Mineral equilibria constraints on open‐system melting in metamafic compositions

The recent development of activity–composition relations for mineral and melt phases in high‐grade metamafic rocks allows mineral equilibria tools to be used to further aid our understanding of partial melting and the mineralogical consequences of melt segregation in these rocks. We show that bulk compositional data from natural amphibolites cover a wide compositional range, with particular variability in the content and ratios of Ca, Na and K indicating that low‐grade metasomatic alteration can substantially alter the igneous protolith chemistry and potentially affect the volume and composition of melt generated. Mineral equilibria calculations for five samples that span the compositional variability in our data set indicate that melting occurs primarily via the fluid‐absent breakdown of amphibole+quartz to produce a pressure‐sensitive peritectic assemblage of augite, orthopyroxene and/or garnet. The introduction of orthopyroxene at the onset of the amphibolite‐to‐granulite‐facies transition at lower pressure results in an increased rate of melt production until quartz is typically exhausted, and this is similarly seen for the introduction of garnet at higher pressure. Calculated melt compositions are dependent on the protolith composition, but initial solidus melting and biotite breakdown produce 1–3 mol.% of K‐rich granitic melts. As hornblende melting proceeds, 15–20 vol.% of either more granodioritic‐to‐tonalitic or granodioritic‐to‐trondhjemitic melt is produced. Once quartz is exhausted, intermediate to mafic melt compositions are produced at ultrahigh‐temperature conditions. Quartz‐rich lithologies with high Ca coupled to low Na and K are the most fertile under orogenic conditions, yielding up to 25 mol.% of sub‐alkalic granitic melt by 850°C. Such rocks did not experience significant subsolidus alteration. Altered compositions with low Ca and elevated Na and K are not as fertile, yielding less than 15 mol.% of alkalic granitic melt by 850°C. These melt volumes are enough to be segregated, and can make a contribution to granite magmatism and intracrustal differentiation that should not be overlooked.     

Sediment yield and transport process assessment from reservoir monitoring in a semi‐arid mountainous river

Soil loss, fluvial erosion, and sedimentation are major problems in semi‐arid environments due to the high associated costs of decreasing services such as provisioning and regulating water resources. The objective of this research is to analyse sediment yield in a mountainous semi‐arid basin, paying special attention to the sources of sediment, the associated uncertainties, and the transport processes involved. The segregation hypothesis along a reservoir of the sediment coming from hillslopes or fluvial systems is also evaluated. For this purpose, bottom‐set and deltaic deposits of a reservoir (110 hm³ ) in southern Spain have been measured and compared with basin erosion and fluvial transport monitoring over a 12‐year period. The volume of sediment stored at the bottomset of the reservoir shows a relative match with parametric predictions based on the Revised Universal Soil Loss Equation/Modified Universal Soil Loss Equation hillslope models and rating curves, estimated as being between 7 and 13 t·ha^?1·year^?1. Similarly, the measured volume of deltaic deposit fits the average value of stochastic simulations from different bedload transport equations. These contributions represent 50–65% of the total volume measured regarding suspended sediment inputs, way above that described in previous works. This highlights the importance of considering bedload when estimating the useful life of reservoirs in semi‐arid environments. The major differences in sediment grain size between hillslopes and river systems, and the size fractions measured along the reservoir, support the assertion of segregation hypothesis. Nonetheless, based on the processes observed and the uncertainty related to modelling, that assertion has to be taken with caution. At basin scale, a specific sediment yield of between 19 and 24 t·ha^?1·year^?1 has been estimated, which includes hillslopes and fluvial contributions. This rate is in the range of sediment yield reported for Mediterranean mountain areas of a torrential character. The pulse‐like nature of the system and the spatial heterogeneity of fluvial and hillslope erosion rates points out the importance of considering mid to long‐term and process‐based approaches and emphasizes the limitations of annual estimations for management purposes.     

基于多源灾情数据的地震灾害损失实时动态评估系统设计与实现

传统的地震灾害损失评估系统,由于基础数据更新不及时,其评估结果准确性较差;随着灾情获取手段的不断丰富完善,利用地震现场实时获取的多源灾情信息,能够实现地震灾害损失实时动态评估。本文通过系统架构、业务功能、业务流程等设计,完成了多源灾情数据的地震灾害损失实时动态评估原型系统的研发。系统的设计与实现有助于震后政府部门实时动态地了解和掌握建筑物破坏、人员伤亡、经济损失等关键灾情信息,能更好地服务于抗震救灾工作。     

黄土梁隧道对自然保护区地下水环境的影响及防治措施

隧道工程的建设对自然保护区的地下水环境影响问题是值得关注的重大问题,本文通过对黄土梁隧道隧址区的地下水环境现状及水文地质条件的调查,初步判定隧道建设对地下水环境的影响主要为涌突水、渗漏水及地下水水质恶化对自然保护区的影响,提出了相应的防治措施。     

地震指数保险在云南漾濞6.4级地震中的作用及启示

指数保险具有触发参数客观、理赔反应迅速的特点,是政策性保险的优先选择。云南省作为地震灾害频发且损失严重地区,率先开展了地震指数保险的试点工作。2021年5月21日,云南省漾濞县发生6.4级地震,触发了地震指数保险赔付。本文对地震指数保险赔偿原则及其在云南试点地区的实施情况等进行介绍,根据漾濞地震损失和赔付情况,总结地震指数保险实施优势和存在的问题,并对地震保险在我国的发展进行展望。     

Performance of solid and perforated U-type breakwaters under regular and irregular waves

An experimental investigation of U-type breakwaters was carried out in a laboratory channel. Both regular and irregular waves were used during testing. Two types of breakwaters such as solid and perforated were studied to analyse the porosity effect of structures. In order to investigate performance of these breakwaters for different immersion depths, four depths of immersions of the solid and perforated breakwaters were selected. Different wave groups were generated over these breakwaters, and the transmission, reflection and energy dissipation characteristics of each breakwater were determined. Three coefficients such as transmission, reflection and energy dissipation coefficients, which were named as C_t, C_r, and C_l, respectively, were used during the evaluation of the test results. The most important parameters governing performance of these breakwaters were determined by using earlier investigations and experimental results. These parameters were expressed as a dimensionless group by using π theory. Based on the test results, empirical expressions were formulated to describe the C_t, C_r, and C_l for different immersion depths of solid and perforated breakwaters under regular and irregular waves.     

Porosity effects on non-breaking surface waves over permeable submerged breakwaters

This study investigated how the porosity of submerged breakwaters affects non-breaking wave transformations. Eight model geometries each with six different porosities, from 0.421 to 0.912, were also considered. Experimental results reveal that the model width has little effect on wave reflection and transmission when the model heights are fixed. The transmission coefficient is maximum at a kh in the range from 1.3 to 2.0 and minimum at a kh around 0.7. The wave reflection maximum is at kh of near 0.5. The energy loss of the primary waves is maximum near kh=0.81 and minimum when the porosity of the model is large. Porosity does affect wave transformation and its influence becomes significant as the heights of the models increase. For the range of porosities tested, wave energy loss from the primary harmonic was found to be almost constant at around 0.4 when kh >1.3, decreasing slowly when kh <1.3; wave energy loss decreases for porosities above 0.75.     

Quantifying spatiotemporal dynamics of agricultural landscapes using remotely sensed data and landscape metrics

This study focuses on the spatiotemporal dynamics of agricultural lands and differences in rapidly developing urban and declining rural counties in Iowa, USA between 1984 and 2000. The study presents an analysis of land-cover maps derived from Landsat TM and ETM+ satellite imagery and different landscape metrics using FRAGSTATS and IDRISI software. The study provides evidence of both loss of croplands and change in fragmentation between 1984 and 2000. Fragmentation in agriculture-dominated areas increased with the development of urban centres and diversification of land uses. Fragmentation of landscapes, including agricultural land, was found to be higher in the urbanized counties, but was stable or even declined over time in these counties. In contrast, in the context of remote rural areas, agricultural landscapes experienced rapid increase in fragmentation and farmland loss. The urban–rural gradient analysis used in this study showed that the highest fragmentation occurred on the city edges. These findings suggest that farmland fragmentation is a complex process associated with socio-economic trends at regional and local scales. In addition, socio-economic determinants of landscape fragmentation differ between areas with diverging development trajectories. Intensive cropland fragmentation in remote agricultural regions, detected by this research, should be further studied and its possible effects on both agricultural productivity and biodiversity should be carefully considered.     

Aberrant Cities: Urban Population Loss in the United States, 1820-1930

Our understanding of population loss from U.S. cities draws primarily from the fate of industrial centers in the decades following World War II. Quite numerous, those cities cast off residents at unprecedented and sustained rates. Prior to this time, few large cities had ended a decade smaller in population size than they began. In order to broaden and deepen our knowledge of why some cities and not others lose population, this paper analyzes cities that shed population in the 19th century. Using Census data and capsule stories developed from city biographies, the paper explores both contextuating and precipitating factors. These findings subsequently become the basis for reflecting anew on urban decline since the mid-20th century.     

Comparative mitochondrial genome analysis of Varunidae and its phylogenetic implications

Complete mitochondrial genomes(mitogenomes) can indicate phylogenetic relationships, as well as useful information for gene rearrangement mechanisms and molecular evolution. Currently, the phylogenetic location of the genus Varuna(Brachyura: Varunidae) has not been well resolved mainly because of limited representatives(only two extant species). Here, we determined a new mitogenome of this genus(Varuna litterata) and added the published mitogenomes to reconstruct the phylogeny of Varunidae. The ...