Study on Activity Features of Xianshuihe Fault Zone with Fault Creep and Short Baseline Observation for the Last 20 Years
详细信息
- 责任者：Liu Guanzhong (State Key Laboratory of Earthquake Dynamics ; Institute of Geology ; China Earthquake Administration ; Beijing 100029 ; China) ; Ma Jin
- 刊名：Chinese Journal of Geophysics
- 出版年：2013
- 卷期：56(3)
- 关键词：活动断层 ; active faults ; 鲜水河断裂带 ; Xianshuihe Fault Zone
- 页码：p.878-891
- 图表：illus., 2 tables, 42 refs.
- 分类号：0300
- issnNo：ISSN0001-5733
- isbnNo：CN11-2074/P
摘要
We derive deformation rates of the fault applying wavelet transform and fault kinematics,by using the data of creepmeter and short baseline from Xianshuihe fault zone.Based on these results and combined with GPS observations,we analyze the segmental character and the spatial-temporal evolution of the fault activities.Our study shows that:(1) The fault activity is different along different segments.The segmental activity of Xianshuihe fault zone is significant.In detail,Luhuo and Daofu fault,extending northwest from Daofu County,are tensional and left-lateral,with comparatively larger strike-slip rates,and their motions are more stable than Qianning and Zheduotang fault.While Qianning and Zheduotang fault to the south of Daofu County tend to be locked,and the states of movement are complex,where Qianning fault is compressive left-lateral and Zheduotang fault is right-lateral.The possible causes of this segmentation include fault bending and the differential movements of sub-block in Bayankala active block.(2) The slipping mode of fault alternates during different period of time.Although Xianshuihe fault is a left-lateral strike-slip active fault,nonetheless,there is reverse strike-slip along some segments before Wenchuan earthquake.The left-lateral creep rates of Luhuo and Daofu fault are decreased in the 2 years before MS8.0 Wenchuan earthquake,and Qianning and Zheduotang fault exhibited right-lateral strike-slip abnormally in 2007.To the end of 2009,the range of reverse strike-slip is still growing.(3) The strike-slip rates observed by different-length measuring lines and the spatial distribution features of deformation belt are different.The strike-slip rates of Xianshuihe fault zone are not consistent at different segement and scale by different observing methods.The creepmeters are 0.01~0.78 mm/a(18.7 m to 65.1 m across fault),and short baselines are 0.02~2.46 mm/a(72m to 288 m across fault),however,GPS observations are 6~11 mm/a(dozens of kilometers across fault),and geological survey results are 5~15 mm/a.At increasing distances perpendicular to the fault,the average creep rate on one side of the fault grows following a logarithm function,and the deformation intensity attenuates following a power function.We infer that the far-field displacement includes the deformation or distributed offset of bilateral blocks of fault.At last,the difference between present fault deformation observations and geological survey results indicates that the fault slip rate is not a constant in time domain.