Theoretical horizontal displacements caused by the 2004 Sumatra earthquake in the Sichuan-Yunnan area have been calculated according to a spherical dislocation theory and an earthquake-fault model. The results show th...Theoretical horizontal displacements caused by the 2004 Sumatra earthquake in the Sichuan-Yunnan area have been calculated according to a spherical dislocation theory and an earthquake-fault model. The results show that the theoretical displacements are basically consistent with the GPS observations in situ. On this basis,we have calculated the co-seismic displacements, strains, changes of gravity and geoid of the whole Earth, including China mainland and vicinity, caused by this earthquake. Key wards:展开更多
Mechanism of the June 4, 2000 southern Sumatra, Indonesia, earthquake (MS=8.0) are estimated from teleseismic body waves recorded by long period seismograph stations of the global seismic network. This solution is mor...Mechanism of the June 4, 2000 southern Sumatra, Indonesia, earthquake (MS=8.0) are estimated from teleseismic body waves recorded by long period seismograph stations of the global seismic network. This solution is more reasonable than those reported by USGS, Harvard CMT and ERI of University of Tokyo. The best double-couple component of this earthquake is 1.51021 Nm, the compensated linear vector dipole component is 1.21020 Nm, and the explosion component is 5.91019 Nm. The focal mechanism is mainly left-lateral strike-slip, with a small thrust component. Nodal plane I: The strike is 199? the dip, 82? and the rake, 5? Nodal plane 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 Nodal plane 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.展开更多
We analyze co-seismic displacement field of the 26 December 2004, giant Sumatra–Andaman earthquake derived from Global Position System observations,geological vertical measurement of coral head, and pivot line observ...We analyze co-seismic displacement field of the 26 December 2004, giant Sumatra–Andaman earthquake derived from Global Position System observations,geological vertical measurement of coral head, and pivot line observed through remote sensing. Using the co-seismic displacement field and AK135 spherical layered Earth model, we invert co-seismic slip distribution along the seismic fault. We also search the best fault geometry model to fit the observed data. Assuming that the dip angle linearly increases in downward direction, the postfit residual variation of the inversed geometry model with dip angles linearly changing along fault strike are plotted. The geometry model with local minimum misfits is the one with dip angle linearly increasing along strike from 4.3oin top southernmost patch to 4.5oin top northernmost path and dip angle linearly increased. By using the fault shape and geodetic co-seismic data, we estimate the slip distribution on the curved fault. Our result shows that the earthquake ruptured *200-km width down to a depth of about 60 km.0.5–12.5 m of thrust slip is resolved with the largest slip centered around the central section of the rupture zone78N–108N in latitude. The estimated seismic moment is8.2 9 1022 N m, which is larger than estimation from the centroid moment magnitude(4.0 9 1022 N m), and smaller than estimation from normal-mode oscillation data modeling(1.0 9 1023 N m).展开更多
Long-term seismic activity prior to the December 26, 2004, off the west coast of northern Sumatra, Indonesia, MW=9.0 earthquake was investigated using the Harvard CMT catalogue. It is observed that before this great e...Long-term seismic activity prior to the December 26, 2004, off the west coast of northern Sumatra, Indonesia, MW=9.0 earthquake was investigated using the Harvard CMT catalogue. It is observed that before this great earth-quake, there exists an accelerating moment release (AMR) process with the temporal scale of a quarter century and the spatial scale of 1 500 km. Within this spatial range, the MW=9.0 event falls into the piece-wise power-law-like frequency-magnitude distribution. Therefore, in the perspective of the critical-point-like model of earthquake preparation, the failure to forecast/predict the approaching and/or the size of this earthquake is not due to the physically intrinsic unpredictability of earthquakes.展开更多
Satellite gravity data of the regional rheological structure of the lithosphere in the vicinity of Sumatra is used as evidence to enable a better understanding of the regional geodynamic environment.The data is interp...Satellite gravity data of the regional rheological structure of the lithosphere in the vicinity of Sumatra is used as evidence to enable a better understanding of the regional geodynamic environment.The data is interpreted using the theory of post-seismic viscoelastic relaxation.Coand post-seismic changes in the gravity field resulting from the 2004 M w 9.3 Sumatra earthquake were calculated from Gravity Recovery and Climate Experiment (GRACE) satellite data.A spatial Gaussian filter,500 km wide,was used in the calculation.The results indicate that there were significant co-seismic jumps in both uplifted and subducted regions.The magnitude of the jump in the subducted zone was ~9 10 8 m/s 2,more significant than the ~2 10 8 m/s 2 jump observed in the uplifted zone.However,a positive gravity change occurred in the uplifted zone very soon after the earthquake.The rheological structure of the lithosphere has a great effect on deformation and its determination is a fundamental part of developing reliable numerical simulations in geodynamics.Based on the temporally-variable gravity field observed by GRACE,the viscous lithospheric structure of the Sumatra area is investigated with a self-gravitating,half space,viscoelastic earth model.The estimated viscosity is of the order of 1.0 10 18 Pa·s and there are differences in the rheological parameters on the two sides of the fault.The factors that affect the viscosity are discussed in connection with the tectonic structure of the Sumatra area.展开更多
基金supported by Basic Research Foundation from Institute of Earthquake Science,CEA(0210240101)
文摘Theoretical horizontal displacements caused by the 2004 Sumatra earthquake in the Sichuan-Yunnan area have been calculated according to a spherical dislocation theory and an earthquake-fault model. The results show that the theoretical displacements are basically consistent with the GPS observations in situ. On this basis,we have calculated the co-seismic displacements, strains, changes of gravity and geoid of the whole Earth, including China mainland and vicinity, caused by this earthquake. Key wards:
基金National Science Foundation of China under grant No.49904004 the SSTCC Climbing project 95-S-05.
文摘Mechanism of the June 4, 2000 southern Sumatra, Indonesia, earthquake (MS=8.0) are estimated from teleseismic body waves recorded by long period seismograph stations of the global seismic network. This solution is more reasonable than those reported by USGS, Harvard CMT and ERI of University of Tokyo. The best double-couple component of this earthquake is 1.51021 Nm, the compensated linear vector dipole component is 1.21020 Nm, and the explosion component is 5.91019 Nm. The focal mechanism is mainly left-lateral strike-slip, with a small thrust component. Nodal plane I: The strike is 199? the dip, 82? and the rake, 5? Nodal plane 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 Nodal plane 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.
基金supported by the Special Fund of Fundamental Scientific Research Business Expense for Higher School of Central Government(Projects for creation teams ZY20110101)NSFC 41090294talent selection and training plan project of Hebei university
文摘We analyze co-seismic displacement field of the 26 December 2004, giant Sumatra–Andaman earthquake derived from Global Position System observations,geological vertical measurement of coral head, and pivot line observed through remote sensing. Using the co-seismic displacement field and AK135 spherical layered Earth model, we invert co-seismic slip distribution along the seismic fault. We also search the best fault geometry model to fit the observed data. Assuming that the dip angle linearly increases in downward direction, the postfit residual variation of the inversed geometry model with dip angles linearly changing along fault strike are plotted. The geometry model with local minimum misfits is the one with dip angle linearly increasing along strike from 4.3oin top southernmost patch to 4.5oin top northernmost path and dip angle linearly increased. By using the fault shape and geodetic co-seismic data, we estimate the slip distribution on the curved fault. Our result shows that the earthquake ruptured *200-km width down to a depth of about 60 km.0.5–12.5 m of thrust slip is resolved with the largest slip centered around the central section of the rupture zone78N–108N in latitude. The estimated seismic moment is8.2 9 1022 N m, which is larger than estimation from the centroid moment magnitude(4.0 9 1022 N m), and smaller than estimation from normal-mode oscillation data modeling(1.0 9 1023 N m).
基金Ministry of Science and Technology Project (2004CB418406).
文摘Long-term seismic activity prior to the December 26, 2004, off the west coast of northern Sumatra, Indonesia, MW=9.0 earthquake was investigated using the Harvard CMT catalogue. It is observed that before this great earth-quake, there exists an accelerating moment release (AMR) process with the temporal scale of a quarter century and the spatial scale of 1 500 km. Within this spatial range, the MW=9.0 event falls into the piece-wise power-law-like frequency-magnitude distribution. Therefore, in the perspective of the critical-point-like model of earthquake preparation, the failure to forecast/predict the approaching and/or the size of this earthquake is not due to the physically intrinsic unpredictability of earthquakes.
基金supported by the Basic Research Project of Institute of Earthquake Science,China Earthquake Administration(Grant No.02092422)the National Key Technology Research&Development Program of China(Grant No.2008BAC35B05)
文摘Satellite gravity data of the regional rheological structure of the lithosphere in the vicinity of Sumatra is used as evidence to enable a better understanding of the regional geodynamic environment.The data is interpreted using the theory of post-seismic viscoelastic relaxation.Coand post-seismic changes in the gravity field resulting from the 2004 M w 9.3 Sumatra earthquake were calculated from Gravity Recovery and Climate Experiment (GRACE) satellite data.A spatial Gaussian filter,500 km wide,was used in the calculation.The results indicate that there were significant co-seismic jumps in both uplifted and subducted regions.The magnitude of the jump in the subducted zone was ~9 10 8 m/s 2,more significant than the ~2 10 8 m/s 2 jump observed in the uplifted zone.However,a positive gravity change occurred in the uplifted zone very soon after the earthquake.The rheological structure of the lithosphere has a great effect on deformation and its determination is a fundamental part of developing reliable numerical simulations in geodynamics.Based on the temporally-variable gravity field observed by GRACE,the viscous lithospheric structure of the Sumatra area is investigated with a self-gravitating,half space,viscoelastic earth model.The estimated viscosity is of the order of 1.0 10 18 Pa·s and there are differences in the rheological parameters on the two sides of the fault.The factors that affect the viscosity are discussed in connection with the tectonic structure of the Sumatra area.