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.

New Study Challenges Jupiter’s Role As Planetary Shield, Protecting Earth From Comet Impacts

Not only is the “Jupiter as shield” concept, implying that the planet shields Earth from comet impacts, not true, but perhaps Jupiter’s most important role in fostering the development of life on Earth was just the opposite — delivering the volatile materials from the outer Solar System needed for life to form. This new simulation study, and the previously underestimated role that Saturn may have also played in the evolution of life on Earth, are presented in an original research article published in Astrobiology.

jupiter

In “Jupiter: Cosmic Jekyll and Hyde”), Kevin Grazier, PhD, at the NASA Jet Propulsion Laboratory in Pasadena, describes the study in which he simulated the evolution of tens of thousands of particles in the gaps between the jovian planets for up to 100 million years. Based on the results, Dr. Grazier concludes that the widely reported shield role attributed to Jupiter is incorrect. The simulations showed that Jupiter teams with Saturn to kick a significant fraction of the particles into the inner Solar System and into orbits that cross Earth’s path. He proposes that a Solar System with one or more planets similar to Jupiter located beyond the region of potential terrestrial planets is beneficial for the development of life.

“In an unprecedented effort to solve the riddle as to whether jovian bodies shield habitable planets from impacts catastrophic to life, Dr. Grazier presents a modeling study that speaks to the incredible complexity of planetisimal evolution in the Solar System,” says Sherry L. Cady, PhD, Editor-in-Chief of Astrobiology and a Chief Scientist at the Pacific Northwest National Laboratory. “In this paper, we learn that the overly simplistic ‘Jupiter as shield’ concept is a thing of the past, and future research in this area will require the continued use of the kinds of robust simulation strategies so effectively employed in Dr. Grazier’s work.”

Wild Winds Whip New England Ahead Of Major Snowstorm

The winter storm battering parts of New England Monday isn’t expected to drop 2 to 3 feet of snow in one go, but officials warn that wild winds and blizzard conditions could still cause power outages and tree damage – and make for an uncomfortable, if not dangerous, commute.

snow

The National Weather Service has issued blizzard warnings from the south of Boston to the South Shore, while areas of eastern New England – including Boston, Hartford, and Providence – are under winter storm warnings. Snow, which began after 8 a.m., may fall at rates of more than an inch an hour in parts of eastern New England, The Weather Channel reports.

But “[i]t’s not just the snow we are talking about – very strong winds, coastal flooding concerns – there could be some power outages, especially south of Boston,” said Cindy Fitzgibbon, meteorologist for Boston’s WCVB 5.

“The heaviest snow will fall this morning into mid/late afternoon across the region,’’ forecasters noted, according to the Boston Globe. “The greatest impact from this storm will not be specific snow amounts, but blizzard conditions.’’

The winter storm, dubbed Mars by The Weather Channel, is a result of a low pressure area off the East Coast – an area that went through what meteorologists call “bombogenesis,” or a sudden central pressure drop of at least 24 millibars in 24 hours.

“ ‘Bombogenesis’ follows from ‘cyclogenesis,’ which refers to the development of a cyclone,” wrote Stu Ostro, a senior meteorologist with The Weather Channel. “Bombs are so named because of the rapidity with which they develop, which evokes explosiveness, and the power that they usually attain once they have gone through the intensification phase specified in the definition.”

Winds of up to 45 miles per hour could blow through eastern New England, while the gusts could hit up to 65 miles per hour on Cape Cod.

Boston Public Schools and dozens of other public and private colleges have canceled classes Monday. The Massachusetts Port Authority has also warned travelers to check their itineraries before heading to Boston’s Logan International Airport, noting that some airlines “have already begun cancelling a number of flights and may be making accommodations for those impacted passengers.”

Massachusetts Gov. Charlie Baker also asked residents to stay off the roads when possible.

Mount Soputan Volcano Erupts In North Sulawesi, Indonesia

Mount Soputan volcano in North Sulawesi province of Indonesia erupted several times on Sunday, spewing a column of hot ash by up to 2.5 km high, official of disaster management agency said.

wpid-chile-volcano

Mount Soputan, located some 60 km from Manado, capital of the province, has high potential for further big eruption which is indicated by persistent tremors with amplitude of 41 mm, Spokesman of National Disaster Management Agency Sutopo Purwo Nugroho disclosed.

Several subdistricts in Minahasa Tenggara district were hit by rains of ash and volcanic materials that the local disaster agency distributes masks to protect local residents from the impact, he told Xinhua via phone.

The authorities have banned villagers or visitors from entering the area of 4 km from the crater, but at the southwest of the crater the evacuation zone is at 6. 5 km, Mr. Sutopo said.

The 1,874- meter high Mount Soputan is one of Indonesia’s active volcanoes whose number is about 129, according to the National Volcanology Agency.

Storm Imogen: Britain Faces 80mph Winds And Heavy Rain

Britain is to be hit by 80mph winds and heavy rain on Monday as Storm Imogen, the ninth major storm this winter, sweeps in from the Channel.

storm

The Met Office has issued amber “be prepared” weather warnings for much of the south-west and yellow “be aware” warnings stretch from southern Wales to the Thames estuary.

Storm Imogen comes at the end of a wet winter in which storms Henry, Gertrude, Frank and Desmond also battered the UK. The Met Office only started naming storms in 2015.

The warnings will be in place from 3am until 6pm on Monday and exposed areas on the south coast are on alert for winds of 80mph. The Met Office has warned that there could be “very large waves”, especially along the north coast of Cornwall and Devon.

Forecaster Craig Snell said: “We have issued a broad yellow warning of wind that encompasses Cardiff, Bristol and into the Thames estuary. There is an amber warning for wind mainly focused on Devon and Cornwall but stretching into central England on Monday morning.

“This means people should be prepared for disruption to travel on roads, rail, bridges and ferries and we could see possible damage to structures and downed trees risk affecting power. The wind will be combined with some hefty showers with some thunder along the south coast.”

There remains some uncertainty about how far north and east the strongest of the winds will extend, but gusts are expected to ease up on Tuesday. There is forecast to be a drier, quieter and colder interlude for many on Wednesday before more wind and rain follows later in the week.

South West Trains said it was planning to run a normal weekend timetable on all routes but that the risk of trees and debris being blown onto the railway might require the train line to “make adjustments to trains in certain areas”.

“In particular, the first trains to run over tracks may need to be cancelled to allow us to ensure these routes are clear and safe to run passenger services,” the statement read. “There may also be changes in the number of carriages to some services.”

The British Met Office and its Irish counterpart Met Eireann last year started following the approach taken by the US National Hurricane Centre and giving storms names in order to better communicate with the public.

Names are given in alphabetical order, though the letters Q, U, X, Y and Z are not used. The two Met offices released the official list of storm names in October and the next storm to hit the UK will be named Jake.

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.