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1.
—A cellular automaton is used to study the relation between the structure of a regional fault network and the temporal and spatial patterns of regional seismicity. Automata in which the cell sizes form discrete fractal hierarchies are compared with those having a uniform cell size. Conservative models in which all the stress is transferred at each step of a cascade are compared with nonconservative ("lossy") models in which a specified fraction of the stress energy is lost from each step. Particular attention is given to the behavior of the system as it is driven toward the critical state by uniform external loading. All automata exhibit a scaling region at times close to the critical state in which the events become larger and energy release increases as a power-law of the time to the critical state. For the hierarchical fractal automata, this power-law behavior is often modulated by fluctuations that are periodic in the logarithm of the time to criticality. These fluctuations are enhanced in the nonconservative models, but are not robust. The degree to which they develop appears to depend on the particular distribution of stresses in the larger cells which varies from cycle to cycle. Once the critical state is reached, seismicity in the uniform conservative automaton remains random in time, space, and magnitude. Large events do not significantly perturb the stress distribution in the system. However, large events in the nonconservative uniform automaton and in the fractal systems produce large stress perturbations that move the system out of the critical state. The result is a seismic cycle in which a large event is followed by a shadow period of quiescence and then a new approach back toward the critical state. This seismic cycle does not depend on the fractal structure, but is a direct consequence of large-scale heterogeneity of these systems in which the size of the largest cell (or the size of the largest nonconservative event) is a significant fraction of the size of the network. In essence, seismic cycles in these models are boundary effects. The largest events tend to cluster in time and the rate of small events remains relatively constant throughout a cycle in agreement with observed seismicity. 相似文献
2.
地震孕育发生的场源关系初步研究 总被引：19，自引：2，他引：19
场和源在地震学和地震预报研究中已成为两个最重要分友。本文应用计算机模型研究地震活动中的场源关系。模型以非线性元件构成的网络系统来模拟含有多个地震活动带的地震构造块体的地震活动。在模型边界上加以定常应变速率，则在模型中可产生高低起伏的轮回式地震活动，并形成应力场强度和应变能高低起伏的准周期变化，各地地震活动轮回有其主体活动地区，不同的轮回之间常显示出地震主体活动区的空间转移。同时，若将模型中达到一定 相似文献
3.
Geng Lumin Zhang Guomin Shi YaolinCenter for Analysis Prediction Beijing China Graduate School Academia Sinica Beijing China 《中国地震研究》1995,(3)
The "field" and "source" are two important branches in seismology and earthquake research.In this paper,we use a computer model to study the relation between the field and the source in earthquake activity.In our modeling,a network of nonlinear elements is used to simulate seismic activity of seismic zones in a seismotectonic block.Constant strain rate is enforced on the boundary of the model,cyclic seismic activity,quasi-periodic variation of stress field intensity,and strain energy are observed with high and low fluctuations.There is a main seismicity area in seismic cycles,and the main seismicity area shows the spatial migration during different seismic cycles.If the precursory area is related to high element stress,it is found that the development of precursors in our model is quite complicated.No certain relation between the precursors and earthquakes has been discovered.Anomalies show different characteristics in the seismic quiet period and active period.All of the seismic zones in the system hav 相似文献
4.
基于有限元方法,参照细胞自动机模型,建立了一个地震活动演化的动力学模型.在这个模型中,根据边界条件和单元介质参数的分布,利用有限元方法确定各单元的应力增长速率.每个单元设定初始应力和摩擦因数,利用破裂准则可得到单元破裂所需时间.当单元破裂后,将破裂单元作为内部边界,利用有限元方法计算由于这个单元破裂对系统其他单元造成的应力调整.根据上述规则,建立一个由30×40个节点组成,在定常位移速率边界条件作用下的地震活动模型,探讨了区域应力场的动态演化、地震活动图像和各种参数变化对地震活动的影响.结果表明该模型在研究地震活动方面有一定优势并具有实用价值. 相似文献
5.
Mariusz BiałEcki 《Acta Geophysica》2015,63(5):1205-1215
This paper outlines an idea for an explanation of a mechanism underlying the shape of the universal curve of the Earthquake Recurrence Time Distributions. The proposed simple stochastic cellular automaton model is reproducing the gamma distribution fit with the proper value of parameter γ characterizing the Earth’s seismicity and also imitates a deviation from the fit at short interevent times, as observed in real data.Thus the model suggests an explanation of the universal pattern of rescaled Earthquake Recurrence Time Distributions in terms of combinatorial rules for accumulation and abrupt release of seismic energy. 相似文献
6.
摩擦消能支撑钢框架结构的弹塑性地震反应时程分析 总被引：1，自引：0，他引：1
本文分析了摩擦消能支撑及框架主体结构弹塑性本构关系，并给出了动力时程分析的计算方法。同时，对六层钢框架模型做了各种工况下的地震反应时程分析。结果表明，摩擦消能支撑钢框架（FEDBF）比抗弯钢框架（MRF）的地震作用明显降低，尤其在强震作用下效果更加明显。 相似文献
7.
Subduction zone seismicity and the thermo-mechanical evolution of downgoing lithosphere 总被引：1，自引：0，他引：1
In this paper we discuss characteristic features of subduction zone seismicity at depths between about 100 km and 700 km, with emphasis on the role of temperature and rheology in controlling the deformation of, and the seismic energy release in downgoing lithosphere. This is done in two steps. After a brief review of earlier developments, we first show that the depth distribution of hypocentres at depths between 100 km and 700 km in subducted lithosphere can be explained by a model in which seismic activity is confined to those parts of the slab which have temperatures below a depth-dependent critical valueT
cr.Second, the variation of seismic energy release (frequency of events, magnitude) with depth is addressed by inferring a rheological evolution from the slab's thermal evolution and by combining this with models for the system of forces acting on the subducting lithosphere. It is found that considerable stress concentration occurs in a reheating slab in the depth range of 400 to 650–700 km: the slab weakens, but the stress level strongly increases. On the basis of this stress concentration a model is formulated for earthquake generation within subducting slabs. The model predicts a maximum depth of seismic activity in the depth range of 635 to 760 km and, for deep earthquake zones, a relative maximum in seismic energy release near the maximum depth of earthquakes. From our modelling it follows that, whereas such a maximum is indeed likely to develop in deep earthquake zones, zones with a maximum depth around 300 km (such as the Aleutians) are expected to exhibit a smooth decay in seismic energy release with depth. This is in excellent agreement with observational data. In conclusion, the incoroporation of both depth-dependent forces and depth-dependent rheology provides new insight into the generation of intermediate and deep earthquakes and into the variation of seismic activity with depth.Our results imply that no barrier to slab penetration at a depth of 650–700 km is required to explain the maximum depth of seismic activity and the pattern of seismic energy release in deep earthquake zones. 相似文献
8.
The rapid release of strain energy is an important phenomenon leading to seismic events or rock failures during the excavation of deep rock.Through theoretical analysis of strain energy adjustment during blasting and mechanical excavation,and the interpretation of measured seismicity in the Jin-Ping Ⅱ Hydropower Station in China,this paper describes the characteristics of energy partition and induced seismicity corresponding to different energy release rates.The theoretical analysis indicates that part of the strain energy will be drastically released accompanied by violent crushing and fragmentation of rock under blast load,and this process will result in seismic events in addition to blasting vibration.The intensity of the seismicity induced by transient strain energy release highly depends on the unloading rate of in-situ stress.For mechanical excavation,the strain energy,which is mainly dissipated in the deformation of surrounding rock,releases smoothly,and almost no seismic events are produced in this gradual process.Field test reveals that the seismic energy transformed from the rock strain energy under high stress condition is roughly equal to that coming from explosive energy,and the two kinds of vibrations superimpose together to form the total blasting excavation-induced seismicity.In addition,the most intense seismicity is induced by the cut blasting delay; this delay contributes 50% of the total seismic energy released in a blast event.For mechanical excavation,the seismic energy of induced vibration(mainly the low intensity acoustic emission events or mechanical loading impacts),which accounts only for 1.5‰ of that caused by in-situ stress transient releasing,can be ignored in assessing the dynamic response of surrounding rock. 相似文献
9.
地震波是一种随机的、不规则作用的动荷载脉冲,可分为振动型和冲击型。不同类型的地震波会对砂土液化和变形等产生重要影响,而传统的砂土震陷计算方法往往忽视这种因素,只考虑最大加速度幅值。通过编写UMAT子程序,在非线性有限元软件ABAQUS中开发亚塑性砂土边界面模型,对不同地震波类型下不同相对密度的砂土进行动单剪试验模拟,得到一系列砂土剪应变及竖向应变的时程曲线,并与室内试验结果进行对比分析。研究表明:在同一工况下,同类型的地震波引起的砂土竖向应变相近,不同类型引起的竖向应变差异明显;振动型地震波比冲击型引起的竖向应变更大。 相似文献
10.
A special experimental technique enabled us to study in detail seismic events on a fault model in a uniaxial stress field. The recording system used made it possible to investigate the radiation pattern for all the events observed including the precise determination of the dislocation origin.The aim of the present paper is (1) to find the relation between shear and tensile displacements, (2) to check a possible influence of the process of tensile crack generation on the seismic energy release and (3) to compare the seismic regime of a single fault before and after the tensile crack generation, respectively.Results prove the dominating importance of shear mechanism for the seismic energy release. The tensile displacement can be seismoactive only under special contact conditions on the fault plane.The existence of tensile cracks at the fault tips changed the pattern of seismic energy radiation. This feature is probably caused by subsequent changes in contact conditions on the fault plane and in the stress field around the fault.A comparison of some results of the present model experiments with the already published results of geological and seismological measurements and investigations shows the analogous character in laboratory and in nature of the process of tectonic earthquake preparation, the displacement course on the fault during the earthquake and the manner of seismic energy release on faults. 相似文献
11.
The stress release model and results from modelling features of some seismic regions in China 总被引：1，自引：0，他引：1
ＴｈｅｓｔｒｅｓｒｅｌｅａｓｅｍｏｄｅｌａｎｄｒｅｓｕｌｔｓｆｒｏｍｍｏｄｅｌｉｎｇｆｅａｔｕｒｅｓｏｆｓｏｍｅｓｅｉｓｍｉｃｒｅｇｉｏｎｓｉｎＣｈｉｎａＪＩＡＮＣＡＮＧＺＨＵＡＮＧ（庄建仓）ＬＩＭＡ（马丽）ＣｅｎｔｒｅｆｏｒＡｎａｌｙｓｉｓａｎ... 相似文献
12.
Based on the studies of earthquake activity, tectonic movement, crustal shortening rate, fault activity, local stress field and historical characteristics of strong earthquake activities in Xinjiang, we divide the south part of Xinjiang into 4 seismotectonic zones, namely, the eastern segment of south Tianshan seismic belt, the Kalpin block, the Kashi-Wuqia junction zone, and the west Kunlun Mountains seismic belt. Using earthquake catalogues from Xinjiang since 1900, and on the basis of integrity analysis of earthquake records in different magnitude ranges, the seismicity state of different seismotectonic zones is analyzed quantificationally by calculating the mean value of annual strain energy release, annual rate of earthquakes with different lower limits of magnitude, b-value, and the parameter m of accelerating strain release model. The characteristic indexes of seismicity state for each of the seismic tectonic zones are then determined, which provide a quantitative basis for earthquake tendency analysis and judgment. 相似文献
13.
—Based on the original stress release model of seismicity proposed by Vere-Jones (1978), this paper has developed a stochastic coupled stress release model of time-dependent seismicity, which considers the earthquake interaction and stress transfer between different seismic subregions. As an example, the model is applied to a statistical analysis of the historical earthquake catalog with magnitude M ≥ 6.0 during the period from 1480 to 1996 in North China. According to the Akaike information criterion (AIC), the results show that the coupled stress release model is better than the original model, which demonstrates the existence of long-range correlations between different seismic subregions. We also apply both the stochastic (original and developed coupled) models to analyze the synthetic catalog produced by a cellular automata model, which is based on mechanics of a slide-spring-damper system to model the fault network. The stress release model provides a good fit to the synthetic regional stress, and the coupled stress release model provides an improvement in fit to the synthetic catalog over the original model. 相似文献
14.
在断层面上引入速率-状态相依摩擦本构关系、考虑铲形逆冲断层几何结构特征、断层下盘和上盘中下地壳及上地幔为黏弹性介质、上盘上地壳为弹塑性介质，本文用二维有限元动力学模型模拟了龙门山断层上大震准周期复发行为、分析了断层上地震孕育位置、地震周期不同阶段的应力/应变场演化特征.不同于近垂直走滑断层上的地震周期行为，大陆铲形逆冲断层上的构造应力的积累和释放过程更复杂、有其独特性.我们得到如下认识：（1）铲形逆冲断层上的地震复发是准周期行为.（2）龙门山断层最大库仑应力位于断层17~20 km深处，应力长期积累和同震释放都在此深度最大，说明地震会在此处孕育、发动.（3）在断层破裂的深部和浅部，同震滑动大小和构造应力释放大小并非同步，而是差异悬殊.（4）地震仅部分释放区域积累的应变能，断层上盘上地壳顶部和底部的褶皱、破裂等永久变形形式也是释放应变能的重要形式.（5）应变能密度增量的演化图像分为：震间、同震、震后期，清晰反应了龙门山断层附近的地震动力学过程.（6）地震发生除释放能量外，同时也对近断层的中地壳和断层底部有很大的应变能加载；这些加载，在震后期可能通过震后滑移、余震或中下地壳乃至上地幔的驰豫形变用几十年时间释放.以上对大陆内铲形逆冲断层上变形特征的了解，有助于我们在其地震周期行为中评估地震危险性. 相似文献
15.
Ito equations are derived for simple stochastic cellular automaton with parameters describing efficiencies for avalanche triggering
and cell occupation. Analytical results are compared with the numerical one obtained from the histogram method. Good agreement
for various parameters supports the wide applicability of the Ito equation as a macroscopic model of some cellular automata
and complex natural phenomena which manifest random energy release. Also, the paper is an example of effectiveness of histogram
procedure as an adequate method of nonlinear modeling of time series. 相似文献
16.
“双向应变结构”是孕育和发生地震可能的供能、储能与放能的一种机制。它既能缓慢地储存弹性势能与重力势能而孕育地震,又能突然快速地释放弹性势能与重力势能而发生地震。由于地震发生时孕震体是(原应变的)应变逆转的自破裂过程,因此当初始破裂发生后,在破裂的前沿区,地震剪切应力在原有应力集中的基础上,还会再次产生一个突然快速增强(使破裂加速)到快速减弱(使破裂减速到停止)的过程,即产生“应变逆转破裂效应”。这样,不仅会大大增加地震破裂前沿区的剪切应力,而且还会大大减小破裂中的阻力,可能使地震发生中的断层强度佯谬得到解释。“双向应变结构”破裂发生地震的具体物理机制,印证了震源体断层运动的复杂性：既产生了剪切错动的破裂运动,又产生了单向的拉张与单向的压缩运动,同时还产生了整体的膨胀与整体的压缩运动。 相似文献
17.
借用细胞自动机的计算处理方法，对地震孕育过程中整个系统能量输入，积累，释放，传播等进行了数字模拟，并研究了复杂地震系统的整体特征，结果表明，整体调整系统，地震时能量的损耗系数，外部构造应力场的驱动力大小会影响到地震系统中能量积累和释放的状况，影响到Ｇ－Ｒ关系中ｂ值的大小。 相似文献
18.
抗震性能是建筑设计中的一项重要指标,需要对地震作用下的建筑结构动力弹塑性损伤情况进行分析。提出一种中强地震下建筑结构动力弹塑性损伤模型研究方法。从有效应力与Cauchy应力张量\,建筑材料损伤演化方程等方面对弹塑性损伤模型基本原理进行分析,以此为理论基础,分析建筑材料应变率与建筑结构损伤能释放率的相关关系,通过Bonora损伤模型获取失效建筑材料损伤指数,并计算整体建筑结构构件损伤指数,以建筑材料损伤指数和建筑结构构件损伤指数为依据,完成中强地震下的建筑结构动力弹塑性损伤模型构建。利用实例进行分析,地震加速度值为0.3g的情况下,该模型的建筑结构相对位移时程曲线与实际位移曲线拟合度较高,且具有较好的建筑结构动力弹塑性损伤模拟精度,表明该模型具有一定的可行性。 相似文献
19.
本文描述了一个解时空反演问题的方法.通过把华北地区看成是由24条主要断裂带组成的地质构造骨架,在15公里深处按照平面应变的理想塑性体处理,用有限单元方法计算了本地区在均匀边界外力作用下发生地震危险的地带.然后用逐次降低断层内摩擦系数的办法,模拟近十二年来历次大地震,计算释放应力后应力场的变化、断层的错动.将计算结果和实测资料进行对比,对各个力学参数和构造骨架进行了多次修改,使它们尽量接近.结果说明本方法能够基本上重复近十二年来的地震迁移规律,并可望对未来的地震危险区提出参考意见.结果还说明地震以后在沿断层错动方向的左前方有一狭窄扇形地带安全度增加,而其余较大地区由于断层处的应力释放使剪破裂的危险度有些增加. 相似文献