HR: 11:00h
AN: U52A-03    [Abstracts]
TI: The Effects of the 2004 Sumatra Earthquake on Earth Rotation: A Comparison Between Theory and Different Observational Techniques
AU: * Johnson, T J
EM: johnson.thomas@usno.navy.mil
AF: U.S. Naval Observatory, 3450 Massachusetts Ave. NW, Washington, DC 20392-5420 United States
AU: Kammeyer, P C
EM: kammeyer.peter@usno.navy.mil
AF: U.S. Naval Observatory, 3450 Massachusetts Ave. NW, Washington, DC 20392-5420 United States
AU: Lambert, S B
EM: sbl@cygx3.usno.navy.mil
AF: U.S. Naval Observatory, 3450 Massachusetts Ave. NW, Washington, DC 20392-5420 United States
AU: Wooden, W H
EM: wooden.william@usno.navy.mil
AF: U.S. Naval Observatory, 3450 Massachusetts Ave. NW, Washington, DC 20392-5420 United States
AB: On 26 December 2004 a large earthquake (Mw=9) shook northern Sumatra, Indonesia, and then shook the whole of humanity by causing probably the deadliest tsunami in recorded history. Conservation of angular momentum, a fundamental principle of physics, indicates that the earthquake also had an effect on Earth rotation. Current theory estimates that this event shifted the mean pole approximately 2.5 cm in the direction of 145E and decreased the length of day by 2.68 microseconds [Chao and Gross, EOS, 86(1), 2005]. This study compares these theoretical results to Earth orientation parameters (EOP) determined using different observational-based techniques and estimates produced by combining these various observational techniques. These various techniques include the Global Positioning System (GPS), Very Long Baseline Interferometry (VLBI), and Satellite Laser Ranging (SLR). For example, daily estimates of EOP from an improved analysis of residuals between numerically-integrated inertial GPS satellite orbits and observed Earth-referenced GPS satellite positions can serve as a source of information on EOP as they actually were after the earthquake. These observational results are then compared to EOP predictions made before the earthquake by the Rapid Service/Prediction Center of the International Earth Rotation and Reference Systems Service, located at the U.S. Naval Observatory. This propagation method can take observations of EOP made before the earthquake and extend them through December 26, giving EOP as they would have been if the earthquake had not occurred plus some amount of prediction error. The uncertainties in the methods of estimating EOP and in the prediction method are briefly discussed. On the basis of the differences between observed EOP after the earthquake and EOP predicted prior to the earthquake, conclusions are drawn concerning both the validity of the theoretical results and the observability of large earthquakes in temporal variations of Earth orientation.
DE: 1200 GEODESY AND GRAVITY
DE: 1239 Rotational variations
DE: 1299 General or miscellaneous
DE: 7200 SEISMOLOGY
SC: Union [U]
MN: 2005 Joint Assembly