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Now, scientists have used seismic data to determine exactly where the sound reminiscent of explosions or gunshots is coming from and what causes it, writes livescience.com.
The scientists presented their findings at the annual meeting of the American Geophysical Union on December 7. This year, due to the COVID-19 pandemic, it occurred virtually. However, it turned out that scientists do not have the answers to all the questions.
The name “Seneca Artillery” does not come from North Carolina, but from Seneca Lake in New York, a similar phenomenon. The looming sounds of the lake, which in his short story The Lake Gun in 1850. described by writer James Fenimore Cooper, had been heard for centuries at that time.
“It sounds like a heavy artillery shot and cannot be explained by any of the known laws of nature. The sound is deep, muffled, distant and impressive. The lake seems to speak to the surrounding hills, which respond exactly to the echo. No convincing theory has ever been put forward to explain these sounds, “wrote JF Cooper.
Residents of the North Carolina coast often report hearing similar sounds, the origins of which are explained from distant storms or earthquakes to professional explosions or even military exercises. To finally discover the source and cause of the sound, the researchers went through the 2013 testimonials and created a catalog of them. They then compared those events with data collected by the EarthScope Transportable Array, a network of 400 mobile atmospheric sensors and seismographs. Launched in 2003, the sensor suite is migrating to the continental United States, and the precisely located seismic data it collects is freely available to the public. Currently operating in Alaska, the network operated in North Carolina from 2013 to 2015.
“We wanted to go through local news articles, create a Seneca artillery certificate catalog, and then try to verify it based on actual seismic-acoustic data,” said Eli Bird, a researcher and geoscience student at the University of North Carolina.
Although Seneca Artillery can shake the earth, scientists have not found any evidence of this phenomenon that matches the seismic records, which have ruled out that earthquakes are the cause of these devastations.
“Generally speaking, we believe it is an atmospheric phenomenon, we do not believe it is due to seismic activity. We suspect that the thunder is spreading through the atmosphere, not the ground. The data that has been the focus of this project are the infrasonic data, not seismic data, ”says Bird, referring to sound that is lower than human frequencies.
One of the atmospheric explanations could be cars: space rocks that, when they reach Earth’s atmosphere, orbit so fast that they explode. Another possibility could be phenomena in the ocean, such as very high waves or thunderstorms offshore. “Atmospheric conditions can be those that intensify in a certain direction or primarily affect a defined area,” says Bird.
The duration of the signals associated with the sound ranged from approximately 1 second to almost 10 seconds. The station near Cape Fear captured the brightest signals. It is curious, but it is in this region with a name that sounds threatening where many testimonies of “Seneca artillery” are registered. However, the array of sensors was not dense enough to pinpoint where the signals were coming from, so more data will be needed to figure out the location of these thunderstorms, the researchers write.
“It’s probably not exactly the same thing that’s causing the roars,” says Bird. Some military aircraft flying in the area cross the sound barrier, so some “artillery” sounds may be sound shock waves. And even in those cases, a natural signal can amplify them even more, he adds.
Having identified the Cape of Fear region as the most promising location for future searches, additional steps to solving this puzzle would involve collecting data over several more years, using an array of at least three stations with three microphones each to triangulate where it came from. the signal as accurately as possible.
“Ideally, a dense array of sensors in the area where signals are most frequently detected will allow for deeper analysis,” the researchers said at an annual meeting of the American Geophysical Union.
Until now, the thunder from Seneca’s artillery remains a mystery.
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