6.4 Magnitude Earthquake Hits Southwest Japan; Aftershocks Reported

TOKYO – A powerful earthquake with a preliminary magnitude of 6.4 struck Kyushu on Thursday, causing some damage but there was no danger of a tsunami.

earthquake-logo

The Japan Meteorological Agency said the quake hit at 9:26 p.m. and was centered in the Mashiki town in the Kumamoto Prefecture where it registered the highest level of 7 on the Japanese seismic scale.

No abnormalities were reported at the Sendai nuclear power plant, officials said.

Keisukei Urata, an official at Uki city, said he was driving home when the quake struck. He said he saw some walls around houses collapsing.

Parts of the ceiling at Uki City Hall collapsed, windows were broken and cabinets fell to the ground, he said.

Kasumi Nakamura, an official in the village of Nishihara near the epicenter, said that the rattling started modestly and grew violent, lasting about 30 seconds.

“Papers, files, flower vases and everything fell on the floor,” he told a telephone interview with NHK TV. He said there were aftershocks.

One aftershock measuring 5.7 struck about 40 minutes later, while Kumamoot experienced an aftershock measuring a lower 6, according to Japan’s Meteorological Agency.

The U.S. Geological Survey put the quake’s preliminary magnitude at 6 and said it was 10 kilometers deep. It did not expect major damage.

Footage on NHK showed a signboard hanging from the ceiling at its local bureau violently shaking. File cabinets rattled, books, files and papers rained down to the floor, and one employee appeared to have fallen off a chair, while others slid underneath their desks to protect their heads.

Magnitude-6.9 Earthquake Hits Myanmar, Felt In India

A magnitude-6.9 magnitude earthquake hit Myanmar on Wednesday, the U.S. Geological Survey reported. There were no immediate reports of injuries, deaths or damage.

earthquake_sign800x

The quake struck around 8:25 p.m. local time at a depth of 83.7 miles underground, USGS reported. Its epicenter was located 46 miles southeast of Mawlaik, in western Myanmar.

The quake was felt in the eastern Indian states of Assam and West Bengal, the Associated Press reported.

Quakes in the region typically are the result of the continental collision of the India and Eurasia plates.

Model Suggests 1812 San Andreas Earthquake May Have Been Set Off By San Jacinto Quake

An assistant researcher professor with California State University has found evidence that the powerful quake that struck southern Californian back in 1812 may have been precipitated by a fault line other than the San Andreas. In his paper published in the journal Science Advances, Julian C. Lozos describes a computer model he created using real world data, what it showed, and why his findings suggest that a future double earthquake could occur someday in the area.

quake

Back in 1812 a major earthquake struck southern California near what is now San Bernardino—modern study of damage from the quake suggested it was approximately a magnitude 7.5 quake. There was little damage because there were few structures in the area back then, though approximately 40 people were killed when a church they were in collapsed. For many years, Earth scientists have assumed that the quake was due solely to activity along the San Andreas Fault. In this new effort, Lozos suggests that the quake may have actually been set off by a quake along the San Jacinto fault line.

Lozos’ findings are part of a study that included field trips to several sites in an area where the San Andreas Fault and the San Jacinto Fault nearly merge. While there, he found evidence of three strands—where sections of fault are separated by bits of crust that has remained intact—one near the San Andreas fault and two near the San Jacinto fault. Each strand is evidence of an earthquake, but reports from people in the area suggest there were only two earthquakes during the time period under study—in 1812 and 1800, which suggested that one of the strands on the San Andreas Fault and one on the San Jacinto Fault were evidence of the same quake. Lozos also looked at other data collected by other researchers doing working on faults in the area—all of it went into a model he built to describe seismic activity in the area surrounding the time frame of the 1812 quake. The model showed that the most likely scenario that could account for the data that has been collected was that a quake had occurred along the San Jacinto fault line and as it made its way near the San Andreas fault line, the disruption caused a quake to occur along that fault line as well.

Lozos is quick to point out that his model is just that and that thus far he has no evidence to suggest that such a double quake is imminent, but he also notes that if it happened before, it could happen again, noting that southern California is long overdue for a pretty big tumbler.

New Study Pinpoints Stress Factor Of Mega-Earthquake Off Japan

Scripps Institution of Oceanography, UC San Diego researchers published new findings on the role geological rock formations offshore of Japan played in producing the massive 2011 Tohoku-oki earthquake, one of only two magnitude 9 mega-earthquakes to occur in the last 50 years.

earthquake

The study, published in the journal Nature, offers new information about the hazard potential of large earthquakes at subduction zones, where tectonic plates converge.

The magnitude 9 quake, which triggered a major tsunami that caused widespread destruction along the coastline of Japan, including the Fukushima nuclear plant disaster, was atypical in that it created an unusually large seismic movement, or slip, of 50 meters (164 feet) within a relatively small rupture area along the earthquake fault.

To better understand what may have caused this large movement, Scripps researchers used gravity and topography data to produce a detailed map of the geological architecture of the seafloor offshore of Japan. The map showed that the median tectonic line, which separates two distinct rock formations, volcanic rocks on one side and metamorphic rocks on the other, extends along the seafloor offshore.

The region over the earthquake-generating portion of the plate boundary off Japan is characterized by variations in water depth and steep topographic gradients of about six kilometers (3.7 miles). These gradients, according to the researchers, can hide smaller variations in the topography and gravity fields that may be associated with geological structure changes of the overriding Japan and subducting Pacific plates.

“The new method we developed has enabled us to consider how changes in the composition of Japan’s seafloor crust along the plate-boundary influences the earthquake cycle,” said Dan Bassett, a postdoctoral researcher at Scripps and lead author of the study.

The researchers suggest that a large amount of stress built up along the north, volcanic rock side of the median tectonic line resulting in the earthquake’s large movement. The plates on the south side of the line do not build up as much stress, and large earthquakes have not occurred there.

“There’s a dramatic change in the geology that parallels the earthquake cycle,” said Scripps geophysicist David Sandwell, a co-author of the study. “By looking at the structures of overriding plates, we can better understand how big the next one will be.”

Earthquakes On Thrust Faults Can Spread 10 Times Farther To A Second Nearby Thrust Fault Than Previously Thought

A team of researchers, including one from the University of California, Riverside, has discovered that earthquake ruptures can jump much further than previously thought, a finding that could have severe implications on the Los Angeles area and other regions in the world.

quake 1jpg

The scientists found that an earthquake that initiates on one thrust fault can spread 10 times farther than previously thought to a second nearby thrust fault, vastly expanding the possible range of “earthquake doublets,” or double earthquakes.

That could mean in areas such as Los Angeles, where there are multiple thrust faults close to each other, an earthquake from one thrust fault could spread to another fault, creating twice as much devastation.

One potential bad scenario involves a single earthquake spreading between the Puente Hills thrust fault, which runs under downtown Los Angeles, and the Sierra Madre thrust fault, located close to Pasadena, said Gareth Funning, an associate professor of earth sciences at UC Riverside, and a co-author of a paper published online today (Feb. 8, 2016) about the research in the journal Nature Geoscience.

Other susceptible areas where there are multiple thrust faults are in close proximity include the Ventura, Calif. area, the Middle East, particularly Tehran, Iran, and the front of the Himalayas, in countries such as Afghanistan, Pakistan, India and Nepal.

The researchers studied a 1997 earthquake in Pakistan, originally reported as a magnitude 7.1 event, showing that it was in fact composed of two ‘subevents’—a magnitude 7.0 earthquake, that was followed 19 seconds later by a magnitude 6.8 event, located 50 kilometers (30 miles) to the southeast.

Funning considers the two earthquakes as subevents of one ‘mainshock,’ as opposed to the second earthquake being an aftershock, because they happened so close together in time and were so similar in size. There were many aftershocks in the following minutes and hours, but most of them were much smaller.

The scientists used satellite radar images, precise earthquake locations, modeling and back projection of seismic radiation to prove the seismic waves from the first subevent caused the second to initiate, effectively ‘jumping’ the 50 kilometer distance between the two. Scientists previously thought an earthquake could only leap up to five kilometers.

The finding has implications for seismic hazard forecasts developed by the United States Geological Survey. The current forecast model does not include the possibility of a similar double earthquake on the thrust faults in the Los Angeles area.

“This is another thing to worry about,” Funning said. “The probability of this happening in Los Angeles is probably pretty low, but it doesn’t mean it can’t happen.”
Funning started work on the paper about 12 years ago as a graduate student at the University of Oxford. He was the first to find the satellite data for the earthquakes in Pakistan, which occurred in a largely unpopulated area, and notice they occurred close together in space and time.

After dropping the work for several years, he, along with lead author Ed Nissen of the Colorado School of Mines, picked it up about three to four years ago, in part because of the possible implications for the Los Angeles area, which has a similar plate boundary, with similar faults, similar distances apart as the region in Pakistan where the 1997 earthquake doublet occurred.

Thrust faults happen when one layer of rock is pushed up over another, often older, layer of rock by compressional forces. Thrust faults came to the attention of Californians after the 1994 Northridge earthquake, about 20 miles northwest of Los Angeles, which occurred on a thrust fault.

Thrust faults are not as well understood by scientists as strike-slip faults, such as the San Andreas, in part because they are not as visible in the landscape, and do not preserve evidence for past earthquakes as well.

Researchers Find New Cause of Strong Earthquakes

A geologic event known as diking can cause strong earthquakes—with a magnitude between 6 and 7, according to an international research team.

quake

Diking can occur all over the world but most often occurs in areas where the Earth’s tectonic plates are moving apart, such as Iceland, Hawaii and parts of Africa in the East African Rift System. As plates spread apart, magma from beneath the Earth’s surface rises into the space, forming vertical magma intrusions, known as dikes. The dike pushes on the surrounding rocks, creating strain.

“Diking is a known phenomenon, but it has not been observed by geophysical techniques often,” said Christelle Wauthier, assistant professor of geosciences, Penn State who led the study. “We know it’s linked with rift opening and it has implications on plate tectonics. Here, we see that it also could pose hazards to nearby communities.”
The team investigated ties between two natural disasters from 2002 in the Democratic Republic of the Congo, East African Rift System. On Jan. 17, the Nyiragongo volcano erupted, killing more than 100 people and leaving more than 100,000 people homeless. Eight months later a magnitude 6.2 earthquake struck the town of Kalehe, which is 12 miles from the Nyiragongo volcano. Several people died during the Oct. 24 earthquake, and Kalehe was inundated with water from nearby Lake Kivu.

“The Kalehe earthquake was the largest recorded in the Lake Kivu area, and we wanted to find out whether it was coincidence that, eight months before the earthquake, Nyiragongo erupted,” said Wauthier.

The researchers used a remote sensing technique, Interferometric Synthetic Aperture Radar, to measure changes to the Earth’s surface before and after both natural disasters.

“This technique produces ground surface deformation maps. Then, you can invert those deformation maps to find a source that could explain the observed deformation. For the deformation observed in January 2002, we found that the most likely explanation, or best-fitting model, was a 12-mile diking intrusion in between Nyiragongo and Kalehe,” said Wauthier.

The researchers used the same technique for the October 2002 magnitude 6.2 earthquake, analyzing seismicity in addition to ground-deformation changes. They found that there was a fault on the border of the East African Rift System that slipped, triggering the earthquake.

“We were able to identify the type of fault that slipped, and we also had the best-fitting model for the dike intrusion,” said Wauthier. “Knowing both of those, we performed a Coulomb stress-change analysis and found that the January 2002 dike could have induced the October 2002 earthquake.”

Coulomb stress-change analysis is a modeling technique that calculates the stress changes induced by a deformation source at potential receiver faults throughout a region. If the Coulomb stress changes are positive, it means that the source is bringing the receiver fault closer to failure—closer to slipping and generating an earthquake. This type of analysis is regularly applied to assess whether an earthquake in one region could trigger a secondary earthquake nearby.

The researchers hypothesized that the dike opening pushed outward against the adjacent rocks. These rocks became strained and passed stress to rocks adjacent to them, accumulating stress on rocks on a fault in the Kalehe area. The dike brought this fault closer to failure and, eight months later, a small stress perturbation could have triggered the start of the magnitude 6.2 earthquake.

“We’ve known that every time magma flows through the Earth’s crust, you create stress and generate seismicity,” said Wauthier. “But these are normally very low magnitude earthquakes. This study suggests that a diking event has the potential to lead to a large earthquake,” said Wauthier.

The researchers report their findings in the current issue of Geochemistry, Geophysics, Geosystems.

Dozens Still Trapped A Day After Taiwan Earthquake

TAINAN, Taiwan – With anxious families waiting nearby, rescuers on Sunday painstakingly pulled more survivors from the remains of a high-rise apartment building that collapsed a day earlier in a powerful earthquake that shook southern Taiwan and killed at least 26 people. More than 100 remained buried in the building’s rubble.

earthqake

The government in Tainan, the worst-hit city, said that more than 170 people had been rescued from the 17-story building, which folded like an accordion after the quake struck.

Mao Yi-chen, 20, was rescued soon after the magnitude-6.4 quake hit before dawn Saturday, and her older sister Mao Yi-hsuan was pulled out Sunday in serious condition. A rescue worker had handed over a photo album and homemade cards found next to her for her family to collect, said local official Wang Ding-yu.

“He said that ‘maybe your home is damaged, but memories of the family can last,'” Wang said.

Tainan Mayor Lai Ching-te said authorities estimated that 124 people were still trapped, many at the bottom of the wreckage. He said rescuers were able to reach many people by using information from residents who got out about the possible locations of those still inside.

Wendy Chuang, a reporter in Taiwan, told CBS Radio News that the building was unrecognizable.

“Actually if no one told me, it’s hard to tell that’s a building because it just fell down and you can’t tell which way it fell down actually,” Chuang said. “You can’t find where’s the doors, where’s the front, where’s the back.”

Two of the trapped, a male and a female at different sides of the building, were talking to rescue workers on Sunday evening, Lai said. He told reporters that rescuers intended to pull them out, and then bring in heavier excavators to remove part of the structure on top to allow access to the areas at the bottom.

The spectacular fall of the high-rise, built in 1989, raised questions about whether its construction had been shoddy. Tainan’s government said the building had not been listed as a dangerous structure, and Taiwan’s interior minister, Chen Wei-zen, said an investigation would examine whether the developer had cut corners.

Eighth-floor resident Huang Guang-wei was pulled out Sunday morning from a different section from where he lived, showing how distorted the building is, Lai said. Rescuers could see Huang only through a 10-centimeter (4-inch) crack and it took eight hours to get him out, Lai said.

Among the fatalities was a 6-month-old baby girl who was pulled from the rubble and rushed to a hospital, where she was pronounced dead. A deceased man believed to be her father was pulled out 40 minutes later, Wang said.

A man in his 60s, whose son escaped and whose daughter-in-law was in serious condition, was trying to help rescuers pinpoint his grandsons. “My 11- and 12-year-old grandsons are still inside on the ninth floor,” said the man, who gave only his surname, Huang. “I told my son not to buy an apartment here; it was suspiciously cheap.”

Beside him, another man nodded in agreement as he waited for news of his own relatives on the seventh floor.

The city government said that 24 of the 26 confirmed deaths from the earthquake were from the building collapse. It said that 171 had been rescued from the building, 91 of whom were sent to hospitals. More than 100 people were rescued from other parts of Tainan, eight of whom received hospital treatment. Nine other buildings in the city collapsed and five careened.

On Sunday, thousands of rescuers worked on different levels of the folded building, which was supported by steel pillars. Rescuer Su Yu-min said they were trying to cut through walls and pillars.

“It takes a few hours to complete a search for just one household and sometimes it takes two hours just to go forward 30 centimeters (12 inches)” when the way is blocked by a wall, he said.

Taiwanese broadcaster EBC showed video of volunteers trying to comfort the mother of a missing 20-year-old man, Chen Guan-yu. “He always thinks of me,” said the woman, whose name was not given. “He worries about me being single and lonely and that no one is taking care of me.”

The quake came two days before the start of Lunar New Year celebrations that mark the most important family holiday in the Chinese calendar.

Earthquakes frequently rattle Taiwan, but most are minor and cause little or no damage, though a magnitude-7.6 quake in central Taiwan in 1999 killed more than 2,300 people.