细胞自动机的多重分形特征和动力学根源

用大量弹簧滑块组成的模型可以模拟地震的复杂性,本文以细胞自动机(CA)为数学工具,结合地震学和岩石力学的结果,考虑了能量的输入和损耗,进行了地震事件的数字模拟。对模型中输出的"地震"事件进行了时间和空间的多分形分析,并对自组织临界(SOC)状态进行了讨论,进而得到事件至少在时间域里的分布呈现出层次结构,符合自相似特征。本文的CA模型属于确定性的混沌系统,而对于处在SOC状态下的大量事件的频度和大小的统计与G-R指数律很好地吻合。结果表明,虽然自组织(SO)可能是更准确的地震表征,但SOC仍然是研究地震现象的很好的模式。     

Evolving Towards a Critical Point: A Review of Accelerating Seismic Moment/Energy Release Prior to Large and Great Earthquakes

—There is growing evidence that some proportion of large and great earthquakes are preceded by a period of accelerating seismic activity of moderate-sized earthquakes. These moderate earthquakes occur during the years to decades prior to the occurrence of the large or great event and over a region larger than its rupture zone. The size of the region in which these moderate earthquakes occur scales with the size of the ensuing mainshock, at least in continental regions. A number of numerical simulation studies of faults and fault systems also exhibit similar behavior. The combined observational and simulation evidence suggests that the period of increased moment release in moderate earthquakes signals the establishment of long wavelength correlations in the regional stress field. The central hypothesis in the critical point model for regional seismicity is that it is only during these time periods that a region of the earth’s crust is truly in or near a "self-organized critical" (SOC) state, such that small earthquakes are capable of cascading into much larger events. The occurrence of a large or great earthquake appears to dissipate a sufficient proportion of the accumulated regional strain to destroy these long wavelength stress correlations and bring the region out of a SOC state. Continued tectonic strain accumulation and stress transfer during smaller earthquakes eventually re-establishes the long wavelength stress correlations that allow for the occurrence of larger events. These increases in activity occur over longer periods and larger regions than quiescence, which is usually observed within the rupture zone of a coming large event. The two phenomena appear to have different physical bases and are not incompatible with one another.     

Assessment of seismic hazard of the Japanese islands based on fractal analysis of GPS time series

Based on the fractal analysis of the time series of the Earth’s surface vertical displacements in the region of the Japanese Archipelago, the maps of the estimates of seismic activity in the region over 2015 are constructed. The analysis of the maps revealed several segments of the territory which are prone to the emergence of significant earthquakes. The characteristic peculiarity is noted in the change of the behavior of the geophysical dynamic system—the Earth’s crust—before the occurrence of seismic events: the mechanism of transition to the critical state demonstrates the energy preservation of the low frequencies with the simultaneous energy decay of the middle and high frequencies, which differs from the behavior of the other dynamical systems.     

分形理论在地震学中的应用研究

分形理论是现代非线性科学中一个非常重要的研究领域,它的思想和方法已经渗透到自然科学的各个领域.在过去的二三十年间,分形科学已经有了很大的发展.它在数学、物理学、材料学、地质勘探、股票预测以及计算机和信息科学等各个自然科学领域,都得到了广泛的应用,同时也给地震学的发展注入了巨大的活力.本文首先简要回顾了分形理论的发展历程,然后就其在地震学各领域的应用进行了概括阐述,最后给出了分形理论在地震学中应用前景的展望.     

分形与混沌理论在地震学中的应用与探讨

分形与混沌理论的研究与发展，揭示了自然界中一大类无规几何形体物理过程的内在规律性及其动力演化过程的内在随机性。这给我们探索自然界中分形客体的几何形态及其与内部物理本质的关系提供了一条暂新的途径。特别是这一理论给我们探讨地震问题，例如：探讨地震活动时空分布的确定性图像、地震演化过程的动力学行为、临界特征以及未来大地震的发生等问题，带来了某些希望。本文较详细地综述了近年来分形与混沌理论在地震学中的应用研究。全文共分５部分。第１部分是孕震过程的一般概述。第２部分描述单分形与多分形在地震学中的某些应用．文中第３部分介绍了混沌动力学中的某些研究在测震学与模型中的应用。第４部分综述了自组织临界现象和闪变噪声的研究．最后，第５部分是分形理论与混沌动力学在地球科学中的应用前景与展望．     

Rethinking Earthquake Prediction

—We re-examine and summarize what is now possible in predicting earthquakes, what might be accomplished (and hence might be possible in the next few decades) and what types of predictions appear to be inherently impossible based on our understanding of earthquakes as complex phenomena. We take predictions to involve a variety of time scales from seconds to a few decades. Earthquake warnings and their possible societal uses differ for those time scales. Earthquake prediction should not be equated solely with short-term prediction—those with time scales of hours to weeks—nor should it be assumed that only short-term warnings either are or might be useful to society. A variety of "consumers" or stakeholders are likely to take different mitigation measures in response to each type of prediction. A series of recent articles in scientific literature and the media claim that earthquakes cannot be predicted and that exceedingly high accuracy is needed for predictions to be of societal value. We dispute a number of their key assumptions and conclusions, including their claim that earthquakes represent a self-organized critical (SOC) phenomenon, implying a system maintained on the edge of chaotic behavior at all times. We think this is correct but only in an uninteresting way, that is on global or continental scales. The stresses in the regions surrounding the rupture zones of individual large earthquakes are reduced below a SOC state at the times of those events and remain so for long periods. As stresses are slowly re-established by tectonic loading, a region approaches a SOC state during the last part of the cycle of large earthquakes. The presence of that state can be regarded as a long-term precursor rather than as an impediment to prediction. We examine other natural processes such as volcanic eruptions, severe storms and climate change that, like earthquakes, are also examples of complex processes, each with its own predictable, possibly predictable and inherently unpredictable elements. That a natural system is complex does not mean that predictions are not possible for some spatial, temporal and size regimes. Long-term, and perhaps intermediate-term, predictions for large earthquakes appear to be possible for very active fault segments. Predicting large events more than one cycle into the future appears to be inherently difficult, if not impossible since much of the nonlinearity in the earthquake process occurs at or near the time of large events. Progress in earthquake science and prediction over the next few decades will require increased monitoring in several active areas.     

基于SOC的活断层系与地震活动性关系的探讨

通过对中国大陆及青藏高原、新疆、华北和东北各构造区的地震活动性的分析,论证了区域地震活动是一种自组织临界现象.利用分形理论中的粗视化网格法,研究了中国大陆以及各构造区断层系的分形特点和分形结构的跨尺度特征.开展了组构具有分形特点的沙堆模型实验.结合断裂力学理论,认为地震的自组织临界现象源于分形几何断层系的自组织临界性动力学过程,地震分维数和断层系分维数之间存在着一种正相关关系,明确了断层系分形和地震活动性分形之间的因果关系.在此基础上,提出了系统组构的分形是系统输出能量的分形的根源的观点,并进一步利用已有的观测资料进行了分析.最后,基于这个观点和区域断层分布可以通过常规的航卫片分析、地面调查和地质勘探等手段确定的事实,提出了利用断层的分维数与地震的分维数的相关关系,对区域地震的概率分布特征进行估计的观点,可为地震的预测预报提供参考.     

Self-organised criticality and fluid-rock interactions in the brittle field

The concept of self-organised criticality (SOC) has recently been suggested as a paradigm for the long-term behaviour of earthquakes, even though many of the currently-proposed models require some tuning of the state variables or local conservation rules to produce the universally-observed Gutenberg-Richter frequency-magnitude distribution witha b value near 1. For example, a systematic negative correlation is predicted between modelb values and the degree of conservation of local force after the slip of a single element in an elastic spring/block/frictional slider model. A similar relation is described here for a cellular automaton model with constitutive laws based on fracture mechanics. Such systems, although critical phenomena in the sense of producing order on all scales, are clearly not universal, and may not in general even be true examples of SOC. Nevertheless they adequately reproduce both the observed power-law (fractal or multifractal) scaling and its reported short-term fluctuation.We also present experimental and field evidence for similar systematic variations inb value with the degree of force conservation (expressed in terms of a normalised crack extension force) during subcritical crack growth involving the physical and chemical influence of pore fluids during a single cycle of failure both in tension and compression. We find that the level of conservation is strongly influenced by fluid-rock interaction under stress, allowing energy partition into processes such as: physico-chemical stress corrosion reactions; the dissolution and precipitation of mineral species on crack surfaces; and the purely mechnical phenomenon of dilatant hardening. All of these are known to occur in the Earth on a local scale, but few have been explicitly included in automaton models of seismicity. The implication is that over long time periods pore fluids may exert a strong physical and chemical influence on the universal state of SOC which the system evolves in a complex interplay of local feedback mechanisms keeping the system near criticality, perhaps most strikingly due to the valve action of faults. In the short term, crustal fluids might nevertheless be responsible for systematic local fluctuations about this average state.     

青藏高原东北部地区的区域地壳现今构造形变系统--陆壳浅源构造地震成因的新认识

依据青藏高原东北部地区的大震 (MS≥ 7)、大震形变带、活动断裂和活动构造体系的资料 ,以地球系统科学、地质力学、地震地质学、现代地震学的理论和方法为主线 ,对该区内大震的“共性”进行了探讨 ,提出了具有三维空间动态的区域地壳现今构造形变系统的新概念 ,并对该区内地震的形成机制、分布规律等科学问题提出了新的见解 .     

微震研究与应用进展

随着地震观测台站密度的不断增加以及地震检测技术的快速发展,微震研究受到了地震学界的广泛关注.与发震周期较长的大地震相比,微震复发周期短、发生频次高,可以获得更高分辨率的地壳内部介质物性和应力状态等变化信息.微震在许多领域具有广泛的应用,如研究断层几何形态、前震与地震成核的关系、余震时空演化特征及余震触发机理、远程动态触...     

Preface to the special issue on complicated features on seismic sources and deep structures

Earthquake is a kind of natural phenomenon in the Earth.Earthquake seismology has been developed quickly since modern digital seismometers were applied to observations.From seismic records,seismologists study source properties of the earthquakes and detect multi-scale structural variations in the crust,mantle,and core.     

Theoretical Error Analysis of the Accuracy of Focal Depth Determination of Near Earthquakes

Focal depth is one of the most difficult seismic parameters to determine accurately in seismology. The focal depths estimated by various methods are uncertain to a considerable degree,which affects the understanding of the source process. The influence of various factors on focal depth is non-linear. The influence of epicentral distance,arrival time residual and velocity model (crust model) on focal depth is analyzed based on travel time formula of near earthquakes in this paper. When wave propagation velocity is constant, the error of focal depth increases with the increase of epicentral distance or the distance to station and the travel time residual. When the travel time residual is constant,the error of focal depth increases with the increase of the epicentral distance and the velocity of seismic wave. The study also shows that the location error perhaps becomes bigger for shallower earthquakes when the velocity is known and the travel time residual is constant. The horizontal error caused by location accuracy increases with the increase of the epicentral distance,the travel time residual and the velocity of seismic waves,thus the error of focal depth will increase with these factors. On the other hand,the errors of focal depth will lead to change of the origin time,therefore resultant outcomes will all change.     

The crustal fluid evolution and the causes of earthquakes(Ⅲ)

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A new model on the cause of Tangshan earthquakes in 1976

Introduction The Tangshan earthquake sequence in 1976 is one of most important events in North China. Although nearly thirty years passed and there are some researches on its cause, it is far from the end. Here we introduce two explanations for the cause of Tangshan earthquakes and point out their defects. One is that there is a diamond block in NEE direction in Tangshan region, which is shaped by cutting action of NingheChangli fault, FengtaiYejituo fault, Luanxian fault and Jiyunhe fau…     

应力减小引起的岩石破坏与地震

最近完成的岩石力学三轴实验表明,岩石的破坏既能由最大主应力的增加引起,又能由中等主应力的变化(增加或减小)或最小主应力的减小引起,因此联系到地震的发生也是如此。地震前必须有一个应力和能量的增加过程,但地震不一定发生在应力和能量的增加过程中,地震也可以发生在应力和能量的减小过程中。文章还讨论了能够引起地壳中应力减小的作用,並从地震活动性方面探索应力减小引起地震的可能性。     

Damage Localization,Sensitivity of Energy Release and the Catastrophe Transition

-- Large earthquakes can be viewed as catastrophic ruptures in the earth's crust. There are two common features prior to the catastrophe transition in heterogeneous media. One is damage localization and the other is critical sensitivity; both of which are related to a cascade of damage coalescence. In this paper, in an attempt to reveal the physics underlying the catastrophe transition, analytic analysis based on mean-field approximation of a heterogeneous medium as well as numerical simulations using a network model are presented. Both the emergence of damage localization and the sensitivity of energy release are examined to explore the inherent statistical precursors prior to the eventual catastrophic rupture. Emergence of damage localization, as predicted by the mean-field analysis, is consistent with observations of the evolution of damage patterns. It is confirmed that precursors can be extracted from the time-series of energy release according to its sensitivity to increasing crustal stress. As a major result, present research indicates that the catastrophe transition and the critical point hypothesis (CPH) of earthquakes are interrelated. The results suggest there may be two cross-checking precursors of large earthquakes: damage localization and critical sensitivity.     

Two species of microcracks

We identify two interrelated but independent species of microcracks with differentorigins and different distributions. One species is the classic high-stress microcracksidentified in laboratory stress-cells associated with acoustic emissions as microcracks openwith increasing stress. The other species is the low-stress distributions of closely-spacedstress-aligned fluid-saturated microcracks that observations of shear-wave splitting （SWS）demonstrate pervade almost all in situ rocks in the upper crust, the lower crust, and theuppermost 400 km of the mantle. On some occasions these two sets of microcracks may beinterrelated and similar （hence ＇species＇） but they typically have fundamentally-differentproperties, different distributions, and different implications. The importance for hydrocarbonexploration and recovery is that SWS in hydrocarbon reservoirs monitors crack alignmentsand preferred directions of fluid-flow. The importance for earthquake seismology is that SWSabove small earthquakes monitors the effects of increasing stress on the pervasive low-stressmicrocrack distributions so that stress-accumulation before, possibly distant, earthquakes canbe recognised and impendin~ earthquakes stress-forecast.     

Seismic zoning of the southern slope of Greater Caucasus from the fractal parameters of the earthquakes, stress state, and GPS velocities

By complex analysis of GPS velocities, seismicity, fractal dimensions of the spatial distribution of seismic epicenters, focal mechanisms of the earthquakes, and stress state of the Earth’s crust, four seismic zones (Balaken-Zagatala, Sheki-Gabala, Shamakhy-Ismailly, and Absheron) are revealed within the southern slope of the Greater Caucasus. The suggested method can be used as a criterion in seismotectonic zoning; it could also be useful in the assessment of seismic hazards in the collision zones.     

张北6.2级地震发生在小震条带上

分析晋、冀、蒙交界地区的地震分布格局,发现张北地震前存在小地震条带。条带由２０余年持续发生的小震组成,与华北地壳应力场最大剪切应力方向相同,是燕山－渤海地震构造带的西延段落。６．２级强震发生在条的东端。文中讨论了张北地震地点预测失误的原因,提出采用地震学和地震地质学交叉,融合的思路,分析观今小地震活动图象、震源机制资料,从构造学,运动学,动力学角度,研究地壳深部地震构造的方法。     

应力减小引起地震

最近完成的岩石力学实验表明,在三轴应力状态下最大主应力的增加、中等主应力的变化(增加或减小)和最小主应力的减小都能导致岩石的破坏。由此启示,地震的发生既可能由地壳中的最大主应力的增加引起,又可能由中等主应力或最小主应力的减小引起。讨论了地壳中可能引起应力减小的作用,并从地震活动的规律性探讨了应力减小引起地震的可能性。指出在地震研究的各个领域中,不仅应考虑应力增加和能量积累过程中发生的地震,还应考虑在应力减小和能量减小过程中引起的地震。