| 长周期形变波及其所反应的短期和临震地震前兆 |
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| 引用本文： | 冯德益,潘琴龙,郑斯华,薛峰,闵祥仪.长周期形变波及其所反应的短期和临震地震前兆[J].地震学报,1984,6(1):41-57. |
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| 作者姓名： | 冯德益 潘琴龙 郑斯华 薛峰 闵祥仪 |
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| 作者单位： | 1. 国家地震局兰州地震研究所
2. 江西省地震办公室
3. 国家地震局分析预报中心 |
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| 摘 要： | 本文应用断裂力学和流变介质中波的传播理论来研究震前长周期形变波的波动源以及这类波传播的一些主要特征,在理论研究结果的基础上,对我国多次较大地震前观测到的短临地震前兆进行了剖析,并从中识别出一些可能与长周期形变波有关的短临地震前兆.首先,从粘滑与破裂这两类主要地震机制出发,提出了粘滑前的预滑与破裂前断裂的预扩展(亚稳态扩展)可能是产生震前长周期波的两类波动源的看法,并着重从理论上讨论了后一类波动源.其次,以地壳流变介质模型为基础,对长周期形变波的传播特性进行了理论研究.选用地壳的广义流变介质模型,求解了所述的两类波动源在这种流变地壳介质中引起的长周期形变波传播的动力学问题,从理论上得出了长周期形变波在地壳内传播的某些一般特征.然后,专门分析了我国多次大地震前实际观测到的短期和临震地震前兆资料,并着重讨论了唐山地震的短临前兆.在这些不同类型的短临地震前兆中,我们得出地下水位、地倾斜及潮位自动记录曲线等的某些振动式及阶跃式短临地震前兆与长周期形变波的理论探讨结果基本相符,因而可以认为它们属于由长周期形变波所反映的地震前兆.在理论研究与实际资料分析的基础上,本文归纳了由长周期形变波所引起的短临地震前兆的一些基本特征,包括传播速度、衰
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LONG-PERIOD DEFORMATIONAL WAVES AND SHORT- TERM AND IMMINENT EARTHQUAKE PRECURSORS |
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| Institution: | 1. Seismological Institute of Lanzhou, State Seismological Bureau;
2. Seismological Office of Jiangxi Province;
3. Analysis and Prediction Centre, State Seismologieal Bureau. |
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| Abstract: | By using the theory of fracture mechanics and the theory of wave propagation in rheo-logical medium the sources and propagation characteristics of long-period deformational waves of the earth before large earthquakes are studied. On the basis of theoretical work, the observational data of short-term and imminent precursors before many strong and moderate earthquakes occurred in China are analyzed, and among them some kinds of precursors which could be related to long-period deformational waves are recognized.Considering brittle fracture and stick-slip as two main types of earthquake mechanism, it is suggested that both pre-slips before stick-slips and crack propagation before rupture may be the sources of long-period deformational waves a large earthquake of which the latter has been emphasized, in our discussion.Taking a complex rheological model of crustal medium, some general characteristics of propagation of long-period deformational waves have been studied and solutions of corresponding dynamic problems for the propagation of long-period waves caused by the two given types of sources were obtained theoreticallyThen, the observational data of short-term and imminent precursors before a series of large earthquakes were analyzed, especially, the precursors before the Tangshan (M=7.8) and Liyang (M =6.0) earthquakes were studied in detail. Among the precursors analyzed, some oscillation-type and step-type changes of precursors can be observed by using automatic recordings of underground water level, tiltmeter and the tidegauge measurements, that might be closely correlated with the long-period deformational waves studied here theoretically.Based on the theoretical and practical results obtained, some general characteristics of short-term and imminent precursors as given rise by the long-period deformational waves have been summarized. They are of the velocity of wave propagation, amplitude attenuation, type of vibration, waveform change, intensity distribution, period range, time of precursory appearance before earthquake and maximum distance of propagation.In conclusion, the methods for observation and analysis of long-period deformational waves and their application to earthquake prediction particularly short-term and imminent prediction and to the study of earthquake source process are briefly discussed. |
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