【摘要】：中國東南部地區(qū)或分布崇山峻嶺,或為新生代盆地覆蓋,因而活動斷裂的發(fā)現(xiàn)與定位極為困難。沿斷裂的地震活動可以成為斷裂現(xiàn)今活動的直接證據(jù),但需要地震的精確定位。文中通過精定位背景地震活動性,初步分析了區(qū)域構(gòu)造活動與背景地震活動的關(guān)系,解譯了研究區(qū)存在的隱伏活動斷裂。利用雙差地震定位法對中國東南部地區(qū)大致22°~35°N,106°~122°E范圍內(nèi)1990-2014年發(fā)生的背景地震開展了重新定位工作,重新定位了51 000多個小震的震源參數(shù)。重新定位的背景地震活動表現(xiàn)出與區(qū)域構(gòu)造活動相一致的分布特征,具有分區(qū)活動性,不同構(gòu)造區(qū)出現(xiàn)不同的分布樣式�，F(xiàn)今活動較弱的構(gòu)造區(qū),地震活動分布離散或稀疏,沒有指示出隱伏活動斷裂的存在。在現(xiàn)今活動較強的構(gòu)造區(qū),地震活動明顯集中成線性條帶狀,線性條帶的展布樣式和方向與區(qū)域構(gòu)造格局和主要斷裂走向一致。以線性條帶分布的背景地震活動性揭示出的隱伏活動斷裂主要分布在東南沿海一帶、桂西北地區(qū)、四川盆地東南緣以及霍山一帶,多數(shù)為以往研究所未發(fā)現(xiàn)的斷裂。重新定位地震在不同構(gòu)造區(qū)的震源深度分布差異明顯,在塊體中部區(qū)域震源深度最淺,主要分布在0~15km,表明脆性變形主要發(fā)生在上地殼,中下地殼為半塑性、塑性變形狀態(tài);在東南沿海一帶,有下地殼地震發(fā)生。震源深度最深的區(qū)域為四川盆地的東南緣一帶,有地震震源深度分布在40~44km,反映了地殼厚度大且下地殼為脆性變形特征,與較低的大地?zé)崃髦岛洼^硬的流變強度相一致。
[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 擄~ 35 擄N ~ (10 ~ 6 擄~ 122 擄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.
【作者單位】： 上海市地震局;中國地震局地質(zhì)研究所 活動構(gòu)造與火山重點實驗室;
【分類號】：P315.2
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本文編號：2303544