关于地震烈度衰减模型的系统偏差

ON THE SYSTEMATIC DEVIATION OF SEISMIC INTENSITY ATTENUATION MODELS

本文讨论在地震危险性分析中目前使用广泛的地震烈度衰减模型,即Cornell建立的点源模型和洪华生(A.H-S.Ang)等建立的断层-破裂模型。与实际烈度资料的比较表明,在等震线狭长的区域,点源模型有系统偏差,通常这种偏差不算严重。为了克服上述偏差,断层-破裂模型引进了破裂长度的概念,但其衰减与实际资料出入较大。与实际地震等震线的比较和计算表明,对大地震沿断层或等震线长轴方向,断层破裂模型总是高估高烈度区而低估低烈度区。此外,本文分析了断层破裂模型产生系统偏差的原因,讨论了点椭圆模型的合理性,并用地震危险性分析实例做了说明。

In this paper,discussions are made on the widely applied intensity attenuation models of seismic hazard analysis: the point-source model introduced by Cornell,C. A. and the fault-rupture model given by Der Kiureghian and A. H-S. Ang. Comparisons with practical intensity data show that there is systematic deviation which isn't very large in the results given by point-source model for regions where isoseismals are of elongated shapes. To reduce the above deviation,the concept of rupture length is introduced into the fault-rupture model,but the attenuation is quite different from practical dam. Comparisons with isoseismals of actual earthquakes and computation show that the results given by the fault-rupture model overestimate the attenuation in high-intensity area and underestimate it in low-intensity area along the directions of fault or the major axis of the isoseismals. The reason causing such systematic deviation in the fault-rupture model is analysed,and the rationality of the empirical ellipse model is discussed,with illustration by examples of seismic hazard analysis.