论文部分内容阅读
根据唐山地区震前11期水准复测资料,对本区的地壳形变的时空变化特征进行了分析.结果表明:唐山地震前1968年—1969年震中区发生了幅度为50毫米、持续时间2年的异常隆起,并在唐山及宝坻附近的唐山断层和蓟运河断层显示出应变积累与无震蠕动叠加的作用.采用了均匀应变积累及弹性位错理论分别计算了唐山、宝坻附近测点由于各处断层蠕动引起的垂直位移理论值,按残差均方根最小的原则确定历年应变积累及蠕动断层参数的最佳值.1969年—1975年唐山地下发生蠕动的断层走向为北东47°、倾角87°、倾向南东的右旋正断层,断层长度为8公里、宽度6公里、断层上界深度为2公里、走滑与倾滑错距分别为104厘米及8厘米,平均应变积累速度为0.9×10~(-7)/年.同时得到断层走向、倾向蠕动速度分别为18.6厘米/年及1.4厘米/年.另外由蓟运河断层结果得到.宝坻附近蠕动断层的规模比唐山小,但蠕动速度比唐山大.本文分析了上述异常隆起及蠕动断层与唐山地震的关系,认为地壳的异常隆起是孕震的早期显示,而无震蠕动可能是浅源地震的又一前兆特征.唐山地震经历了长期应变积累—体积膨胀—蠕动—形变反向(或蠕动速度减慢)—发震的过程.
The temporal and spatial variations of the crustal deformation in this area are analyzed based on the data of eleven pre-earthquake re-measurements in the Tangshan area.The results show that before the Tangshan earthquake, a magnitude of 50 mm and a duration of 2 years occurred in the epicentral region between 1968 and 1969 Anomalous uplift and the accumulation of Tangshan fault and Jiyunhe fault near Tangshan and Baodi show the superposition of strain accumulation and no-creep motions.Using uniform strain accumulation and elastic dislocation theory, The theoretical value of vertical displacement caused by fault creep is the best value of strain accumulation and peristaltic fault parameters according to the principle of the smallest residual root mean square.The movement of Tangshan subsurface during 1969-1975 is 47 ° North East, 87 °, with a right-lateral normal fault southeastern. The fault length is 8 km and its width is 6 km. The fault upper bound is 2 km in depth. The slip and slip slip distances are 104 cm and 8 cm, respectively. The average strain accumulation rate is 0.9 × 10 ~ (-7) / year. At the same time, the direction of faults was obtained and the tendency creep speed was 18.6 cm / year and 1.4 cm / year respectively. In addition, the result of the Jiyunhe fault was that the peristaltic fault Is smaller than Tangshan, but its creep speed is higher than that of Tangshan.The relationship between the above mentioned anomalous uplift and peridotomy and the Tangshan earthquake is analyzed in this paper. It is believed that the anomalous uplift of the crust is an early indication of seismogenic activity, Another precursor feature is that the Tangshan earthquake experienced a long-term strain accumulation-volume expansion-creep-deformation reversal (or slowing of the creep speed) -sensing.