On Fröhlich's solution for Boussinesq's problem

The concentration factor introduced by O. K. Fröhlich is visualized as a procedure for examining the pattern of load transfer from surface loads to the interior of a geomaterial. The historical details that led to the introduction of the concentration factor are scant although it is widely used in the area of soil mechanics problems associated with tillage‐induced soil compaction. The purpose of this note is to examine the concentration factor in terms of the geomechanics of an elastic continuum and to identify the precise conditions that are satisfied by the distribution of stresses and strains that accommodate the concentration factor. Copyright © 2013 John Wiley & Sons, Ltd.     

Magnetic susceptibility variations of the Ediacaran cap carbonates in the Yangtze platform and their implications for paleoclimate

Magnetic susceptibility (MS) data were obtained from 11 sections of the Doushantuo (Ediacaran) cap carbonate that directly overlies the Nantuo glacial diamictite in the southeastern margin of the Yangtze platform. The MS data revealed two regionally correlatable peaks at the bottom and top of the cap carbonate, separated by an interval of low values. The lower MS peak coincides with high percentage of insoluble siliciclastic residues that are compositionally identical to the matrix of the underlying diamictite, suggesting its origin controlled mainly by detrital components during the first phase of cap carbonate deposition at the end of the glaciation. The upper MS peak is associated with high clay content and iron sulfides, and can be interpreted as either derived from enhanced greenhouse weathering that could have brought more terrigenous components into the ocean, or the result of ocean anoxia at the late stage of cap carbonate deposition that could led to formation of abundant iron sulfides. The regionally consistent MS curves from the cap carbonates provided the first geophysical record for the rapid climate change from icehouse to greenhouse conditions in the aftermath of the Neoproterozoic “snowball Earth” event.     

中山市河涌水体及污水处理厂中 合成麝香的分布规律

对中山市5个区域的48条主要河涌水体与2间污水处理厂各工艺流程水体进行样品采集,运用固相微萃取进行前处理并结合气相色谱—质谱联用技术,检测各样品中佳乐麝香、吐纳麝香和酮麝香这3种合成麝香的含量,并分析其分布特征以及探讨污水处理厂处理工艺中合成麝香的浓度变化规律。结果表明：1）合成麝香已经普遍存在于中山市的河涌水体中。中山市西部地区和南部地区的河涌水体中合成麝香总含量相对其他区域最低,中部地区河涌水体中合成麝香含量亦较低。2）中山市雁企涌和魁魁涌等28条河涌水体中的主要合成麝香为佳乐麝香,一埒涌和乌沙涌等13条河涌水体的主要合成麝香为酮麝香,仅有苏埒涌和石军涌等7条河涌水体的主要合成麝香为佳乐麝香和酮麝香这2种合成麝香。3）氧化沟和A2/O工艺均能对合成麝香产生一定的去除效果。污水处理厂A对佳乐麝香、吐纳麝香和酮麝香的去除率分别为86.94%、72.15%和89.36%;而污水处理厂B对以上3种合成麝香的去除率分别为82.09%、85.73%和87.90%。4）2间污水处理厂的二沉池以及污水处理厂A的紫外消毒亦可对合成麝香产生进一步的去除效果;2间污水处理厂均能对酮麝香产生比佳乐麝香和吐纳麝香更高的去除率。     

CMIP6模式对亚洲陆地生态系统的模拟评估与预估

基于国际耦合模式比较计划第六阶段（CMIP6）模式模拟以及观测数据,评估了9个CMIP6模式对亚洲地区叶面积指数（LAI)、总初级生产力（GPP）和净初级生产力（NPP）的模拟性能。模拟评估结果表明,9个CMIP6模式能够较好地模拟出亚洲地区陆地生态系统LAI、GPP和NPP的时空分布特征。综合来看,多模式集合（MME）模拟效果最佳,其模拟的LAI、GPP和NPP与观测的空间相关系数分别达到0.90、0.81和0.89,均方根误差在0.5左右。在此基础上,利用MME结果进一步预估了亚洲地区陆地生态系统在SSP1-2.6、SSP2-4.5和SSP5-8.5情景下的未来变化。总体而言,亚洲地区LAI、GPP和NPP到21世纪末都呈现上升趋势。其中,温室气体高排放情景下的上升趋势大于温室气体低排放情景下的上升趋势,亚洲中高纬度地区的增幅大于低纬度地区的增幅。从区域平均来看,到21世纪末期,与当今气候态相比,北亚LAI、GPP和NPP的增幅最大,其在SSP5-8.5情景下分别增加68%、106%和90%;东南亚增幅最小,分别为15%、34%和39%。在SSP1-2.6情景下,北亚LAI、GPP和NPP在21世纪末的增幅分别为23%、29%和26%;东南亚分别为3%、10%和11%,意味着未来全球变暖背景下亚洲区域陆地生态系统变绿和固碳幅度加强。     

两次强震峰值速度比及其余震分布特征

基于甘肃地震台网和青海地震台网对岷县-漳县MS6.6地震和门源MS6.4地震的波形记录,采用FFT方法分别计算这两次地震三分向的峰值速度,讨论分量之间峰值速度比的分布特征,进而研究其震源性质。结果表明,岷县-漳县地震具有逆冲兼左旋位错性质,南北向能量明显大于东西向;门源地震以逆冲为主,略具左旋走滑特征,两个水平分量的能量相当。结合这两次地震的余震序列分布特征及其他学者的研究结果推测,岷县-漳县地震的发震断层应该是位于临潭-宕昌断裂西北侧且与其平行的一条次级断裂;门源地震的发震断层应该是冷龙岭断裂西北侧的次级断裂,但受到冷龙岭断裂活动控制。     

Tjörnes fracture zone. New and old seismic evidences for the link between the North Iceland rift zone and the Mid-Atlantic ridge

The Tjörnes facture zone (TFZ) connects the EW extension of the Mid-Atlantic ridge north of Iceland to the extension of the North volcanic zone (NVZ) of Iceland. Earthquakes up to magnitude 7 (Ms) can occur in TFZ, volcanic eruptions have been observed and large crustal deformations are expected in similar way as have been observed in the NVZ. Most of the zone is below ocean, which limits the historical information and geological observations. For studying the dynamics of the zone we must rely on interpretation and modelling based on seismic observations, especially on microearthquake observations for the last 10 years. In this paper we demonstrate how microearthquakes can be applied to map the details of the plate boundary, and how this information can be applied to find epicenters and fault planes of large historical earthquakes, also how seismic information can be applied in dynamic modelling and to infer spatial and temporal interplay in activity, and to enhance hazard assessment.     

The Double Solid Reactant Method for modeling the release of trace elements from dissolving solid phases: I. Outline and limitations

A Double Solid Reactant Method was elaborated from a suggestion of Marini (Geological sequestration of carbon dioxide: Thermodynamics, kinetics, and reaction path modeling. Developments in Geochemistry, Elsevier, Amsterdam, 2007) to simulate the release of trace elements during the progressive dissolution of solid phases. The method is based on the definition, for each dissolving solid, of both an entity whose thermodynamic and kinetic properties are known (either a pure mineral or a solid mixture) and a special reactant, that is, a material of known stoichiometry and unknown thermodynamic and kinetic properties. The special reactant is utilised to take into account the concentrations of trace elements in the dissolving solid phase. In this communication, the influence of several trace elements on the ΔG _f ^o, ΔG _r ^o and log K of the minerals considered by Lelli et al. (Environ Geol, 2007) and Accornero and Marini (Geobasi, 2007a; Proceedings of IMWA symposium, Cagliari, 27–31 May 2007b) was evaluated assuming ideal mixing in the solid state. These effects were found to be negligible for albite and the leucite–latitic glass, limited for muscovites and chlorites, and slightly more important for apatites. These influences become progressively higher with increasing concentration of trace elements in these minerals. Based on these deviations in thermodynamic parameters, special reactants should not include oxide components with molar fractions higher than 0.003. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.

From orthogneiss to migmatite: Geochemical assessment of the melt infiltration model in the Gföhl Unit (Moldanubian Zone, Bohemian Massif)

The Gföhl Unit is the largest migmatite terrain of the Variscan orogenic root domain in Europe. Its genesis has been until now attributed to variable degrees of in situ partial melting. In the Rokytná Complex (Gföhl Unit, Czech Republic) there is a well-preserved sequence documenting the entire migmatitization process on both outcrop and regional scales. The sequence starts with (i) banded orthogneiss with distinctly separated monomineralic layers, continuing through (ii) migmatitic mylonitic gneiss, (iii) schlieren migmatite characterised by disappearance of monomineralic layering and finally to (iv) felsic nebulitic migmatite with no relics of the original banding.

While each type of migmatite shows a distinct whole-rock geochemical and Sr–Nd isotopic fingerprint, the whole sequence evolves along regular, more or less smooth trends for most of the elements. Possible mechanisms which could account for such a variation are that the individual migmatite types (i) are genetically unrelated, (ii) originated by equilibrium melting of a single protolith, (iii) formed by disequilibrium melting (with or without a small-scale melt movement) or (iv) were generated by melt infiltration from external source. The first scenario is not in agreement with the field observations and chemistry of the orthogneisses/migmatites. Neither of the remaining hypotheses can be ruled out convincingly solely on whole-rock geochemical grounds. However in light of previously obtained structural, petrologic and microstructural data, this sequence can be interpreted as a result of a process in which the banded orthogneiss was pervasively, along grain boundaries, penetrated by felsic melt derived from an external source.

In terms of this melt infiltration model the individual migmatites can be explained by different degrees of equilibration between the bulk rock and the passing melt. The melt infiltration can be modelled as an open-system process, characterised by changes of the total mass/volume and accompanied by gains/losses in many of the major- and trace elements. The modelling of the mass balance resulted in identification of a component added by a heterogeneous nucleation of feldspars, quartz and apatite from the passing melt. This is in line with the observed presence of new albitic plagioclase, K-feldspar and quartz coatings as well as resorption of relict feldspars. At the most advanced stages (schlieren and nebulitic migmatites) the whole-rock trace-element geochemical variations document an increasing role for fractional crystallization of the K-feldspar and minor plagioclase, with accessory amounts of monazite, zircon and apatite.

The penetrating melt was probably (leuco-) granitic, poor in mafic components, Rb rich, with low Sr, Ba, LREE, Zr, U and Th contents. It probably originated by partial melting of micaceous quartzo-feldspathic rocks.

If true and the studied migmatites indeed originated by a progressive melt infiltration into a single protolith resembling the banded orthogneiss, this until now underappreciated process would have profound implications regarding rheology and chemical development of anatectic regions in collisional orogens.     

The Yenice–Gönen active fault (NW Turkey): Active tectonics and palaeoseismology

The Yenice–Gönen Fault (YGF) is one of the most important active tectonic structures in the Biga peninsula. On March 18, 1953, a destructive earthquake (M_w = 7.2) occurred on the YGF, which is considered to be a part of the southern branch of the North Anatolian Fault Zone (NAFZ). A 70 km-long dextral surface rupture formed during the Yenice–Gönen Earthquake (YGE).In this study, structural and palaeoseismological features of the YGF have been investigated. The YGF surface ruptures have been mapped and three trenches were excavated at Muratlar, Karaköy and Seyvan sites.According to the palaeoseismic interpretation and the results of ¹⁴C AMS dating, Seyvan trench shows that an earthquake of palaeoseismic age ca. 620 AD ruptured a different strand of the 1953 fault, producing rather significant surface rupture displacement, while there are indications that at least two older events occurred during the past millennia. Another set of trenches excavated near Gönen town (Muratlar village) revealed extensive liquefaction not only during the 1953 event, but also during a previous earthquake, dated at 1440 AD. The Karaköy trench shows no indications of recent reactivations.Based on the trenching results, we estimate a recurrence interval of 660 ± 160 years for large morphogenic earthquakes, creating linear surface ruptures. The maximum reported displacement during the 1953 earthquake was 4.2 m. Taking into account the palaeoseismologically determined earthquake recurrence interval and maximum displacement, slip-rate of the YGF has been calculated to be 6.3 mm/a, which is consistent with present-day velocities determined by GPS measurements. According to the geological investigations, cumulative displacement of the YGF is 2.3 km. This palaeoseismological study contributes to model the behaviour of large seismogenic faults in the Biga Peninsula.     

Land use land cover classification of Orissa using multi-temporal IRS-P6 awifs data: A decision tree approach

An attempt has been made to understand the potential of temporal Advanced Wide Field Sensor (AWiFS) data aboard IRS-P6 (Resourcesat) to generate the land use land cover information along with the net sown area. The temporal data sets were georeferenced, converted to top of atmosphere reflectance and classified using decision tree classifier, See5. Results indicate that the temporal data set could give a better definition of training sites thereby resulting in good overall kappa (kappa = 0.8651) as well as individual classification accuracies. However, co-registration of temporal datasets accuracies also has got a significant influence on the classification accuracy. Temporal variation in cloud infestation and availability of appropriate data sets within the season (before harvest of the crop) has also affected the classification accuracy.