Major quake hits Haiti

One of the poorest countries in the world, Haiti, has been hit by a 7.0-magnitude Earthquake. Initial reports talk about big number of dead and injured in the streets of Haiti's capital Port-au-Prince. The highly impoverished country is not in a position to provide basic emergency services to help the injured. The quake struck at 4:53pm on Tuesday, and as night fell people were out in the streets - screaming and crying for help.

Sun and moon trigger deep tremors on San Andreas Fault

The faint tug of the sun and moon on the San Andreas Fault stimulates tremors deep underground, suggesting that the rock 15 miles below is lubricated with highly pressurised water that allows the rock to slip with little effort, according to a new study by University of California, Berkeley, seismologists.

"Tremors seem to be extremely sensitive to minute stress changes," said Roland Bürgmann, UC Berkeley professor of earth and planetary science.

Fault weaknesses, the centre cannot hold for some geologic faults

This is a view of the Zuccale Fault, Elba, Italy from a distance. Photo: Cristiano Collettini, Universita degli Studi di Perugia, Italy,Some geologic faults that appear strong and stable, slip and slide like weak faults. Now an international team of researchers has laboratory evidence showing why some faults that "should not" slip are weaker than previously thought.

"Low-angle normal faults – faults that dip less than 45 degrees – are a problem," said Chris Marone, professor of geosciences, Penn State. "Standard analysis shows that these faults should not slip because it is easier to form a new fault than to slip on this orientation."

Pre-eruption earthquakes offer clues to volcano forecasters

Like an angry dog, a volcano growls before it bites, shaking the ground and getting "noisy" before erupting. This activity gives scientists an opportunity to study the tumult beneath a volcano and may help them improve the accuracy of eruption forecasts, according to Emily Brodsky, an associate professor of Earth and planetary sciences at the University of California, Santa Cruz.

Brodsky will present recent findings on pre-eruption earthquakes on, December 16, at the fall meeting of the American Geophysical Union in San Francisco.

Lower rate of quakes along some subduction zones

Most earthquakes occur along fault lines, which form boundaries between two tectonic plates. As the relative speed of the plates around a fault increases, is there a corresponding increase in the number of earthquakes produced along the fault? According to this study published in the December issue of BSSA, the answer depends upon the type of tectonic boundary. On certain types of boundary, the efficiency of earthquake production actually depends on the fault slip rate.

Seismic hazard assessments consider many factors, including relative plate velocity. It is important to understand whether there is a linear relationship between relative plate velocity along a fault and the production of earthquakes in order to estimate risk to populations and manmade structures from seismic activity.

Quake prediction model developed

The tsunami after 2004 Indian Ocean earthquakeA trio of papers in Nature suggests way to narrow size and location range of future earthquakes

The third in a series of papers in the journal Nature completes the case for a new method of predicting earthquakes.The forecasting model developed by Danijel Schorlemmer, of the USC College of Letters, Arts and Sciences, aims to predict the rough size and location of future quakes. Testing of the model is underway.

Small faults in southeast Spain reduce earthquake risk of larger ones

A team of Spanish scientists, studying recent, active deformations in the Baetic mountain range, have shown that the activity of smaller tectonic structures close to larger faults in the south east of the Iberian Peninsula partially offsets the risk of earthquakes.

"There are large faults in the eastern part of the Baetic mountain range, which are active and occasionally cause moderate, low magnitude earthquakes (measuring less than 5 on the Richter scale)", Antonio Pedrera, lead author of the study and a researcher in the Department of Geodynamics at the University of Granada (UGR), tells SINC.

New technique helps find more aftershocks for earthquake

Aerial view of the San Andreas Fault.Photo:Ikluft/WikimediaUsing a technique normally used for detecting weak tremors, scientists at the Georgia Institute of Technology discovered that the 2004 magnitude 6 earthquake along the Parkfield section of the San Andreas fault exhibited almost 11 times more aftershocks than previously thought. The research appears online in Nature Geoscience and will appear in print in a forthcoming edition.

"We found almost 11 times more events in the first three days after the main event.

Scientists obtain rocks moving into seismogenic zone

An international group of scientists aboard the Deep-Sea Drilling Vessel CHIKYU, operated by the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) for the Integrated Ocean Drilling Program (IODP), return from a 40-day scientific expedition off the shore of the Kii Peninsula, Japan on Oct. 10, 2009. Expedition 322, called "Subduction Inputs" in the multi-stage project, conducted drilling, logging and sampling beneath the ocean floor to investigate input material that will be transported to the seismogenic zone by the plate subduction system.

The drilling operations were carried out at two sites in the Shikoku Basin, the back-arc basin of the Izu-Bonin volcanic chain where the Philippine Sea Plate dives down into the Nankai Trough at a rate of about 4 cm per year.

At the first site C0011, scientists began coring from a depth of 340 meters below the seafloor. The coring, however, had to be abandoned at a depth of 881 meters because of damage of the drill bit. At the second site C0012, coring was carried out from depths 60 meters to 576 meters below the seafloor, and successfully collected the targeted sedimentary and basement rock samples.

Dr. Michael Underwood, professor at University of Missouri, USA, and co-Chief Scientists of the expedition said, "We identified an interface of Miocene sediment and basement rock around 540 meters beneath the seafloor and successfully sampled basaltic pillow lava rocks that make up the basement."

He added "These sedimentary and volcanic rocks in the lower part of Shikoku Basin are key intervals for generating large earthquake slip after they are transported to the seismogenic zone. Studying their petrological, geotechnical, frictional and hydrogeological properties prior to subduction is expected to contribute significantly to the understanding of rupture dynamics in the seismogenic zone."

The science party included 26 onboard research specialists from international member countries. "Scientists observed, measured and analysed geological samples by day and night working shifts in the onboard laboratories," said Dr. Saneatsu Saito from JAMSTEC who led research activities as another co-Chief Scientist.

He explained the importance of the variety of data obtained, "The sand-rich volcanic sediments were confirmed in large quantity and may have been transported from the easterly located Izu-Bonin Arc about 5 to 11 million years ago. Other sandstones contain abundant minerals derived from land, implying the extensive supply of sand to the Shikoku Basin from the Japanese islands."

Prof. Underwood added, "Analysis of pore water and hydrocarbon gases retrieved from the sedimentary layers above the basement indicates multiple sources and migration paths of fluids. These results have important implications for understanding the properties of fluids within the seismogenic zone."

Waterbourne diseases feared after Sumatra earthquake

Heavy rains in Sumatra could lead to the spread of waterbourne diseases following the earthquake which has killed hundreds of people, ActionAid has warned.

ActionAid’s Hanizam Ghani in Banda Aceh said: “Parts of Sumatra are experiencing heavy rains which are worsening an already dreadful situation. There is a real fear that unhygienic conditions could lead to the spread of waterborne diseases like diarrhoea and cholera.”

With houses, hotels and hospitals destroyed, the death toll is expected to rise sharply,

Medical services need to reach people in time to avoid long-term disabilities from initial injuries. Special needs of women and children such as security and nutrition must be considered.

Hanizam Ghani continued: “Our experience of previous earthquakes such as Indonesia, Kashmir and Gujarat shows that what people need immediately are tents, food, water and medical supplies. But as well as meeting physical needs, psychological care is also vital following a traumatic event like this.”

ActionAid said its assessment teams will soon be in the area and aim to work with local people on the ground as part of the rescue and relief operations.

Buildings that survive earthquake test in style

After a shaking test, a (formerly flat) steel fuse shows the deformation caused by the energy it dissipated during shaking. The fuses are designed to absorb damage and are easily replaced after an earthquake.Stanford scientists and others create a structural design that lets buildings rock during earthquakes, then pull themselves into plumb when the shaking stops, confining damage to replaceable steel "fuses."

A new earthquake-resistant structural system for buildings, just successfully tested in Japan, will not only help a multi-story building hold itself together during a violent earthquake, but also return it to standing up straight on its foundation afterward, true and plumb, with damage confined to a few easily replaceable parts.

The team that designed the system was led by researchers at Stanford University and the University of Illinois. During testing on a massive shake table, the system survived simulated earthquakes in excess of magnitude 7, bigger than either the 1994 Northridge earthquake or the 1989 Loma Prieta earthquake in California.

"This new structural system has the potential to make buildings far more damage-resistant and easier to repair, so people could reoccupy buildings a lot faster after a major earthquake than they can now," said Greg Deierlein, professor of civil and environmental engineering at Stanford, who led the team that designed the new system.

The system dissipates energy through the movement of steel frames that are situated around the building's core or along exterior walls. The frames can be part of a building's initial design or could be incorporated into an existing building undergoing seismic retrofitting. They are economically feasible to build, as all the materials employed are commonly used in construction today and all the parts can be made using existing fabrication methods.

"What is unique about these frames is that, unlike conventional systems, they actually rock off their foundation under large earthquakes," Deierlein said.

Schematic diagram of the rocking frame set up for shake-table testing. The steel-braced frame is shown in red. The white structure behind the frame simulates the weight of a three-story building. The inset shows the replaceable steel fuse, in yellow, at the base of the rocking frame. Behind and in front of the fuse are the vertical steel cables that pull the building back into plumb after an earthquake. During testing, the frame was sandwiched between two of the white structures.The rocking frames are steel braced-frames, the columns of which are free to rock up and down within steel "shoes" secured at their base. To control the rocking and return the frame to vertical when the shaking stops, steel tendons run down the center of the frame from top to bottom. These tendons are made of high-strength steel cable strands twisted together and designed to remain elastic during shaking. When shaking is over, they rebound to their normal length, pulling the building back into proper alignment.

At the bottom of the frame sit steel "fuses" designed keep the rest of the building from sustaining damage.

"The idea of this structural system is that we concentrate the damage in replaceable fuses," Deierlein said. The fuses are built to flex and dissipate the shaking energy induced by the earthquake, thereby confining the damage. Like electrical fuses, the steel fuses are easily replaced when they "blow out."
Deierlein and his colleagues conducted shake testing of the new system in the last few weeks at the Hyogo Earthquake Engineering Research Center in Miki City, Japan.

Using different types of fuses and various shaking parameters, they conducted four major tests, the last on Aug. 24. They had previously developed and tested the individual components of the system and performed computational analyses to simulate the system's performance at laboratories at Stanford and the University of Illinois.

"We are really delighted," said Greg Deierlein, who is the principal investigator on the project and oversaw the testing in Japan. "This is the first time we've put this whole system together to see how it would respond dynamically in a building as if it were subjected to an earthquake. It performs well under extreme earthquake shaking."

Deierlein said that while various researchers have been working for 10 or 15 years on some of the ideas and techniques encompassed in the new system, this is the first time anyone has put them all together to demonstrate their performance.

How the tests were done

The tests of the new system were conducted using a three-quarters size model of a standard modern three-story office building with a footprint 120 by 180 feet. The 26-foot tall model sat on a massive vibrating shake table – the largest in the world, measuring over 3,000 square feet in size – that is designed to reproduce the shaking from different earthquakes.

For testing, Deierlein's group constructed a complete three-story steel-braced frame that is sandwiched between two concrete and steel structures in which they concentrated all the mass that would normally be in a building that size. Each of the three stories weighed 100 metric tons.

The researchers subjected their model to ground motions recorded during the 1995 Kobe, Japan, earthquake, magnitude 6.9, and the 1994 Northridge earthquake, magnitude 6.7. The U.S. Geological Survey characterises the Northridge temblor as the most costly in U.S. history, with losses estimated at more than USD40 billion. The Kobe earthquake caused over 6,000 fatalities and economic losses are estimated to have been three to five times greater than Northridge.

System survived even extreme shaking

For some of the shake tests, Deierlein said his group amplified the ground motion shaking from the actual earthquake records to simulate the shaking that would happen during the largest earthquake that each fault is considered likely to generate.

"The rocking frame after that shaking is still virtually undamaged, except that we have these fuses in there that yield and deform, that absorb the energy," Deierlein said.

For the fourth and final test, the group used a motion from the Northridge earthquake and scaled it up 1.75 times greater than the recorded motion, well in excess of the Maximum Considered Earthquake. "The only damage that occurred to the test frame was in the replaceable fuses," said Deierlein. "This final test demonstrated that the rocking frame is a reliable and effective system."

"Most buildings that we design today for large earthquakes are designed such that when there is a large earthquake, the building, in a sense, sacrifices itself to save the occupants," Deierlein said. Buildings that survive earthquakes often have to be torn down because they are too deformed or damaged during the shaking for it to be economical, or even physically possible, to repair them.

"In this design, we are thinking ahead to minimising the damage that is going to be left in place after the earthquake," Deierlein said. The elastic behavior of the steel tendons, each of which consists of seven steel wires similar to the wire used in modern suspension bridges, is particularly critical to preventing residual deformation of the building by pulling it back into plumb when the shaking stops.

Other advantages and sustainability benefits

In addition to saving lives and minimising repair costs, widespread use of the new techniques could offer other benefits.

"If more buildings are habitable right after an earthquake, you will have less disruption to society," Deierlein said. That could greatly reduce how long economic downturns and social disruptions linger after a major earthquake. And there are potential environmental benefits.

"If you think of the sustainability issues, imagine if you have a city where you have to end up tearing down large numbers of buildings," he said. "In terms of the environmental issues, there are tremendous costs for disposing of construction materials in landfills, coupled with the impacts of manufacturing the materials used for rebuilding.

"We are trying to look at the embodied energy of all of the materials that are used in the building, the things that go into the concrete and steel making, for example," Deierlein said. "By prolonging the longevity of buildings, you have a really positive sustainability impact."

A hoped-for ripple effect

Deierlein said the system he and his colleagues have developed is applicable to steel-framed buildings up to about 15 stories tall, but that the general approach could be modified for other types of buildings.

"We hope that this concept implemented in this braced-frame structure could have much broader applications in terms of spurring the development of these same ideas, but applied to alternate materials and alternate configurations," Deierlein said. "The concept of using this controlled rocking with steel tendons that behave elastically and these energy-dissipating fuses is a general concept that could be applied in different materials and in different forms."

Other Stanford researchers working with principal investigator Deierlein on the project, all in the department of civil and environmental engineering, include co-principal investigator Associate Professor Sarah Billington, Professor Emeritus Helmut Krawinkler and doctoral candidate Xiang Ma.

The other co-principal investigator is Jerome Hajjar, a professor of civil and environmental engineering at the University of Illinois. The team also includes professional structural engineers David Mar of Tipping Mar and Associates of Berkeley, and Gregory Luth of Gregory P. Luth and Associates of Santa Clara. International collaborators include researchers from the Tokyo Institute of Technology and Hokkaido University.

The shake testing was conducted using the Earthquake Defense (E-Defense) shake table at the Hyogo Earthquake Engineering Research Center in Miki City, Japan.

The research is funded by the National Science Foundation, the National Research Institute for Earth Science and Disaster Prevention in Japan, the American Institute of Steel Construction and other industry groups.

Listening to rocks helps to understand earthquakes

When Apollo punished King Midas by giving him donkey ears, only the king and his barber knew. Unable to keep a secret, the barber dug a hole, whispered into it, “King Midas has donkey ears,” and filled the hole. But plants sprouted from the hole, and with each passing breeze, shared the king’s secret.

Earth, as it turns out, has other secrets to divulge. From the pounding of the surf and the rumbling of thunder, to the gentle rustling of leaves, Earth is not a quiet planet. The key is, knowing how to listen to the ever-present ambient noise.

University of Illinois seismologist Xiaodong Song and graduate student Zhen J. Xu have become good listeners, especially to the sounds beneath our feet. Using a technique called “ambient noise correlation,” Xu and Song have observed significant changes in the behaviour of parts of Earth’s crust that were disturbed by three major earthquakes.

“The observations are important for understanding the aftermath of a major earthquake at depth,” Song said, “and for understanding how the rock recovers from it and begins again to accumulate stress and strain for future earthquakes.”

The pair report their findings in a paper accepted for publication in the Proceedings of the National Academy of Sciences, and posted on the journal’s Web site.

Researchers have used ambient noise to image Earth’s interior and to monitor changes in seismic velocity near active volcanoes.

Xu and Song used the technique to examine how surface waves (extracted from ambient noise) between seismic stations change with time, because of earthquake-induced changes in the surrounding rock.

Xu and Song were not measuring the time it took for earthquake waves to travel from the epicentre to a seismic station. Rather, they were measuring the time it took for surface waves to travel from one station to another. Because the distance between stations is fixed, the technique allowed researchers to detect very tiny changes in seismic velocity.

“The observations allow us to see not just what happened at the surface, but what happened at depth, and how it affects not just the rupture area, but also the surrounding area,” Xu said.

In their study, the researchers examined the three largest and most recent earthquakes in Sumatra, Indonesia. The earthquakes took place on Dec. 26, 2004; March 28, 2005; and Sept. 12, 2007.

The earthquakes occurred along the Sumatra subduction zone, where a portion of the Indian tectonic plate dives beneath the Eurasian plate. Fault rupture lengths ranged from 450 kilometres for the 2007 earthquake to 1,200 kilometres for the 2004 earthquake.

“We observed a clear change in surface wave velocity over a large area after each of the earthquakes,” Xu said.

In one set of measurements, for example, a surface wave travelling between two particular seismic stations normally required 600 seconds to complete the journey. Following the 2005 earthquake, this time shifted by 1.44 seconds, which is a significant change. But, in all cases, the seismic velocities returned to normal levels within two to three months, indicating that elastic properties in the surrounding rock had recovered.

The most plausible explanation for the time shifts, the researchers write, is increased stress and relaxation in Earth’s upper crust in the immediate vicinity of the rupture, as well as in the broad area near the fault zone. Using ambient noise correlation, the researchers can observe changes in stress several hundreds of kilometres from the source region.

The researchers also observed an unusual time shift that took place a month before the 2004 earthquake. More data is needed, however, to draw a conclusion and to determine whether it was a precursory signal to a major earthquake.

To that end, Xu and Song are studying last year’s devastating earthquake in Wenchuan county in southwest China. An abundance of data was recorded at nearly 300 seismic stations in the source region by seismologists in China. The analysis of respective time shifts will help the researchers better understand how the fault and surrounding behaved before and after the earthquake.

“We need to densify our monitoring network,” Song said. “With this natural source that’s on all the time, and enough paths between different seismic stations, we can see not only changes in time, but also changes in space. So we can have a spatial and temporal image of what’s going on both before and after a major earthquake.”

The work was funded by the National Science Foundation and the Air Force Research Laboratory.