Network of stations with seismometers and air pressure sensors detected the blast waves.-
Meteor trail over eastern Russia is seen in this image from the Russian Emergency Ministry.
Credit: Russian Emergency Ministry
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Trajectory of the meteor as it neared impact in Russia.
Credit: Wikimedia Commons
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Is it a bird, a plane, a...meteor? A view of the meteor as it streaked by buildings in Russia.
Credit: Russian Emergency Ministry
Download the high-resolution JPG version of the image. (101 KB)
Hole in the ice at Russia's Lake Chebarkul, said to be caused by the meteor.
Credit: Wikimedia Commons
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As the meteor streaked by then crashed, window glass in eastern Russia shattered.
Credit: Russian Emergency Ministry
Download the high-resolution JPG version of the image. (142 KB)
Infrasound pressure waves are detected by a sensor installed in an EarthScope TA station.
Credit: IRIS
Download the high-resolution JPG version of the image. (509 KB)
A network of seismographic stations recorded spectacular
signals from the blast waves of the meteor that landed near
Chelyabinsk, Russia, as the waves crossed the United States.
The National ScieMeteornce Foundation- (NSF) supported stations are used to study earthquakes and the Earth's deep interior.
While
thousands of earthquakes around the globe are recorded by seismometers
in these stations--part of the permanent Global Seismographic Network
(GSN) and EarthScope's temporary Transportable Array (TA)--signals from
large meteor impacts are far less common.
The meteor explosion
near Chelyabinsk on Feb. 15, 2013, generated ground motions and air
pressure waves in the atmosphere. The stations picked up the signals
with seismometers and air pressure sensors.
The ground motions
were recorded by the GSN and the TA. The pressure waves were detected
by special sensors that are part of the TA.
"The NSF-supported
Global Seismic Network and EarthScope Transportable Array made
spectacular recordings of the Chelyabinsk meteor's impact," says Greg
Anderson, program director in NSF's Division of Earth Sciences.
"These
recordings of seismic waves through the Earth, and sound waves through
the atmosphere, are good examples of how these facilities can help
global organizations better monitor earthquakes, clandestine nuclear
tests and other threats."
Incoming! Then outgoing!
The Chelyabinsk meteor exploded in the atmosphere at approximately 9.20 a.m. local time.
The blast caused significant damage in the city, breaking thousands of windows and injuring more than 1,000 people.
Energy
from the blast created pressure waves in the atmosphere that moved
rapidly outward and around the globe. The blast also spread within the
Earth as a seismic wave.
The two wave types--seismic wave and pressure wave--travel at very different speeds.
Waves
in the ground travel quickly, at about 3.4 kilometers per second.
Waves in the atmosphere are much slower, moving at about 0.3 kilometers
per second, and can travel great distances.
GSN stations in
Russia and Kazakhstan show the ground-traveling wave as a strong, abrupt
pulse with a duration of about 30 seconds.
The atmospheric
waves--referred to as infrasound--were detected across a range of
inaudible frequencies and were observed at great distances on infrasound
microphones.
When the infrasound waves reached the eastern
United States--after traveling 8.5 hours through the atmosphere across
the Arctic from the impact site in Russia--they were recorded at TA
stations at the Canadian border.
The infrasound waves reached Florida three hours later, nearly 12 hours after the blast.
Infrasound
sensors at TA stations along the Pacific coast and in Alaska also
recorded the blast, but with signatures that were shorter and simpler
than those recorded by stations in the mid-continent and along the
southeastern seaboard.
The duration of the signals, and the
differences between the waveforms in the east and west, scientists
believe, are related to the way in which energy travels and bounces on
its long path through the atmosphere.
EarthScope Transportable Array
The
Transportable Array is operated by the IRIS (Incorporated Research
Institutions for Seismology) Consortium as part of NSF's EarthScope
Project. It consists of 400 stations traversing the United States,
recording at each site along the way for two years.
Each of the
TA stations was originally equipped with sensitive broadband
seismometers for measuring ground motions, but in 2010, NSF awarded the
University of California, San Diego, in cooperation with IRIS, funding
to add pressure and infrasound sensors.
These special sensors
help scientists understand how changes in pressure affect ground motions
recorded by the TA's seismometers and provide a view of regional
pressure changes related to weather patterns.
The sensors also record events such as tornadoes, derechos, rocket launches, chemical explosions--and meteor impacts.
The Chelyabinsk meteor is the largest signal recorded to date.
In
2013, the Transportable Array will reach states in the Northeast,
completing its traverse of the contiguous United States and southern
Canada.
Global Seismographic Network
The GSN's primary mission is collecting data to monitor worldwide earthquakes and to study the Earth's deep interior.
It's
funded jointly by NSF and the U.S. Geological Survey and is managed and
operated by IRIS in collaboration with the U.S. Geological Survey's
Albuquerque Seismological Laboratory and the University of California,
San Diego.
As part of a worldwide network of seismic stations,
data from the GSN have contributed over the past three decades to the
monitoring of nuclear explosions at test sites in the United States, the
former Soviet Union, India, Pakistan and Korea. For example, GSN
stations provided observations of the Korean nuclear test on Feb. 12,
2013.
-NSF-
The National Science Foundation (NSF) is an independent federal
agency that supports fundamental research and education across all
fields of science and engineering. In fiscal year (FY) 2012, its budget
is $7.0 billion. NSF funds reach all 50 states through grants to nearly
2,000 colleges, universities and other institutions. Each year, NSF
receives over 50,000 competitive requests for funding, and makes about
11,000 new funding awards. NSF also awards nearly $420 million in
professional and service contracts yearly.
The National Science Foundation (NSF).-
Guillermo Gonzalo Sánchez Achutegui
ayabaca@gmal.com
ayabaca@hotmail.com
ayabaca@yahoo.com
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