Dynamic Rupture in a 3-D Particle-based Simulation of a Rough Planar Fault

An appreciation of the physical mechanisms which cause observed seismicity complexity is fundamental to the understanding of the temporal behaviour of faults and single slip events. Numerical simulation of fault slip can provide insights into fault processes by allowing exploration of parameter spaces which influence microscopic and macroscopic physics of processes which may lead towards an answer to those questions. Particle-based models such as the Lattice Solid Model have been used previously for the simulation of stick-slip dynamics of faults, although mainly in two dimensions. Recent increases in the power of computers and the ability to use the power of parallel computer systems have made it possible to extend particle-based fault simulations to three dimensions. In this paper a particle-based numerical model of a rough planar fault embedded between two elastic blocks in three dimensions is presented. A very simple friction law without any rate dependency and no spatial heterogeneity in the intrinsic coefficient of friction is used in the model. To simulate earthquake dynamics the model is sheared in a direction parallel to the fault plane with a constant velocity at the driving edges. Spontaneous slip occurs on the fault when the shear stress is large enough to overcome the frictional forces on the fault. Slip events with a wide range of event sizes are observed. Investigation of the temporal evolution and spatial distribution of slip during each event shows a high degree of variability between the events. In some of the larger events highly complex slip patterns are observed.     

地质复杂度与成矿预测之间的关系--以兰坪盆地为例

地质复杂度是由赵鹏大院士提出的地质异常圈定方法之一。它综合了地质、遥感等各种有利的成矿因素，充分发挥其定量化和综合性分析的特点，对各种控矿因子进行加权得分，进而圈定了6个成矿远景区。     

算法复杂性与川滇地区11个地震带(区)地震预报的研究

以川滇地区11个地震带(区)为对象,研究了将算法复杂性C(n)用于地震预报的可能性。文中以1a为时间窗,0.5a为滑动步长,按2.5≤M<3.5,3.5≤M<4.5和M≥4.5分成3档,将各地震带(区)地震序列转换成由3种符号组成的字符串,从而计算各地震带(区)算法复杂性C(n)随时间变化曲线,规定了预报判据和预报规则,总体上取得了略高于随机瞎报的预报效能,显示了将算法复杂性用于地震预报研究有一定的前景。     

Computational complexity of spatial reasoning with directional relationship

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南屯煤矿构造复杂性分析

矿井构造严重制约着煤矿的建设与生产．对其研究不仅要定性更要定量分析。在分析南屯煤矿地质构造的基础上,利用模糊综合评判方法对井田构造复杂性进行定量分析,其结果与实际基本一致。井田总体构造偏于简单,简单和较简单的单元占总数的70．4％。但在井田东部及东北部构造偏于复杂。因此采区应首先布置在中西部,采用综合机械化开采和普通机械化采煤方法;在矿井东部及东北部宜采用爆破采煤方法,同时要注意煤矿水害的防治。模糊综合评判方法为矿井地质构造定量研究提供了有效途径。     

Modeling Mediterranean forest structure using airborne laser scanning data

The conservation of biological diversity is recognized as a fundamental component of sustainable development, and forests contribute greatly to its preservation. Structural complexity increases the potential biological diversity of a forest by creating multiple niches that can host a wide variety of species. To facilitate greater understanding of the contributions of forest structure to forest biological diversity, we modeled relationships between 14 forest structure variables and airborne laser scanning (ALS) data for two Italian study areas representing two common Mediterranean forests, conifer plantations and coppice oaks subjected to irregular intervals of unplanned and non-standard silvicultural interventions. The objectives were twofold: (i) to compare model prediction accuracies when using two types of ALS metrics, echo-based metrics and canopy height model (CHM)-based metrics, and (ii) to construct inferences in the form of confidence intervals for large area structural complexity parameters.Our results showed that the effects of the two study areas on accuracies were greater than the effects of the two types of ALS metrics. In particular, accuracies were less for the more complex study area in terms of species composition and forest structure. However, accuracies achieved using the echo-based metrics were only slightly greater than when using the CHM-based metrics, thus demonstrating that both options yield reliable and comparable results. Accuracies were greatest for dominant height (Hd) (R² = 0.91; RMSE% = 8.2%) and mean height weighted by basal area (R² = 0.83; RMSE% = 10.5%) when using the echo-based metrics, 99th percentile of the echo height distribution and interquantile distance. For the forested area, the generalized regression (GREG) estimate of mean Hd was similar to the simple random sampling (SRS) estimate, 15.5 m for GREG and 16.2 m SRS. Further, the GREG estimator with standard error of 0.10 m was considerable more precise than the SRS estimator with standard error of 0.69 m.     

大规模图中低复杂度分布式算法浅析

近年来大规模图分析问题在网络大数据领域发挥着重要作用.经典的图分析问题包括求图的直径、半径、围长、聚类系数、紧密中心度和介数中心度等.集中式算法求解这些图计算问题一般都需要问题规模的平方甚至立方以上复杂度,显然不适用于大规模图.本文旨在从分布式算法角度介绍对这些基本图计算问题具有最坏性能保证的低复杂度（线性时间）算法.此外,本文还将介绍如何通过通信复杂性理论证明分布式图计算问题的下界.     

Effects of temporal variation of the seaweed Caulerpa prolifera cover on the associated crustacean community

The aim of this study was to establish the effect of temporal variation of the alga Caulerpa prolifera cover on the composition and stability of the associated crustacean community. Forty‐five crustacean species were found, amphipods and tanaidaceans being the most abundant groups. The stations were grouped mainly based on the gradient of algal cover, independently of location or sampling period (MDS analyses). Considering separately epifaunal and infaunal species, the epifauna occurred mainly at high cover (HC) and medium–low cover (MLC) stations, while the infauna occurred at MLC and unvegetated (UV) stations. Infaunal species were predominant in all stations and sampling periods, and the abundance and numbers of epifaunal species showed a clear dependence of algal cover. To quantify the loss of biodiversity due to the plant cover variations, we applied the average and variation in taxonomic distinctness (Δ⁺ and Λ⁺, respectively). The HC stations, especially those with fewer algal cover variations along the study period, showed few fluctuations of Δ⁺,and Λ⁺ was usually located near mean; however, UV stations tended to fall in the area where the statistical power of the test is reduced and showed more oscillations of Λ⁺. The ability of these indices to test the fauna composition in function of the alga presence is discussed.     

Place,Learning Progressions,and Progress

This commentary response reflects on the thoughts offered by Solem, Mohan, Rawling, and Lambert regarding Larsen and Harrington's article titled “Developing a Learning Progression for Place” (2018).