Acceleration response spectra for the earthquakes of the southwestern flank of the Baikal Rift Zone

The acceleration response spectra of earthquakes with M = 4–6.5 in the southwestern part of the Baikal Rift Zone have been studied. The absorption properties of the medium and the attenuation of seismic signals in the study area were determined. Average acceleration response spectra were obtained for regional earthquakes. A comparative analysis of the acceleration response spectra was made for earthquake focal mechanisms with different senses of motion: reverse fault, reverse slip, strike slip, and oblique slip. The effect of the sense of fault motion in the seismic source on acceleration response spectra was determined.     

Precambrian Geochronology, Chronotectonic Framework and Model of Chronocrustal Structure of the Zhongtiao Mountains

The Zhongtiao Mountains, a typical exposure area of Precambrian rocks, are a concentration area of vari-ous types of copper deposit. The rocks were dated using several dating methods. Based on the age data ob-tained by means of three methods, several aspects are dealt with: (1) the dating results obtained by differentmethods and their geological implications have been compared; (2) a chronotectonic framework has been con-structed by means of these reliable ages, which indicates that the ages of the rocks of the Proterozoic mobilebelt fall in a time span of 2400 to 2000 Ma during which global magmatic records are lacking and reflects theages of important events in the mobile belt; (3) according to the ages of inherited zircons, neodymium modelage of the depleted mantle sources (T_(DM)) and geochemical and geological data, a model of Precambrianchronocrustal structure has been constructed, representing a typical for the North China craton.     

Fractal and Multifractal Modeling of Hydrothermal Mineral Deposit Spectrum： Application to Gold Deposits in Abitibi Area, Ontario, Canada

A number of fractal/multifractal methods are introduced for quantifying the mineral de-lmsit spectrum which include a number-size, grade-tonnage model, power spectrmn model,multi-fractal model and an eigeavalue spectrmn model The first two models characterize mineral deposits spec-tra based on relationships among the measures of mineral deposits.These include the number of deposits,size of deposits,concentration and volume of mineral deposits.The last three methods that deal with the spatial-temporal spectra of mineral deposit studies are all expected to be popularized in near future.A case study of hydrothermal gold deposits from the Abitibi area,a world-class mineral district is used to demonstrate the principle as well as the applications of methods proposed in this paper,It has been shown that fractal and multifractal models are generally applicable to modeling of mineral deposits and occurrences.Clusters of mineral deposits were identified by several methods including the power spectral eral deposits in the Timmins and Kirkland Lake camps.     

Selection of the most appropriate method to determine the carbonate content for engineering purposes with particular regard to marls

Because of the influence of carbonates on the geotechnical properties of foundation and construction materials in civil engineering, a simple, precise, and inexpensive method of determining soil-carbonate content is needed. A large number of methods exist to determine the carbonate content in soils; but, for diverse reasons (precision (accuracy), cost, sensitivity, etc.) not all are appropriate in a civil-engineering laboratory. In the present work, different laboratory methods to determine the carbonate content in soils have been compared in order to choose the most appropriate one. The most suitable method has been selected on the basis of a number of general criteria: precision (accuracy), equipment cost, operating and maintenance costs, staff requirements, and sensitivity of the equipment. According to these general criteria, three methods can be considered suitable: flame photometry, volumetric calcimeter, and EDTA complexometry. These three methods present errors of less than 5%, involve low to medium cost, and the maintenance operations are simple. In addition, a suitability index has been defined (depending on three specific criteria: degree of precision (accuracy), level of standardization, and suitability of the operation method and type of ion analysed) which enabled the selection of the most appropriate from among the three methods. For the study, marl samples were taken from quarries used to construct the impermeable cores of three dams in the upper Guadalquivir River Basin (S Spain), as well as Standard samples were made with pure and inert calcium carbonate. Finally, it is concluded that the volumetric method (Bernard calcimeter) is the overall best technique to determine the carbonate content in civil-engineering laboratories.     

Geo-Characterization at selected accelerometric stations in Crete (Greece) and comparison of earthquake data recordings with EC8 elastic spectra

To estimate the seismic response according to Eurocode (EC8) and almost all other national codes, site conditions have to be properly characterized so that soil amplification and the corresponding peak ground motion can be calculated. In this work, different geophysical and geotechnical methods are combined in order to define the detailed ground conditions in selected sites of the Hellenic Accelerometric Network (HAN) in Crete. For this purpose, the geological information of the sites and shear wave velocity, calculated from surface wave measurements, is used. Additionally, ground acceleration data recorded through HAN have been utilized from intermediate depth earthquakes in the broader area of South Aegean Sea. Using the recorded ground motion data and the procedure defined in EC8, the corresponding elastic response spectrum is calculated for the selected sites. The resulting information is compared to the values defined in the corresponding EC8 spectrum for the seismic zone that includes the island of Crete. The comparison shows that accurate definition of ground type through geological, geotechnical and geophysical investigations is important. However, our current comparison focuses on the distribution of values rather than the absolute values of EC8-prescribed spectra, and the results should be considered in this context.     

Site-Specific Analysis of Strong Motion Data from the September 7, 1999 Athens,Greece Earthquake

The strong ground motion from Athens, Greece 07/09/1999 earthquake has been recorded by eighteen (18) stations, fourteen (14) within the central Athens area and four (4) at the centers of nearby towns. The ground conditions for most of the recording sites were identified, based on previous geotechnical investigations carried out in the wider area of the sites, and consequently correlated to the seismic motion characteristics. Hence, it has been possible to evaluate the accuracy of different seismological methods for site characterization and also estimate soil effects on peak ground acceleration and elastic response spectra. In addition, preliminary estimates are drawn for the seismic motion characteristics at the epicentral area, where no strong motion recordings are available. The detailed soil profiles at the recordingsites are placed in the Appendix.     

Local Site Effect Due to Past Earthquakes in Kolkata

Kolkata, capital of West Bengal, India, presently congested with moderate to high rise buildings, has undergone low to moderate damages due to past earthquakes. The city is situated on the world’s largest delta island with soft thick alluvial soil layer. In this study, an attempt has been made to study ground response due to a number of past earthquakes, 1897 Shillong earthquake, 1964 Calcutta earthquake and 2011 Sikkim earthquake, for the purpose of preliminary microzonation of the Kolkata city. For this, synthetic ground motions have been generated at bedrock level by stochastic method. By using 1D wave propagation technique, the synthetic ground motion has been computed at surface level for 144 borehole locations in the city. Contours of PGA, PGV and PGD parameters in the city have been drawn for these three earthquakes. Response spectra for these three earthquakes have also been computed and an optimum response spectrum has been determined. A good correlation has been obtained with predicted ground motion at surface level of the city with the reported intensity and damages occurred in buildings of Kolkata during past earthquakes. The scenario of simulated ground motion for the past three earthquakes depicts that Kolkata city is very much prone to damages even due to moderate far and near source earthquakes.     

A comparative study on linear and nonlinear site response analysis

Site response analysis is usually the first step of any seismic soil-structure study. Geotechnical earthquake engineers and engineering geologist have been trying to find both practical and most appropriate solution techniques for ground response analysis under earthquake loadings. The paper attempts to give a critical overview of the field of site response analysis. In this paper, the influences of nonlinearity on the site response analysis summarized and were evaluated with a numerical example. Site response of a two layered soil deposit with the assumption of linear and rigid base bedrock (or viscoelastic half-space) was analyzed by using linear and nonlinear approaches. The amplification spectrum of the soil column is computed between the top and the bottom of this soil deposit. Nonlinear analysis was compared with the linear method of analysis. Steps involved in ground response analyses to develop site-specific response spectra at a soil site are briefly summarized. Some of the well-known site response analysis methods are summarized and similarities and differences between linear and nonlinear methods are compared by a numerical example.     

Multi-scale rock surface area quantification—a systematic method to evaluate the reactive surface area of rocks

An integration of methods to quantify the surface area of porous solid materials with a broad span of spatial resolution is presented. The application of it is to detect and quantify the rock surface area modifications caused by fluid-rock interactions on different scales from several nanometres to metres. The new approach is to study the fluid-accessible surface area of rock fragments during dissolution processes.In this paper, diverse methods for surface quantification at different levels of surface detail were adapted for the application of rock surface quantification and porosimetry measurements. The geometric external surface area of rock fragments can be determined by paraffin wax coating and, in special cases, by parallelepiped surface estimations. This geometrical surface area of rock polyhedrons is equal to the macroscopic bounding surface area of a rock volume. Representative surface details on the scale of micrometres to millimetres on geometrical surface area can be quantified by mechanical roughness analyses. The resultant roughness factors are compared to optical roughness quantifications by confocal laser scanning microscopy and white light interferometry and can indicate modifications of the pore space up to several hundred nanometres. The comparison of rock pore space data, measured by both mercury intrusion porosimetry and nitrogen adsorption, quantifies the surface area of pores with a diameter of approximately 2 nm.These various surface data at different levels of detail were integrated to get an estimation of this surface area, which affects fluid-rock interactions. The proposed concept has the potential to trace the multi-scale rock surface area evolution in response to fluid-rock interaction processes.The importance of this concept is its application beyond the laboratory survey. For example, additionally to their specific surface area, the reactive surface area of rock particles in a mining dump is controlled by geometrical size and surface roughness of particles.     

Evaluating the seismic hazard to the National Capital (Delhi) Region,India, from moderate earthquakes using simulated accelerograms

The National Capital Region (NCR) of India is exposed to high seismic hazard and risk due to a great earthquake in the central seismic gap of Himalaya and/or due to moderate-size earthquake within NCR. The high population density, rapid growth of infrastructure, and old engineering structures in the region make it more vulnerable to the human as well as economic loss due to moderate-size earthquakes also. The evaluation of seismic hazard is the first step to prepare a proper mitigation plan for the region. The aim of this paper is to evaluate the seismic hazard and risk due to moderate-size earthquakes in the vicinity of NCR. For this purpose, a suit of accelerograms have been generated from hypothetical moderate-size earthquakes (M 5.5 and 6.0) in the region. A basic fault-plane solution is assumed for this purpose. The ranges of the different parameters like depth of focus and stress drop values have been used in order to examine the effect of these parameters on hazard. The accelerograms have been synthesized using two basic velocity models, one representing a hard site and the other a site with a significant low-velocity cover. These two velocity models represent the ridge area and trans-Yamuna river area in the NCR. The decay of peak ground acceleration (pga) values with distance is fast in trans-Yamuna region (with low-velocity surface layer of 100 m) as compared to that of ridge area (with low-velocity surface layer of 1 m). Also, the decay of pga becomes slower if we increase the depth of focus from 10 to 20 km. The response spectra (5% damping) of the synthetic accelerograms for the three periods T = 0.4s, 0.75s, and 1.25s have been estimated and presented in the form of decay curves. The amplifications as a function of epicentral distance and stress drop have also been estimated. We note that the amplifications in 100-m layer case do not occur uniformly at all the distances, rather it is dependent on the angle of incidence of energy into the layers. The pga values are generally amplified by more than twice with increase in stress drop from 100 to 400 bars. The seismic exposure of the population in Delhi city has been presented. The results presented in this study may serve as an important input in the planning of mitigation and disaster management programs in the National Capital Region.     

分形理论识别粤北澄江地区铀矿潜力评价中的异常

以粤北澄江地区地面γ能谱测量、土壤Rn测量及分量化探测量数据为基础,应用分形理论研究三种(放射性)物化探方法所测数据的异常下限,并与传统方法所求的异常下限对比。研究表明,分形理论能更好地反应异常分布和富集的规律。分析三种(放射性)物化探方法的异常特征,推测了该区可能存在4条(隐伏)断裂构造,预测了可能的赋矿部位,为该区进一步的铀矿找矿工作提供了依据和建议。     

An attempt to reconstruct some features of the May 6, 1976, Friuli earthquake by means of aftershocks

The goal of the present work is to reconstruct some features of the May 6, 1976, Friuli earthquake in different sites of the area involved. The starting data for the elaboration are: seismograms of aftershocks at various sites; very detailed geological knowledge of the sites; accelerographs of the main shocks at Tolmezzo. Only aftershocks having magnitudes 2.5–4 and epicentres located within the most damaged area were considered. Fourier and response spectra for the events considered at the sites were computed. The problem is to establish the differences between, on the one hand, the Fourier and response spectra of the main shock, and on the other hand the aftershocks. Since one of these sites (Peonis) has about the same conditions (topography, geology, epicentral distance for the May 6 shock) as Tolmezzo, similarity in shaking and the shape of the spectra were assumed at the two sites for the main shock. On the basis of the known mean spectral ratios (computed on the aftershocks) between Peonis and the other sites, and the same ratio between the main shock and the aftershocks at Peonis, the spectral features of the May 6 shock at all the other sites were computed.     

Ground-Space Correlation of TM Data and Its Application to the Prediction of Gold Deposits

It has been inferred and proved by the remote sensing equations under rational hypotheses in atmospheric physics that there is a linear correlation between the ground reflective brightness Wij and the total reflective brightness Rij received in different bands with a remote sensor. Nine models delineating the ground-space correlation between the ground spectra and the optimal bands of images of the typical gold deposits have been established based on the ground-space correlativity and field measurements of the ground spectra of the typical gold deposits in the Ailaoshan area. According to the 9 correlation models, TM images were inverted into ground-space correlation images that are related to the typical gold deposits within the area and then recognized by a computer. Research on the ground . spectra and TM data in the Ailaoshan area shows that the correlation analysis of the ground spectra and TM data of gold deposits can be effectively applied to the prediction of gold deposits, location of prospecti     

Direct measurement of U-238 and disequilibrium state in geological samples by low energy scintillation gamma spectroscopy

A method has been developed to determine the state of disequilibrium and uranium content in geological samples using low energy gamma scintillation spectrometry. Ore standards in radioactive equilibrium were prepared in different concentrations and their low energy spectra were compared with those of chemical uranium standards of the same concentrations. The standards were analysed carefully for their U contents using X-ray fluorescence and high resolution gamma spectrometers. Counts of the complex peak under which 63 keV and 93 keV photopeaks take place in ore spectra were compared with the counts in corresponding channels of chemical uranium spectra. For standards in equilibrium it was found that (26 ± 2)% of the counts under complex peak came from Th-234 and also there was a constant relation between Th-234 (63 keV and 93 keV) and Pb-210 (47 keV) counts. The technique was applied to the geological samples for which eU concentrations had been measured previously by means of high energy gamma spectroscopy in the same laboratory.     

Evaluation and comparison of GIS based landslide susceptibility mapping procedures in Kulekhani watershed, Nepal

The goal of this paper is to evaluate and compare the consistency of GIS-based heuristic and bivariate landslide susceptibility mapping techniques in the Himalayan region, taking the Kulekhani watershed of central Nepal as an example. For this purpose, a heuristic and two statistical bivariate landslide susceptibility mapping methods are applied, and three separate landslide susceptibility zonation maps are produced. The maps are compared using three approaches: landslide density analysis, success rate analysis, and agreed area analysis. A comparison of the values obtained from landslide density analysis and the curves of success rate analysis indicate that the two bivariate methods produce almost identical results, whereas the map produced with the heuristic method differs significantly from the others. On the other hand, the agreed area analysis highlights significant spatial differences in the maps obtained from the three methods. Although the three approaches evaluate the consistency of susceptibility maps, only the agreed area analysis is capable of spatially comparing them. Hence, this approach proves to be more suitable for spatially and quantitatively evaluating the consistency of various landslide susceptibility zonation maps.     

Site amplification investigation in Dhaka, Bangladesh, using H/V ratio of microtremor

The degree of damage during earthquakes strongly depends on dynamic characteristics of buildings as well as amplification of seismic waves in soils. Among the other approaches, microtremor is, perhaps, the easiest and cheapest way to understand the dynamic characteristics of soil. Non-reference microtremor measurements have been carried out in 45 locations in and around the capital Dhaka city of Bangladesh. Subsoil investigations (Standard Penetration Test and Shear Wave Velocity) have also been executed in those locations. Soil model has been developed for those locations for site response analysis by means of the program SHAKE. Among those 45 locations, predominant frequency of microtremor observation varies from 0.48 to 3.65 Hz. Out of those 45, for 35 locations Transfer function obtained from the program SHAKE have higher frequency compared to microtremor H/V ratio and for one location it has lower predominant frequency. For six locations, frequencies obtained from two methods are identical. For three other locations, there are no similarities between predominant frequency obtained from microtremor and transfer function. The seismic Vulnerability Index (Kg) for 45 sites varies between 0.45 and 31.85. Ten sites have been identified as having moderate vulnerability of soil layers to deform.     

一维土层非线性地震反应分析的解析递推格式法

引入“结构动力学数值分析解析递推格式法”求解软土地基地震反应分析问题。就一维地基非线性地震反应分析问题,将解析递推格式方法与等效线性化方法在各种场地土的计算结果进行了比较,结果表明：(1) 对软土层地震反应分析时,两种方法计算结果差别较大; （2）入射波幅值较强时,两种方法计算结果差别较大;（3）对于中等硬度土层、入射波幅值较弱时,计算结果相似, 并验证了该方法的实用有效性。     

Distribution of Fe in the octahedral sheet of trioctahedral micas by polarized EXAFS

The distribution of Fe atoms within the octahedral sheet of a series of trioctahedral micas has been investigated by polarized Fe K-edge EXAFS spectroscopy. Single crystals have been oriented in the X-ray beam with the layer plane at 35° with respect to the electric field vector. At this “magic angle”, contributions to the EXAFS spectrum of nearest cation shells are equal to those recorded on a completely disoriented powder. The average number of Fe and Mg cations surrounding each Fe atom has been determined and compared with those deduced from NMR spectra. It is shown that the distribution of Fe atoms is not random, the deviation from this distribution depending on the fluorine content. The agreement between these independent results proves the reliability of the structural information deduced from EXAFS and NMR spectra as well as the usefulness of these two methods in analyzing the local distribution of cations in minerals.     

Differential single-frequency GPS monitoring of the La Valette landslide (French Alps)

Recently, Global Positioning System (GPS) surveying techniques have been increasingly employed to monitor landslide movement. Here we present an application of GPS to monitor the La Valette landslide, located in the Ubaye Valley in the southern French Alps. This complex landslide is composed by an upper rotational part, a central part with generally translational movement and a lower part, which occasionally transforms into mud flows during intense rainfall events. Displacement rates average a few centimeters per month, with velocity peaks of some centimeters per day during periods of strong activity. GPS data presented in this study were acquired with two single-frequency GPS receivers Magellan connected to multipath-resistant antennas. The data were processed with the Magellan software MSTAR. Nine points have been set in the studied area, seven of them in the moving area, one in a stable area near the landslide and one on the facing slope, which is used as reference point. For each observation, one GPS receiver is placed on the reference point for the whole day and the second one is placed on each monitored point for 1-h sessions. The distance between the base and monitored point ranges from 480 to 1660 m. Eight survey campaigns were made between October 2000 and October 2002, to follow the evolution of the surface displacements. The maximum cumulative 3-D displacement observed in the area was about 21 m during the period in the center part of the landslide, corresponding to an average rate of movement of about 3 cm/day. The accuracy achieved during the GPS measurements has been evaluated to be about 2.4 cm in E–W direction, about 11 cm in N–S direction and about 7.4 cm in elevation in the worst case. The GPS results have been compared with traditional surveying techniques (EDM) carried out on the same site by RTM Service (Restauration des Terrains en Montagne). The velocities obtained by the two methods are similar. The advantage of the GPS technique is the collection of data for the three spatial coordinates (x, y, z) of each point, which allow to calculate the 3-D displacement vector. These measurements have been combined with SAR interferometric data in order to analyse the temporal evolution of the different landslide sectors.