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海城7.3级地震发生前后,震区及其周围的地表都显示了明显的变动。震前几十年内,已存在大面积垂直形变,而震中正处于两条地形变高梯度带的交汇处。在震前18个月内,距离震中约200公里的金县台短水准测量记录到了地形变从平稳—开始倾斜—反向—加速—缓慢转向这样一组资料,为这次地震的中、短期预报提供了依据。震后的测量资料给出了这次地震引起的地形变的幅值和范围。由地形变资料推知的地震时地壳的应力状态与从其他观测资料所推知的相当一致。 在这次海城地震预报的实践中,地形变观测采用了点、线、面相结合的方式,并与其他观测紧密配合,是预报大地震的一次较为成功的尝试。
Haicheng 7.3 earthquake occurred before and after the earthquake area and the surrounding surface all showed significant changes. Within a few decades before the earthquake, there has been a large area of vertical deformation, and the epicenter is at the intersection of two geomorphic gradient zones. During the 18 months before the earthquake, a short leveling survey of Jinxiantai, about 200 km from the epicenter, recorded a set of data that the terrain changed from a smooth-start-dip-reverse-accelerate- Forecast provided the basis. The measured data after the earthquake give the magnitude and range of the terrain deformation caused by this earthquake. The earth’s crustal stress state deduced from the geomorphic data is in good agreement with that from other observational data. In the practice of Haicheng earthquake prediction, the combination of point, line and surface was used for the observation of the terrain and closely matched with other observations. This is a relatively successful attempt to forecast a large earthquake.