结构阻尼识别中的目标函数问题
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摘要
本文用震源力学理论和方法研究了徐淮地区从１９７０年以来构造应力场的方向和强度的时空变化过程．结果表明：以唐山地震为分界线，本区的应力场Ｐ轴取向由震前平均６１．８°变为震后平均７７．７°．如果将本区以宿北断裂为界分为南区和北区两个部分，则北区的Ｐ轴取向从６８．１°变到７１．２°，而南区的Ｐ轴取向由６２．５°变到８３．６°，南区的变化明显大于北区．对于水平剪切应力值来说，７６年前后应力值较高且变化剧烈，从７７年至８７年应力值缓慢下降，而从８７年开始应力值迅速上升并伴有起伏．上述应力场的时空分布特征可以解释为什么井筒破裂主要发生在宿北断裂以南地区，并且主要发生在幼年以后．因而我们认为，徐淮地区煤矿井筒破裂与构造应力场的变化有很大关系．
In this paper, the time-space variation of tectonic stress field of Xuzhou-Huaibei area in both direction and tensity since 1970 is studied. The result shows that the average direction of P axis of stress field has turned from 61.8°before the Tangshan earthquake to 77.7°after that and if the area is divided into northern and southern parts bounded by Subei fault, the P axis direction is turned from 68.1°to 71.2°in the northern part, while that in southern part is turned from 62.5°to 83.6°.The variation of P axis direction in southern part is much larger than that in northern part. As to horizontal shear stress, it was high in magnitude and changed enormously around 1976,slowly droped from 1977 to 1987, and has rapidly increased since 1987. In terms of the feature of time-space distribution of the local stress field, it can be well explained that the coal mine-wall damage occured mainly to the south of Subei fault after 1987.Hence we consider that the coal mine-wall damage is highly related to the variation of local stress field.
In this paper, the time-space variation of tectonic stress field of Xuzhou-Huaibei area in both direction and tensity since 1970 is studied. The result shows that the average direction of P axis of stress field has turned from 61.8°before the Tangshan earthquake to 77.7°after that and if the area is divided into northern and southern parts bounded by Subei fault, the P axis direction is turned from 68.1°to 71.2°in the northern part, while that in southern part is turned from 62.5°to 83.6°.The variation of P axis direction in southern part is much larger than that in northern part. As to horizontal shear stress, it was high in magnitude and changed enormously around 1976,slowly droped from 1977 to 1987, and has rapidly increased since 1987. In terms of the feature of time-space distribution of the local stress field, it can be well explained that the coal mine-wall damage occured mainly to the south of Subei fault after 1987.Hence we consider that the coal mine-wall damage is highly related to the variation of local stress field.
引文
1陈培善等．从断裂力学观点研究地震的破裂过程和地震预报．地球物理学报，V．20，N．3．19772陈培善等．唐山地震前后京津唐张地区的应力场．地球物理学报，V．21N．1，19783孙若昧等．阻尼最小二乘法联合测定震源位置和介质速度参数．地震，N4，1986
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