【摘要】 利用大岗山水库附近水库地震监测台网记录资料,对水库蓄水前库区附近中小地震活动开展精确定位和震源机制计算分析。重新定位结果显示水库库区附近地震主要丛集分布在4个区域,地震活动并未沿研究区内主干断裂展布,而是明显形成多条NE-SW向小规模地震条带。磨西断裂中北段以西地震活动在深度上呈现从北向南由浅向深渐变的特征,磨西断裂中南段附近则表现为从北向南由深向浅渐变,其中未来水库蓄水区域地震深度呈现北深南浅,该特征可能使得水库蓄水后库首或库中段更易受库水下渗影响而诱发地震活动。中小地震震源反演结果显示以走滑型错动为主,受小型断裂构造走向的随机性影响,震源机制节面走向无明显的优势方向,但节面倾角较大,节面均表现为近垂直向下延伸。库区附近应力场反演结果虽然表现出一定的离散特征,但总体上与大区域应力场一致,易发生走滑型错动。更多还原

【Abstract】 Based on the data obtained from the Dagangshan reservoir area that was recorded by an earthquake-monitoring network,we calculate and analyze the precise location and focal mechanism of medium-small earthquakes that occurred near the reservoir before its impoundment.The results show that the earthquakes near the reservoir are mainly distributed in four areas,not along the main principal faults.However,the earthquakes clearly form many NE-SW trending small earthquake belts.The inversion results of the focal mechanism of the medium-small earthquakes show that they were mainly caused by strike-slip fractures,influenced by the irregular trend of small faults.Furthermore,the trend of nodal plane of the focal mechanism has no obvious advantage direction,but its inclination degree is high and the nodal plane is almost vertical.The inversion results of the stress field near the reservoir reveal a disperse stress distribution,similar to the stress field of larger region and is susceptible to strike-slip fracturing.更多还原