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为了研究青藏高原隆起的原因,根据西藏地区的地震活动性和交通等方面的情况,于1976—1977年分别在西藏札木、当雄地区设立了区域地震台网。本文根据所观测的小震资料,用和达法测定了小震的时空参数。采用圆盘形剪切位错震源模式,考虑了传播介质的吸收和地震仪频率特性的影响,计算了小震的震源参数。结果表明: 1.小震具有局部密集和震源深度浅的特点,当雄地区小震震源面向南倾斜。 2.小震的平均应力降为几巴至几十巴。 3.对地震纵波而言,介质的品质因子较低,Q_P的平均值为150。 4.在厚度为二、三十公里的地壳上部,地震纵波的平均传播速度较低,V_P的平均值为5.65公里/秒。
In order to study the causes of the uplift of the Qinghai-Tibet Plateau, regional seismic networks were set up in Zhaomu and Dangxiong areas of Tibet in 1976-1977, respectively, according to the seismicity and traffic conditions in Tibet. In this paper, based on the observed data of small earthquakes, the space-time parameters of small earthquakes are determined by the method of reaching and reaching. The disk-shaped shear dislocation source mode is adopted, the influence of the propagation medium and the frequency characteristics of the seismometer is considered, and the source parameters of the small earthquakes are calculated. The results show that: 1. The small earthquakes have the characteristics of local concentration and shallow depth of source. 2. Small earthquakes average stress down to a few bar to tens of bar. For seismic longitudinal waves, the quality factor of the medium is lower, and the average Q_P is 150. 4. In the upper part of the crust with thickness of two to thirty kilometers, the average propagation velocity of seismic longitudinal waves is low, with an average V_P of 5.65 km / s.