Evidence for Holocene activity of the Yilan-Yitong fault,northeastern section of the Tan-Lu fault zone in Northeast China |
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| Institution: | 1. State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China;2. Sorbonne Universités, UPMC Univ Paris 06, UMR 7193, Institut des Sciences de la Terre Paris (iSTeP), F-75005 Paris, France;3. CNRS, UMR 7193, Institut des Sciences de la Terre Paris (iSTeP), F-75005 Paris, France;4. Université d''Orléans, ISTO, UMR 7327, 45071 Orléans, France;5. CNRS/INSU, ISTO, UMR 7327, 45071 Orléans, France;6. BRGM, ISTO, UMR 7327, BP 36009, 45060 Orléans, France;1. State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China;2. Key Laboratory of Earth and Planetary Physics, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China;3. Innovation Academy for Earth Science, CAS, Beijing 100029, China;4. University of Chinese Academy of Sciences, Beijing 100049, China;5. Department of Earth and Space Sciences, Southern University of Science and Technology, Shenzhen, Guangdong 518055, China;6. Institute of Geophysics, China Earthquake Administration, Beijing 100081, China;1. School of Resources Environment and Safety Engineering, University of South China, Hengyang, China;2. CAS Key Laboratory of Crust-Mantle Materials and Environments, School of Earth and Space Sciences, University of Science and Technology of China, Hefei, China |
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| Abstract: | The Tan-Lu fault zone (TLFZ) is the largest of the major faults in eastern China. Many strong earthquakes have occurred on its section in North China, but no quake greater than M ⩾ 6 has been documented in history at its northeastern section, the Yilan-Yitong fault (YYF) in Northeast China. It is usually considered that this fault has been inactive since late Quaternary and incapable of generating moderate-sized quakes. This conclusion is, however, questioned by our recent work based on high-resolution satellite image interpretation and field investigation. We found a 70-km-long surface scarp near Fangzheng county in Heilongjiang province (HLJP) and a 20-km-long scarp near Shulan county in Jilin province (JLP), and both are associated with the YYF. The trenches across these two scarps reveal a 14C displacement date of 1730 ± 40 years BP at Fangzheng and of 4410 ± 30 years BP at Shulan. The dextral offsets of the Songhua River and Second Songhua River and nearly horizontal fault striations indicate that the new activity of the YYF has been dominated by dextral strike slipping with a normal component. These new data suggest that, at least for partial sections, the YYF has been active since the Holocene, implying a potential seismic hazard. However, current quake-protection standards in this region are very low due to the previous view that the YYF fault has not been active since the late Quaternary. If an M ⩾ 7 quake takes place on this fault, it will be a devastating event. Therefore, it is necessary to conduct a detailed study on the whole YYF and to reassess its future seismic risk. |
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| Keywords: | Tan-Lu fault zone Yilan-Yitong fault Fault scarp Holocene activity |
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