青藏高原西北地区与南北地震带地震活动性研究

Seismicity in the Northwestern Tibetan Plateau and North-South Seismic Belt

通过研究青藏高原地区地震的发震时间和空间分布规律,发现青藏高原西北地区70%的6级以上地震发生在青藏高原地震活动高潮时期,以青藏高原西北地区地震的发震时间为基准,以一年的时间窗口去检测南北地震带发生的地震,发现青藏高原西北地区与南北地震带中强震发震时间接近,具有很强的关联。青藏高原西北地区发生的地震与南北地震带南、北、中段的地震活动相关性各不相同,地震活动频次上呈现出与南北地震带北段相关性最弱,与南段相关性最强,但在震级上表现出与南北地震带北段和中段强震活动关系密切,与滇缅构造转换区的中震联系紧密,图像信息方法为两个地区地震活动相关性提供了证据。研究同时发现以海原地震为起始地震时南北地震带的强震具有由北向南往复迁移的特征,南北地震带中段和滇缅构造转换区的地震迁移次数更多,表明两个地区地震活动确实联系紧密。这项研究对于南北地震带的地震危险性评价和“源线模式”地震预测方法具有重要的意义。

In this study,the temporal and spatial distribution of earthquakes in the Tibetan Plateau was investigated;the results showed that over 70%of earthquakes with M≥6 in the northwest of the Tibetan Plateau occurred during the peak period of seismicity.Based on the earthquakes that occurred in the northwest of the Tibetan Plateau,the earthquakes that occurred in the south-north seismic belt within a one-year time window were detected,and it was found that the occurrence time of medium-strong earthquakes in the northwest of the Tibetan Plateau was close to that of the earthquakes in the north-south seismic belt.The earthquakes that occurred in the northwest of the Tibetan Plateau had different correlations with those in the south,north,and middle sections of the north-south seismic belt.Regarding the frequency of seismicity,the correlation with that in the north section of the north-south seismic belt was the weakest,and the correlation with that in the south section was the strongest.However,in magnitude,the earthquakes that occurred in the northwest of the Tibetan Plateau were closely related to the large earthquakes in the north and middle sections of the north-south seismic belt and the medium earthquakes in the Yunnan and Myanmar structural transformation area.Furthermore,the large earthquakes in the north-south seismic belt were found to have the characteristics of reciprocating migration from north to south when the Haiyuan earthquake is taken as the initial earthquake.The earthquake migration between the middle part of the north-south seismic belt and the Yunnan Myanmar structural transformation area was more frequent,which indicates a close relationship exists between the seismic activities in the two regions.This study is of great significance to the seismic risk assessment of the north-south seismic belt.