Earth Science What Nasa Has To Say About The Tsunami And Earthqake

Discussion in 'Earth Science' started by Mizar, Jan 11, 2005.

  1. Mizar

    Mizar Premium Member

    Alan Buis (818) 354-0474

    Jet Propulsion Laboratory, Pasadena, Calif.



    Gretchen Cook-Anderson/Dolores Beasley (202) 358-0836/1753

    NASA Headquarters, Washington, D.C.



    News Release: 2005-009 January 10, 2005


    NASA Details Earthquake Affects on the Earth



    NASA scientists using data from the Indonesian earthquake calculated it affected Earth's rotation, decreased the length of day, slightly changed the planet's shape, and shifted the North Pole by centimeters. The earthquake that created the huge tsunami also changed the Earth's rotation.



    Dr. Richard Gross of NASA's Jet Propulsion Laboratory, Pasadena, Calif., and Dr. Benjamin Fong Chao, of NASA's Goddard Space Flight Center, Greenbelt, Md., said all

    earthquakes have some affect on Earth's rotation. It's just they are usually barely noticeable.



    "Any worldly event that involves the movement of mass affects the Earth's rotation, from seasonal weather down to driving a car," Chao said.



    Gross and Chao have been routinely calculating earthquakes' effects in changing the Earth's rotation in both length-of-day as well as changes in Earth's gravitational field. They also study changes in polar motion that is shifting the North Pole. The "mean North pole" was shifted by about 2.5 centimeters (1 inch) in the direction of 145 degrees East Longitude. This shift east is continuing a long-term seismic trend identified in previous studies.



    They also found the earthquake decreased the length of day by 2.68 microseconds. Physically this is like a spinning skater drawing arms closer to the body resulting in a faster spin. The quake also affected the Earth's shape. They found Earth's oblateness (flattening on the top and bulging at the equator) decreased by a small amount. It decreased about one part in 10 billion, continuing the trend of earthquakes making Earth less oblate.



    To make a comparison about the mass that was shifted as a result of the earthquake, and how it affected the Earth, Chao compares it to the great Three-Gorge reservoir of China. If filled, the gorge would hold 40 cubic kilometers (10 trillion gallons) of water. That shift of mass would increase the length of day by only 0.06 microseconds and make the Earth only very slightly more round in the middle and flat on the top. It would shift the pole position by about two centimeters (0.8 inch).



    The researchers concluded the Sumatra earthquake caused a length of day change too small to detect, but it can be calculated. It also caused an oblateness change barely detectable, and a pole shift large enough to be possibly identified. They hope to detect the length of day signal and pole shift when Earth rotation data from ground based and space-borne position sensors are reviewed.



    The researchers used data from the Harvard University Centroid Moment Tensor database that catalogs large earthquakes. The data is calculated in a set of formulas, and the results are reported and updated on a NASA Web site.



    The massive earthquake off the west coast of Indonesia on December 26, 2004,

    registered a magnitude of nine on the new "moment" scale (modified Richter scale) that indicates the size of earthquakes. It was the fourth largest earthquake in one hundred years and largest since the 1964 Prince William Sound, Alaska earthquake.



    The devastating mega thrust earthquake occurred as a result of the India and Burma plates coming together. It was caused by the release of stresses that developed as the India plate slid beneath the overriding Burma plate. The fault dislocation, or earthquake, consisted of a downward sliding of one plate relative to the overlying plate. The net effect was a slightly more compact Earth. The India plate began its descent into the mantle at the Sunda trench that lies west of the earthquake's epicenter. For information and images on the Web, visit:



    http://www.nasa.gov/vision/earth/lookingatearth/indonesia_quake.html .



    For details on the Sumatra, Indonesia Earthquake, visit the USGS Internet site:



    http://neic.usgs.gov/neis/bulletin/neic_slav_ts.html .



    For information about NASA and agency programs Web, visit:



    http://www.nasa.gov .



    JPL is managed for NASA by the California Institute of Technology in Pasadena.
     
  2. Bleys

    Bleys Phoenix Takes Flight Staff Member

    Great stuff Mizar!

    This blew me away though:

    It boggles the mind (at least mine) that a human built structure can actually have an effect on the rotation and shape of the Earth.

    B.
     
  3. Mizar

    Mizar Premium Member

    Alan Buis (818) 354-0474

    Jet Propulsion Laboratory, Pasadena, Calif.



    Eliane Moreaux (011) 33-5-61-27-33-44

    Centre National d'Estudes Spatiales, Toulouse, France



    NEWS RELEASE: 2005-013 January 11, 2005


    NASA/French Satellite Data Reveal New Details of Tsunami



    For the first time, orbiting satellites have observed and measured a major tsunami event in open ocean, the Indian Ocean tsunami that resulted from the magnitude 9 earthquake southwest of Sumatra on December 26. The measurements are of tremendous value to researchers worldwide and will aid our understanding of these events.



    U.S. and French teams working in parallel with altimetry data from the joint NASA/French Space Agency Jason and Topex/Poseidon oceanography satellites have independently confirmed the satellites' measurements of the height of the tsunami waves as they radiated from the earthquake's epicenter. The satellites flew over the Bay of Bengal about 150 kilometers (93 miles) apart approximately two hours after the quake.



    "These two satellites make only about 13 Earth revolutions daily, with each orbit passing over the Earth approximately 3,000 kilometers (1,864 miles) away from its last," said Dr. Philip Callahan of NASA's Jet Propulsion Laboratory, Pasadena, Calif. Callahan has been searching for tsunami signals in satellite radar altimeter data since Topex/Poseidon's launch in 1992. "There is a very low probability of capturing observations in any given location within two hours of an event like this. The fact that Jason captured the tsunami's signals is serendipitous, but is nevertheless a major boon for oceanographers," he said.



    "The observations made by Jason and Topex/Poseidon are unique and of tremendous value for testing and improving tsunami computer models and developing future tsunami early warning systems," said JPL's Dr. Lee-Lueng Fu, Jason and Topex/Poseidon project scientist. "The satellite altimeter data currently take a minimum of five hours to process, so they cannot provide early warning of such events," said Fu. Dr. Callahan received the Jason data the morning of December 27.



    The new images are available online at: http://photojournal.jpl.nasa.gov/catalog/PIA07219



    The main figure displays changes in sea surface height from previous observations made along the same ground track 20 to 30 days before the earthquake, showing the signals of the tsunami waves. The inset is a computer model of simulated changes in sea surface height created by Kenji Satake of the National Institute of Advanced Industrial Science and Technology, Japan. It provides a basin-wide perspective for interpreting the Jason and Topex/Poseidon satellite observations, which are in good agreement with the model.



    The satellites recorded a maximum sea surface elevation gain (deviation from normal) of 50 centimeters (1.6 feet) on the open ocean about 1,200 kilometers (746 miles) south of Sri Lanka at the leading crest of a tsunami wave raging out of the Bay of Bengal. It was followed by a trough of sea surface depression of 40 centimeters (1.3 feet) below normal. The distance from one wave crest to the next was about 800 kilometers (500 miles). The first wave was followed by a second with a crest height of 40 centimeters (1.3 feet) above normal. Near the northern end of the Bay, two waves with crest heights of 40 centimeters (1.3 feet) and 20 centimeters (0.66 feet) above normal were approaching the coasts of Myanmar. Spreading across the Bay of Bengal from the earthquake zone offshore from Western Sumatra, these tsunami waves eventually reached shallow waters along the coasts of Sumatra, Sri Lanka, Thailand and Southern India. Their open ocean speeds reduced from that of a jet plane, 800 kilometers (500 miles) per hour, to about 32 kilometers (20 miles) per hour, building the open ocean wave heights of 0.5 meters (1.6 feet) or less to walls of water up to 10 meters (33 feet) high with great destructive power.



    Jason and Topex/Poseidon are collaborative satellite missions of NASA and the French Space Agency, Centre National d'Estudes Spatiales. The primary objectives of the two missions are to make long-term measurements of the height of the world's sea surface to better understand ocean circulation and its effects on climate.



    "The information on sea surface height from these satellites has many other applications, and can be used to aid navigation, offshore operations, hurricane forecasting, fisheries, etcetera," said Dr. Yves Menard, Jason and Topex/Poseidon project scientist at the Centre National d'Estudes Spatiales. "The detection of these tsunami waves provides yet another demonstration of the important value of satellite radar altimeter observations."



    NASA and the French Space Agency are working with the National Oceanic and Atmospheric Administration and the European Organization for the Exploitation of Meteorological Satellites to develop the next radar altimeter mission, the Ocean Surface Topography Mission, targeted for launch in 2008. It will make radar altimeter measurement a routine operation of those organizations in the future.



    Additional information is available at: http://sealevel.jpl.nasa.gov/and http://www.jason.oceanobs.com/html/portail/general/welcome_uk.php3 .
     
  4. Mizar

    Mizar Premium Member

    Alan Buis (818) 354-0474

    Jet Propulsion Laboratory, Pasadena, Calif.



    Gretchen Cook-Anderson (202) 358-0836

    NASA Headquarters, Washington, D.C.



    Image Advisory: 2005-019 January 19, 2005


    New NASA Imagery Sheds Additional Perspectives On Tsunami



    Newly released imagery from three NASA spaceborne instruments sheds valuable insights into the Indian Ocean tsunami that resulted from the magnitude 9 earthquake southwest of Sumatra on December 26.



    The images offer several unique views of portions of the affected region. The data are and will be used by scientists and government agencies to assist with disaster recovery, mitigate the effects of future natural hazards and increase our understanding of how and why tsunamis strike. The data were acquired by the Multi-angle Imaging SpectroRadiometer and the Advanced Spaceborne Thermal Emission and Reflection Radiometer instruments on NASA’s Terra spacecraft, as well as from the Shuttle Radar Topography Mission.



    To access the new images available on the Web, visit:

    http://www.nasa.gov/vision/earth/lookingatearth/tsunami-images.html .



    The Multi-angle Imaging SpectroRadiometer imagery includes the only known animations produced by a remote sensing instrument to capture tsunami waves in motion as they make landfall. The image set and animations were collected December 26 as Terra passed over the eastern Indian coast about an hour and a half after the first waves hit shore. The first animation shows tsunami waves breaking along the shores of the Indian state of Andhra Pradesh, near the mouth of the Godavari River. Because the instrument’s multiple cameras imaged the coast over several minutes and the waves were unusually large, the instrument captured unique time-lapse imagery of them. The resolution is 275 meters (900 feet). The still images show frames from four of the instrument’s cameras, and span a period of about two and a half minutes. In the second animation, waves break further to the south, near the mouth of the Krishna River.



    The data indicate the location and timing of some of the waves, their angle relative to the shoreline and their speed, estimated from these data to be about 30 kilometers (19 miles) per hour. Together with measurements of ocean depth, these data can be used to refine models of how tsunamis originate and travel. Better understanding of how tsunamis interact with coastal areas is one factor needed to improve near-real-time forecasts of tsunami arrival times and effects, and to reduce damage from such waves in the future.



    Terra’s Advanced Spaceborne Thermal Emission and Reflection Radiometer instrument acquired images of the area around Phuket on the Indian Ocean coast of Thailand on December 31. The pair of simulated natural color images shows a 27-kilometer (17-mile) stretch of coast north of the Phuket airport on December 31, along with an image acquired two years earlier. The changes along the coast are self-evident, clearly indicating the extent of vegetation stripped by the waves. The images are being used to create damage assessment maps for the U.S. Agency for International Development Office of Foreign Disaster Assistance. The resolution is 15 meters (49.2 feet).



    The separate image trio depicts these same before/after views and contrasts them with a third view created with Shuttle Radar Topography Mission data. Elevations below 10 meters (33 feet) are highlighted in red, and include most of the areas inundated by the tsunami, though offshore ocean depth variations, coastal landforms, distance from the coast and additional factors control the damage extent. Still, elevation measurements as provided by the Shuttle Radar Topography Mission, give a general indication of areas at risk, and can help planners better predict which areas of a region are in the most danger and help develop mitigation plans in the event of particular flood events.



    The Shuttle Radar Topography Mission has also produced a color-coded shaded relief map of the island nation of Sri Lanka, highlighting regions below 10 meters (33 feet) in elevation. The data were collected during the 11-day Space Shuttle mission in February 2000 and released publicly in July 2003. The low coastal elevations extend 5 to 10 kilometers (3.1 to 6.2 miles) inland and are especially vulnerable to flooding associated with storm surges, rising sea level and tsunami.



    The Multi-angle Imaging SpectroRadiometer was built and is managed by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Japan’s Ministry of Economy, Trade and Industry built the Advanced Spaceborne Thermal Emission and Reflection Radiometer. NASA’s Goddard Space Flight Center, Greenbelt, Md., manages the Terra satellite. The Shuttle Radar Topography Mission is a collaboration of NASA, the National Geospatial-Intelligence Agency and the German and Italian space agencies.



    For more information about the three instruments/missions on the Web, visit:



    http://asterweb.jpl.nasa.gov/



    http://www-misr.jpl.nasa.gov/ and



    http://www.jpl.nasa.gov/srtm .



    JPL is managed for NASA by the California Institute of Technology in Pasadena.



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