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Journal: |
Journal of Geophysical Research 2018 No.11
clicks:259 |
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Title:
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Author:
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Chang Liu1 , Peiyu Dong2 , Bojing Zhu3 , and Yaolin Shi4 |
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Adress: |
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Abstract:
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The 2008 Wenchuan earthquake (Mw 7.9) unilaterally ruptured the Longmen Shan fault (LMSF)
along eastern Tibet. The earthquake rupture propagated about 270 km northeastward, whereas it
propagated only about 20 km southwestward along the strike of the fault. Although a significant attention
has been paid to the question of predominantly unilateral propagation, the primary reasons for this type of
propagation remain unclear. In this research, we examined the change of Coulomb stress along the LMSF
caused by the historical earthquakes near and on the LMSF from 1725 to 2008. We found that the 14
preceding large earthquakes (M ≥ 6.5) on the Xianshui He fault cast a stress shadow on the SW segment of
the LMSF, which was not activated by the 2008 Wenchuan earthquake rupture. The 1970 Dayi earthquake
on the SW segment of the LMSF contributed significantly to this stress shadow. Compared with the
segment of the 2008 Wenchuan earthquake rupture, this stress shadow caused strong stress contrasts of
214, 22, and 80 kPa in the seismic gap of the very SW segment of the LMSF, the rupture zone of
the 2013 Lushan earthquake, and the seismic gap between the 2008 Wenchuan and 2013 Lushan
earthquake ruptures, respectively. Stress contrasts in these values were consistent with tectonic loading
over 165, 17, and 62 years, respectively, by integrating an interseismic stress-loading rate of 1.3 kPa/a. We
proposed that this stress shadow might have created a barrier at the SW segment, preventing the
earthquake rupture propagating southwestward. |
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