Automatic reconstruction of surge deposit thicknesses. Applications to some Italian volcanoes

The energy cone concept has been adopted to describe some kinds of surge deposits. The energy cone parameters (height and slope) are evaluated through a regression technique which utilizes deposit thicknesses and the correspondent quotes and heights of the energy cone. The regression also allows to evaluate a coefficient of proportionality linking the deposit thickness to the distance between topographic surface and energy line for a given eruption. Moreover, if an accurate topography is available (in this case a reconstruction of a digitalized topography of the Phlegrean Fields and of the Vesuvius), the energy cone parameters, obtained by the backfitted technique, can be used to evaluate the order of magnitude of the deposit volumes.The hazard map for a surge localized at the Solfatara (Phlegraean Fields, Naples) has been computed. The values of the energy cone parameters and the volume have been assumed to be equal to those estimated with the regression technique applied to a past surge eruption in the same area.     

基于多台站的接收函数和重力联合反演确定莫霍面起伏和地壳平均波速比

地壳厚度和波速比是研究地壳结构和组分的两个重要参数,可为区域构造研究提供重要约束。接收函数被广泛地用于确定地壳厚度和波速比,例如H-κ方法或H-κ-c方法,但是该方法只能确定台站下方的地壳厚度和速度比,当地震台站分布稀疏时,很难约束台站间的横向不均匀性。另一方面,重力数据也可用于莫霍面的起伏变化研究,它在横向上覆盖很好,有较高的分辨率,但在纵向上分辨率相对较低。为此,本研究提出了一种联合反演算法求解莫霍面深度和地壳波速比参数。联合反演算法综合考虑了接收函数在纵向上的较高分辨率和重力数据在横向上的较高分辨率,同时拟合区域内所有台站上的接收函数和区域重力数据。模型测试表明联合反演算法较单一的接收函数反演更精确,特别是对于地壳厚度的确定。     

东太平洋Juan de Fuca板块的大地电磁研究

本研究做为电磁感应国际合作研究项目—EMSLAB计划的一部分,主要目的在于确定东太平洋年轻的海洋板块——Juan de Fuca板块及其周围地区岩石圈和软流圈的电性结构。 在对海底观测的大地电磁资料定性和定量分析的基础上,进行了二维数学模拟。在二维模型中,海洋地形和已知的表层构造被确定。通过改变模型的重要参数,评价响应函数和观测资料之间偏差的增加,检验模型的可靠性。结果表明,Juan de Fuca板块深部存在两个导电层,一个在40km,另一个在200km左右。这里岩石圈比其它较老板块的岩石圈薄     

Effects of vertical irregularity and thickness of unreinforced masonry infill on the robustness of RC framed buildings

Presence of irregularities in reinforced concrete (RC) buildings increases seismic vulnerability. During severe seismic shaking, such buildings may suffer disproportionate damage or even collapse that can be minimized by increasing robustness. Robustness is a desirable property of structural systems that can mitigate susceptible buildings to disproportionate collapse. In this paper, the effects of vertical irregularity and thickness of unreinforced masonry infill on the robustness of a six‐story three‐bay RC frame are quantified. Nonlinear static analysis of the frame is performed, and parametric study is undertaken by considering two parameters: absence of masonry infill at different floors (i.e., vertical irregularities) and infill thickness. Robustness has been quantified in terms of stiffness, base shear, ductility, and energy dissipation capacity of the frame. It was observed that the infill thickness and vertical irregularity have significant influence on the response of RC frame. The response surface method is used to develop a predictive equation for robustness as a function of the two parameters. The predictive equation is validated further using 12 randomly selected computer simulations. Copyright © 2013 John Wiley & Sons, Ltd.     

An Integrated Hydrochemical Approach to Deduce the Response of an Aquifer System During Its History of Abstraction

The investigation of the regional flow characteristics of aquifers is important with respect to aquifer management. To determine regional flows, use can be made of hydraulic and hydrochemical data. In a study of a Chalk Aquifer System in the south of Lincolnshire, England, a combined hydrochemical approach using major, minor and isotope chemistry is described. The chemical data have been used because hydraulic information is difficult to interpret both locally and regionally as a consequence of multi-layered hydraulic zones, nonhomogeneous fissure zones, and variable erosional features. By characterizing ground-water types on the basis of major ion chemistry, and subsequently interrelating with minor ion distributions (notably iodide supported by strontium), a reasonable assessment of operative flow paths and mechanisms has been made. Substantiation of the conclusions reached using major and minor ion chemistry is provided by the environmental isotope data of carbon and tritium.     

海域天然气水合物的地震研究进展

海域天然气水合物的地震研究是在岩石物性分析成果的指导下,用地震技术进行真假BSR的识别和含水合物沉积层物性预测.海域天然气水合物地震研究的进展主要表现在：物性分析理论模型由简单模型发展到最大程度模拟实际情况的复杂模型;地震勘探方法已由常规的单道、多道地震发展到多频地震、高分辨率二维、三维地震和海底多分量地震;地震资料处理由常规处理发展到突出BSR特征的“三高”和叠前时间偏移处理;从利用速度、振幅结构研究识别天然气水合物发展到AVO、多属性判别、多弹性参数和多物性参数反演识别天然气水合物、预测其物性参数.这些新技术、新方法的应用,加快了海域天然气水合物调查进度,提高了天然气水合物地球物理识别的可靠性.     

Groundwater modelling to quantify the effect of water harvesting structures in Wagarwadi watershed,Parbhani district,Maharashtra, India

Marathwada Agricultural University, Pharbani, has developed about 560 hectares of Wagarwadi watershed in Pharbani district since 1987. Groundwater monitoring on 16 observations wells at weekly intervals commenced in January 1992, and rainfall and pan evaporation has been measured daily at a hydrometeorological station situated in the nearby university campus. Aquifer parameters, namely, transmissivity and specific yield, have been estimated by carrying out a pumping test on a large diameter well. Groundwater recharge resulting from rainfall has been estimated using a water balance model of the soil moisture zone considering soil zone thickness and crops grown. The SCS (Soil Conservation Service) curve number method was used for surface runoff estimation. The groundwater flow model has been constructed using the nested squares, finite difference method. Nested square meshes of sizes 160 m×160 m and 80 m×80 m have been used and the steady-state condition of aquifer system was simulated in the model assuming the June 1992 water level configuration under equilibrium conditions. The model has been calibrated for transient conditions incorporating additional seepage from the water harvesting structures and their contribution to the groundwater regime has been assessed. © 1998 John Wiley & Sons, Ltd.     

Rayleigh波勘探中“之”字形频散曲线“起跳点”频率研究

当层状介质中存在低速层的时候,实际提取到的Rayleigh波频散曲线往往会发生“之”字形回折.已有研究表明,“之”字形回折与各模式的激发能量有关.特别的,“之”字形回折的“起跳点”(发生“之”字形回折的点)与介质参数有一定关系,因此在应用中它反映了介质的一些特征.但是,这一关系是怎样的还没有人进行详细研究.本文计算了三...     

Geophysical investigation of the Sandalp rock avalanche deposits

In the study of rock avalanche phenomena, numerical modelling makes use of back analyses of the rock avalanche propagation for calibration of the modelling assumptions and parameters. The back analyses require knowledge of the run-out area boundaries and the thickness distribution of the deposit. Geophysical methods can be applied to retrieve the thickness distribution, but, due to strong heterogeneities and logistic problems they are seldom applied. The aim of this work is to assess the potential of integrated geophysical methods to recognise and characterise a deposit created by two rock avalanches which occurred in the Sandalp valley (Switzerland) in 1996. The topography of the site before and after the rock avalanche is known and can be used as a benchmark. Resistivity tomography, seismic P-wave tomography, and active and passive surface wave analysis have been applied on several profiles deployed both on the rock avalanche deposit and in the surrounding area. Innovative approaches for surface wave analysis based on laterally constrained inversion and multimodal inversion have been applied to the data. A comparison of the results of the geophysical investigations with the topographic benchmark has shown the capability of the geophysical methods to locate the bottom of the deposit in the areas where the contrast with the host sediments properties is significant. In these areas, the deposit has higher resistivities and lower seismic velocities than the underlying materials. In the areas where the deposit is thicker and richer in fine-grained materials the geophysical parameters are not able to discriminate between the rock avalanche deposit and the underlying sediments. As a secondary task, the geophysical methods also allowed the bedrock pattern to be outlined.     

中子照相转换屏的角度响应研究

在定量中子照相散射校正时需要考虑中子转换屏对不同角度入射中子的响应,中子转换屏的角度响应研究在中子照相散射校正中具有很重要的意义。本文在理论上推导中子转换屏的角度响应的解析式,并利用蒙特卡罗程序MCNP5对该解析式进行验证。利用蒙特卡罗方法对中子转换屏角度响应的影响因素进行研究。给出中子转换屏的角度响应与转换屏厚度以及入射中子能量之间的关系,中子转换屏的角度响应随着转换屏的厚度增大而增大,随着入射中子能量的增大而减小,并得到6LiF-ZnS(Ag)转换屏的最佳厚度为0.3mm。      

Road evaluation with ground penetrating radar

This paper provides a status report of the Ground Penetrating Radar (GPR) highway applications based on studies conducted in both Scandinavia and the USA. After several years of research local transportation agencies are now beginning to implement GPR technology for both network and project level surveys. This paper summarizes the principles of operation of both ground-coupled and air-launched GPR systems together with a discussion of both signal processing and data interpretation techniques. In the area of subgrade soil evaluation GPR techniques have been used to nondestructively identify soil type, to estimate the thickness of overburden and to evaluate the compressibility and frost susceptibility of subgrade soil. In road structure surveys, GPR has been used to measure layer thickness, to detect subsurface defects and to evaluate base course quality. In quality control surveys, GPR techniques have been used for thickness measurements, to estimate air void content of asphalt surfaces and to detect mix segregation. Future developments are described where the technique has great potential in assisting pavement engineers with their new pavement designs and in determining the optimal repair strategies for deteriorated roadways.     

南黄海残留盆地宏观分布特征研究

由于前新生代残留盆地具有埋深大、构造复杂的特点,采用综合地球物理研究方法成为圈划残留盆地宏观分布及预测残留盆地油气资源的重要方法技术．本文以南黄海地区为例,以重、磁数据为主体,以钻井、地震等高精度数据为先验信息做约束,采用带约束界面反演方法求取重力基底,同时根据求取的磁性基底计算了中、古生界的残余厚度,给出了前新生界残留盆地宏观分布特征．结合石油地质条件,圈划了油气资源有利区．研究结果表明南黄海北部坳陷北部和东北部中生界残余厚度较大,中部隆起与勿南沙隆起古生界残余厚度巨大,是较好的前新生代油气前景区．     

Elastic waves in nonhomogeneous media under 2D conditions: II. Numerical implementation

The purpose of this work is to present three methods of analysis for elastic waves propagating in two dimensional, elastic nonhomogeneous media. The first step, common to all methods, is a transformation of the governing equations of motion so that derivatives with respect to the material parameters no longer appear in the differential operator. This procedure, however, restricts analysis to a very specific class of nonhomogeneous media, namely those for which Poisson's ratio is equal to 0.25 and the elastic parameters are quadratic functions of position. Subsequently, fundamental solutions are evaluated by: (i) conformal mapping in conjunction with wave decomposition, which in principle allows for both vertical and lateral heterogeneities; (ii) wave decomposition into pseudo-dilatational and pseudo-rotational components, which results in an Euler-type equation for the transformed solution if medium heterogeneity is a function of one coordinate only; and (iii) Fourier transformation followed by a first order differential equation system solution, where the final step involving inverse transformation from the wavenumber domain is accomplished numerically. Finally, in the companion paper numerical examples serve to illustrate the above methodologies and to delineate their range of applicability.     

Arctic sea ice thickness variations from CryoSat-2 satellite altimetry data

Arctic sea ice plays an important role in Earth's climate and environmental system. Sea ice thickness is one of the most important sea ice parameters. Accurately obtaining the sea ice thickness and its changes has great significance to Arctic and global change research. Satellite altimeters can be used to derive long-term and large-scale changes in sea ice thickness. The leads detection is vital in sea ice thickness estimation by using satellite altimetry. Different leads detection methods are compared with remote sensing images, and results show that the detection method that uses waveform parameters can obtain improved results. The model for the conversion of freeboard to thickness is optimized by considering the incomplete penetration of snow for radar altimeters. We derive the estimates of the Arctic sea ice thickness for November 2010 to December 2019 by using the CryoSat-2 altimetry data. The sea ice thickness from the IceBridge and draft data from the upward-looking sonar are used to validate our thickness results. Validations show that the accuracy of our thickness estimates is within 0.2 m. Variations in the Arctic sea ice thickness are analyzed using the PIOMAS model and air and sea surface temperatures. A sharp increase in sea ice thickness is found in 2014.     

An enhanced temperature index model for debris-covered glaciers accounting for thickness effect

Debris-covered glaciers are increasingly studied because it is assumed that debris cover extent and thickness could increase in a warming climate, with more regular rockfalls from the surrounding slopes and more englacial melt-out material. Debris energy-balance models have been developed to account for the melt rate enhancement/reduction due to a thin/thick debris layer, respectively. However, such models require a large amount of input data that are not often available, especially in remote mountain areas such as the Himalaya, and can be difficult to extrapolate. Due to their lower data requirements, empirical models have been used extensively in clean glacier melt modelling. For debris-covered glaciers, however, they generally simplify the debris effect by using a single melt-reduction factor which does not account for the influence of varying debris thickness on melt and prescribe a constant reduction for the entire melt across a glacier.In this paper, we present a new temperature-index model that accounts for debris thickness in the computation of melt rates at the debris-ice interface. The model empirical parameters are optimized at the point scale for varying debris thicknesses against melt rates simulated by a physically-based debris energy balance model. The latter is validated against ablation stake readings and surface temperature measurements. Each parameter is then related to a plausible set of debris thickness values to provide a general and transferable parameterization. We develop the model on Miage Glacier, Italy, and then test its transferability on Haut Glacier d’Arolla, Switzerland.The performance of the new debris temperature-index (DETI) model in simulating the glacier melt rate at the point scale is comparable to the one of the physically based approach, and the definition of model parameters as a function of debris thickness allows the simulation of the nonlinear relationship of melt rate to debris thickness, summarised by the Østrem curve. Its large number of parameters might be a limitation, but we show that the model is transferable in time and space to a second glacier with little loss of performance. We thus suggest that the new DETI model can be included in continuous mass balance models of debris-covered glaciers, because of its limited data requirements. As such, we expect its application to lead to an improvement in simulations of the debris-covered glacier response to climate in comparison with models that simply recalibrate empirical parameters to prescribe a constant across glacier reduction in melt.     

The effectiveness assessment of gas accumulation processes in Kuqa depression,Tarim Basin,Northwest China

The effectiveness of gas accumulation processes is controlled by several main geological factors in-cluding charging force,features of gas conduit,sealing properties of caprock,etc. Based on the analysis and statistics of the large-medium size gas accumulations in China,the main parameters,in-cluding the excess pressure difference between the source rock and reservoir bed,the area coefficient of the gas conduit,and the thickness or displacement pressure of caprock,and the criteria for the as-sessment of gas accumulation processes have been established. Using the parameters and the criteria above,the effectiveness of gas accumulation processes in the Kuqa depression was quantitatively evaluated. By integrating the parameters of the excess pressure difference between the source rock and reservoir bed,the area coefficient of fault conduit system,and the caprock thickness in gas charging period,a comprehensive assessment of the effectiveness of gas accumulation in the Kuqa depression has been made. The result reveals that the Tubei-Dawan area,the Central Kelasu area and the Dongqiu-Dina area are three highly-effective areas for gas accumulation in the Kuqa depression.     

On the vibratory motion of a non-homogeneous cylinder having a periodic shearing force prescribed on the plane end

Summary In this paper the torsional vibrations of a semi-infinite circular cylinder of nonhomogeneous material, when there is a periodic shearing force prescribed on the plane end, has been discussed.     

井中磁源瞬变电磁响应特征研究

井中瞬变电磁波勘探是一个全空间地球物理场问题.采用Gaver-Stehfest逆拉氏变换方法,正演计算了瞬变信号激励下接收线圈上的电磁场响应.分析了包含井眼泥浆、套管、水泥环和地层的轴对称多层介质模型的电磁场响应特征,考察了各层介质参数对井中瞬变电磁响应的影响.不同电导率井眼泥浆的电磁场响应衰减曲线表明,井眼泥浆电导率...     

Travel time residuals in southeastern Europe

The Pn travel time relative residuals, in respect to a crustal model of the Aegean area, have been determined for 103 permanent seismological stations in southeastern Europe, western Turkey and the Middle East. The values of these residuals are considered to depend mainly on the crustal thickness beneath the seismological stations. Based on these values seven regions with different crustal thickness, varying between 31 Km and 42 Km, have been defined. The crust in these regions is continental. A region with very high negative residuals has been defined in the Middle East (Egypt, Israel, Lebanon). These negative residuals are attributed to different crustal structure of the eastern Mediterranean (oceanic crust with an extra thick sedimentary layer) and not the crustal thickness at the station sites.Independently from the interpretation, these Pn residuals can be used successfully to considerably improve (up to 2 Km) the determination of the earthquake foci locations.     

On twisting of a non-homogeneous circular disk,due to a tangential traction of the boundary of a concentric circular hole

Summary In this note, the stresses and displacements due to tangential traction on the inner boundary of a nonhomogeneous annular circular disk, the outer boundary of the disk being kept fixed have been investigated. Some numerical results are given at the end.