福建莆田2013年8月系列地震的疲劳损伤分析

Analysis of Fatigue Damage Caused by A Series of Earthquakes at Putian， Fujian on August 2013

摘要:

以大地承力结构疲劳损伤的视角，基于材料在循环载荷作用过程的疲劳损伤断裂理论，通过疲劳损伤能量的动态信号计算，跟踪计算承力岩层的疲劳损伤能量。2013年8月福建莆田地区所发生的一系列地震，由福建莆田监测站点所获取的地震动信号进行疲劳损伤能量的计算，对承力岩层疲劳损伤能量变化过程进行了跟踪计算和分析；分析结果表明所计算得出的对应承力岩层疲劳损伤能量有如下规律：①所对应的承力岩层在24小时内，疲劳损伤能量随着时间不断发生着变化。②疲劳损伤能量这期间在M2.2以上地震发生前的数天，都呈现出明显的周期性过程，这种周期性表现为一个昼夜（24小时）为疲劳损伤能量的一个变化周期。③对应在M2.2以上的地震发生之前，疲劳损伤能量的最明显上升过程的变化，都大约发生在北京时间21时至6时时间段。④所发生的地震震级越高， 数天前的北京时间21至6时时间内的疲劳损伤能量则对应上升越明显。

Abstract:

Earthquakes are among the most serious natural disasters. The causes of earthquake are very complex，with trigger factors covering many fields of science.Scientists have been attempting to develop approaches for earthquake prediction for decades，with the aims being to define processes involved in earthquakes and to minimize the losses caused by earthquake disasters.Therefore，earthquake prediction has become an active area of research.Thus far，accurate and reliable earthquake prediction is still not possible，worldwide.The fundamental reason is that we have not fully mastered the mechanism，development，and occurrence processes.Fracture of materials acted on by cycling load is called fatigue.The damage process of materials under dynamic loading is known as fatigue process.The damage process of fatigue consists of initiation of cracks and rapid expansion of the cracks.The strata bear a cycling load due to the rotation of the earth and other seasonal factors.The crack of strata often appears due to damage process of fatigue under a variety of internal and external periodic dynamic loads.The damage process also consists of initiation cracks，confluence of cracks and expansion of cracks.This paper follows the theory of fatigue damage and the calculation method of dynamic signal fatigue damage energy.Fatigue failures are one of the most common failure models when the materials are burdened by cyclic loading.Furthermore，it is well known that nearly 80% of destruction of materials is due to fatigue.A mathematic calculation model of damage energy is conducted in this paper based on system analysis theory.With the model，the damage energy during the fatigue process can be calculated rapidly using a signal.The processes of fatigue failure are evaluated by this quantitative research.The results obtained in this paper will improve our understanding of seismic fatigue.We analyzed the seismic dynamic signals recorded at Putian seismic station in Fujian on August，2013 using theory of fatigue damage.A series of earthquakes occurred in August 2013 in the Putian area，with the Putian monitoring station being about 30 km from the epicenter. Signals corresponding to a series of earthquakes were acquired by the Putian station on a time interval of one hundredth of a second.The bearing capacity of rock fatigue damage was calculated，and shows that the calculated bearing rock fatigue damage energy has the following rules：（1） the fatigue damage energy of a rock formation changes with time.（2） Fatigue damage energy is circular before the earthquake，and the cycle for fatigue damage energy is one day （24 hours）.（3） the most obvious changes of fatigue damage energy occurred between 21:00 and 06:00 and between 12:00 and 15:00 Beijing time. （4） Earthquake magnitude was higher between 12:00 and 15:00，while fatigue damage energy was also higher before the earthquake.