中国东南部地区背景地震重新定位及隐伏活动构造初步研究
发布时间：2018-10-31 21:03
【摘要】：中国东南部地区或分布崇山峻岭,或为新生代盆地覆盖,因而活动断裂的发现与定位极为困难。沿断裂的地震活动可以成为断裂现今活动的直接证据,但需要地震的精确定位。文中通过精定位背景地震活动性,初步分析了区域构造活动与背景地震活动的关系,解译了研究区存在的隐伏活动断裂。利用双差地震定位法对中国东南部地区大致22°~35°N,106°~122°E范围内1990-2014年发生的背景地震开展了重新定位工作,重新定位了51 000多个小震的震源参数。重新定位的背景地震活动表现出与区域构造活动相一致的分布特征,具有分区活动性,不同构造区出现不同的分布样式。现今活动较弱的构造区,地震活动分布离散或稀疏,没有指示出隐伏活动断裂的存在。在现今活动较强的构造区,地震活动明显集中成线性条带状,线性条带的展布样式和方向与区域构造格局和主要断裂走向一致。以线性条带分布的背景地震活动性揭示出的隐伏活动断裂主要分布在东南沿海一带、桂西北地区、四川盆地东南缘以及霍山一带,多数为以往研究所未发现的断裂。重新定位地震在不同构造区的震源深度分布差异明显,在块体中部区域震源深度最浅,主要分布在0~15km,表明脆性变形主要发生在上地壳,中下地壳为半塑性、塑性变形状态;在东南沿海一带,有下地壳地震发生。震源深度最深的区域为四川盆地的东南缘一带,有地震震源深度分布在40~44km,反映了地壳厚度大且下地壳为脆性变形特征,与较低的大地热流值和较硬的流变强度相一致。
[Abstract]:It is difficult to find and locate active faults in southeast China due to the distribution of high mountains or the cover of Cenozoic basins. The seismic activity along the fault may be a direct evidence of the present activity of the fault, but the precise location of the earthquake is needed. In this paper, the relationship between regional tectonic activity and background seismicity is preliminarily analyzed, and the hidden active faults in the study area are interpreted by precise location of background seismicity. The background earthquakes occurred in the range of 22 掳~ 35 掳N ~ (10 ~ 6 掳~ 122 掳E) from 1990 to 2014 in southeast China were relocated by using the double difference seismic location method, and the focal parameters of more than 51,000 small earthquakes were relocated. The relocated background seismicity shows the distribution characteristics consistent with the regional tectonic activity, and has the zonal activity, and different distribution patterns appear in different tectonic areas. In the weakly active tectonic area, the distribution of seismicity is discrete or sparse, which does not indicate the existence of concealed active faults. In the active tectonic area, the seismicity is obviously concentrated into a linear strip, and the distribution pattern and direction of the linear belt are consistent with the regional tectonic pattern and the main fault strike. In the background of linear belt distribution seismicity reveals that the concealed active faults are mainly distributed in the southeast coastal area northwest Guangxi the southeastern margin of Sichuan basin and the Huoshan area most of which are not found in previous research. The focal depth distribution of the relocating earthquake in different tectonic areas is very different, and the focal depth is the shallowest in the middle of the block, mainly distributed at 0 ~ 15 km, indicating that brittle deformation mainly occurs in the upper crust, and the middle and lower crust is semi-plastic and plastic deformation. There are earthquakes in the lower crust along the southeast coast. The area with the deepest focal depth is the southeastern margin of the Sichuan Basin, and the focal depth of the earthquake is 40 ~ 44km, which reflects the large thickness of the crust and the brittle deformation of the lower crust, which is consistent with the lower heat flow value and the hard rheological strength.
【作者单位】： 上海市地震局;中国地震局地质研究所 活动构造与火山重点实验室;
【分类号】：P315.2
，
本文编号：2303544
[Abstract]:It is difficult to find and locate active faults in southeast China due to the distribution of high mountains or the cover of Cenozoic basins. The seismic activity along the fault may be a direct evidence of the present activity of the fault, but the precise location of the earthquake is needed. In this paper, the relationship between regional tectonic activity and background seismicity is preliminarily analyzed, and the hidden active faults in the study area are interpreted by precise location of background seismicity. The background earthquakes occurred in the range of 22 掳~ 35 掳N ~ (10 ~ 6 掳~ 122 掳E) from 1990 to 2014 in southeast China were relocated by using the double difference seismic location method, and the focal parameters of more than 51,000 small earthquakes were relocated. The relocated background seismicity shows the distribution characteristics consistent with the regional tectonic activity, and has the zonal activity, and different distribution patterns appear in different tectonic areas. In the weakly active tectonic area, the distribution of seismicity is discrete or sparse, which does not indicate the existence of concealed active faults. In the active tectonic area, the seismicity is obviously concentrated into a linear strip, and the distribution pattern and direction of the linear belt are consistent with the regional tectonic pattern and the main fault strike. In the background of linear belt distribution seismicity reveals that the concealed active faults are mainly distributed in the southeast coastal area northwest Guangxi the southeastern margin of Sichuan basin and the Huoshan area most of which are not found in previous research. The focal depth distribution of the relocating earthquake in different tectonic areas is very different, and the focal depth is the shallowest in the middle of the block, mainly distributed at 0 ~ 15 km, indicating that brittle deformation mainly occurs in the upper crust, and the middle and lower crust is semi-plastic and plastic deformation. There are earthquakes in the lower crust along the southeast coast. The area with the deepest focal depth is the southeastern margin of the Sichuan Basin, and the focal depth of the earthquake is 40 ~ 44km, which reflects the large thickness of the crust and the brittle deformation of the lower crust, which is consistent with the lower heat flow value and the hard rheological strength.
【作者单位】： 上海市地震局;中国地震局地质研究所 活动构造与火山重点实验室;
【分类号】：P315.2
，
本文编号：2303544
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