岩石磁学能揭示岩石的磁性矿物组合，通过断裂岩不同的磁性矿物组合可揭示地震过程中磁性矿物变化、地震摩擦温度及地震滑移机制等基础地震地质问题。2008年 Mw 7.9级汶川地震使两条断裂带同时发生地表破裂，包括映秀-北川和灌县-安县断裂地表破裂带，破裂带上地震断裂岩为岩石磁学提供了大量的研究对象。本研究主要以汶川地震地表破裂带上两个探槽内断裂岩为对象，包括映秀-北川地表破裂带上的八角庙探槽和灌县-安县地表破裂带上的九龙探槽，结合目前已发表的地表及 WFSD-1孔的研究成果，从岩石磁学角度探讨汶川地震断裂带经历的地震滑移机制：①综合映秀-北川地震断裂带上八角庙探槽和其它位置的断裂岩岩石磁学研究，结果显示该地震断裂带附近断层泥的高磁化率源于新生的亚铁磁性矿物，如磁铁矿和磁赤铁矿等，故映秀-北川地震断裂曾经历高温快速热增压地震滑移机制；②灌县-安县地震断裂带上九龙探槽内断层泥略低的平均磁化率源于其铁的硫化物含量比断层角砾及侏罗纪砂岩多，铁的硫化物可能源于地震过程或断裂岩抬升到地表后的地表作用，如果断层泥中铁的硫化物多含量源于地震过程，则灌县-安县地震断裂带曾经历低温慢速机械润滑地震滑移机制；③两条断裂经历的不同地震滑移机制可能受控于断裂深部结构，如断层产状，映秀-北川地震断裂带的陡倾角易产生高温快速地震滑移，而灌县-安县地震断裂带的缓倾角更易产生低温慢速地震滑移。%Rock-magnetism can be used to decipher the magnetic carrier materials,and it has been widely used in seismogeological research,such as the magnetic mineral change,friction temperature and earthquake slip dynamic during large earthquake.The 2008 Mw 7.9 Wenchuan Earthquake induced two major earthquake surface rupture zones,including the Yingxiu-Beichuan and Guanxian-Anxian earthquake surface rupture zones.The earthquake fault rocks close to the two surface rupture zones give a good chance for the rock-magnetism.In this study,the fault-rocks magnetic studies in the two trenches close to the two Wenchuan Earthquake surface rupture zones were used to discuss the earthquake slip dynamics, including the Bajiaomiao and Jiulong trenches along the Yingxiu-Beichuan and Guanxian-Anxian earthquake surface rupture zones,respectively.This study also combined with the recent rock magnetism from the earth surface and WFSD-1.The results show that:① The rock magnetism,from the Bajiaomiao trench and other previous researches,shows that the high susceptibility of the fault gouge along the Yingxiu-Beichuan earthquake fault zone was caused by the new by formed ferrimagnetic minerals,such as magnetite and hematite,so the Yingxiu-Beichuan earthquake fault had experienced high temperature and rapid speed thermal pressurization earthquake slip mechanism;② The rock magnetism from the Jiulong trench implied that the slightly low average susceptibility of fault gouge was caused by high content of Fe-sulfides than that of fault breccia and Jurassic sandstones,which was possibly induced by earthquake process or earth surface process after the fault rocks exposed to the surface.If the high content of Fe-sulfides was induced by earthquake process,the Guanxian-Anxian earthquake had experienced the low temperature and slow speed mechanical lubrication earthquake slip mechanism;③ The different earthquake slip mechanism was possibly controlled by the deep structure of the two earthquake faults,such as the fault occurrence.The steep dip character of the Yingxiu-Beichuan fault could be easy to induce high temperature and rapid speed earthquake slip mechanism,while the low dip angle feature of the Guanxian-Anxian earthquake fault could be easy to induce low temperature and slow speed earthquake slip mechanism.
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