An Early morning That Shook the World: The Seismology of 9/11
A variation of this story was first released in September 2016 to mark 15 years because the Sept. 11 attacks. We have actually upgraded it here to mark the 20th anniversary.
“Two aircrafts just struck the World Trade Center,” she said. I did, and I saw the burning buildings. In prospering hours, I viewed on live TV, gasping as the towers came down, and deadly-looking clouds of particles roiled over lower Manhattan.
As I learned later, my wife remained in her glassed-in office at a federal court when the airplanes hit. At around a quarter to nine, her structure trembled. Another construction-crane accident, she figured. Simply after nine, a much bigger effect traveled through the flooring and up into the bones of her feet. Her big windows neglecting Duane Street and beyond bowed far in and after that far back out, however did not break. “Like they were made of Jello,” she later said.
She crawled under her desk. When it appeared safe, she searched for into the blue, cloudless sky of that day. Smoke and flames were raving from a great void in the North Tower. Countless papers and glossy littles metal rained through the air. Looking down into the narrow street, she saw a wave of human beings filling it side to side, everyone running away in the very same instructions.
Currently, with thick black smoke continuing to stream from the Trade Center, federal marshals informed everyone to evacuate the structure. “Walk north,” they stated. A couple of blocks on, a male told Ruby that he had actually seen a huge plane fly into one of the structures; he showed by running himself hard into a mailbox.
Someplace around Broadway and Canal, Ruby looked back and saw the black-smoke pillar of fire from the South Tower unexpectedly turn white, and surge out increasingly; she didnt know then, however she was seeing the collapse of the building, the very first to fall. The tight dress shoes she had used to the workplace were too agonizing for treking; she took them off and continued barefoot, reaching our house on West 104th Street some time in the afternoon, having walked about 7 miles.
The following morning, we left Stella with a sitter and walked back up to St. Lukes Hospital holding hands. Our plan was to contribute blood for the survivors we understood must be flooding in. There were no survivors; the medical facility was dead quiet, and we were told no blood was needed.
Former site of the World Trade Center, photographed from the street, 9 am Aug. 11, 2016. At right, the new Freedom Tower. (All images: Kevin Krajick).
Seismologist Won-Young Kim heard the first reports in his automobile as he drove to Columbia Universitys Lamont-Doherty Earth Observatory. Lamont is situated in Palisades, N.Y., on the west bank of the Hudson River, 21 miles north of the attacks. From here, part of Kims task was to run a network of lots of seismometers created to keep an eye on the U.S. Northeast for earthquakes. They also in some cases capture manufactured seismic waves generated by explosions or other sources.
In a short time, it ended up being challenging to listen to the news; the seismology department was becoming swamped by calls from press reporters and all kinds of federal government authorities. Had the seismic network selected up anything?
” Up to then, all I knew was, something horrible took place,” stated Kim. With all the inquiries coming in, Kim started believing that perhaps he and the other staff could be of some use. “I believed, yes, maybe there is a seismic signal,” stated Kim.
Kim received his first question, from a New York Times reporter, soon after the collapse of the South Tower. Kim rushed over to the huge rotating drum that continually tapes its signals on paper. With signals coming in digitally from 33 other seismometers scattered across the area, Kim headed to his office to attempt and work out the exact time and magnitude of the collapse.
After that, all he did for the next day or more was gaze at data, make computations, consult colleagues and try to get a couple of hours of sleep. He does not recall ever seeing visual pictures of the aircraft impacts or the falling structures until the following night, when he finally went house and saw on tv what most other individuals had already seen a hundred times.
Over succeeding weeks, Kim and his coworkers developed exact seismic signatures of both the jet effects and the building collapses. Their very first main item, coauthored by 12 Lamont seismologists and college student, was a November 2001 paper published by the American Geophysical Union, It described the waves produced by the attacks, their possible effects, and the exact timing of each event. Dealing with federal private investigators, the New York Fire Department, the Port Authority and others, they distributed seismic information, which was later combined with images, videos and eyewitness reports to form a thorough account of the attacks.
Visitors to the underground September 11 Museum view part of the massive maintaining wall that surrounded the towers structures. Seismic waves from the aircraft impacts and tower collapses first gone through this wall and into the earths crust.
The seismologists identified that the aircrafts had struck the towers at 8:46:26 and 9:02:54, provide or take a couple of seconds– in the case of the descent on, about 2 minutes earlier than first reported by media. To make the estimation, in part they had to represent the 17-some seconds it would have taken for the waves to take a trip from the stunned towers upper floorings down through their structures and an adjacent concrete retainer wall. External through complexes of shallow crustal rocks. Initially, the hard schist and amphibolite of lower Manhattan; then the gneisses of upper Manhattan; on to the shales and sandstones underlying the Hudson River; and lastly up through the excellent sill of volcanic rock that forms the towering Palisades on the rivers west bank, where Lamont sits. Much of the energy also traveled through the river itself.
The jet strikes created seismic waves similar to small earthquakes of magnitudes 0.9 and 0.7 respectively– most likely only a little part of the total energy created when the planes hit the buildings. Kim thinks the majority of that energy was released in fireballs and airborne shock waves. This helped discuss my partners testimony: She felt the first impact just weakly, due to the fact that intervening buildings mostly blocked the waves (and her view). For the 2nd, she remained in an effective direct line. The shape of the seismic waves looked quite unlike those of natural earthquakes, which come from under the surface, said Kim. These had begun from above. “More like sounding a bell,” he stated.
Seismograms of the jet effects and subsequent collapses of the World Trade Center towers, as tape-recorded 21 miles away at Lamont-Doherty Earth Observatory. The records helped identify the precise time of each occasion. (Kim et al., Eos Transactions, 2001).
According to the seismic information, the collapse of the South Tower came at 9:59:04. The South Tower collapse created seismic waves similar to a magnitude 2.1 earthquake. Once again, Kim determined that most of the energy did not reach the ground; it was generally utilized up converting steel, concrete– and human beings– to dust.
Seismic signals from the crash of the pirated United Air 93 near Shanksville, Penn. (Kim, Baum, 2004).
“It was more steady than the huge towers,” said Kim. There was some speculation that this structure and others close by were fatally harmed by the earlier strong ground shaking, but the seismic analyses suggested otherwise. These findings assisted engineers more with confidence judge which other still-standing neighboring structures were weakened, and which were safe.
In the days following the attacks, Kim and numerous others found something else: Among more than 8 million New Yorkers, there are few degrees of separation. For our part, Ruby and I had rung in the millennial New Year, Jan. 1, 2000, at the Brooklyn home of our close good friends Bob and Sally. Shortly after the attacks, Bob called to tell me Dave Fontana was missing in the wake of the South Tower collapse.
” Everyone on my little street, they had a cousin, or a buddy,” said Kim. “It was really painful.” Among them: several previous Lamont geophysics trainees who worked in or near the Trade. Extremely skilled at manipulating computer systems and evaluating complex data, they had actually figured out they could make a lot more money crunching stock prices for Wall Street than plotting earthquakes.
One of Kims former trainees, a Chinese immigrant named Jing-Hua Shi, could not be grabbed 3 days. She turned up OK. Another was 41-year-old Weibin Wang, who had immigrated from China and studied earthquake mechanics at Lamont. In 1999, he signed up with the financial firm Cantor Fitzgerald. In March 2001 he ended up being an American resident. He lived in a suburban house not far from Kim with his partner, Wen Shi, and their three kids. On weekends, he cooked for them and took the kids to piano lessons. He was on the 103rd flooring of the north tower when the plane struck, and was never ever spoken with again.
Some time later on, Kim and Gerald Baum of the Maryland Geological Survey tried to help pinpoint the time when the pirated United Airlines flight 93 knocked into a field near Shanksville, Penn., killing everyone on board. And Kim could not come up with any signal at all from the crash of a Boeing 757 into the Pentagon at about 9:37 am.
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Save.
Conserve.
August 22, 2016: Seismologist Won-Young Kim pulls out the original paper seismogram showing the jet effects and subsequent collapses of the World Trade Center towers (marked by white labels). “It was a really uncomfortable day,” he said.
At initially he believed they were incremental collapses. “I was very surprised, they were still doing it that day,” he stated. “I believed they would have stopped, however they continued.”.
For the seismologists, the events highlighted the reality that New York City did not have a single operating seismic station. This, although Manhattan is cut by numerous known faults, has a history of small to moderate earthquakes, and might be based on much bigger ones. In 2002, Kim and his associates filled some of the space by installing stations in Central Park and at Fordham University in the Bronx.
Their research fed into the last narrative of the U.S. 9-11 Commission, published in 2004. An image of among their seismograms is preserved at Ground Zero in the September 11 Museum.
At the time of the attacks, Kim and his household were all still people of South Korea, where Kim grew up. “I understood, I dont feel pain when I read in the news about something bad taking place in Korea. A few months later on, he and his household all applied for U.S. citizenship.
Bought to return to work simply three days after the attacks, Ruby had to stroll every day in sight of the towering, cigarette smoking pile of twisted metal, debris and dust, where workers were pulling out red-hot steel beams, and carrying out a helpless search for life. The streets were littered with aircraft parts, pieces of Fire Department trucks and a lot of unidentifiable debris.
She still works close by. 5 years ago, approaching the 15th anniversary of the attacks, I checked out the 9/11 Memorial, and took some of the photos you see here. Not her: she has actually never ever set foot in the location
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He and 11 others in his team died after racing up 45 stories inside the South Tower, attempting to conserve individuals. He had firmly insisted on the date since he wanted it to be nine-one-one, the number people call for assistance
“I thought, yes, perhaps there is a seismic signal,” stated Kim. Kim received his very first question, from a New York Times press reporter, quickly after the collapse of the South Tower. Over prospering weeks, Kim and his associates worked up precise seismic signatures of both the jet effects and the building collapses. The shape of the seismic waves looked rather unlike those of natural earthquakes, which originate under the surface area, said Kim. “It was more steady than the big towers,” said Kim.
