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震源深度是地震学中最难准确测定的参数之一,各种方法对于震源深度的估计都具相当程度的不确定性,影响着人们对震源过程的认识。各种因素对震源深度的影响是非线性的,本文从近震走时公式入手,分析了震中距、到时残差和速度模型(地壳模型)对震源深度的影响。当地震波传播速度一定时,震源深度的误差随着震中距或台站距离的增大和走时残差的增大而增大。走时残差一定时,震源深度误差随着震中距的增大和地震波速度的增大而增大。研究也表明,当速度已知,走时残差一定时,越浅的地震,定位误差可能越大。定位精度产生的水平误差随着震中距、走时误差和地震波速度的增大而增大,震源深度误差也将增大。另外,震源深度的误差会导致发震时刻的变化,随之而来的结果都会因此而改变。
Source depth is one of the most difficult and accurate parameters in seismology. Various methods have a considerable degree of uncertainty for the estimation of source depth, affecting people’s understanding of the source process. The influence of various factors on the focal depth is nonlinear. Based on the formula of the near-strike travel time, the paper analyzes the influence of epicenter distance, arrival residual velocity and velocity model (crustal model) on focal depth. When the propagation velocity of the earthquakes is constant, the error of the focal depth increases with the increase of epicenter distance or station distance and the increase of travel time residual. When the residual time is constant, the depth error of focal source increases with the increase of epicenter distance and the increase of seismic velocity. The research also shows that, when the velocity is known and the travel time residual is constant, the shallower the earthquake, the positioning error may be larger. The horizontal error caused by the positioning accuracy increases with the increase of epicenter distance, travel time error and seismic velocity, and the focal depth error will also increase. In addition, the depth of the source error will lead to changes in seismogenic time, the resulting results will change accordingly.