Aftershocks of the deadly earthquake from Lake Hebgen in Yellowstone National Park in 1959 were discovered more than 60 years later, a study shows.
More than 3,000 small earthquakes that occurred between June 2017 and March 2018 were found to have resulted from the 7.2 magnitude earthquake.
On August 17 at 11.37 a.m. that year, the Yellowstone National Park violently shook for about 30 seconds, causing a huge landslide and killing 28 people.
The shock was strong enough to allow the ground to fall six feet deep into some parts and cause the groundwater to swell up in wells as far as Hawaii.
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Aftershocks of the Hebgen Lake earthquake, which occurred 60 years ago in Yellowstone National Park, are still being discovered, a study shows. Pictured here, a map of the Maple Creek swarm, made using data from the seismograph stations of the University of Utah
Since then, 3,345 earthquakes near Maple Creek have been detected via seismography stations and found to be late after-shock after the 1959 earthquake.
Seismicity in the volcanic area of Yellowstone consists mainly of earthquake eruptions, often referred to as & # 39; swarms & # 39 ;.
According to geoscientists from the University of Utah, earlier swarms of magmatic currents were triggered in 1985, 2008-2009 and 2010.
But the eruption of earthquakes that occurred in 2017-2018 differed.
They determined the precise location for these earthquakes by measuring the ratio and speed and discovered that the source area was where the 1959 earthquake occurred.
Aftershocks usually occur near the mainshock.
The researchers said that the quakes fell along the same fault line and were oriented in the same way as the earthquake in Hebgen Lake.
The small earthquakes occurred in the Yellowstone National Park, outside the volcano caldera of Yellowstone.
Guanning Pang and Keith Koper, who both led the study, say that the phenomena of tremors occurring decades after the event are not unusual.
Plot of size versus time in color-matching subsets of earthquakes. The warm colors mark earthquakes in the northern cluster and the cool colors mark the earthquakes in the southern cluster
Geoscientists from the University of Utah discovered the 3,345 earthquakes near Maple Creek via seismograph station detectors and found that they were late aftershocks after the 1959 earthquake
& # 39; These kinds of earthquakes in Yellowstone are commonplace & # 39 ;, said Mr. Koper, director of the Seismograph Stations of the University of Utah.
& # 39; These swarms are very common. This was a little longer and had more events than usual. & # 39;
& # 39; There are formulas to predict how much aftershocks you should see, & # 39; he said.
For Hebgen Lake, there seemed to be a shortage of after-shocks. Now that we have had this, it has made things right with the original expectations. & # 39;
Together, the more than 3000 small earthquakes of the Maple Creek swarm can be divided into two clusters.
The northern cluster consists of aftershocks in Lake Hebgen.
The earthquakes fell along the same fault line and were oriented in the same way as the Hebgen Lake event, the study claimed.
In addition, the team saw no signs that the northern cluster was caused by motion of magma and other liquids underground.
The southern cluster of the Maple Creek swarm seems to have a different origin.
Although the northern cluster was in line with the Hebgen lake error, the arrangement of the southern cluster was rotated about 30 degrees and the earthquakes were about 1 km shallower than the northern cluster.
The researchers concluded from this that although shaking in the northern cluster affected the southern cluster, the primary cause of southern shaking was likely underground movement of magma.
& # 39; Because they were so close, there was some feedback and influence between the two sections, & # 39; said Mr. Koper.
The results highlight how earthquakes differ from other natural hazards such as floods, hurricanes, or forest fires that are left when they are over.
& # 39; Earthquakes do not happen as a single discrete event in time, & # 39; he said.
The ghost of aftershocks can go on for months, years or even, as Maple Creek shows, for decades.
The study was published in Geophysical Research Letters.
THE MEN EARTHQUAKE
The earthquake in Hebgenmeer in 1959 measured a force of 7.2 on the Richter scale.
It happened at 11:37 am and almost immediately the shaking caused a huge landslide that buried 19 people under 73 million tons of debris
It killed 28 people west of the park and caused measurable changes in Old Faithful Geyser, a cone geyser in Yellowstone National Park in Wyoming and other hydrothermal functions.
Yellowstone National Park houses more than 10,000 hydrothermal functions and as they are part of a large, complex system of heat, water, stone and gas, they change over time.
The earthquake in Hebgenmeer in 1959 measured a force of 7.2 on the Richter scale. It happened at 11:37 am and almost immediately the shaking caused a huge landslide. Pictured, the land and trees after the landslide
Sixty years after the earthquake, the scars remain in the area.
The local rock caused a huge dive into the gorge carved by the Madison River.
Because this foliation immersed shallowly, it cut the steep wall of the valley, creating a plane of weakness.
When the mighty force of the earthquake shook this weak point, the mountain broke and collapsed, and there was nowhere where the loose rock could go down.
Within an instant, the mountain filled the valley and pushed down the Madison River. Behind the natural dam, the earthquake lake has been created, complete with forests of drowned trees.
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