| In this paper,the first chapter,the historical background of how the concept of the seismic moment tensor was proposed and the development of the research work of seismic moment tensor inversion and seismic source process inversion were reviewed briefly.In the second chapter,the basic theory and method of how to use far-field body-waves to invert for the seismic moment tensor were expatiated systematically. The moment tensor solutions of the March 25,1998,Antarctic plate earthquake (Mw=8.1,IRIS) and the June 4,2000,southern Sumatra,Indonesia,earthquake (Ms=8.0) were inverted using teleseismic body waves recorded by long period seismograph stations of the IRIS global seismic network.The moment tensor solution obtained in this research for the March 25,1998,Antarctic plate earthquake shows that:The double-couple (DC) component of this earthquake is 3.7X 1021Nm,the moment magnitude is A/w=8.3,the compensated linear vector dipole (CLVD) component is -1.5 X 1020Nm,about -4% of the DC,and the explosion (EP) component is l.lX1020Nm,about 3% of the DC. NP I:The strike is 194,the dip,89,and the rake,-177;NP II:The strike is 104,the dip,87,and the rake,-1. P axis:The azimuth is 59 and the plunge,8;T axis:The azimuth is 329 and the plunge,2;B axis:The azimuth is 206 and the plunge,87. The focal mechanism is mainly left-lateral strike-slip,with a very small normal fault slip component. The NP II is the fault plane. On the whole,the main shock ruptured from the east to the west. The aftershocks were distributed on (or near) the fault plane and were triggered by the stress redistribution in the medium in the nearby region of the fault plane.The result for the June 4,2000,southern Sumatra earthquake shows that:The focal mechanism is mainly left-lateral strike-slip,with a small thrust component. The double-couple (DC) component of this earthquake is 1.5X 1021Nm,the moment magnitude is A/w=8.1,the compensated linear vector dipole (CLVD) component is 1.2X 1020Nm,about 8% of the DC,and the explosion (EP) component is -5.9 X 1019Nm,about 4% of the DC. NP I:The strike is 199,the dip,82,and the rake,5;NP II:The strike is 109,the dip,85,and the rake,172. P axis:The azimuth is 154 and the plunge,2;T axis:The azimuth is 64 and the plunge,10;B axis:The azimuth is 256 and the plunge,80. The P-waveforms recorded at different stations show prominent directivity. The directivity shows that the NP I is the fault plane,and that the earthquake ruptured unilaterally from the northeast to the southwest,nearly perpendicular to the strike of the Java trench. The strike-slip faulting was caused by asymmetrical distribution of barriers on the subducting plate. The NNE-SSW distributed aftershocks occurred on,or near,the fault plane of the main shock;while the NW-SE distributed aftershocks,on,or near,the Mentawai fault. A kinematic source model proposed in this paper explains well the mechanism of this earthquake,the characteristics of the aftershock distribution,and the reason why no tidal wavesgenerated by this great earthquake.In Chapter 3,the basic theory and method of retrieving source time functions from far-field seismic records to invert for the temporal-spatial source process were expatiated systematically. And the method was used to study the temporal-spatial source process of the June 4,2000,southern Sumatra,Indonesia,MS8.0 earthquake. The result obtained in this study shows that:The source time functions retrieved from P- and S-waves recorded at different stations distributed at different azimuths show prominent directivity. The source time function directivity is in accordance with the P waveform directivity,clearly showing that the nodal plane of strike 199 is the fault plane and that the earthquake ruptured unilaterally from the northeast to the southwest. The source duration is about 16s. The fault area is about 95km in length and 60 km in width. The average static slip is estimated to be about llm. The maximum static (final) slip is 27 m. The average static stress drop is about 90 MPa. The highest static stress drop...
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