美国最近三代地震区划图中的断裂震源模型

活断层与古地震定量数据在美国近三代地震区划图中的应用基本上体现了各阶段活断层研究的最新成果,其中断裂震源模型起到了桥梁的作用,并不断得到完善。在1996年地震区划图中引入了特征地震模型与截断的G—R模型,用以表述断层的震级一频度分布关系。在2002年地震区划图中更明确地处理了参数的不确定性,并引入逻辑树概念,同时在特征地震模型中试用了多段破裂模型。在2008年地震区划图中引用了更为广泛的逻辑树来描述地震构造几何形态、地震震级和复发周期的不确定性,其中特征地震模型包括：单段破裂和多段破裂的特征地震模型,以及给定震级的浮动地震模型（或不固定分段模型）。这些经验值得在我国第五代地震区划图的编制工作中借鉴。

Fault Source Models Used in the United States National Seismic Hazard Maps of the Last Three Versions

Fault source models implemented in the United States National Seismic Hazard Maps of the last three versions have been improved to keep with the development of active fault studies, in which the geometric features, dips, slip styles, segmentation, recurrence and magnitude-frequency distributions are all important factors. The uncertainties of these factors can be illuminated by logic trees and weighted. Two types of fault sources are incorporated into the the seismic hazard maps (Type A and B). Type-A faults are well-known faults that are defined using published information on fault geometry, earthquake sequences, slip rates, and dates of previous earthquakes. Detailed, fault-specific models are developed for each Type-A fault. The models include characteristic earthquakes on single segments, multi-segment ruptures, and earthquakes that are shifted uniformly along the fault (the "floating earthquake" or "unsegmented" model). Type-B faults are characterized by published information on slip rates and fault geometry. Type-B fault sources are modeled assuming the moment is released both as characteristic earthquakes and in earthquakes that follow a truncated Gutenberg-Richter model from 6.5 to the maximum magnitude.