运用细胞自动机模型模拟强震前地震活动时间演化过程

强震发生前震源及其周围地区可能会出现前震活动, 这种前震活动可以分为二种: 一种为连续型, 即前震的频度或震级随时间渐渐增大, 直至主震发生; 另一种为不连续型, 前震的频度和震级先增大后减小, 然后发震。 这种现象不但在破裂声发射试验中观测到, 也在中国大陆地区多次强震前被观测到。 文中基于细胞自动机模型, 引入时间-状态依从摩擦本构关系, 即把自组织非线性系统的普适特征与真实断层摩擦的具体特征结合起来, 研究了强震前短期前兆地震活动的时间演化过程的机理。 文中研究了模型中各参数对模拟事件时间过程的影响, 结果表明, 静摩擦强度在断层上的分布, 或是说静摩擦系数的离散程度直接影响强震前地震活动时间演化过程。     

Numerical analysis model of horizontal displacement of active faults

In this paper, a numerical model was presented for interpreting the movement feature of an active fault zone. This model was based on the analytic solution, given by Crouch (Crouch, 1976), for the problem of displacement discontinuity in an infinite elastic solid, making full use of geodetic and geological data and it was constructed by the boundary element method. A numerous test computation shows that if you want to catch the possible seismic precursor from the displacement’s vector, you have to associate the computation with geological survey in a deep going way, otherwise you would fail in your propose. This method is valid for analysing the zone of strike-slip fault and it has some values for dealing with other analogous problems. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,15, 153–158, 1993.     

Linking landscape morphological complexity and sediment connectivity

Connectivity relates to the coupling of landforms (e.g. hillslopes and channels) and the transfer of water and sediment between them. The degree to which parts of a catchment are connected depends largely on the morphological complexity of the catchment's landscape. Landscapes can have very different and distinct morphologies, such as terraces, V‐shaped valleys or broad floodplains. The objective of this study is to better understand and quantify the relation between landscape complexity and catchment connectivity. We hypothesize that connectivity decreases with increasing landscape morphological complexity. To quantify the connectivity–complexity relationship virtual digital elevation models (DEMs) with distinct morphologies were used as inputs into the landscape evolution model LAPSUS to simulate the sediment connectivity of each landscape. Additionally, the hypothesis was tested on six common real DEMs with widely different morphologies. Finally, the effects of different rainfall time series on catchment response were explored. Simulation results confirm the hypothesis and quantify the non‐linear relation. Results from the exploration of sediment connectivity in response to sequences of rainfall events indicate that feedback between erosion and deposition are more important for certain landscape morphologies than for others: for a given rainfall input, a more effective sediment connectivity and erosion response may be expected from rolling or V‐shaped catchments than from dissected or stepped landscapes. Awareness of the differences in the behaviour and response of different morphologies to catchment processes provides valuable information for the effective management of landscapes and ecosystems through efficiently designed soil and water conservation measures. Copyright © 2013 John Wiley & Sons, Ltd.     

Assessing effects of model complexity and structure on predictions of hydrological responses using serial and parallel model design

By utilizing functional relationships based on observations at plot or field scales, water quality models first compute surface runoff and then use it as the primary governing variable to estimate sediment and nutrient transport. When these models are applied at watershed scales, this serial model structure, coupling a surface runoff sub-model with a water quality sub-model, may be inappropriate because dominant hydrological processes differ among scales. A parallel modeling approach is proposed to evaluate how best to combine dominant hydrological processes for predicting water quality at watershed scales. In the parallel scheme, dominant variables of water quality models are identified based entirely on their statistical significance using time series analysis. Four surface runoff models of different model complexity were assessed using both the serial and parallel approaches to quantify the uncertainty on forcing variables used to predict water quality. The eight alternative model structures were tested against a 25-year high-resolution data set of streamflow, suspended sediment discharge, and phosphorous discharge at weekly time steps. Models using the parallel approach consistently performed better than serial-based models, by having less error in predictions of watershed scale streamflow, sediment and phosphorus, which suggests model structures of water quantity and quality models at watershed scales should be reformulated by incorporating the dominant variables. The implication is that hydrological models should be constructed in a way that avoids stacking one sub-model with one set of scale assumptions onto the front end of another sub-model with a different set of scale assumptions.     

鲜水河断裂带的地震模拟

本文运用由弹簧—滑块模型来模拟走滑断层的地震活动,讨论了模型中断层强度、断层滑块间弹簧强度、滑块与驱动盘之间片簧强度、滑块摩擦力的影响,以及初始条件敏感性。并以我国最为典型的一条走滑断层———鲜水河断裂带为例,运用试错法调整模型参数以使发生的地震最大限度地逼近实际发生的地震,并利用最终结果讨论了鲜水河断裂带今后的活动性。     

Systematic increase in model complexity helps to identify dominant streamflow mechanisms in two small forested basins

This study shows how the use of increasing model complexity allows us to hypothesize about dominant streamflow mechanisms in two small Brazilian forested basins. Nine different structures from SUPERFLEX, an objective framework to systematically increase hydrological model complexity, were tested and we extended the flexible modelling methodology to error models as well. We show that applying a rigorous methodology in a model evaluation framework, with residual analysis and control of model complexity, is essential for testing a model as a hypothesis for dominant hydrological controls. Our results indicate that the model architecture was more important than the increase in the number of model parameters. Better performing models were those with a parallel structure, which confirms our a priori belief about the dominant runoff mechanisms of the studied catchments, characterized by a rapid response to rainfall, but also a constant river discharge fed by water storage on the thick soil layer.     

Earthquake behavior of variable rupture-scale on active faults and application of the cascade-rupturing model

IntroductionThe earlier concept of the characteristic earthquakes means those earthquakes recurring along the same portion of active fault zones, and having nearly the same size, displacement and rupture scale (Schwartz, Coppersmith, 1984). However, more and more evidences have suggested that the rupture(s scale of earthquakes recurred on an individual fault portion has variability (Thatcher, 1990). For instance, the rupture of the 1906 San Francisco, California, earthquake with magnitude 8.…     

Modelling centennial sediment waves in an eroding landscape – catchment complexity

Sediment flux dynamics in fluvial systems have often been related to changes in external drivers of topography, climate or land cover. It is well known that these dynamics are non‐linear. Recently, model simulations of fluvial activity and landscape evolution have suggested that self‐organization in landscapes can also cause internal complexity in the sedimentary record. In this contribution one particular case of self‐organization is explored in the Sabinal field study area, Spain, where several dynamic zones of sedimentation and incision are observed along the current river bed. Whether these zones can be caused by internal complexity was tested with landscape evolution model (LEM) LAPSUS (Landscape Process Modelling at Multi‐dimensions and Scales). During various 500 year simulations, zones of sedimentation appear to move upstream and downstream in eroding river channels (‘waves’). These waves are visualized and characterized for a range of model settings under constant external forcing, and the self‐organizing process behind their occurrence is analysed. Results indicate that this process is not necessarily related to simplifications in the model and is more generic than the process of bed‐armouring that has recently been recognized as a cause for complexity in LEM simulations. We conclude that autogenic sediment waves are the result of the spatial propagation in time of feedbacks in local transport limited (deposition) and detachment limited (erosion) conditions. Copyright © 2014 John Wiley & Sons, Ltd.     

Robust inversion analysis of local gravity anomalies caused by geological dislocation model of faults

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走滑型断层地表永久位移预测模型研究

论述了断层地表永久位移概率地震危险性分析方法的发展过程和应用现状,指出了断层地表破裂预测模型研究的意义。根据我国最近的活动断层地表破裂震后调查结果,基于走滑型断层地表破裂数据,拟合了地表破裂预测模型。采用地震活动性模型和地表破裂预测模型,计算了则木河断裂地表迹线上的永久位移危险性曲线,对预测模型在工程场地地震危险性分析中的应用,提出了建议。     

Usingalarge3Dcelautomationmodeltosimulateenergyfrequency,spaceandtimedistributionofearthquakes

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On the faults of western Hexi Corridor and its nearby regions, northwestern China:Thrust faults and strike-slip faults of Late Cenozoic

Introduction Hexi Corridor, a corridor extended over 1 000 km and with a strike of WNW-ESE, is locatedbetween Alxa uplift and northern Qilianshan Caledonian folding belt of northern Qinghai-Xizang(Tibet) Plateau (Figure 1). In the paper, we will discuss the regions between Altun fault and Yu-mushan of the western Hexi Corridor, where the climate is arid, which results in sparse vegetation,but abundant oil and gas resource, and being one of the most important petroleum industry base…     

A mechanical model for deformation and earthquakes on strike-slip faults

A two-dimensional model for stress accumulation and earthquake instability associated with strike-slip faults is considered. The model consists of an elastic lithosphere overlying a viscous asthenosphere, and a fault of finite width with an upper brittle zone having an elastoplastic response and a lower ductile zone having an elastoviscoplastic response. For the brittle, or seismic, zone the behavior of the fault material is assumed to be governed by a relation which involves strain hardening followed by a softening regime, with strength increasing with depth. For the fault material in the ductile, or aseismic, section, the viscous effect is included through use of a nonlinear creep law, and the strength is assumed to decrease with depth. Hence, because of the lesser strength and the viscous effect, continuous flow occurs at great depths, causing stress accumulation at the upper portion of the fault and leading to failure at the bottom of the brittle zone. The failure is initially due to localized strain softening but, with further flow, the material above the softened zone reaches its maximum strength and begins to soften. This process accelerates and may result in an unstable upward rupture propagation.Relations are developed for the history of deformation within the lithosphere, specifically for the velocity of particles within the fault and at the ground surface. The boundary-element method is used for a quantitative study, and numerical results are obtained and compared with the recorded surface deformation of the San Andreas fault. The effects of geometry and material properties on instability, on the history of the surface deformation, and on the earthquake recurrence time are studied. The results are presented in terms of variations of ground-surface shear strain and shear strain rate, and velocity of points within the fault at various times during the earthquake cycle.It is found that the location of rupture initiation, the possibility of a sudden rupture as opposed to stable creep, and also the ground deformation pattern and its history, all critically depend on the mechanical response of the material within the fault zone, especially that of the brittle section. Shorter earthquake recurrence times are obtained for shallower brittle zones and for a stiffer lithosphere. Lower viscosities of the aseismic zone and the absence of asthenospheric coupling tend to suppress instability and promote stable creep. The model results thus suggest that the overall viscosity of the ductile creeping zone must exceed a minimum value for a sudden upward propagating rupture to take place within the seismic section.     

The model of double bounds of stochastic stress in seismic risk analysis of faults

In this paper, the major idea is: when seismic stress accumulates to a certain extent, a stick slip earthquake will occur on the fault plane. The seismic stress before and after the stick slip earthquake occurrence are both stochastic variables. According to this idea, the model of double bounds of stochastic stress is proposed, and also it is used to analyse the seismic risk of Xian Shui River Fault Zone in the coming 30 years, the result is similar to what the Seismological Bureau of Sichuan Province has predicted. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,15, 477–483, 1993.     

地震及其前兆的观测研究与地震预测

通过对地震灾害及预测观察研究现状的分析,解析了地震预测研究中存在的问题和不足,指出了地震及其前兆观测在预测研究中的作用,同时认为,地震前兆观测既不能盲目,也不能随波逐流也进行,其进展以决于地震孕育机理的深入理解和有效观测途径或方法的选择,并简述了２０年来在震前准静电场观测研究中取得进展和体会。     

Stress interactions between normal faults and adjacent strike-slip faults of 1997 Jiashi earthquake swarm

During a 4-month period starting from 21 January, 1997, an earthquake swarm of seven major events (Ms≥6.0) struck the Jiashi region at the northwestern corner of the Tarim Basin in Xinjiang,, China. Previous relocation studies suggested that these strong earthquakes had occurred along at least two parallel rupture zones. According to the relocated hypocenters and focal mechanisms of the events, we have constructed fault models for these seven earthquakes to calculate the Coulomb stress changes produced by each of these events. Furthermore, we extended our model calculations to include an ad- jacent 1996 Ms=6.9 Artushi earthquake, which occurred one year before the Jiashi earthquake swarm. Our calculations show that the Coulomb stress change caused by the preceding events was around 0.05 MPa at the hypocenter of the 4th event, and higher than 0.08 MPa at the hypocenters of the 2nd, 3rd, 5th and 6th events. Our results reveal a Coulomb stress interactive cycle of earthquake triggering between two adjacent normal and strike-slip faults.     

A cellular model of river meandering

River meandering has been successfully modelled using vector based methods, but these can not simulate multiple or braided channels. Conversely, cellular braided river models fail to replicate meandering. This paper describes a new method to simulate river meandering within a cellular model (CAESAR). A novel technique for determining bend radius of curvature on a cell by cell basis is described, that importantly allows regional information on bend curvature to be transferred to local points. This local curvature is then used to drive meandering and lateral erosion through two methods. Key difficulties are identified, including the deposition of material on point bars and cut off development, but the method illustrates how meandering can be integrated within a cellular framework. This demonstrates the potential to produce a single model that can incorporate both meandering and braiding. Copyright © 2006 John Wiley & Sons, Ltd.     

工程场地断裂评价及对策研究

工程场地断裂的正确评价是确保工程顺利进行和安全运营的基本保证。结合建设中的宿迁三线船闸，通过资料分析、现场考察和地球物理勘探以及钻探等手段，对通过闸址区而直接影响船闸群安全的场地断裂进行了系统的分析和评价。并结合场地条件特点，提出了船闸抗震和抗场地断裂设计的若干对策。     

The influence of biogeochemical conditions and level of model complexity when simulating cometabolic biodegradation in sorbent-water systems

Eighteen models with different levels of complexity for representing sorption, mass transfer, and biodegradation are used to simulate the biodegradation of toluene (primary substrate) and TCE (cometabolic substrate). The simulations are conducted for hypothetical completely mixed systems of various scenarios with regard to sorbent, microbial composition, and solute concentrations. The purpose of the suite of simulations is to investigate the sensitivity of different modeling approaches in simulating the bio-attenuation of co-existing solutes in sorbent-water systems. The sensitivity of results to the modeling approach depends on the biogeochemical conditions of the system. For example, the results are insensitive to the type of sorption model in systems with low sorption strength and slow biodegradation rates, and insensitive to the biodegradation rate model if mass transfer controlled. Differences among model results are generally greater when evaluated in terms of total mass removal rather than aqueous phase concentration reduction. The fate of the cometabolite is more sensitive to the proper consideration of co-solute effects than is the fate of the primary substrate. For a given system, graphical comparison of a characteristic mass transfer rate coefficient (α_mt) versus a characteristic biodegradation rate coefficient (α_bio) provides an indication of how sensitivity to the different processes may be expected to change with time and can guide the selection of an appropriate level of model complexity.     

断层结构非均匀性对地震活动性影响的细胞自动机模拟

基于断层强度分布的非均匀性,构建了由81×81个细胞单元组成的4种不同匀质度及其各自6种不同随机构型共计24个非均匀二维单断层模型样本,并通过设计的细胞自动机模拟程序,在保持其它模拟参数不变的条件下对它们进行了模拟试验．研究结果表明,随着断层结构非匀质度的增加,其宏观变形破坏行为由相对脆性向塑性变化;地震序列类型依次表现出主震型、前震-主震-余震型和震群型;震级分布表现出非均匀性依次减小; 地震发生在时间上表现为一种确定性的随机过程,即小震随机、中强地震丛集和大震准周期的特点．此外,结构几何分布的随机性也对地震序列的特点有较显著的影响,但这种随机差异性随着结构非匀质程度的增加逐渐减小．