Analyses On the Variation of the Earth's Rotation Rate Induced by the Earthquake

The mass redistribution caused by an earthquake (EQ)induces changes of the inertia tensor of the Earth,hence exciting variation of the earth's rotation i.e change of LOD.In general,a larger earthquake produces a greater displacement filed,which has greater effects upon the earth rotational properties. Using the fault plane parameters,the epicenter location and the expression given by Dahlen as well as the step fuction,the accumulative change of the equatorial moment of the inertia of the Earth for 1977-1994 data in the Harvard table are estimated in this paper.It is shown that the change of LOD by single earthquake is independent of the size of the earthquake,which is radom ,but the accumulative effects of LOD induced by the earthquakes show the non-radomness and exhibit secular behaviour.The earthquakes speed up the Earth's spin.It might be regarded as the accelerative mechanism of the non-tidal variation.