Earthquake prediction: a critical review

Earthquake prediction research has been conducted for over 100 years with no obvious successes. Claims of breakthroughs have failed to withstand scrutiny. Extensive searches have failed to find reliable precursors. Theoretical work suggests that faulting is a non-linear process which is highly sensitive to unmeasurably fine details of the state of the Earth in a large volume, not just in the immediate vicinity of the hypocentre. Any small earthquake thus has some probability of cascading into a large event. Reliable issuing of alarms of imminent large earthquakes appears to be effectively impossible.     

Earthquake prediction: the null hypothesis

The null hypothesis in assessing earthquake predictions is often, loosely speaking, that the successful predictions are chance coincidences. To make this more precise requires specifying a chance model for the predictions and/or the seismicity. The null hypothesis tends to be rejected not only when the predictions have merit, but also when the chance model is inappropriate. In one standard approach, the seismicity is taken to be random and the predictions are held fixed. 'Conditioning' on the predictions this way tends to reject the null hypothesis even when it is true, if the predictions depend on the seismicity history. An approach that seems less likely to yield erroneous conclusions is to compare the predictions with the predictions of a 'sensible' random prediction algorithm that uses seismicity up to time t to predict what will happen after time t. The null hypothesis is then that the predictions are no better than those of the random algorithm. Significance levels can be assigned to this test in a more satisfactory way, because the distribution of the success rate of the random predictions is under our control. Failure to reject the null hypothesis indicates that there is no evidence that any extra-seismic information the predictor uses (electrical signals for example) helps to predict earthquakes.     

The basis for earthquake prediction

Summary. Recent advances in understanding the behaviour of shear waves propagating in the crust make the routine prediction of earthquakes seem practicable. Accumulating evidence suggests that most of the Earth's crust is pervaded by distributions of fluid-filled cracks and microcracks that are aligned by the contemporary stress-field so that the cracked rockmass is effectively anisotropic to seismic waves. This causes shear-waves to split, and shear-wave splitting is observed whenever shear-waves propagating along suitable raypaths in the crust are recorded by three-component instruments. These distributions of cracks are known as extensive-dilatancy anisotropy or EDA. Many characteristics of the crack- and stress-geometry can be monitored by analyzing shear-waves propagating through the cracked rockmass. Observations of temporal variations of the behaviour of shear-wave splitting in seismic gaps confirm these hypotheses, and suggest that stress changes before earthquakes may be monitored by analyzing shear-waves. In particular, monitoring earthquake preparation zones with three-component shear-wave vertical-seismic-profiles could lead to techniques for the routine prediction of earthquakes.     

The forest transition: a theoretical basis

Summary A theoretical basis for the forest transition (the change from contraction to expansion of national forest area) is suggested in terms of increasing agricultural adjustment to land quality. This adjustment, operating through a process of learning by farmers, results in the concentration of agricultural production in smaller areas of better land, and the agricultural abandonment of larger areas of poorer land, which are then available for reforestation through natural regeneration or planting.     

Biosphere-human feedbacks: a physical geography perspective

Biogeography has many connections to people but fewer to human geography. Biogeography is connected to the four dimensions of anthropogenic global change, but most of this research is tied to land-use change. Biogeographers have studied several ways in which land use affects the patterns and dynamics of organisms, mostly in reference to remnants of habitat destruction, but the human dimensions of this relationship are more explicit in changing habitat quality. How biogeography affects land use is also studied, but research on topics such as ecosystem services needs more contributions from geographers. Feedbacks between people and the other organisms with which we live, with more fully linked models, are a general subject in which biogeographers can contribute to progress in the human dimensions of global change.     

A new theoretical treatment of compaction and the advective-diffusive processes in sediments: a reviewed basis for radiometric dating models

Classical treatment of mass conservation of solids in growing sediments states an advection-diffusion equation for the bulk sediment density. Thus, the diffusion coefficient has to account for elemental processes of exchange of solid particles by pore water or reciprocally. Nevertheless, in a gravity field, these exchanges are forced and cannot be treated as diffusion but as mass flow. A compaction potential energy is defined so that its spatial gradients force a mass flow involving a conductivity function. This leads to a more consistent definition of mass sedimentation rates and to a writing of the continuity equation for density involving only an advection term. Typical bulk density profiles show an asymptotic increase with depth. With the present formulation, this can be obtained as a steady-state solution under constant sedimentation rate and constant conductivity, while the classical formulation fails to do it. Alternatively, it can be found that under these conditions, the compaction potential is a linear function of the bulk density. The mass flow due to compaction and the compaction potential are found for several sediment cores from literature data. From this basis, the advection-diffusion equation for a particle-associated tracer is rewritten. In particular, when the mass flow term due to compaction is considered, the resulting sub-grid scale processes lead to a different formulation of the diffusive fluxes: they are proportional to the gradients of specific concentration in solids instead of the concentration per unit bulk volume. This new formulation is most suitable to find out analytical solutions for radiometric dating models involving mixing and compaction. Numerical solutions are found for the new and the classical treatment for some particular cases to illustrate differences.     

一种新的气候变化敏感区的定义方法与预估

气候变化敏感区的研究是气候变化研究的一个重要方向,前人对气候变化敏感区的定义大多基于单一的指标,而对综合性指标研究较少。基于柯本气候分类法所划分出的中国气候类型分布及其变化频次,提出一种新的气候变化敏感区定义方法,并使用该方法划分中国的气候变化敏感区,气候类型变化频繁的区域被认为是敏感区。选取CESM模型中等碳排放（RCP 4.5）下的模拟数据计算2006-2013年、21世纪40年代和90年代气候类型的变化,以此预估未来30~80年间气候变化敏感带的变化。结果显示：依据本文提出的方法划分的气候变化敏感区,与降水变化敏感区有较好拟合;中国气候变化最敏感的区域分布在黑河腾冲线附近、秦岭淮河一线、青藏高原西部和天山以北部分地区,气候最为稳定的区域分布在青藏高原中东部、昆仑山、祁连山以北、天山以南、贺兰山以西的大片区域和大兴安岭附近;未来30~80年间,西部（贺兰山、横断山以西）地区气候变化敏感区基本不变,而东部地区的气候变化敏感区则逐渐向北偏移。     

黄秉维院士开创自然地理研究新方向

黄秉维先生一生致力于综合自然地理研究, 是卓越的自然地理学家。更加难能可贵的是, 在成绩面前他总能看到地理学的弱点和自身工作的不足, 提出革新自然地理学的思想, 从而开启了中国综合自然地理研究的新方向, 对中国地理学界产生了深刻影响, 成为中国20世纪自然地理研究的一代宗师。     

Avalanche prediction in Scotland: II. Development of a predictive model

The paper presents a method for predicting avalanche activity from meteorological data which is suitable for Scottish snow conditions. Two main types of avalanche are distinguished. Direct-action avalanches are the result of fresh snow accumulation and may release after approximately 200 mm of fresh snow has fallen over a period of a few days. They become extremely likely if a further 100 mm falls in a single day. Climax avalanches are the result of strength loss in the snow cover, due either to thawing or persistent cold. Thaws may produce an avalanche after only three or four days with maximum temperatures around 2°C. Alternatively, if maximum temperatures remain below ?4°C for over a week, and especially if cold weather persists for two weeks, slab avalanches of dry snow are likely to occur. Between these two types are several possible avalanche situations in which fresh snow accumulation is combined with high or low temperatures. Topography plays a passive role, and determines where avalanche activity is most likely. Free faces, smooth surfaces and slopes in the lee of major storms respond most rapidly to the onset of avalanche conditions.     

Response of a Resilient Community to Natural Disasters: The Gorkha Earthquake in Nepal, 2015

The ability of a community to withstand and recover from adversities including natural and man-made disasters has emerged as a major policy issue in recent years. This research aims to assess the role of institutional initiatives in building resilient communities and their response to natural disasters like the Gorkha earthquake in Nepal in 2015. The work is based on data collected from primary and secondary sources along with field observations. It is evident that resilient communities are equipped with greater coping capacities in the face of natural disasters and have reduced vulnerability to future hazards. Institutional capacity building and resilient construction including the School Earthquake Safety Program ensured better disaster preparedness. The traditional open spaces and building designs added to the structural resilience. There is, however, a need to build back better and to communicate earthquake-resistant designs to the affected communities.