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峨边-金阳断裂带北部峨边地区的地应力状态 及构造分析
投稿时间:2019-10-27  修订日期:2020-02-07  点此下载全文
引用本文:
DOI:10.19762/j.cnki.dizhixuebao.2020059
摘要点击次数: 55
全文下载次数: 60
作者单位E-mail
李兵 中国地震局地壳应力研究所 lange506@163.com 
郭启良 中国地震局地壳应力研究所  
姜大伟 中国地震局地壳应力研究所  
中文摘要:峨边-金阳断裂带是凉山褶断隆起和宜宾-雷波构造带的分界带,地震活动性参数b值结果显示该断裂北段处于低应力水平,为查明该区的地应力状态,分别于2013年和2014年在该断裂的北部峨边地区开展了2个钻孔的水压致裂地应力测量工作。测量结果表明:2个钻孔的最大水平主应力(SH)方向介于北西50°至北西68°之间,趋于北西至北西西向,与震源机制解和区域应力场结果相一致; DPS-1孔位于向斜的轴部,应力水平应高于其周边;2个钻孔SH值介于5.89MPa-14.50MPa之间,现今应力水平较低,这与b值结果相一致;峨边地区在300m深度以上的SH值与峨边-金阳断裂带南段和安宁河断裂附近的应力值相近,随着深度的增加小于南段和安宁河断裂的值;DPS-1孔三向主应力的相对大小表现为Sv>SH>Sh,有利于正断层的活动,与峨边-金阳断裂的逆冲性质不一致,主要与峨边-金阳断裂带在测孔区域的水平构造活动减弱有关,在浅部其构造作用强度已经弱于区域应力场;YJP-1孔小于150m的深度上三向应力表现为逆冲型应力状态,大于225m的深度表现为走滑型应力状态,随着深度的增加,应力状态将转变为正断型应力状态,这也反映了峨边-金阳断裂带北部水平构造活动已减弱。根据实测资料,结合库伦破坏准则和应力莫尔圆,探讨了最大剪应力与平均主应之比(μm)与断层稳定性的关系,并定性分析了地形、地质构造和金口河MS5.0级地震前的应力调整对测孔区域应力状态可能产生的影响,结果表明:地形和地质构造对测孔区域应力状态的影响较小;DPS-1孔有效应力条件下的μm值处于高值,这有利于正断层的滑动,但是会抑制逆断层的活动,表明峨边-金阳断裂带更稳定,这与实际情况相一致;地震前的应力调整对DPS-1孔应力状态的影响较小。研究结果对了解峨边-金阳断裂带北部的背景应力场具有参考意义。
中文关键词:峨边-金阳断裂带  金口河Ms5.0级地震  马边地区  地应力状态  Byerlee准则  断层稳定性  
 
In-situ stress state and tectonic analysis of the northern part of the Ebian-Jinyang fault zone in the Ebian area
Author NameAffiliationE-mail
LIBing School of Earth and Space SciencesUniversity of Science and Technology of China lange506@163.com 
GUOQILIANG Institute of Crustal Dynamics, China Earthquake Administration  
jiangdawei Institute of Crustal Dynamics, China Earthquake Administration  
Abstract:The Ebian-Jinyang Fault Zone is the boundary zone between Liangshan fold fault uplift and Yibin-Leibo tectonic fault. The seismicity parameters of b value shows that the northern section of the fault is at a low stress level. To find out the crustal stress state in this area, the hydraulic fracturing crustal stress measurement of two bore holes was carried out respectively in 2013 and 2014. The measurement results show that the maximum horizontal principal stress direction of the two boreholes is between NW 50° and NW 68°,tending to be NW-NWW, which is consistent with the results of focal mechanism solution and regional stress field; the stress level of DPS-1 hole, which is located on the axis of the syncline, should be higher than that of the surrounding area; the SH value is between 5.89MPa and 14.50MPa. At present, the stress level is low, which is consistent with the seismicity parameters of b value; the SH of the Ebian area whose depth is more than 300m is similar to the value of the stress near the southern part of the Ebian-Jinyang Fault Zone and the Anning River Fault Zone, and as the depth increases, the SH is less than that near the southern part of the Ebian-Jinyang Fault Zone and the Anning River Fault Zone; the principal stresses of DPS-1 hole in three dimensions are expressed as Sv>SH>Sh, which is beneficial to the activity of normal fault and is inconsistent with the thrust property in the Ebian-Jinyang Fault Zone. The main reason is the weakening of thrust tectonic activity in the northern part of Ebian-Jinyang Fault Zone, and consequently, the intensity of its tectonics is already weaker than the regional stress field. The three-dimension stress of YJP-1 hole at a depth of less than 150m shows a thrust stress state, while that at a depth of more than 225m shows a strike slip stress state. As the depth increases, the stress state will change to a normal fault stress state. It is also a reflection of the weakening of thrust tectonic activity in the northern part of Ebian-Jinyang Fault Zone. Based on the measured data, combining the Coulomb failure criterion and the stress Mohr"s circle, the relationship between μm ( the ratio of maximum shear stress to average principal stress) and stability of the fault is discussed, and the possible effects of earthquake, topography and geological structure, and the stress adjustment prior to the MS5.0 earthquake of Jinkouhe on the stress state of the measured hole area are analyzed qualitatively. The results show that topography and geological structure have little influence on the stress state of the measured hole area. The μm of DPS-1 hole in the condition of effective stress is high,which is beneficial to the sliding of normal fault, but it will restrain the activity of reverse fault. This shows that Ebian-Jinyang Fault Zone is more stable, and is consistent with the actual situation. Stress adjustment prior to the earthquake has little influence on the stress state of DPS-1 hole. All these results are of great significance to understand the background stress field in the northern part of Ebian-Jinyang Fault Zone.
keywords:Ebian-Jinyang fault  Jinkouhe MS5.0 earthquake  Mabian area  In-situ stress state  Byerlee’s Criterion  fault stability
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