is that wireless sensors can be easily retrofitted," adds Niedermayer.

What's also new is that the system can adapt to the different rotational speeds of the parts being examined -- such as the wheels on a train -- and in doing so, deliver incredibly precise data at whatever speed the train happens to be traveling. It used to be that sensors were designed to work at constant rotational speeds. Although this setup may be easier to manage, it means that the diagnostic quality suffers. Thanks to analysis algorithms, this is set to change. But developing these algorithms is a balancing act: "Since the system is intended to work without batteries, the algorithms mustn't drain unnecessary energy by using up excessive computing power," explains Niedermayer. As MoSe uses energy harvesting, it can tap energy from the vibrations and heat generated as the parts rotate.

Over the next couple of years a prototype will be developed that will be tested in a tram run by the German city of Brandenburg an der Havel. The system could then be used for monitoring purposes in suburban or long-distance trains.

Source: Fraunhofer-Gesellschaft

Archaeologists reveal layout of medieval city at Old Sarum

Old Sarum -- aerial photo. Credit: Image courtesy of University of Southampton

Archaeologists from the University of Southampton have revealed for the first time the plan of a network of buildings in a once thriving medieval city at the historic site of Old Sarum, near Salisbury.

A research team of students and academics carried out a geophysical survey of the ancient monument, scanning ground at the site with state-of-the-art equipment to map the remains of buried structures. They concentrated their survey around the inner and outer baileys of what was once a fortification, with its origins in the Iron Age and the Roman conquest.1

Their investigations reveal the layout of a settlement including structures from the late 11th century, contemporary with the construction of a cathedral and castle. The city was inhabited for over 300 years, but declined in the 13th century with the rise of New Sarum (Salisbury).

The project findings mainly concentrate on the medieval period and highlight:

* A series of massive structures along the southern edge of the outer bailey defensive wall, perhaps suggesting large buildings of a defensive nature.
* An open area of ground behind these large structures, perhaps for mustering resources or people, or as part of a circular route through the city..
* Residential areas in the south east and south west quadrants of the outer bailey alongside the inner bailey ditch.
* Evidence of deposits indicating industrial features, such as kilns or furnaces.
* Features suggesting quarrying at the site after the 1300s and following the city's decline -- indicating a later period of habitation at the site..

Archaeologist Kristian Strutt, Experimental Officer and Director of Archaeological Prospection Services at the University of Southampton, says: "Archaeologists and historians have known for centuries that there was a medieval city at Old Sarum, but until now there has been no proper plan of the site.

"Our survey shows where individual buildings are located and from this we can piece together a detailed picture of the urban plan within the city walls."

The research was conducted as part of the Old Sarum and Stratford-Sub-Castle Archaeological Survey Project, directed by Kristian Strutt and fellow Southampton archaeologists Timothy Sly and Dominic Barker. Old Sarum is under the custodianship of English Heritage, who kindly granted permission for the investigation to take place.

Heather Sebire, Property Curator at English Heritage, comments: "Having the team of archaeologists on site over the summer gave our visitors a chance to find out more about how important historic landscapes are surveyed. The use of modern, non-invasive surveying is a great start to further research at Old Sarum.

"From this work we can surmise much about the site's past and, whilst we can't conclusively date the findings, it adds a new layer to Old Sarum's story. We welcome the chance to find out more about our sites, and look forward to exploring ideas for further research in the future."

The team used a variety of techniques to examine the outer and inner bailey of the site. These included the use of topographic survey methods and geophysical survey techniques -- comprising of magnetometry, earth resistance, ground penetrating radar (GPR) and electric resistivity tomography (ERT) survey.

Kristian Strutt concludes: "Our research so far has shown how the entire outer bailey of the monument was heavily built up in the Middle Ages, representing a substantial urban centre. Results have given us compelling evidence as to the nature of some of the structures. It is clear, however, that there is more non-intrusive work that could be carried out to further expand our understanding of the site."

The team hopes to return to complete the survey of the inner and outer baileys and survey the Romano-British settlement to the south of Old Sarum in Easter 2015. The project fieldwork in 2014 was used as a training season for undergraduate and postgraduate archaeology students at the University, continuing a long tradition of research-led teaching at some of the most impressive archaeological sites in the south of England. Previous fieldwork has been conducted by students at Portchester Castle, Netley Abbey and Bishop's Waltham Palace in Hampshire, and at Bodiam Castle in East Sussex.

Source: University of Southampton

Camera trap images help wildlife managers ID problem tigers in India

Researchers with WCS and other partners in India are camera traps to ID individual tigers in conflict and relocate them out of harm's way for the benefit of both tigers and people. Credit: WCS

Researchers with the Wildlife Conservation Society and other partners in India are using high-tech solutions to zero in on individual tigers in conflict and relocate them out of harm's way for the benefit of both tigers and people.

In recent tiger-conflict cases involving both a human fatality and the predation of livestock, both occurring near two of India's national parks, WCS scientists helped to identify problem tigers using stripe pattern-matching software and additional information to make the connections. Both tigers have been captured and relocated to a nearby zoo.

Reducing human-wildlife conflict while promoting human welfare and conservation in important wildlife habitats is one of many topics under discussion of the World Parks Congress, a once-in-a-decade event focusing on the management and expansion of the world's protected area networks and the wildlife they contain. The congress, which took place in Sydney, Australia concluded today.

A new paper titled "Photographic Database Informs Management of Conflict Tigers" appears in the latest version of the journal Oryx. The authors are: Ullas Karanth, N. Samba Kumar, and Divya Vasudev of WCS's India Program.

"The vast majority of tigers generally avoid humans and focus only on natural prey species," said Dr. Ullas Karanth, WCS's Director for Science-Asia and lead author on the paper. 

"Using scientific methods to locate individuals involved in conflict with humans and livestock helps us to mitigate threats to people and prevent the capture of the wrong tigers, especially wherever tigers may venture beyond protected area borders."

While tigers struggle to survive in other landscapes across their range through Asia, the big cats in the Malenad Tiger Landscape of southwest India have thrived, becoming one of the largest tiger populations in the world with an estimated 400 animals.

Part of this conservation success has been due to a WCS research program focused on the identification of individual tigers. The system uses unique stripe patterns to identify and track individual animals, and software programs have greatly improved the speed and accuracy of the process. Since the initiation of the research protocol, more than 750 tigers have been identified from six protected areas in the Malanad Tiger Landscape in the Western Ghats across India. The system also enables researchers to keep track of other data such as home range locations, age and ex of individual animals, activity patterns. Over the longer term it even enables estimation of survival and recruitment rates and changes in numbers, all of which can be used to inform management decisions on wild tigers.

The tiger database has become a key factor in finding and capturing problem tigers. One of the recently captured animals was involved in the loss of human life near Bandipur National Park in late December of 2013. Scientists managed to get pictures of the animal from camera traps set up near the area of conflict and discovered a match with an animal photographed over a 5-year period and probably past its prime. Old tigers unable to catch natural prey animals can sometimes resort to hunting livestock, bringing them in conflict with people.

Another tiger, involved in the killing of cattle in a village next to Nagarahole National Park, was by contrast a 2-3 year old youngster some 35 kilometers from locations in which it was previously photographed. Scientists concluded this young tiger was likely searching for a territory, beyond protected areas.

Once ranging across Asia from Turkey to Indonesia, the tiger has been decimated by a combination of habitat destruction, overhunting of prey animal, poaching for the illegal trade and retaliatory killing by humans. The total wild population has been reduced in numbers from perhaps 100,000 at the turn of the 20th Century to a current estimate of fewer than 3,500 animals remaining in only 6 percent of the species' historic range.

Source: Wildlife Conservation Society

Flu at the zoo and other disasters: Experts help animal exhibitors prepare for the worst

After experiencing power outages during a 2007 ice storm in Springfield, Mo., Dickerson Park Zoo officials improved their backup power and heating systems to keep animals -- like Henry, pictured here -- safe and warm. Credit: Dickerson Park Zoo

Here are three disaster scenarios for zoo or aquarium managers: One, a wildfire lunges towards your facility, threatening your staff and hundreds of zoo animals. Two, hurricane floodwaters pour into your basement, where thousands of exotic fish and marine mammals live in giant tanks. Three, local poultry farmers report avian influenza (bird flu) in their chickens, a primary source of protein for your big cats.

What do you do?

These are among the many potential disasters the managers of zoos and aquariums ponder in their emergency preparedness drills and plans. But these stories are not just worst-case scenarios: The events described above actually happened, and the aftermath -- often heroic, and sometimes tragic -- depended in large part on the institutions' preparedness training, planning and forethought in calmer times.

When bad weather strikes or illness invades, zoos and aquariums are among the most vulnerable facilities affected, said University of Illinois veterinarian Yvette Johnson-Walker, a clinical epidemiologist who contributes to emergency response training efforts at animal exhibitor institutions. She is a clinical instructor in the department of veterinary clinical medicine at Illinois, and lead author of a new paper on emergency preparedness at zoos and aquariums in the journal Homeland Security & Emergency Management.

Some animals are likely to suffer if the electricity goes out for long, she said. Others are large, skittish and dangerous under normal conditions.

Training caretakers and keepers to minimize their own risks while attending to their animals in an emergency is a challenge, but leads to the best outcomes, she said.

In 2012, Johnson-Walker joined forces with Yvonne Nadler, a project manager with the Zoo and Aquarium All Hazards Preparedness Response and Recovery Center, to bring vital emergency training to accredited animal exhibitor institutions in Illinois, Indiana and Missouri. This effort, funded by the U.S. Department of Agriculture and supported by the Association of Zoos & Aquariums, has since expanded, providing training to staff from zoos and aquariums in 23 states.

The trainings, dubbed "Flu at the Zoo," focus on avian influenza, a viral disease that spread in the 2000s among wild and captive birds and also infected hundreds of people, primarily in Asia, Africa and the Middle East. Bird flu serves as a useful model scenario to help train participants in basic preparedness skills.

One such skill is familiarity with the Incident Command System (ICS), a framework developed by firefighters and adopted by the Federal Emergency Management Agency (FEMA) that allows first responders to quickly set up their emergency response operation and assign vital tasks. The ICS has long been used by public safety, law enforcement and public health entities involved in emergency response.

"We wanted zoos and aquariums to have a seat at the table when there's planning for how we're going to respond to emergencies, and to be able to fit into the system, know who to talk to and how to communicate," Johnson-Walker said.

It's also important to recognize the other responders and understand their roles, she said. If the event involves a disease like bird flu, the USDA, FEMA, National Institutes of Health, state veterinarian, state and federal wildlife services, public health authorities, veterinary organizations, police, hospitals and perhaps even local poultry operations will be involved in the response. Knowing who does what can speed communication in a crisis.

Planning also helps managers make best use of the limited supplies or equipment they have on hand, Nadler said.

"There are certain types of livestock trailers, for example, that can be adapted to moving big cats," she said. "Is that your preferred method of movement? Of course it isn't, but in an emergency that might be your only option."

One beneficiary of the emergency training, Melinda Arnold, knows firsthand the value of preparedness. Arnold is public relations director for Friends of the Zoo, affiliated with Dickerson Park Zoo in Springfield, Missouri. The zoo suffered a blackout during a 2007 ice storm that shut off power for most of the city for several days.

"We did have backup generators," Arnold said. "The greatest problem with the generators was that those fueling stations in town that did have gas didn't have power, so they couldn't pump the gas."

Zoo staff had to travel many miles outside of the affected area with gas cans to collect gas to run the backup generators, she said.

"Now we have some propane-powered backups," Arnold said.

A more recent incident at the zoo, the accidental death of a zookeeper in 2013, caused Dickerson Park Zoo officials to re-evaluate all of their safety protocols. Even though the zookeeper had decades of experience and was guarded by a protective barrier, a skittish elephant rushed him at an unguarded moment, and he fell and was trampled to death.
"It made us step back, not only in our elephant management but in all areas of the zoo, and look at our safety procedures and points of contact with dangerous animals and evaluate those safety conditions and make improvements," Arnold said.

The preparedness plans, drills, discussions and training all help zoos and aquariums reassess their procedures, even those that seem to be safe after decades of operations and no major incidents, she said.

Source: University of Illinois at Urbana-Champaign

Combatting illegal fishing in offshore marine reserves

Fishing boat. Credit: Henry Wolcott

Conservation scientists say there needs to be a new approach to protecting offshore marine reserves.

Illegal fishing in marine reserves will be a major focus at the IUCN World Parks Congress, which has opened in Sydney.

Researchers at the ARC Centre of Excellence for Coral Reef Studies (Coral CoE) at James Cook University, who are attending the conference, have found a way to predict illegal fishing activities to help authorities better protect marine reserves.

Marine reserves are the most common strategy used to protect and maintain marine ecosystems around the world.

The International Convention of Biological Diversity aims to have 10 per cent of the world's marine areas protected by 2020.

Many countries are contributing to this target by protecting remote, offshore areas. For example, the United States recently created the world's largest fully protected marine reserve, covering almost 1.27 million square kilometres in the central Pacific Ocean.

But scientists are concerned that while a great deal of effort is being made to create reserves, many countries are simply not able to enforce the laws that are supposed to protect them.

fishing gear. Image: Todd Steiner, Sea Turtle Restoration Project
The majority of fishers obey the law, but some don't.

"The success of protected areas depends on whether people comply with the regulations," says Professor Joshua Cinner from Coral CoE.

"Enforcement and compliance issues for large off-shore marine parks are fundamentally different to near-shore protected areas," Professor Cinner says.

He explains that the biggest problems facing countries trying to enforce offshore marine reserves is their distance from land and the difficulty and cost of patrolling large tracts of ocean.
"The distances to these areas can be very large. They are a long way from prying eyes and quite often the regulations are such that you have to actually catch people illegally fishing to prosecute them," Professor Cinner says.

"It can be extremely difficult for authorities to catch illegal fishers in the act."

In a bid to combat the problem, researchers at Coral CoE examined five years' worth of data collected from the World Heritage-listed Cocos Island National Park, a unique marine protected area in the Pacific Ocean about 500 kilometres off the west coast of Costa Rica.
From the records they were able identify illegal fishing patterns and predict both when and where illegal fishing was likely to happen.

They found that illegal fishing was concentrated in a few 'hotspots' and really ramped up during specific lunar phases of some months.

Professor Bob Pressey, also from Coral CoE, says authorities could use this knowledge to match patrols to the time and place when illegal fishers are most likely to be in action.
"Using a targeted approach helps authorities catch and deter illegal fishers, while saving money on patrols," Professor Pressey says.

"Rather than just hoping you can catch illegal fishers effectively by random patrols, we have used previous patrols to look for patterns which tell us when and where people fish illegally," adds Professor Cinner.

Study lead author, Coral CoE PhD candidate, Adrian Arias says the model of predicting illegal patterns from old records can be used to increase the success of patrols in other locations.

"Our research in Costa Rica showed how a systematic and periodic analysis of patrol records can help to increase the probability of catching illegal fishers. This could be done pretty much anywhere that patrol data are available," he says.

Professor Cinner adds that by better targeting limited resources, authorities have a greater chance of successfully protecting marine parks.

"Targeting resources is particularly important for developing countries such as Costa Rica, which have taken on the conservation challenge but don't have the same funding to ensure compliance as a country such as Australia."

Source: ARC Centre of Excellence in Coral Reef Studies

Improving forecasts for rain-on-snow flooding

Flooding in January 2009 closed a section of Interstate 5 south of Seattle.Washington State Dept. of Transportation Credit: Image courtesy of University of Washington

Many of the worst West Coast winter floods pack a double punch. Heavy rains and melting snow wash down the mountains together to breach riverbanks, wash out roads and flood buildings.

These events are unpredictable and difficult to forecast. Yet they will become more common as the planet warms and more winter precipitation falls as rain rather than snow.

University of Washington mountain hydrology experts are using the physics behind these events to better predict the risks.

"One of the main misconceptions is that either the rain falls and washes the snow away, or that heat from the rain is melting the snow," said Nicholas Wayand, a UW doctoral student in civil and environmental engineering. He will present his research Dec. 18 at the annual meeting of the American Geophysical Union.

Most of the largest floods on record in the western U.S. are associated with rain falling on snow. But it's not that the rain is melting or washing away the snow.

Instead, it's the warm, humid air surrounding the drops that is most to blame for the melting, Wayand said. Moisture in the air condenses on the cold snow just like water droplets form on a cold drink can. The energy released when the humid air condenses is absorbed by the snow. The other main reason is that rainstorms bring warmer air, and this air blows across the snow to melt its surface. His work support previous research showing that these processes provide 60 to 90 percent of the energy for melting.

Places that experience rain-on-snow flooding are cities on rivers that begin in the mountains, such as Sacramento, California, and Centralia, Washington. In the 1997 New Year's Day flood in Northern California, melting snow exacerbated flooding, which broke levees and caused millions of dollars in damage. The biggest recent rain-on-snow event in Washington was the 2009 flood in the Snoqualmie basin. And the Calgary flood in summer of 2013 included snow from the Canadian Rockies that caused rivers to overflow their banks.
The UW researchers developed a model by recreating the 10 worst rain-on-snow flooding events between 1980 and 2008 in three regions: the Snoqualmie basin in Washington state, the upper San Joaquin basin in central California and the East North Fork of the Feather River basin in southern California.

Their results allow them to gauge the risks for any basin and any incoming storm. The three factors that matter most, they found, are the shape of the basin, the elevation of the rain-to-snow transition before and during the storm, and the amount of tree cover. Basins most vulnerable to snowmelt are treeless basins with a lot of area within the rain-snow transition zone, where the precipitation can fall as snow and then rain.

Trees reduce the risk of flooding because they slow the storm's winds.

"If you've ever been in a forest on a windy day, it's a lot calmer," Wayand said. That slows the energy transferred from condensation and from contact with warm air to the snowpack.
Simulations also show that meltwater accounted for up to about a quarter of the total flooding. That supports earlier research showing that snow is not the main contributor to rain-on-snow floods, but cannot be neglected since it adds water to an already heavy winter rainstorm.

The complexity of mountain weather also plays a role.

"The increase in precipitation with elevation is much greater than usual for some of these storms," said Jessica Lundquist, a UW associate professor of civil and environmental engineering. "Higher flows can result from heavier rainfall rates at higher elevations, rather than from snowmelt."

In related work, Lundquist's group has developed a tennis-ball snow sensor and is measuring growth and melt of the snowpack in the foothills east of Seattle. The scientists aim to better understand how changes in climate and forestry practices might affect municipal water supplies and flood risks.

Wayand and another student in the group have developed a high school curriculum for Seattle teachers to explain rain-on-snow events and the physics behind why they occur. They hope to begin teaching the curriculum sometime next year.

The other collaborator on the work being presented in San Francisco is Martyn Clark at the National Center for Atmospheric Research in Colorado.

Source: University of Washington

The Rising above the risk: America's first tsunami refuge

Artist rendering: entry view. Credit: TCF Architecture

Washington's coast is so close to the seismically active Cascadia Subduction Zone that if a megathrust earthquake were to occur, a tsunami would hit the Washington shoreline in just 25 minutes.

One coastal community is preparing for such a disaster by starting construction on the nation's first tsunami evacuation refuge, large enough to shelter more than 1,000 people who are within 20-minute walking distance.

The vertical evacuation-refuge will be the roof of the gym of the new school in Grays Harbor County, Washington. The Ocosta Elementary School and Tsunami Safe Haven will be the first of its kind in the nation and will be the culmination of 18 years of effort, said Tim Walsh, who is a Chief Hazard Geologist at the Department of Natural Resources and has been working on this project since The National Tsunami Hazard Mitigation Program was formed in 1995.

Walsh will present the project design for the school and structure, along with the detailed tsunami modeling used to find the best location for the refuge, at the Annual Meeting for the Geological Society of America in Vancouver, Canada, on 21 October.

The Cascadia subduction zone is a 700-mile-long (over 1,000 kilometers) fault along the West Coast, where the Juan de Fuca Plate is being forced under the North American Plate. The subduction zone is capable of producing massive earthquakes; scientists have calculated that magnitude-9 earthquakes along this fault line could generate a massive tsunami that would hit the coastlines of British Columbia, Washington, Oregon, and California within 20 to 30 minutes.

"It used to be thought that Cascadia was not an active fault," said Walsh. Not only has Cascadia been found to be an active fault, it has a 10 percent chance that it will cause an earthquake in the next 50 years, he said.

"It is more than 10 times more likely than the chance you will be killed in a traffic accident," said Walsh. "But you aren't looking at the statistics of a single person, but an earthquake that would have an effect on thousands of miles of shoreline."

The biggest challenge was at the very beginning, trying to come up with a location that could be effective and accessible to people, said Walsh. "It was difficult in the beginning to go to the public meetings in these communities and present the hazards, but have no solution for them," he said.
Project Safe Haven brought together structural engineers, oceanographers, geographers, and scientists from many other disciplines to create a safe and accessible refuge.

Walsh and his colleagues used a model called GeoClaw to research the risk a tsunami, factoring in and any potential landslides caused by the wave or megaquake. Using this model in the community for Grays Harbor County, the scientists determined the best place for the school, and what how much force the structure would have to withstand to protect refugees.

The school will be built on a dune ridge, so the roof of the evacuation shelter will be about 55 feet (almost 17 meters) above sea-level. The structure is designed to withstand earthquakes and the impact of a storm surge, with reinforced concrete cores at each corner of the gym and staircases leading to the room. The school, and refuge, is expected to be finished and operating for the 2015-2016 academic year.

Walsh would like to see other scientists and community groups working together to create novel solutions for tsunami risk, he said. Currently the Washington coast has very few tall buildings, and barely any are taller than three stories, leaving thousands of people at risk in the event of a tsunami, he said.

Source: Geological Society of America

Study of Chilean quake shows potential for future earthquake

The Iquique earthquake took place on the northern portion of the subduction zone formed when the Nazca tectonic plate slides under the South American plate. Credit: USGS

Near real-time analysis of the April 1 earthquake in Iquique, Chile, showed that the 8.2 event occurred in a gap on the fault unruptured since 1877 and that the April event was not what the scientists had expected, according to an international team of geologists.

"We assumed that the area of the 1877 earthquake would eventually rupture, but all indications are that this 8.2 event was not the 8.8 event we were looking for," said Kevin P. Furlong, professor of geophysics, Penn State. "We looked at it to see if this was the big one."

But according to the researchers, it was not. Seismologists expect that areas of faults will react the same way over and over. However, the April earthquake was about nine times less energetic than the one in 1877 and was incapable of releasing all the stress on the fault, leaving open the possibility of another earthquake.

The Iquique earthquake took place on the northern portion of the subduction zone formed when the Nazca tectonic plate slides under the South American plate. This is one of the longest uninterrupted plate boundaries on the planet and the site of many earthquakes and volcanos. The 8.2 earthquake was foreshadowed by a systematic sequence of foreshocks recorded at 6.0, 6.5, 6.7 and 6.2 with each foreshock triggering the next until the main earthquake occurred.

These earthquakes relieved the stresses on some parts of the fault. Then the 8.2 earthquake relieved more stress, followed by a series of aftershocks in the range of 7.7. While the aftershocks did fill in some of the gaps left by the 8.2 earthquake, the large earthquake and aftershocks could not fill in the entire gap where the fault had not ruptured in a very long time. That area is unruptured and still under stress.
The foreshocks eased some of the built up stress on 60 to 100 miles of fault, and the main shock released stress on about 155 miles, but about 155 miles of fault remain unchanged, the researchers report today (Aug. 13) in Nature.

"There can still be a big earthquake there," said Furlong. "It didn't release the total hazard, but it told us something about this large earthquake area. That an 8.8 rupture doesn't always happen."
The researchers were able to do this analysis in near real time because of the availability of large computing power and previously laid groundwork.

The computing power allowed researchers to model the fault more accurately. In the past, subduction zones were modeled as if they were on a plane, but the plate that is subducting curves underneath the other plate creating a 3-dimensional fault line. The researchers used a model that accounted for this curving and so more accurately recreated the stresses on the real geology at the fault.

"One of the things the U.S. Geological Survey and we have been doing is characterizing the major tectonic settings," said Furlong. "So when an earthquake is imminent, we don't need a lot of time for the background."

In essence, they are creating a library of information about earthquake faults and have completed the first level, a general set of information on areas such as Japan, South America and the Caribbean. Now they are creating the levels of north and south Japan or Chile, Peru and Ecuador.
Knowing where the old earthquake occurred, how large it was and how long ago it happened, the researchers could look at the foreshocks, see how much stress they relieved and anticipate, at least in a small way, what would happen.

"This is what we need to do in the future in near real time for decision makers," said Furlong.

Source: Penn State