昆仑山口西8.1级地震前祁连山地震带附近形变异常的演化特征

Evolutional characteristics of ground deformation observed along the Qilian Mt. Before the Kunlun Mountain M_S 8.1 earthquake

昆仑山口西8.1级地震前在我国祁连山地震带附近观测到一系列的巨幅形变异常,这些异常包括了地倾斜、地应力和地应变等测项。文中对这些形变异常进行了研究,并给出了昆仑山口西8.1级地震前形变异常的分布特征:乐都、兰州、门源和肃南地倾斜异常的幅度、持续时间与昆仑山口西8.1级地震震级之间满足形变异常特征与地震强度之间的一般性统计关系;德令哈地应力观测曲线在震前出现了较明显的转折,最大应力扰动方向与地震方位密切相关;武都应变观测曲线在昆仑山口西8.1级地震前出现了幅度较大的异常,最大剪应变方向为西偏北23°～44°,应变变化幅度与地震震级之间也满足上述统计关系。研究结果表明,祁连山地震带附近出现的一系列应力、应变和倾斜巨幅异常与昆仑山口西8.1级地震有一定的相关性。

A series of deformation anomalies with great amplitude along the Qilian seismic belt have been observed prior to the Kunlun mountain M_S 8.1 earthquake. Studied the characteristics of ground tilt, stress and strain, we have obtained the following results: the amplitudes and duration of tilts observed at Ledu, Lanzhou, Menyuan and Sunan station satisfied the general statistic relationship between them and the magnitudes of strong earthquakes; Observed stress curve has obvious turn, the direction of maximum stress change is closely related to the azimuth of earthquake location. The observed strain cure at Wudu station shows clear anomaly, and the direction of maximum shear strain is NW 23°～44°, and the strain amplitude also satisfied the above-mentioned relationship. So the researched results demonstrated that the stress, strain and tilt anomalies are related to the Kunlun Mountain M_S 8.1 earthquake.