汶川地震后青藏高原东北缘中等地震活动特征分析

Analysis on Activity Characteristics of Moderate Earthquakes in Northeastern Margin of Tibetan Plateau after the Wenchuan Earthquake

摘要:

汶川地震后青藏高原东北缘地区发生了多次M_L≥4.0地震,本文利用甘肃数字地震台网的资料,采用CAP方法计算得到了31次M_L≥4.0地震的震源机制解,并对结果进行分析与讨论。研究表明:受汶川地震的影响,青藏高原东北缘区域应力场的调整过程使得中等地震分区、丛集活动,地震类型表现出明显的区域特征。31次中等地震的最大主应力方位显示,祁连山地震带优势方向为NE向,甘东南地区近EW向,表明区域应力场呈现局部性的特征。

Abstract:

On the basis of data of Gansu Seismological Network, the focal mechanism solutions of 31 M_L≥4.0 earthquakes which occurred in the northeastern margin of Tibetan Plateau after Wenchuan earthquake were obtained in the paper by using the CAP method, and then the results were analyzed and discussed. The results showed that because of the adjustment process of regional stress field in northeastern margin of Tibetan Plateau which was influenced by Wenchuan earthquake, activities of moderate earthquakes there presented zoning and clustering, and earthquake types had obviously regional characteristics. The maximum of principal stress azimuth of 31 moderate earthquakes revealed that predominant azimuth in Qilianshan seismic belt was NE and that in southeastern Gansu was nearly EW, which showed a localized characteristic of regional stress field.