Entire Himalayan Arc Can Produce Large Earthquakes

The main fault at the foot of the Himalayan mountains can likely generate destructive, major earthquakes along its entire 2,400-kilometer (1,500-mile) length, a new study finds. Combining historical documents with new geologic data, the study shows the previously unstudied portion of the fault in the country Bhutan is capable of producing a large earthquake and did so in 1714.

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“We are able for the first time to say, yes, Bhutan is really seismogenic, and not a quiet place in the Himalayas,” said György Hetényi, a geophysicist at the University of Lausanne, Switzerland and lead author of the new study accepted for publication in Geophysical Research Letters, a journal of the American Geophysical Union.

The Himalayas have produced some of the world’s largest earthquakes, like the April 2015 Gorkha earthquake that devastated Nepal. But scientists had not been able to prove whether every region along the 2,400-kilometer arc was seismogenic, or capable of producing quakes. Bhutan was one of the last open gaps along the mountain chain: the country had no records of recent major earthquakes and no major seismological work had been done there.

Confining a major earthquake to Bhutan in 1714, like the new study does, means the entire Himalayan arc has experienced a major earthquake in the past 500 years, according to the study’s authors. By filling this gap, the new study helps the millions of residents in the region understand its potential for natural hazards, according to Hetényi.

“We provide a longer and therefore more representative record of seismicity in Bhutan, and this makes better hazard estimates,” he said.

A nation apart

The highest mountain range on Earth, the Himalayas are the product of the Indian tectonic plate subducting under the Eurasian Plate. The mountains span a northwest to southeast arc roughly 2,400 kilometers (1,500 miles) long, nearly the distance between the U.S. East and West coasts.

Throughout the 20th century, Bhutan, a small nation east of Nepal sandwiched between India and China, had been relatively isolated from the outside world and scientists were rarely allowed inside its borders. Until recently, researchers thought Bhutan could be the only major segment of the Himalayas not to have experienced a major earthquake in the last 500 years, according to Hetényi.

But, after a magnitude 6 earthquake struck the country in 2009, the government opened the door for scientists to perform geophysical research, Hetényi said.

Hetényi and his colleagues made several trips to the country from 2010 to 2015 to catalog small earthquakes in the area and study how the structure of the Indian Plate changes as it subducts below the crushing belt of mountains. One question they were hoping to answer was whether Bhutan had historically experienced any major destructive earthquakes.

Historical records of earthquakes in Bhutan are rare, but by luck Hetényi stumbled upon a biography of famous 18th century Buddhist monk and temple builder Tenzin Lekpai Dondup. The biography described a quake in early May of 1714 that destroyed the Gangteng monastery Dondup helped build.

The biography and other historical records indicated there were many aftershocks, meaning it could have been a major quake, according to Hetényi.

However, this description alone did not pinpoint where the quake occurred.

“When you only have very local devastation descriptions, you never know whether this devastation is due to an intermediate earthquake that occurred locally, nearby the chronicler, or whether it’s the result of a bigger earthquake that occurred over greater distances,” said Laurent Bollinger, a geologist at the French Alternative Energies and Atomic Energy Commission who was not involved in the new study.

While in Bhutan, several of Hetényi’s colleagues dug trenches around the fault line to see if one side of it had moved vertically with respect to the other side — which would be considered evidence of a major earthquake. That study, led by Romain Le Roux-Mallouf, a geologist at the University of Montpellier, France, found evidence of rock uplift on one side of the fault had taken place between 1642 and 1836. Hetényi combined the results from that study with historical records of the 1714 earthquake to pinpoint where the 1714 quake happened and how large it was.

Hetényi’s analysis revealed the 1714 quake likely caused the rock uplift his colleagues observed around the fault. The earthquake likely occurred in west central Bhutan, where most of the population lives, and had a magnitude of at least 7.5 to 8.5, Hetényi said. By comparison, the April 2015 Gorkha earthquake had a magnitude of 7.8.

“It’s a really significant event that happened 300 years ago,” he said.

The results suggest the 1714 quake was significant enough to unzip a large segment of the thrust — possibly between 100 to 300 kilometers (60 to 200 miles) of the fault. The new study closes the seismic gap in the Himalayan arc and could help scientists better understand the earthquake potential in the densely populated Himalaya region, according to Hetényi.

Study: Full Moon Can Trigger Big Earthquakes

Could California’s long-dreaded “Big One” be triggered by a full moon?

Perhaps, says a new study out Monday that claims large earthquakes are more likely during unusually high tides, which occur during full and new moons.

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High tides, which typically occur twice a day, are caused when ocean water is moved by the gravitational pull of the moon. But twice a month, during a full or new moon, tides are especially high because the moon, earth and sun all line up together. (These twice-monthly tides are known as “spring” tides.)

Big quakes can occur when this additional weight of tidal water strains geological faults, according to the study. Though this theory is not new, this is the first study to display a firm, statistical link.

“The probability of a tiny rock failure expanding to a gigantic rupture increases with increasing tidal stress levels,” the study said.

Precisely how large earthquakes occur is not fully understood, but scientists say they may grow via a cascading process where a tiny fracture builds up into a large-scale rupture. If so, the authors’ results imply that the likelihood of a small fracture cascading into a large earthquake are greater during high tides.

The study was led by Satoshi Ide, a seismologist at the University of Tokyo and appeared in the peer-reviewed British journal Nature Geoscience.

Ide found that some of the most devastating recent earthquakes, such as the 2004 Sumatra quake that killed 230,000 people and the 2011 quake in Japan that killed 15,000, both hit during periods of high tide. In fact, his research team determined that nine of the 12 biggest quakes on record happened near or on days with full or new moons.

The scientists found no clear correlation between high tides and small earthquakes.

The study could help improve earthquake forecasting, the authors say, in places that are especially vulnerable to high seismic activity

“Scientists will find this result, if confirmed, quite interesting,” said University of Washington seismologist John Vidale, who was not part of the study. He cautions that “even if there is a strong correlation of big earthquakes with full or new moons, the chance any given week of a deadly earthquake remains miniscule,” making predictions rather unhelpful.

The study’s other authors are Suguru Yabe and Yoshiyuki Tanaka, also of the University of Tokyo.

UPDATE :16 Dead, 250 Injured In Tanzania Earthquake

At least 16 people died and 253 were injured in a 5.7-magnitude earthquake that struck northwest Tanzania and was felt throughout the Great Lakes region, local authorities said Sunday.

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As rescuers scrambled to find survivors from Saturday’s quake, Tanzanian premier Kassim Majaliwa headed to the worst-hit city, Bukoba, to attend a ceremony at its stadium.

“This tragic event is unprecedented. We’ve never known this in our country,” he told mourners. “The government is with you. It will not abandon you.”

President John Magufuli, who is from the region, said he was “deeply saddened”.

A group of 15 boys at a secondary boarding school in Bukoba district are believed to be among the 16 dead and 253 injured, according to Salum Kijuu, governor of Kagera province where Bukoba is located.

More than 800 buildings have been destroyed, including 44 public ones, Kijuu told AFP.

Across the border in Uganda, an unknown number of homes have also been razed by the quake which struck at 1227 GMT at a depth of 40 kilometres (24 miles) in the region near Lake Victoria.

In the Ugandan village of Minziro in the district of Rakai, residents appealed for help on Sunday, describing terrifying scenes of rocks crashing down nearby hillsides.

“I am sure the government can’t reconstruct our houses but in the meantime it can aid us with construction materials for tents,” victim Masembe Remegio told AFP. Earthquakes are fairly common in the Great Lakes region but are almost always of low intensity.

Tremors across the region The quake’s epicentre was 23 kilometres (15 miles) east of the northwestern Tanzanian town of Nsunga, in Bukoba district, and was felt in Rwanda, Burundi,Uganda and Kenya, the US Geological Survey said. Bukoba city suffered

widespread damage, with 270 houses destroyed and electricity disrupted, the Red Cross said in a statement. Its main hospital was stretched to nearly full capacity and had limited stocks of medicine.

“Telecommunications have been disrupted and we are trying to get a clear picture of the damage to hospitals and other essential infrastructure,” Andreas Sandin, Red Cross operations coordinator in East Africa and the Indian Ocean Islands, said in a statement.

No damage was reported in Tanzania’s economic capital, Dar es Salaam, which is located some 1,400 kilometres southeast of Bukoba. In Rwanda the shaking was felt across the country, with hotel staff and half-dressed visitors seen rushing out of their rooms in the capital, Kigali, when the quake struck.

5.9-Magnitude Earthquake Shakes Northern Tanzania, Killing at Least 11

A 5.9-magnitude earthquake has left at least 11 dead in the Lake Victoria region of northern Tanzania on Saturday.

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According to the Associated Press, the country’s president, John Magufuli, said that many had been killed by the quake that struck at 3:27 p.m. local time.

Magufuli said he was “shocked by reports of the earthquake that caused the death of many people, injury to others and destruction of property,” according to the press release issued by the president’s office.

Regional police commander Augustine Olomi said most of the deaths occurred in brick structures in the town of Bukoba. Photos posted to social media show significant damage in the city of 70,000, according to the BBC.

“This incident has caused a lot of damage,” Deodatus Kinawila, the district commissioner of Bukoba, told the BBC. He later said the “situation is calm and under control.”

The quake, which was considered shallow at a depth of 25 miles, according to the U.S. Geological Survey and was reportedly felt as far away as western Kenya, parts of Uganda and in Kigali, Rwanda.

Earthquakes Can Trigger Near-Instantaneous Aftershocks On Different Faults

According to a new study by scientists at Scripps Institution of Oceanography at the University of California San Diego, a large earthquake on one fault can trigger large aftershocks on separate faults within just a few minutes. These findings have important implications for earthquake hazard prone regions like California where ruptures on complex fault systems may cascade and lead to mega-earthquakes.

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In the study, published in the Sept. 9 issue of the journal Science, Scripps geophysicist Peter Shearer and Scripps graduate student Wenyuan Fan discovered 48 previously unidentified large aftershocks from 2004 to 2015 that occurred within seconds to minutes after magnitude 7 to 8 earthquakes on faults adjacent to the mainshock ruptures.

In one instance along the Sundra arc subduction zone, where the magnitude 9 Sumatra-Andaman mega-earthquake occurred off the coast of Indonesia in 2004, a magnitude 7 quake triggered two large aftershocks over 200 kilometers (124 miles) away. These aftershocks miles away reveal that stress can be transferred almost instantaneously by the passing seismic waves from one fault to another within the earthquake fault system.

“The results are particularly important because of their seismic hazard implications for complex fault systems, like California,” said Fan, the lead author of the study. “By studying this type of triggering, we might be able to forecast hosting faults for large earthquakes.”

Large earthquakes often cause aftershock sequences that can last for months. Scientists generally believe that most aftershocks are triggered by stress changes caused by the permanent movement of the fault during the main seismic event, and mainly occur near the mainshock rupture where these stress changes are largest. The new findings show that large early aftershocks can also be triggered by seismic wave transients, where the locations of the main quake and the aftershock may not be directly connected.

“Multiple fault system interactions are not fully considered in seismic hazard analyses, and this study might motivate future modeling efforts to account for these effects,” said Shearer, the senior author of the study.

UPDATE :Italy Earthquake: Death Toll Passes 240, As Rescue Efforts Continue

The death toll in the Italian earthquake stands at 241 as thousands of rescuers continue efforts to find survivors.

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Dozens are believed trapped in ruined Amatrice, Accumoli and Pescara del Tronto, in mountainous central Italy.

Rescuers have advised journalists and bystanders to leave Amatrice urgently, as “the town is crumbling”, the BBC’s Jenny Hill says.
New cracks appeared in the town’s hospital after strong aftershocks.

Officials revised down the number of dead after earlier giving a figure of 247.

The search for survivors went on through the night, amid hundreds of tremors and an aftershock which rocked already damaged buildings.

More than 4,300 rescuers are using heavy lifting equipment and their bare hands.

Many of the victims were children, the health minister said, and there were warnings the toll could rise further.

The heaviest death toll was in Amatrice – 184, officials said. Another 46 died in Arquata, and 11 in Accumoli.

The 6.2-magnitude quake hit at 03:36 (01:36 GMT) on Wednesday 100km (65 miles) north-east of Rome.

Some aftershocks were felt as far away as Rome.

“We are sleeping in the car and there were shocks all night. When the biggest one came, the car started moving and shaking,” said Monica, a survivor from Amatrice.

At the scene: BBC’s Damian Grammaticas in Pescara del Tronto

Two firemen burrowed deep into the rubble looking for a survivor. “It’s a dog,” one of them shouted out.

For half an hour the men kept digging. They passed water down to be given to the animal. And eventually they worked it free, then emerged, carrying it to the surface. There was a ripple of congratulations through the crowd.

“It doesn’t matter to us if it’s a person or an animal, we save it,” said Gianni Macerata, the fire officer in charge.

So the digging goes on. But so little is left of Pescara del Tronto it is unlikely that more survivors will be found here.

It seems unlikely too that this ancient little place, that has stood for centuries, can ever be rebuilt. Hundreds of years of history ended in an instant.

A tented camp has been set up, as so many buildings are now unsafe.

Prime Minister Matteo Renzi was chairing an emergency cabinet meeting on Thursday. The agenda included reconstruction plans for the devastated area.

Grief and anger in Italian press

Rescuers said they had pulled five bodies from the ruins of the Hotel Roma in Amatrice. As many as 70 tourists were staying at the hotel when the quake struck. Many are feared to be in the rubble, though several were pulled out and given medical care.

Many of those affected were Italians on holiday in the region. Some were in Amatrice for a festival to celebrate a famous local speciality – amatriciana bacon and tomato sauce.

Late on Wednesday there were cheers in the village of Pescara del Tronto when a young girl was pulled alive from the rubble after being trapped for 17 hours. Almost all the houses there had collapsed, the mayor said.

Among the victims was an 18-month-old toddler, Marisol Piermarini, whose mother Martina Turco survived the deadly 2009 earthquake in L’Aquila and moved away from there after the experience, Italian news agency Ansa reported.

Ms Turco was being treated in hospital after being pulled from the rubble in the village of Arquata del Tronto, Ansa said.

he mayor of Amatrice said three-quarters of the town had been destroyed and no building was safe for habitation.

The country is no stranger to earthquakes: the 2009 L’Aquila tremor killed more than 300 people and in May 2012 two tremors nine days apart killed more than 20 people in the northern Emilia Romagna region.

UPDATE :Strong Earthquake Shakes Italian Towns

AMATRICE, Italy — A strong earthquake in central Italy reduced three towns to rubble as people slept early Wednesday, with reports that as many as 50 people were killed and hundreds injured as rescue crews raced to dig out survivors.

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The toll was likely to rise as crews reached homes in more remote hamlets where the scenes were apocalyptic “like Dante’s Inferno,” according to one witness.

“The town isn’t here anymore,” said Sergio Pirozzi, the mayor of Amatrice. “I believe the toll will rise.”

The magnitude 6 quake struck at 3:36 a.m. (0136 GMT) and was felt across a broad swath of central Italy, including Rome, where residents felt a long swaying followed by aftershocks. The temblor shook the Lazio region and Umbria and Le Marche on the Adriatic coast.

Premier Matteo Renzi planned to head to the zone later Wednesday and promised: “No family, no city, no hamlet will be left behind.”

The hardest-hit towns were Amatrice and Accumoli near Rieti, some 100 kilometers (80 miles) northeast of Rome, and Pescara del Tronto some 25 kilometers further east. Italy’s civil protection agency said the preliminary toll was 38 dead, several hundred injured and thousands in need of temporary housing, though it stressed the numbers were fluid.

The ANSA news agency said 35 of the dead were in Amatrice alone, with another 17 dead in the province of Ascoli Piceno, which includes Pescara del Tronto, for a reported total topping 50.

The center of Amatrice was devastated, with entire buildings razed and the air thick with dust and smelling strongly of gas. Amatrice, birthplace of the famed spaghetti all’amatriciana bacon-tomato pasta sauce, is made up of 69 hamlets that rescue teams were working to reach.

Rocks and metal tumbled onto the streets of the city center and dazed residents huddled in piazzas as more than 40 aftershocks jolted the region into the early morning hours, some as strong as 5.1.

“The whole ceiling fell but did not hit me,” marveled resident Maria Gianni. “I just managed to put a pillow on my head and I wasn’t hit luckily, just slightly injured my leg.”

Another woman, sitting in front of her destroyed home with a blanket over her shoulders, said she didn’t know what had become of her loved ones.

“It was one of the most beautiful towns of Italy and now there’s nothing left,” she said, too distraught to give her name. “I don’t know what we’ll do.”

As daylight dawned, residents, civil protection workers and even priests began digging out with shovels, bulldozers and their bare hands, trying to reach survivors. There was relief as a woman was pulled out alive from one building, followed by a dog.

“We need chain saws, shears to cut iron bars, and jacks to remove beams: everything, we need everything,” civil protection worker Andrea Gentili told The Associated Press. Italy’s national blood drive association appealed for donations to Rieti’s hospital.

But just a few kilometers to the north, in Illica, the response was slower as residents anxiously waited for loved ones to be extracted from the rubble.

“We came out to the piazza, and it looked like Dante’s Inferno,” said Agostino Severo, a Rome resident visiting Illica. “People crying for help, help. Rescue workers arrived after one hour… one and a half hours.”

The devastation harked back to the 2009 quake that killed more than 300 people in and around L’Aquila, about 90 kilometers (55 miles) south of the latest quake. The town sent emergency teams Wednesday to help with the rescue.

“I don’t know what to say. We are living this immense tragedy,” said a tearful Rev. Savino D’Amelio, a parish priest in Amatrice. “We are only hoping there will be the least number of victims possible and that we all have the courage to move on.”

Another hard-hit town was Pescara del Tronto, in the Le Marche region, where the main road was covered in debris. The ANSA news agency reported 10 dead there without citing the source, but there was no confirmation.

Residents were digging their neighbors out by hand since emergency crews hadn’t yet arrived in force. Photos taken from the air by regional firefighters showed the town essentially flattened; Italy requested EU satellite images of the whole area to get the scope of the damage.

“There are broken liquor bottles all over the place,” lamented Gino Petrucci, owner of a bar in nearby Arquata Del Tronto where he was beginning the long cleanup.

The Italian geological service put the magnitude at 6.0; the U.S. Geological Survey reported 6.2 with the epicenter at Norcia, about 170 kilometers (105 miles) northeast of Rome, and with a relatively shallow depth of 10 kilometers (6 miles).

“Quakes with this magnitude at this depth in our territory in general create building collapses, which can result in deaths,” said the head of Italy’s civil protection service, Fabrizio Curcio. He added that the region is popular with tourists escaping the heat of Rome, with more residents than at other times of the year, and that a single building collapse could raise the toll significantly.

The mayor of Accumoli, Stefano Petrucci, said six people had died there, including a family of four, and two others. He wept as he noted that the tiny hamlet of 700 swells to 2,000 in the summer months, and that he feared for the future of the town.

“I hope they don’t forget us,” he told Sky TG24.

In Amatrice, the Rev. Fabio Gammarota, priest of a nearby parish, said he had blessed seven bodies extracted so far. “One was a friend of mine,” he said.

The mayor, Pirozzi, estimated dozens of residents were buried under collapsed buildings and that heavy equipment was needed to clear streets clogged with debris.

A 1997 quake killed a dozen people in central Italy and severely damaged one of the jewels of Umbria, the Basilica of St. Francis in Assisi, filled with Giotto frescoes. The Franciscan friars who are the custodians of the basilica reported no immediate damage from Wednesday’s temblor.

Pope Francis skipped his traditional catechism for his Wednesday general audience and instead invited pilgrims in St. Peter’s Square to recite the rosary with him.