Tempo-spatial rupture process of the 1997 Mani, Xizang (Tibet), China earthquake of M S=7.9 |
| |
| Authors: | Li-Sheng Xu and Yun-Tai Chen |
| |
| Institution: | (1) Institute of Geophysics, China Seismological Bureau, 100081 Beijing, China |
| |
| Abstract: | An earthquake of M
S=7.4 occurred in Mani, Xizang (Tibet), China on November 8, 1997. The moment tensor of this earthquake was inverted using
the long period body waveform data from China Digital Seismograph Network (CDSN). The apparent source time functions (ASTFs)
were retrieved from P and S waves, respectively, using the deconvolution technique in frequency domain, and the tempo-spatial
rupture process on the fault plane was imaged by inverting the azimuth dependent ASTFs from different stations. The result
of the moment tensor inversion indicates that the P and T axes of earthquake-generating stress field were nearly horizontal, with the P axis in the NNE direction (29°), the T axis in the SEE direction (122°) and that the NEE-SWW striking nodal plane and NNW-SSE striking nodal plane are mainly left-lateral
and right-lateral strike-slip, respectively; that this earthquake had a scalar seismic moment of 3.4×1020 N·m, and a moment magnitude of M
W=7.6. Taking the aftershock distribution into account, we proposed that the earthquake rupture occurred in the fault plane
with the strike of 250°, the dip of 88° and the rake of 19°. On the basis of the result of the moment tensor inversion, the
theoretical seismograms were synthesized, and then the ASTFs were retrieved by deconvoving the synthetic seismograms from
the observed seismograms. The ASTFs retrieved from the P and S waves of different stations identically suggested that this
earthquake was of a simple time history, whose ASTF can be approximated with a sine function with the half period of about
10 s. Inverting the azimuth dependent ASTFs from P and S waveforms led to the image showing the tempo-spatial distribution
of the rupture on the fault plane. From the "remembering" snap-shots, the rupture initiated at the western end of the fault,
and then propagated eastward and downward, indicating an overall unilateral rupture. However, the slip distribution is non-uniform,
being made up of three sub-areas, one in the western end, about 10 km deep ("western area"); another about 55 km away from
the western end and about 35 km deep ("eastern area"); the third about 30 km away from the western end and around 40 km deep
("central area"). The total rupture area was around 70 km long and 60 km wide. From the "forgetting" snap-shots, the rupturing
appeared quite complex, with the slip occurring in different position at different time, and the earthquake being of the characteristics
of "healing pulse". Another point we have to stress is that the locations in which the rupture initiated and terminated were
not where the main rupture took place. Eventually, the static slip distribution was calculated, and the largest slip values
of the three sub-areas were 956 cm, 743 cm and 1 060 cm, for the western, eastern and central areas, respectively. From the
slip distribution, the rupture mainly distributed in the fault about 70 km eastern to the epicenter; from the aftershock distribution,
however, the aftershocks were very sparse in the west to the epicenter while densely clustered in the east to the epicenter.
It indicated that the Mani M
S=7.9 earthquake was resulted from the nearly eastward extension of the NEE-SWW to nearly E-W striking fault in the northwestern
Tibetan plateau.
Contribution No. 99FE2016, Institute of Geophysics, China Seismological Bureau.
This work is supported by SSTCC Climb Project 95-S-05 and NSFDYS 49725410. |
| |
| Keywords: | Mani earthquake Xizang (Tibet) tempo-spatial rupture process source time function |
| 本文献已被 SpringerLink 等数据库收录！ |
|
