震后松弛过程的粘弹性模型在1997年Mw7.6玛尼地震中的应用研究

Study of Visoelastic Rheological Model for Posteismic Relaxation:A Case Study on 1997 Mw7.6 Manyi Earthquake

采用麦克斯韦体模型、标准线性体模型和伯格斯体模型，具体研究了1997年玛尼地震在衰减时间1～100a间的震后位移场和库仑应力场。结果表明：①在1～5a的短期内，采用标准线性体和伯格斯体模型的震后位移场具有时空上的一致性；而在10a以上的中长期内，麦克斯韦单元开始起主要作用，表现为采用麦克斯韦体和伯格斯体模型的震后位移场具有时空上的一致性。②虽然应力阴影区和应力触发区随时间而同步扩展，但短期内，采用标准线性体和伯格斯体模型的粘弹性库仑应力场的空间结构具有一致性；而中长期内，采用麦克斯韦体和伯格斯体模型的粘弹性库仑应力场的空间结构具有一致性。为更好地解释震后形变及粘弹性库仑应力触发响应，流变模型的选择需要根据研究的时间段和观测数据源具体确定。

To quantitatively assess the differences born from rheological models on postseismic displacements and viscoelastic Coulomb stress changes, for 1997 Manyi earthquake after decay time from 1 year to 100 years when employing three linear rheologieal models, namely, Maxwellian model, standard linearsolid model, and Burges model. The results show that： （1） During transient phase, from 1 to 5 years after Manyi event, standard linearsolid model and Burges model are nearly the same as the other two ones. While during the later phase, starting from 10 years later, Maxwell element does and so are those with Maxwellian model and Burges one. （2） Similar is their influence on spatial pattern of viscoelastic Coulomb stress changes, though stress shadows and stress-triggering zones enlarge with time. Such tempo- spatial patterns of postseismic displacement field and viscoelastic Coulomb stress changes are consistent with the point that Burges rheological model is general compared with the other two. The uniqueness of rheological model should be figured out by a case-to-case study in volving some kind of recursive determination of rhological model through multiple data sources such as GPS, InSAR, levelling, and those measured at different time-intervals so as to explain kinemics of displacement because of postseismic relaxation.