Rotation and strain seismology

Asymmetric continuum theory points to the equal roles of the rotation motions and those related directly to shear or confining strains. The strain motions could be quite independent or mutually related with the eventual phase shifts, while the displacements have only a mathematical sense; a real displacement may appear along the fracture slip only. Formally, any deformation could be presented as related to the displacements; however, its origin in a fracture source should be considered either as belonging to an individual process or to complex correlated events; in these cases, the confining, shear and rotation strains can be related mathematically to the different displacement fields. Some of these related deformations could be emitted from a source with a phase shift, while the observed displacements (deduced from records) result as a sum of these independent displacements. An important influence on a source process and on the premonitory micro-events has the material defects, their distribution, and mobility. The defect arrays lead to a concentration of stresses and their local reorganization. Thus, in this paper, we consider the induced stresses and strains related to defect content and to its modification and redistribution. Moreover, an important role in understanding the complex correlated events in a source plays the release?Crebound mechanism. The release?Crebound mechanism in an earthquake source processes leads to a possible direct or phase-shifted correlations between the emitted motions; in this aspect, a propagation of the coupled strain and rotation waves is discussed. In particular, we consider the point fracture events as related either to a confining load or/and to the shear and rotation processes; we discuss the related effects and their meaning when discussing the fault plane mechanism and emitted waves. In some important seismic regions, we have the recording system which permits to record the strains and rotations. However, we should point that the wordwide seismological network is not adequate to record the complex strain deformations released in the fracture processes and remains quite insufficient to understand the global stress changes and related strain waves of a very low period. Consideration on a recording mechanism of the long displacement waves indicates the insufficiencies of the present global recording system and points that recording of the global strain and rotation waves is an important and urgent task.     

Differences in the abiotic parameters of water in coastal lakes in the light of the EU water framework directive: An example of the Polish southern Baltic coast

Coastal lakes have a specific hydrological regime determined by the influence of sea and inland water and the local hydrographic conditions. There are several problems concerning the protection and assessment of water quality of these bodies. The most important features differentiating coastal lakes from other lakes are: high salinity, a wide range of seasonal and short-term water quality changes, and specific aquatic ecosystems adapted to these conditions. These matters have not been sufficiently taken into account in the existing classifications and typologies of lakes in Poland. The problem has not been solved by the establishment of the adequate reference conditions and new guidelines for the classification of water status (which are being prepared according to the Common Strategy for the Implementation of the Water Framework Directive) regarding inland surface waters (rivers and lakes) and marine waters (coastal and transitional). An important issue is to define criteria which would help to distinguish all those hydrographic objects and to establish water quality standards for them.     

137Cs示踪法研究湟水上游和布哈河下游区域土壤侵蚀强度

通过¹³⁷Cs示踪技术,并采用土壤剖面核素单位面积浓度与背景值之间的理论模型,对布哈河下游和青海湖东北岸湟水上游区域的土壤侵蚀进行了研究,结果表明：¹³⁷Cs面积活度与植被盖度之间存在着正相关关系,两区域相关系数为0.93。湟水上游河谷土壤侵蚀模数在87.62～1 458.41 t·km^-2·a^-1之间,采样点平均土壤侵蚀模数为933.31 t·km^-2·a^-1。布哈河下游区域土壤侵蚀模数在431.03～2 072.39 t·km^-2·a^-1之间,采样点平均土壤侵蚀模数为1 256.97 t·km^-2·a^-1。布哈河下游区域较湟水上游区域侵蚀严重,在较长的时期内两地大部分区域均处于轻度侵蚀阶段,湟水上游北部和布哈河下游西北部处于微度侵蚀阶段。     

Intermittent generation of mafic enclaves in the 1991–1995 dacite of Unzen Volcano recorded in mineral chemistry

Mafic enclaves in the 1991–1995 dacite of Unzen volcano show chemical and textural variability, such as bulk SiO₂ contents ranging from 52 to 62 wt% and fine- to coarse-grained microlite textures. In this paper, we investigated the mineral chemistry of plagioclase and hornblende microlites and distinguished three enclave types. Type-I mafic enclaves contain high-Mg plagioclase and low-Cl hornblende as microlites, whereas type-III enclaves include low-Mg plagioclase and high-Cl hornblende. Type-II enclaves have an intermediate mineral chemistry. Type-I mafic enclaves tend to show a finer-grained matrix, have slightly higher bulk rock SiO₂ contents (56–60 wt%) when compared with the type-III mafic enclaves (SiO₂?=?53–59 wt%), but the overall bulk enclave compositions are within the trend of the basalt–dacite eruptive products of Quaternary monogenetic volcanoes around Unzen volcano. The origin of the variation of mineral chemistry in mafic enclaves is interpreted to reflect different degree of diffusion-controlled re-equilibration of minerals in a low-temperature mushy dacitic magma reservoir. Mafic enclaves with a long residence time in the dacitic magma reservoir, whose constituent minerals were annealed at low-temperature to be in equililbrium with the rhyolitic melt, represent type-III enclaves. In contrast, type-I mafic enclaves result from recent mafic injections with a mineral assemblage that still retains the high-temperature mineral chemistry. Taking temperature, Ca/(Ca?+?Na) ratio of plagioclase, and water activity of the hydrous Unzen magma into account, the Mg contents of plagioclase indicate that plagioclase microlites in type-III enclaves initially crystallized at high temperature and were subsequently re-equilibrated at low-temperature conditions. Compositional profiles of Mg in plagioclase suggest that older mafic enclaves (Type-III) had a residence time of ~100 years at 800 °C in a stagnant magma reservoir before their incorporation into the mixed dacite of the 1991–1995 Unzen eruption. Presence of different types of mafic enclaves suggests that the 1991–1995 dacite of Unzen volcano tapped mushy magma reservoir intermittently replenished by high-temperature mafic magmas.     

Compressibility of Sands of Various Geologic Origins at Pre-crushing Stress Levels

This study quantifies the influence of various intrinsic soil properties including particle roundness, R, sphericity, S, 50% size by weight, D ₅₀, coefficient of uniformity, C _u, and the state property of relative density, D _r, on the compression and recompression indices, C _c and C _r, of sands of various geologic origins at pre-crushing stress levels. Twenty-four sands exhibiting a wide range of particle shapes, gradations, and geologic origins were collected for the study. The particle shapes were determined using a computational geometry algorithm which allows characterization of a statistically large number of particles in specimens. One dimensional oedometer tests were performed on the soils. The new data was augmented with many previously published results. Through statistical analyses, simple functional relationships are developed for C _c and C _r. In both cases, the models utilized only R and D _r since other intrinsic properties proved to have lesser direct influence on the compression indices. However, previous studies showed that the contributions of S and C _u are felt through their effects on index packing void ratios and thus on D _r. The accuracy of the models was confirmed by comparison of predicted and observed C _c and C _r values.     

拉萨市空气含氧量变化研究

对拉萨市空气含氧量进行了研究,分析了该值的日变化、逐日变化,并结合气象因子分析了可能导致该变化的原因。结果表明:拉萨市含氧量一天内有明显的峰值和谷值;含氧量变化与相对湿度显著负相关,与温度、气压不能通过相关性检验;与海平面地区含氧量相比,拉萨市含氧量变化不大;含氧量与每立方米空气中氧气的质量没有直接关系,不能用来衡量空气中氧气的绝对含量。      

1975-2008 年西藏色林错湖面变化对气候变化的响应

根据1975 年地形图、80 年代至2008 年的TM、CBERS 卫星遥感资料和近34 年(1975-2008 年) 的气温、降水量、蒸发量、最大冻土深度等气候资料分析得出,西藏那曲地区西部的色林错及其周围的错鄂、雅根错的面积在近30 年来呈较显著的扩大趋势,到2008 年面积分别为2196.23 km2、279.24 km²、103.07 km²,与1975 年分别增长了574.46 km²、11.59 km2和68.13 km²,增长速度分别为35.4%、4.3%和195%。色林错从1999-2008 年湖面扩大速度为20%,平均上涨了420 km²/10a,已超过纳木错面积,成为西藏第一大咸水湖。冰雪融水量的增加是湖泊上涨的根本原因,其次与降水量的增加和蒸发量的减少、冻土退化等暖湿化的气候变化存在很大关系。