摘要
At first time,we observed the postseismic deformation,which actually is a kind of creep after slip,along the intra-plate active fault associated with the Wenchuan earthquake.To understand the near-field postseismic deformation following 2008 Wenchuan earthquake in Sichuan Province of China,we compared the fault scarp or flexure scarp profiles measured in different campaigns.Our result shows that among total 19 observation sites,on 13 sites (68% of 19) fault scarps fall back with an average about 9.7% decrease;on 5 sites (26% of 19) fault scarps present no change;and on one site (6% of 19) fault scarp continues to uplift with 12.8% increase.The variety of fault scarp we observed results mainly from near-field postseismic deformation,after slip occurred in shallow.Based on our observations,the following are demonstrated: except for the southwestern end near Yingxiu Town where coseismic slip deficit and some elastic energy residue exist there,fall back (68%) or non-changing (26%) of fault scarp shows energy balance or energy deficit due to overthrust,implying that the likelihood of occurrence of strong aftershocks of ≥ M7 becomes very small in these energy-released areas.Moreover,we suggest that a minimum of 10% error due to near-field postseismic deformation should be considered when evaluating the magnitude of historic and paleoearthquake or slip rate based on the fault scarp displacement,even though the error caused by erosion has been accounted already.
At first time, we observed the postseismic deformation, which actually is a kind of creep after slip, along the intra-plate active fault associated with the Wenchuan earthquake. To understand the near-field postseismic deformation following 2008 Wenchuan earthquake in Sichuan Province of China, we compared the fault scarp or flexure scarp profiles measured in different campaigns. Our result shows that among total 19 observation sites, on 13 sites （68% of 19） fault scarps fall back with an average about 9.7% decrease; on 5 sites （26% of 19） fault scarps present no change; and on one site （6% of 19） fault scarp continues to uplift with 12.8% increase. The variety of fault scarp we observed results mainly from near-field postseismic deformation, after slip occurred in shallow. Based on our observations, the following are demonstrated： except for the southwestern end near Yingxiu Town where coseismic slip deficit and some elastic energy residue exist there, fall back （68%） or non-changing （26%） of fault scarp shows energy balance or energy deficit due to overthrust, implying that the likelihood of occurrence of strong aftershocks of≥M7 becomes very small in these energy-released areas. Moreover, we suggest that a minimum of 10% error due to near-field postseismic deformation should be considered when evaluating the magnitude of historic and paleoearthquake or slip rate based on the fault scarp displacement, even though the error caused by erosion has been accounted already.
基金
supported by the National Natural Science Foundation of China (40841019 and 40872128)
the special funds from the Ministry of Science and Technology of China for Scientific Investigation of Wenchuan Earthquake Rupture
关键词
变形
震后
近场
地震破裂
汶川
滑动速率
断层崖
活动断裂
Wenchuan earthquake, near-field postseismic deformation, fault scarp and flexure scarp, energy residue and deficit
