摘要:
为查明长乐—南澳断裂带现今地应力状态和活动现况,在该断裂带中段泉州市区北侧开展了600 m深度钻探工程和随深度系统水压致裂现今原位地应力测量工作,在钻探深度内成功完成了21段地应力大小测试和4段最大水平主应力方向测试。随深度系统的地应力测量结果表明:①水平主应力量值处于高值状态且三个主应力大小之间关系为 SH>Sh>SV,表明区域构造作用强烈且水平应力起主导作用,易于逆断层发生。②现今最大水平主应力方向为北西西向,反映北东向的长乐—南澳断裂带中段现今活动具有右行走滑的特征。③基于实测数据计算得到μm 和 R,μm=0.44~0.76,反映了该区域相对很高的应力积累水平;R=0.44~0.65,说明此应力状态有利于该区域内断层的活动。依据实测地应力结果表明,长乐—南澳断裂带中段的应力状态已经达到断层活动的临界值,断裂活动进入临界状态,具有逆断层发生滑动的潜在危险性,值得重点关注和深入研究。研究成果为长乐—南澳断裂带中段现今活动性研究补充了新的动力学数据,为地震地质研究和城市安全评价提供了依据。
Abstract:
To explore the in-situ stress in the Changle-Nan’ao fracture belt and its present activity, the authors gathered data from 21 segments for in-situ stress measurement and from 4 segments for orientation of major principal stress varying intervals along the drill hole with total depth of 600 m located inside a granite-rich region in the northern part of Quanzhou City. Combined with the high in-situ stress data ofSH>Sh>Sv, the core sampling of the structure features of shallow earth crust rock formation reveals that current horizontal principal stresses play a leading role in reverse fault activity. Moreover, measured maximum principal in-situ stress strikes in NWW direction and reflects present compressive properties, with dextral slip activity, of the middle segment. Calculated through measured principal stresses, the magnitudes of feature parametersμm andR reach 0.44~0.76 and 0.44~0.65 respectively, which reflect the high-stress accumulative capability of the regional crust and availability for the activity of fault movement in this area. The measured results indicate that the state of in-situ stress has reached the critical value, the activity of the fault is approaching the critical state, and the potential risk of the reverse fault has the tendency of sliding and shearing failure. With pre-existing research result, these new dy-namic data will allow us to open new research avenues for understanding the present active features of the middle segment of the Changle-Nan’ao fracture belt and to provide a basic guarantee for the earthquake research and ur-ban safety.
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