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以2013年4月22日内蒙古通辽MS5.3地震为研究对象,在序列统计分析的基础上,通过HypoD D双差定位和震源机制求解,分析了之前的ML4.4地震与MS5.3地震的关系。结果表明,通辽MS5.3地震是在震中区中小地震长期平静和震前短期活动增强的背景下发生的一次中强地震;地震精确定位结果显示,通辽MS5.3地震序列整体呈NW向展布,延伸约10km,ML≥3.0余震集中发生于主震南侧约2km处;MS5.3主震和ML4.4前震的震中相距约1.8km,震源深度分别为7.208、7.089km,表明两者的震源位置比较接近,可能发生于同一断层面;震源机制结果表明,通辽MS5.3主震的震源机制为走滑型,余震震源机制类型比较凌乱,由前期的走滑为主转变为后期的正断层和逆冲型;3次较大前震的震源机制解具有一致性,均为正断层,一定程度上表现了震中区地壳介质在宏观破裂前存在明显的各向异性,具体表现为裂隙的定向排列,这种“一致性”的震兆状态在应力的进一步作用下孕育发生了主震。根据地震序列的时空分布特点和震源机制相似性,综合判定通辽MS5.3地震应为前震-主震-余震型。
Based on the statistical analysis of the series of earthquakes in the Tongliao MS5.3, Inner Mongolia, on April 22, 2013, HypoD D double-difference localization and source mechanism were used to solve the problems. The previous ML4.4 and MS5.3 earthquakes relationship. The results show that the Tongliao MS5.3 earthquake is a moderate-strong earthquakes in the background of the long-term moderate and moderate earthquakes in the epicenter area and the short-term seismic activity before earthquakes. The precise location of the earthquakes shows that the sequence of Tongliao MS5.3 Earthquake is NW distribution , Extending about 10 km. ML≥3.0 aftershocks occurred about 2 km to the south of the main shock. The epicenters of MS5.3 and ML4.4 precursors were 1.8km away from each other and the focal depths were 7.208 and 7.089km, respectively. The results show that the source mechanism of the Tonglian MS5.3 mainshock is a strike-slip type, and the types of focal mechanisms of aftershocks are relatively unorganized. The focal strike changes from the early strike-slip to the later positive Fault and thrust type. The focal mechanism solutions of the three larger foreshocks are consistent and all are normal faults. To some extent, there is obvious anisotropy of the crustal medium before the macroscopic rupture in the epicenter area, which is manifested as the orientation of the fractures Arrangements, this “consistency ” earthquake state in the stress under the influence of the occurrence of the main shock occurred. According to the spatiotemporal distribution of seismic sequences and the similarity of focal mechanisms, it is concluded that the Tongliao MS5.3 earthquake should be a foreshock-mainshock-aftershock model.