Geophysical investigations of the Platanares geothermal site, Honduras, Central America

Geophysical studies were carried out in Platanares in Western Honduras, as part of an investigation of the geothermal resource potential of Honduras by Los Alamos National Laboratory in cooperation with the Honduran government and the U.S. Geological Survey. Geological and geochemical studies later followed by exploratory bore-holes indicate this area of rugged topography has the best geothermal potential in Honduras. In order to better understand the geology of the area, gravity, audiomagnetotelluric and telluric surveys were carried out. The site is in a graben of Tertiary volcanics and Cretaceous red beds, with numerous hot springs along faults in the center of the graben. Gravity mapped the thickness of low-density tuffs and the position of associated normal faults. It also indicated the presence of persuasive, shallow, highly silicified, high-density tuffs and gravels. The electrical surveys mapped shallow, high-resistivity silicified zones and faults as low-resistivity zones. The red beds below the tuffs are considered to contain the geothermal reservoir, but their maximum thickness could not be determined by these surveys due to the lack of density contrast and the high surface electrical conductivities. Three geologic cross-sections constructed by others have been re-evaluated using gravity modeling and analysis of eletrical anomalies, showing general agreement but in detail significant differences.     

Geophysical investigations of the plumbing system of Stromboli volcano (Aeolian Islands,Italy)

In this work, we report the results of an integrated approach using both seismological and geodetic data provided by the INGV-CT (Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Catania) Stromboli volcano monitoring systems, in order to improve the knowledge of its plumbing system. In particular, we investigated the relationships between the June 1999 seismic swarm, occurring in the area of Stromboli, and the possible activation of the NE–SW oriented volcano-tectonic structure. We analyzed this seismic swarm proposing new locations and a morphological analysis of the waveforms. This approach allowed us to demonstrate that there are relationships between the tectonic activity near Stromboli and the rising of magma. This evidence supports the hypothesis that during the 1999 swarm an intrusive process started from a crustal level where earthquakes were located (about 10–15 km b.s.l.).     

Cladocere remains in recent sediments as indices of cultural eutrophication of Lake Como

Cladocera remains, organic matter, nitrogen, chlorophyll derivatives have been examined in the sediments to follow the trophic evolution of Lake Como. Trophic levels result to be increased in these last ten years in the four basins considered;Bosmina remains register recent and significant increases everywhere, whileSida, Acroperus, Daphnia andChydorus seem to disappear or on the strong decrease at present in the southern basins, more subject to the human pressure. Correlation coefficients are highly significant among organic matter, nitrogen, chlorophyll derivatives and Cladocera remains, giving stronger evidence for the strict interdependence among nutrients, producers and consumers.     

Paleomagnetic studies of Paleolithic site deposits in the Matzuka Cave (Northern Caucasus)

As a result of detailed paleomagnetic and magnetic studies of Paleolithic site deposits in the Matuzka Cave, a record of the Matuzka geomagnetic excursion in lithologic layer 7 has been discovered and studied. Such characteristic features as the geomagnetic field direction, position of the virtual geomagnetic pole, geomagnetic field intensity (roughly estimated) after and during the excursion, and climatic conditions coeval with its existence make the Matuzka excursion similar to the ～130-ka Blake excursion. This dates at ～130 ka the formation of layer 7 with ancient archaeological findings.     

Scientific investigations by the Polar Geophysical Institute on the Spitsbergen archipelago

In October 2010, it will be 50 years since the founding of the Polar Geophysical Institute of the Kola Science Center, Russian Academy of Sciences. The paper covers the scientific investigations conducted by the Polar Geophysical Institute on the Spitsbergen archipelago. Brief information is given regarding both the history and the current stage of investigations by the Academy of Sciences on Spitsbergen. The experimental equipment installed at the Barentsburg Observatory of the Polar Geophysical Institute is described. The scientific problems that the Polar Geophysical Institute is solving in this region are discussed.     

Non-invasive Geophysical Surveys in Search of the Roman Temple of Augustus Under the Cathedral of Tarragona (Catalonia,Spain): A Case Study

An integrated geophysical survey has been conducted at the Tarragona’s Cathedral (Catalonia, NE Spain) with the aim to confirm the potential occurrence of archaeological remains of the Roman Temple dedicated to the Emperor Augustus. Many hypotheses have been proposed about its possible location, the last ones regarding the inner part of the Cathedral, which is one of the most renowned temples of Spain (twelfth century) evolving from Romanesque to Gothic styles. A geophysical project including electrical resistivity tomography (ERT) and ground probing radar (GPR) was planned over 1 year considering the administrative and logistic difficulties of such a project inside a cathedral of religious veneration. Finally, both ERT and GPR have been conducted during a week of intensive overnight surveys that provided detailed information on subsurface existing structures. The ERT method has been applied using different techniques and arrays, ranging from standard Wenner–Schlumberger 2D sections to full 3D electrical imaging with the advanced Maximum Yield Grid array. Electrical resistivity data were recorded extensively, making available many thousands of apparent resistivity data to obtain a complete 3D image after a full inversion. In conclusion, some significant buried structures have been revealed providing conclusive information for archaeologists. GPR results provided additional information about shallowest structures. The geophysical results were clear enough to persuade religious authorities and archaeologists to conduct selected excavations in the most promising areas that confirmed the interpretation of geophysical data. In conclusion, the significant buried structures revealed by geophysical methods under the cathedral were confirmed by archaeological digging as the basement of the impressive Roman Temple that headed the Provincial Forum of Tarraco, seat of the Concilium of Hispania Citerior Province.     

Geophysical and Hydrologic Studies of Lake Seepage Variability

Variations in lake seepage were studied along a 130 m shoreline of Mirror Lake NH. Seepage was downward from the lake to groundwater; rates measured from 28 seepage meters varied from 0 to ?282 cm/d. Causes of this variation were investigated using electrical resistivity surveys and lakebed sediment characterization. Two‐dimensional (2D) resistivity surveys showed a transition in lakebed sediments from outwash to till that correlated with high‐ and low‐seepage zones, respectively. However, the 2D survey was not able to predict smaller scale variations within these facies. In the outwash, fast seepage was associated with permeability variations in a thin (2 cm) layer of sediments at the top of the lakebed. In the till, where seepage was slower than that in the outwash, a three‐dimensional resistivity survey mapped a point of high seepage associated with heterogeneity (lower resistivity and likely higher permeability). Points of focused flow across the sediment–water interface are difficult to detect and can transmit a large percentage of total exchange. Using a series of electrical resistivity geophysical methods in combination with hydrologic data to locate heterogeneities that affect seepage rates can help guide seepage meter placement. Improving our understanding of the causes and types of heterogeneity in lake seepage will provide better data for lake budgets and prediction of mass transfer of solutes or contaminants between lakes and groundwater.     

Magnetic and mineralogical characteristics of rocks at the Mezmaiskaya cave Paleolithic site (Northern Caucasus)

The results of magnetic and microprobe studies of the rock sequences in the Mezmaiskaya cave at the unique multilayer Paleolithic site are discussed. The magnetic properties of rocks are analyzed for 17 layers (upwards from layer 4 to layer 1\1) dated from over 73 ka ago to recent times. The rocks of layer 1C (Early Upper Paleolithic, ∼38 ka) are found to have the highest magnetic susceptibility (K) (up to 2500 × 10⁻⁶ SI), which is related to the intensive activity of [Homo sapiens]. The minimum K corresponds to the rocks of layer 2, which is overlain by layer 1D. The sizes of magnetic grains vary throughout the rock section. The largest grains are found in the middle part of the section in the Middle Paleolithic layers 2B3, 2B2, 2B1, 2A, and 2. The superparamagnetic fraction is identified in all layers. This fact supports the view that the cave was open as early as the formation of layer 4. According to the thermomagnetic data on the saturation magnetization and the temperature curves of magnetic susceptibility, magnetite is the main carrier of the rock magnetization; some samples contain iron hydroxides. Samples with iron sulfides (pyrite) are abundant. The study of the hysteresis parameters of rocks showed that the question on whether sulfide-bearing rocks are suitable for reliable paleomagnetic determinations requires further laboratory research into the origin of magnetite in the rocks. The chemical composition of rocks composing layer 2B3 and layers 1D (∼39 ka) and 2B1 (∼45 ka), in which the presence of volcanic ash has been previously established according to the presence of volcanic glass, was determined by detailed microprobe analysis. A wide variety of chemical elements (up to 18 items) was recognized in layers 1D and 2B1. The iron, titan, chrome, manganese content, and concentrations of other components vary from grain to grain. The microprobe analysis of samples from layers 1D and 2B1 revealed a set of magnetic particles with compositions characteristic of volcanic rocks, which supports the ash origin of these layers. Layer 2B3 is established not to be volcanic ash. The results on the volcanic glass in the rocks of layers 1D and 2B1 were published by Golovanova and her colleagues in Current Anthropology in October 2010 [Golovanova et al., 2010].     

南黄海北部构造演化的地球物理认识

南黄海北部坳陷是研究中朝板块和下扬子板块在海区碰撞效应,以及古、中、新生代沉积盆地的地质构造特征和油气资源前景的重点地区.该海域虽经历了40多年的调查与研究,未获得油气的重大突破,与早年调查研究方法的单一、技术手段的落后和对基础地质构造认识不清、勘探思路的偏颇有关.近十年来,通过对新的地球物理资料及已有钻井的综合分析和...     

湖泊沉积物中元素相态的连续提取分析—以岱海为例

如何利用湖泊/海洋沉积物地球化学代用指标有效地指示环境很大程度取决于元素的来源及其在沉积物中赋存形态的确定.对位于半干旱区的内蒙古岱海14个沉积物样品的连续提取实验及18个元素在水可溶态、可交换态、碳酸盐结合态、铁锰氧化物结合态、有机物结合态及残留态等六种赋存相态中含量变化进行了测试和研究,结合沉积物的矿物组成,结果表明在岱海流域内只经历了较弱的化学风化过程,除了Ca和Sr外,其他元素主要赋存于残留态中,只发生了很小程度的活化溶解.受元素亲合性和湖水物理化学状态的制约,出溶的Sr与Ca的赋存相态基本一致,而出溶的Pb、Be、Co、Cu、K、Mn、Fe等元素则与自生碳酸盐、有机质表现出一定的亲合性.元素在不同赋存相态中分布为地球化学环境代用指标的提取和解释提供了机理性的实验依据.     

International Geophysical Calendar1997(Final)

（Seothersideforinfoffllationonuseofthiseqlendar）NOreSonotherdates回ndmpramsofinterest："一2．GAW（GlbWatch）一eanywamlnapefOfCl1angesingreenhousepeses．ozwebo,aodfongrangetransportofpohutants（See'：2L;：：J：：C7C：：：Tg2：：：：：l：：：：：：ary'"'"。Proo。m。。1997。。r、ene。。Phen。men。。n。。elr。。。。。'沈盛装出编邹邹装广脸器点精、'。。ml。1。7。Ph。。P-一fi。nsient。l。r。。Iiv。。。。sc。u－'"'一dingat16OOUTonthenrstdayoftheintervaIsindicated．andendieqat：nsi：：CC…     

Geophysical investigation of buried Pleistocene subglacial valleys in Northern Germany

Buried Pleistocene subglacial valleys are extensively used as groundwater reservoirs by waterworks in northern Germany, although little is known about the locations and size of these valleys and the internal structure of the sediment fill. This lack of knowledge about important groundwater reservoirs is a challenge for geophysics.This paper summarizes the geophysical investigation of two buried Pleistocene subglacial valleys in northern Germany—the Ellerbeker Rinne and the Bremerhaven–Cuxhavener Rinne—including seismic, gravity, and airborne electromagnetic (AEM) surveys. Seismic sections show the detailed structure of the paleovalleys. The reliability of interpretation is enhanced by vertical seismic profiles in wells. The maximum depths of the Ellerbeker Rinne and the Bremerhaven–Cuxhavener Rinne were found to be 360 and about 400 m, respectively. Gravity survey revealed Bouguer anomalies above the sediment fill of both buried valleys. The Ellerbeker Rinne produces a negative residual anomaly of −0.5 mGal, whereas the sediments of the Bremerhaven–Cuxhavener Rinne produce a positive anomaly. The latter one is superimposed by negative gravity anomalies due to near-surface structures. The Bremerhaven–Cuxhavener Rinne can be mapped by airborne electromagnetics at locations without saltwater intrusion, which would affect the measurements. The electrical conductivity of the clay layer at the top of the valley fill differs significantly from that of the surrounding sand. The combined use of these three geophysical methods, which measure different physical parameters, leads to a better understanding of the subsurface geology and the hydrogeology of the Pleistocene subglacial valleys.     

Geophysical survey on the tectonic and sediment distribution of Qinghai Lake basin

1 Introduction in China, with an area of 4400 km2 and a drainage area With the advancement of global change study, peo- of nearly 29,660 km2[2]. Occurring at a “climatic triple ple are paying more and more attention to the conti- junction” among the East Asian monsoon, Indian nental environment (in which we reside), its evolution Monsoon and the Westerly Jet Stream, it lies in the and its future tendency. As a component of the global transitional belt of the east monsoonal humid areas sys…     

中国地球物理学会第15届学术年会(1999)

中国地球物理学会第１５届学术年会于１９９９年１０月２０日至２４日在安徽省合肥市隆重召开,来自中国科学院、国土资源部、高等院校、地震、石油、煤炭、水利、铁道、有色金属、核工业、气象、文物、电力等部门的３９３名代表参加了会议．代表中有院士５人、高级职称者２９１人,３５岁以下者占２７％．大会收到报告４１９篇,会上共宣读论文２３８篇． １０月 ２０日上午,大会开幕式在中国科技大学水上厅举行,由学会副理事长陈 院士主持．理事长刘光鼎院士致开幕词,他感谢安徽省人民政府、省科协、省地矿局、省地球物理学会及其他有…     

中国地球物理学会第17届学术年会(2001)

在新世纪第一年的 1 0月 ,第 1 7届中国地球物理学术年会在祖国春城昆明市召开 .会议正式注册代表 40 3名 ,非注册代表 5 1名 .陈院士主持了 1 0月 1 4日上午的开幕式 ,云南省科协主席涂济民、云南省地球物理学会理事长谢应齐、云南大学校长吴松出席了会议 .中国地球物理学会理事长刘光鼎院士致开幕词 .总结过去 ,展望未来 ,他提出了 4个方面的工作 :1 .在“三个代表”的思想指引下 ,加强精神文明建设 ,办好“会员之家” ,迎接新全球化的挑战 ;2 .抓住我国将进入ＷＴＯ的机遇 ,学会成立了“中国方圆标志委员会勘探勘察认证工作站” ,将于 …     

Integrated geophysical methods for the characterisation of an archaeological site (Massenzio Basilica — Roman forum, Rome, Italy)

A geophysical study that involved different techniques was carried out with the aim to improve the knowledge of the archaeological site where the Basilica of Maxentius was founded and to discern individual covered structures (foundations).Vertical Electrical Sounding (VES), seismic refraction and Electrical Resistivity Tomography (ERT) studies were performed in the archaeological site. VES and seismic refraction allowed to characterise the main geological formations of the hill where the Basilica was built and to distinguish the concrete floor and backfilling. Electrical data were processed using different algorithms; their results were compared to appraise the inverted models' robustness.ERT inversion algorithms were used to delineate shape and size of a much more complex structure, that were originally expected from archaeological excavation plan. The results of the commercial program were used as a posteriori information to include them in the algorithm proposed by the authors; the sequential use of the programs defined a processing procedure.The integrated use of different geophysical techniques reduced a great deal the intrinsic ambiguities of each method. Direct explorations (boreholes and archaeological excavations) confirmed the geophysical results.     

Acquisition and processing of electric,magnetic and GPR data on a Roman site (Victimulae,Salussola, Biella)

A multi-method geophysical survey has been carried out on a Roman archaeological site, where part of an apse had previously been found and then refilled by archaeologists during an excavation test. Magnetic gradient measurements were performed over the whole study area and a sub-area of interesting anomalies beside the excavation test site was found. Two-dimensional filtering of a more detailed magnetic gradient map and 2D inversion of magnetic profiles were performed, using an on-purpose implemented software, in order to reduce the effect of noise and to stress the eventual presence of buried structures in agreement with the archaeologists' hypothesis. Resistivity tomography and GPR profiles were carried out along some selected profiles to obtain information on the vertical distribution of the anomalous bodies. GPR profiles, carried out in the area containing the test excavation, supplied good results, particularly when processed as time slices. The whole structure of the apse was clearly outlined. The authors were then able to suggest to the archaeologists further excavation tests on the basis of GPR results and of the filtered magnetic gradient map. A comparison of the results of the applied surveying methodologies has supplied an example of the relative strengths and weaknesses of the different electric, magnetic and GPR techniques.     

Geophysical models for the tectonic framework of the Lake Vostok region, East Antarctica

Aerogeophysical and seismological data from a geophysical survey in the interior of East Antarctica were used to develop a conceptual tectonic model for the Lake Vostok region. The model is constrained using three independent data sets: magnetic, seismic, and gravimetric. A distinct change in the aeromagnetic anomaly character across Lake Vostok defines a crustal boundary. Depth to magnetic basement estimates image a 400-km-wide and more than 10-km-deep sedimentary basin west of the lake. Analysis of teleseismic earthquakes suggests a relatively thin crust beneath Lake Vostok consistent with predictions from kinematic and flexural gravity modelling. Magnetic, gravity, and subglacial topography data reveal a tectonic boundary within East Antarctica. Based on our kinematic and flexural gravity modelling, this tectonic boundary appears to be the result of thrust sheet emplacement onto an earlier passive continental margin. No data presently exist to date directly either the timing of passive margin formation or the subsequent shortening phase. The preserved thrust sheet thickness is related to the thickness of the passive margin crust. Because a significant amount of time is required to erode the thrust sheet topography, we suggest that these tectonic events are Proterozoic in age. Minor normal reactivation of the thrust sheet offers a simple mechanism to explain the formation of the Lake Vostok Basin. A low level of seismicity exists in the vicinity of this tectonic boundary. The existence of a crustal boundary in the Antarctic interior provides new constraints on the Proterozoic architecture of the East Antarctic craton.