青藏高原北部地区地震窗口特征及其预报意义

CHARACTERISTICS OF SEISMIC WINDOWS ANOMALY AND PREDICTION SIGNIFICANCE IN NORTH AREAS OF QINGFHAI-XIZANG PLATEAU

摘要:

利用青藏高原北部地区弱震活动资料筛选出3个具有中短期预报效能的地震窗口,分析了M_S ≥ 5.0地震前各个窗口的异常特征,提取出半定量的中短期预报指标.即:在中强地震前80%的异常出现在地震前1~6个月,以中心异常出现时间向后推1~6个月作为预测的发震时间;异常幅度与未来震级之间没有明显的对应关系.对于7级以上大地震,古浪窗的显著异常主要对应边界水平剪切走滑活动断裂上发生的地震;舟曲窗和乌海窗的显著异常主要对应活动块体内部挤压逆冲断裂上发生的地震.而5~6级的中等地震没有明显的对应规律.

Abstract:

Three seismic windows with mid-short period prediction effectiveness are selected through a study on seismicity in North areas of Qinghai-Xizang plateau. The anomalous feature in the seismic windows before strong earthquake(M_S >5.0)is analyzed and the half-quantity predition criteria for midshort period are attained. The result shows that 80% anormalous occur 1 to 6 mouthes before strong earthquake, so we consider 1~6 months as strong event time after some anomalous occur in the mid-point of seismic windows. There is no intimate relationship between the anomal amplitude and the follow ing earthquake. The Gulang seismic window is corresponding with the earthquake in large and shear strike-slip fault, The main anomalous in Zhouqu and Wuhai windows is corresponding with the earthquake in constrain thrust fault in the internal plateau. But there is no apparently relationship between the earthquake(5.0 < Ms < 6.0)and anomalous in seismic windows.