There is on the FAQ page of U.S. Geological Survey site the following information regarding consequences of Sumatra earthquake on geoid: http://earthquake.usgs.gov/eqinthenews/2004/usslav/neic_slav_faq.html Question: What effect did this earthquake have on the rotation of the earth? Answer: Richard Gross at JPL has modeled the coseismic effect on the Earth's rotation of the December 26 earthquake in Indonesia by using the PREM model for the elastic properties of the Earth and the Harvard centroid-moment tensor solution for the source properties of the earthquake. The result is: change in length of day: -2.676 microseconds polar motion excitation X : -0.670 milliarcseconds polar motion excitation Y: 0.475 milliarcseconds Since the length of the day can be measured with an accuracy of about 20 microseconds, this model predicts that the change in the length-of-day caused by the earthquake is much too small to be observed. And, since the location of the earthquake was near the equator, this model predicts that the change in polar motion excitation is also rather small, being about 0.82 milliarcsecond in amplitude. Such a small change in polar motion excitation will also be difficult to detect. Mgr. Antonin Vitek, CSc. Office: Main Library, Academy of Sciences of the Czech Republic Home: Kytin 127, CZ-25210 Mnisek p. B., Czech Republic My satellite home page: http://www.lib.cas.cz/www/space.40/index.html Office e-mail: AVITEK@LIB.CAS.CZ ------------------------------------------------------------------------- Subscribe/Unsubscribe info, Frequently Asked Questions, SeeSat-L archive: http://www.satobs.org/seesat/seesatindex.html
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