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基于等效弹性球模型,由分析P波波谱的斜率和低频成分,测定了海城地震(M=7.3)前后,震源及其邻近地区内微震震源参数(地震矩、应力降和震源尺度),以及相应路径上的介质品质因子—Q值。 结果表明:(1)海城地震前,发生在震源区内及沿北东向断裂带上的震级相近的小地震,其应力降高于震后相应地区小震的应力降,与此相应,震源尺度则震前比震后要小。(2)震前沿北东向断裂带应变能积累的范围大于余震分布区域,显示出北东向的构造运动在海城地震孕育过程中起了重要作用。(3)震前,海城地震震源区周围介质强度较高,Q值分布比较均匀,约为500—600;震后,在震中西南方向上Q值明显减小,约为180。 文中还初步提出了分析小震群震源参数,结合区域地质构造的特征,以及其他前兆现象预报未来大地震的可能性。
Based on the equivalent elastic sphere model, the microseismic source parameters (seismic moment, stress drop and source scale) of the source and its adjacent areas were measured before and after the Haicheng earthquake (M = 7.3) by analyzing the slope and low frequency components of the P wave spectrum. As well as the medium quality factor -Q value on the corresponding path. The results show that: (1) Before the Haicheng earthquake, small earthquakes of similar magnitudes occurred in the source region and along the north-east fault zone, and their stress drop was lower than that of the small earthquakes in the corresponding area after the earthquake. Correspondingly, Before the earthquake, the source scale was smaller than that after the earthquake. (2) The range of strain energy accumulation in NE-trending fault zone is greater than the aftershock distribution area before the earthquake, indicating that the NE-trending tectonic movement played an important role in the gestation of Haicheng earthquake. (3) Before the earthquake, the intensity of medium around the source area of Haicheng earthquake was high and the Q value distribution was relatively uniform, about 500-600. After the earthquake, the Q value in the southwest of the epicenter obviously decreased to about 180. The paper also initially proposed the possibility of predicting future earthquakes by analyzing source parameters of small swarms and combining features of regional geological structures with other precursory phenomena.