The first part of this investigation analyzes the deep earthquake occurrences in Nazca subducting under South America. The depth taken is to get information about possible influences from the unknown materials and for...The first part of this investigation analyzes the deep earthquake occurrences in Nazca subducting under South America. The depth taken is to get information about possible influences from the unknown materials and formations under the crust. The results revealed the presence of malleable material, which is unbreakable and, therefore, unable to trigger earthquakes. The structure of those elements is diamagnetic, attracting ionized particles from the Van Allen belt region in the ionosphere. The charged particles travel towards Earth’s surface, enhanced during the geomagnetic storms. The South Atlantic Magnetic Anomaly (SAMA) found that the deformation suffered by the anomaly moving from South Africa to South America is, possibly due to a bulge of unknown flexible material buried underneath the oceanic and continental crust. The continental part is strengthening in weakness because the background also has a high amount of diamagnetic material in this region, and it would not happen over the Atlantic Ocean, where part of the deformation is placed.展开更多
We use magnetic field data observed by the Swarm mission from 2014 to 2020 to construct,for the first time,a two-dimensional(2 D)lithospheric magnetic anomaly model of Egypt and its surrounding area.Nighttime data dur...We use magnetic field data observed by the Swarm mission from 2014 to 2020 to construct,for the first time,a two-dimensional(2 D)lithospheric magnetic anomaly model of Egypt and its surrounding area.Nighttime data during quiet geomagnetic conditions has been expanded in terms of the Legendre polynomial in harmonic terms N=6-50.The damped least square method has been used to estimate the model coefficients based on the lithospheric magnetic data.Modeled data at two different altitudes(438-448 km and 503-511 km)were compared with the CHAOS model.Results exhibit that the 2 D model is superior to the CHAOS model in the capability of extracting more information about small-scale crustal anomaly field.At low altitudes(438-448 km),the strength of the anomaly field increases,but the noise of the external fields has greatly reduced at high altitudes(503-511 km).Besides,the magnetic anomaly field at low altitudes has illuminated short-scale anomalies that didn’t appear at high altitudes.Both the total and vertical magnetic anomaly vectors showed their ability to reveal tectonic structures compared with Moho depth map and the geological maps.展开更多
The Curie point depth is the depth at which the ferromagnetic mineral loses paramagnetism,which corresponds to a temperature of 550-580 degrees Celsius.This parameter is of great significance for constraining the ther...The Curie point depth is the depth at which the ferromagnetic mineral loses paramagnetism,which corresponds to a temperature of 550-580 degrees Celsius.This parameter is of great significance for constraining the thermal state of the lithosphere and can be used as an important reference for the evaluation of the prospects for dry hot rock exploration.We use aeromagnetic anomaly radial power spectrum based on the fractal magnetization model to calculate the Curie depth in the Subei Basin.We use the conventional method to preprocess the aeromagnetic data and process aeromagnetic data with selecting the appropriate wave number,domain,window size and fractal parameters to calculate the depth of the bottom of the magnetic source in the Subei Basin,which is approximated as Curie depth.The Curie depth of Subei basin ranges from 18 km to 37 km,with an average Curie depth of 23 km.The Curie depth of Baoying(20 km)and Jianhu(22 km)area is relatively shallow,and that of the surrounding area is relatively deep.In most areas,the Curie depth corresponds to the terrestrial heat flow.展开更多
Magnetic theory and application to a complex volcanic area located in Southern Italy are here discussed showing the example of the Gulf of Naples, located at Southern Italy Tyrrhenian margin. A magnetic anomaly map of...Magnetic theory and application to a complex volcanic area located in Southern Italy are here discussed showing the example of the Gulf of Naples, located at Southern Italy Tyrrhenian margin. A magnetic anomaly map of the Gulf of Naples has been constructed aimed at highlighting new knowledge on geophysics and volcanology of this area of the Eastern Tyrrhenian margin, characterized by a complex geophysical setting, strongly depending on sea bottom topography. The theoretical aspects of marine magnetometry and multibeam bathymetry have been discussed. Magnetic data processing included the correction of the data for the diurnal variation, the correction of the data for the offset and the leveling of the data as a function of the correction at the cross-points of the navigation lines. Multibeam and single-beam bathymetric data processing has been considered. Magnetic anomaly fields in the Naples Bay have been discussed through a detailed geological interpretation and correlated with main morpho-structural features recognized through morpho- bathymetric interpretation. Details of magnetic anomalies have been selected, represented and correlated with significant seismic profiles, recorded on the same navigation lines of magnetometry. They include the continental shelf offshore the Somma-Vesuvius volcanic complex, the outer shelf of the Gulf of Pozzuoli offshore the Phlegrean Fields volcanic complex, the relict volcanic banks of Pentapalummo, Nisida and Miseno, the Gaia volcanic bank on the Naples slope, the western slope of the Dohrn canyon, the Magnaghi canyon’s head and the magnetic anomalies among the Ischia and Procida islands.展开更多
When a pig mounted with permanent magnets gets stuck in the pipeline,it can be located by detecting the magnetic anomalies on the ground using a single-axis magnetic sensor.In order to collect the magnetic anomaly eff...When a pig mounted with permanent magnets gets stuck in the pipeline,it can be located by detecting the magnetic anomalies on the ground using a single-axis magnetic sensor.In order to collect the magnetic anomaly efficiently through single-axis magnetic sensor,a geometric detection model and calculation method for singleaxis magnetic anomaly detection is established in this paper.The distribution of magnetic inclination and declination of the measuring points is obtained.The results indicate that the magnetic inclination of all measuring points vary within a small range of 2°,and this value is highly dependent on the magnetic sensor which is configured aboveground around the geomagnetic inclination.However,the magnetic declination at different points of detection surface is subject to the geomagnetic components and the Y-axis component of the magnetic field of magnets.The magnetic declinations distribute irregularly and vary in a wide range.Therefore,to achieve a high-efficiency detection with the single-axis sensor,the sensor shall be placed in such a manner that the magnetic inclination thereof coincides with the geomagnetic inclination.The magnetic declination of the sensor can be calculated using s,the superposed Y-axis component induced by the permanent magnets,and the corresponding formula given in this paper.The article demonstrates the feasibility of locating a blocked pig in the pipeline based on the single-axis magnetic anomaly detection.It will have a practical significance in guiding the engineering detection.展开更多
To aid the magnetic anomaly detection(MAD)of underground ferromagnetic pipelines,this paper proposes a geometric modeling method based on the magnetic dipole reconstruction method(MDRM).First,the numerical modeling of...To aid the magnetic anomaly detection(MAD)of underground ferromagnetic pipelines,this paper proposes a geometric modeling method based on the magnetic dipole reconstruction method(MDRM).First,the numerical modeling of basic pipe components such as straight sections,bends and elbows,and tee joints are discussed and the relevant mathematical formulations for these components are derived.Next,after analyzing the function of MDRM and various element division strategies,the sectional division and blocked division methods are introduced and applied to the appropriate pipeline components to determine the volume and center coordinates of each element,establishing the general models for the three typical pipeline components considered.The resulting volume and center coordinates of each component are the fundamental parameters for determining the MAD forwarding of underground ferromagnetic pipelines using the MDRM.Finally,based on the combination and transformation of the basic pipeline components considered,the visualized geometric models of typical pipeline layouts including parallel pipelines,pipelines with elbows,and a pipeline with a tee joint are constructed.The results demonstrate the feasibility of the proposed method of geometric modeling for the MDRM,which can be further applied to the finite element modeling of these and other components when analyzing MAD data.Furthermore,the models with output parameters proposed in this paper establish a foundation for the inversion of MAD.展开更多
This study focuses on the Kakobola region and its surroundings where cavities discovered in its basement may represent a major risk for the hydroelectric dam erected on the Lufuku River near the Kakobola city and the ...This study focuses on the Kakobola region and its surroundings where cavities discovered in its basement may represent a major risk for the hydroelectric dam erected on the Lufuku River near the Kakobola city and the civil engineering works in the study area. In order to deepen the studies related to this understudied region and provide decision-makers with information that will enable them to make the necessary and appropriate decisions regarding the development of this area, a study based on the analysis of geomagnetic data was carried out using certain methods revealing more shallow than deep structures, and others highlighting the limits of both shallower and deeper structures. Total magnetic anomalies and reduced to equator (RTE) magnetic anomalies were used to map the subsurface of the Kakobola region and its surroundings. In order to detect the edges of magnetized structures, the horizontal gradient magnitude (HGM), the analytic signal (AS), the horizontal gradient of tilt angle (HGTA), the tilt angle (TA), the theta map (TM), the enhanced total horizontal derivative of the tilt angle (ETHDR), the tilt angle of the horizontal gradient (TAHG), and the tilt angle of analytic signal (TAAS) were used. The study area is characterized by two areas of low values of magnetic anomalies and two other sources of high magnetic anomalies located in the bed and the neighborhood of the two major rivers in the region. The shallow sources of magnetic anomalies are lying in the bed and the vicinity of the same rivers in the study area. The magnetic sources in the study area are connected and almost linear. Several magnetic lineaments identified in this region by different methods present several preferential directions, but the most predominant directions are NE-SW, NW-SE, W-E and NE-SW.展开更多
Forward modelling of gravity and magnetic data was done simultaneously to show the correlation between gravity and magnetic anomalies on a measured heat flux region. The results were used to characterize the heat sour...Forward modelling of gravity and magnetic data was done simultaneously to show the correlation between gravity and magnetic anomalies on a measured heat flux region. The results were used to characterize the heat source structures in Eburru area. Modelling was done using Oasis montaj geosoft software which is an iteration process where the gravity and magnetic anomalies were calculated and compared to the observed residual anomaly until there was a fit. The start model was constructed based on depths from Euler deconvolution and models constrained using stratigraphy data from the existing wells in the study area. <span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">Forward modelling of gravity and magnetic data revealed intrusions within the Earth’s subsurface with depth to the top of the sources ranging from </span></span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">739 m</span></span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> to </span></span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">5811 m</span></span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">. The density of the sources ranges between </span></span></span></span><span><span><span><span style="font-family:""><span style="font-family:Verdana;">3.0 g/cm</span><sup><span style="font-family:Verdana;">3</span></sup></span></span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> and </span></span></span></span><span><span><span><span style="font-family:""><span style="font-family:Verdana;">3.2 g/cm</span><sup><span style="font-family:Verdana;">3</span></sup></span></span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> while their magnetic susceptibility was zero. This implies that intrusions from the mantle with a magnetic susceptibility of zero have temperatures exceeding the curie temperature of rocks. The density of the intrusions modelled was higher than 2.67 </span></span></span></span><span><span><span><span style="font-family:""><span style="font-family:Verdana;">g/cm</span><sup><span style="font-family:Verdana;">3</span></sup></span></span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">, the average crustal density, hence it explains the observed positive gravity anomaly. </span></span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">The results also revealed that areas with high heat flux have shallow heat sources and if the heat sources are deep, then there must be a good heat transfer mechanism to the surface.</span></span></span></span>展开更多
Generally, a magnetic target can be described with six parameters, three describing the position and three describing the magnetic moment. Due to a lack of sufficient components from one magnetometer, we need more tha...Generally, a magnetic target can be described with six parameters, three describing the position and three describing the magnetic moment. Due to a lack of sufficient components from one magnetometer, we need more than one magnetometer when locating the magnetic target. Thus, a magnetometer array should be designed. The baseline of the array is an important factor that affects the localization accuracy of the target. In this paper, we focus on the localization of a static target by using a scalar magnetometer array. We present the scalar magnetometer array with a cross-shaped structure.We propose a method of determining the optimal baseline according to the parameters of the magnetometer and detection requirements. In the method, we use the traditional signal-to-noise ratio(SNR) as a performance index, and obtain the optimal baseline of the array by using the Monte Carlo method. The proposed method of determining the optimal baseline is verified in simulation. The arrays with different baselines are used to locate a static magnetic target. The results show that the location performance is better when using the array with the optimal baseline determined by the proposed method.展开更多
The intersection of the Kyushu-Palau Ridge(KPR)and the Central Basin Rift(CBR)of the West Philippine Basin(WPB)is a relic of a trench-trench-rift(TTR)type triple-junction,which preserves some pivotal information on th...The intersection of the Kyushu-Palau Ridge(KPR)and the Central Basin Rift(CBR)of the West Philippine Basin(WPB)is a relic of a trench-trench-rift(TTR)type triple-junction,which preserves some pivotal information on the cessation of the seafloor spreading of the WPB,the emplacement and disintegration of the proto-Izu-Bonin-Mariana(IBM)Arc,and the transition from initial rifting to steady-state spreading of the Parece Vela Basin(PVB).However,the structural characteristics of this triple-junction have not been thoroughly understood.In this paper,using the newly acquired multi-beam bathymetric,gravity,and magnetic data obtained by the Qingdao Institute of Marine Geology,China Geological Survey,the authors depict the topographic,gravity,and magnetic characteristics of the triple-junction and adjacent region.Calculations including the upward continuations and total horizontal derivatives of gravity anomaly are also performed to highlight the major structural features and discontinuities.Based on these works,the morphological and structural features and their formation mechanisms are analyzed.The results show that the last episode amagmatic extension along the CBR led to the formation of a deep rift valley,which extends eastward and incised the KPR.The morphological and structural fabrics of the KPR near and to the south of the triple-junction are consistent with those of the western PVB,manifesting as a series of NNE-SSW-and N-S-trending ridges and troughs,which were produced by the extensional faults associated with the initial rifting of the PVB.The superposition of the above two reasons induced the prominent discontinuity of the KPR in deep and shallow crustal structures between 15°N‒15°30′N and 13°30′N‒14°N.Combined with previous authors’results,we propose that the stress produced by the early spreading of the PVB transmitted westward and promoted the final stage amagmatic extension of the CBR.The eastward propagation of the CBR destroyed the KPR,of which the magmatism had decayed or ceased at that time.The destruction mechanism of the KPR associated with the rifting of the PVB varies along strike the KPR.Adjacent to the triple-junction,the KPR was destroyed mainly due to the oblique intersection of the PVB rifting center.Whereas south of the triple-junction,the KPR was destroyed by the E-W-directional extensional faulting on its whole width.展开更多
The south segment of the China North-South Seismic Belt is located in the southeast margin of the Qinghai Tibet Plateau.This region is characterized by the frequent seismic activity in Chinese mainland.In this paper,t...The south segment of the China North-South Seismic Belt is located in the southeast margin of the Qinghai Tibet Plateau.This region is characterized by the frequent seismic activity in Chinese mainland.In this paper,the geomagnetic field model NGDC-720 and the data of terrestrial heat flow are used to investigate the distribution of crustal magnetic anomalies,the depth of Curie surface,and the characteristics of the crustal thermal structure in the south segment of the North-South Seismic Belt.The distribution characteristics of the vertical component AZ and the magnetic declination AD in the area with earthquakes over a magnitude of 6 and their aftershocks since 1970 are focused on.The results show that the earthquakes are mainly observed in the area of negative magnetic anomaly or the strong and weak transition zone.It especially shows in the AD.The Curie surface in the study area varies significantly,ranging from 20.8 to 31 km.The uplift area of the Curie surface is consistent with the high-value area of terrestrial heat flow.The high geothermal area corresponds to the strong earthquake activity area.The focal depth of most strong earthquakes is shallower than the depth of the Curie surface.The strong earthquakes mainly occur in the deep-shallow transition zones of the Curie surface.The results can be used as a reference for strong earthquake prediction in this area.展开更多
One of the measurement geophysical methods to investigate kimberlite pipes is by using the magnetic method. The acquired field data in this study uses <span style="font-family:Verdana;">two proton-prec...One of the measurement geophysical methods to investigate kimberlite pipes is by using the magnetic method. The acquired field data in this study uses <span style="font-family:Verdana;">two proton-precession magnetometers for the mapping of magnetic anomalies</span><span style="font-family:Verdana;"> due to kimberlites. Three different magnetic maps are obtained from the result of total magnetic field data processing on Oásis Montaj software programme. These maps include magnetic anomaly maps through statistical analyses, total magnetic field intensity map and map of the analytic signal. Based on the interpretation of these maps a structure is identified with SWW-NEE directions in which magnetic signatures that indicate the presence of kimberlite pipes are observed. As the interpretation of the magnetic anomalies is a complicated process due to their dipolar nature, the analytic signal is generated, where is possible to observe the typical shape of these anomalies.</span>展开更多
Long-wavelength(>500 km)magnetic anomalies originating in the lithosphere were first found in satellite magnetic surveys.Compared to the striking magnetic anomalies around the world,the long-wavelength magnetic ano...Long-wavelength(>500 km)magnetic anomalies originating in the lithosphere were first found in satellite magnetic surveys.Compared to the striking magnetic anomalies around the world,the long-wavelength magnetic anomalies in China and surrounding regions are relatively weak.Specialized research on each of these anomalies has been quite inadequate;their geological origins remain unclear,in particular their connection to tectonic activity in the Chinese and surrounding regions.We focus on six magnetic high anomalies over the(1)Tarim Basin,(2)Sichuan Basin(3)Great Xing’an Range,(4)Barmer Basin,(5)Central Myanmar Basin,and(6)Sunda and Banda Arcs,and a striking magnetic low anomaly along the southern part of the Himalayan-Tibetan Plateau.We have analyzed their geological origins by reviewing related research and by detailed comparison with geological results.The tectonic backgrounds for these anomalies belong to two cases:either ancient basin basement,or subduction-collision zone.However,the geological origins of large-scale regional magnetic anomalies are always subject to dispute,mainly because of limited surface exposure of sources,later tectonic destruction,and superposition of multi-phase events.展开更多
As one of the main controlling factors of oil and gas accumulation,faults are closely related to the distribution of oil and gas reservoirs.Studying how faults control petroliferous basins is particularly important.In...As one of the main controlling factors of oil and gas accumulation,faults are closely related to the distribution of oil and gas reservoirs.Studying how faults control petroliferous basins is particularly important.In this work,we investigated the plane positions of major faults in the China seas and its adjacent areas using the normalized vertical derivative of the total horizontal derivative(NVDR-THDR)of the Bouguer gravity anomaly,the fusion results of gravity and magnetic anomalies,and the residual Bouguer gravity anomaly.The apparent depths of major faults in the China seas and its adjacent areas were inverted using the Tilt-Euler method based on the Bouguer gravity anomaly.The results show that the strikes of the faults in the China seas and its adjacent areas are mainly NE and NW,followed by EW,and near-SN.Among them,the lengths of most ultra-crustal faults are in the range of 1000–3000 km,and their apparent depths lie between 10 km and 40 km.The lengths of crustal faults lie between 300 km and 1000 km,and their apparent depths are between 0 km and 20 km.According to the plane positions and apparent depths of the faults,we put forward the concept of fault influence factor for the first time.Based on this factor,the key areas for oil and gas exploration were found as follows:the east of South North China Basin in the intracontinental rift basins;the southeast region of East China Sea Shelf Basin,the Taixinan and Qiongdongnan basins in the continental margin rift basins;Zhongjiannan Basin in the strike-slip pull-apart basins;the Liyue,Beikang,and the Nanweixi basins in the rifted continental basins.This work provides valuable insights into oil and gas exploration,mineral resource exploration,and deep geological structure research in the China seas and its adjacent areas.展开更多
This work aims to examine the functionality of a new Augmented Iteratively Re-weighted and Refined Least Squares algorithm(AIRRLS)to generate a 3D model of magnetic susceptibility property from a potential field magne...This work aims to examine the functionality of a new Augmented Iteratively Re-weighted and Refined Least Squares algorithm(AIRRLS)to generate a 3D model of magnetic susceptibility property from a potential field magnetometry survey.Whereby this algorithm ameliorates an lp norm Tikhonov regularization cost function through replacing a set of weighted linear system of equations.It leads to constructing a magnetic susceptibility model that iteratively converges to an optimum solution,meanwhile the regularization parameter performs as a stopping criterion to finalize the iterations.To tackle and suppress the intrinsic tendency of a sought target responsible for generating a magnetic anomaly and to not be imaged at shallow depth in inverse modeling,a prior depth weighting function is imposed in the principle system of equations.The significance of this research lies in improvement of the performance of the inversion,where the running time of an lp norm problem after incorporating a pre-conditioner conjugate gradient solver(PCCG)in cases of large scale geophysical dataset.Forasmuch as this study attempts to image a geological target with low magnetic susceptibility property,it is assumed that there is no remanent magnetization.The applicability of the algorithm is tested for a synthetic multi-source data to demonstrate its performance in 3D modeling.Subsequently,a real case study in Semnan province of Iran,is investigated to image an embedded porphyry copper layer in a sequence of sediments.The sought target consists of a concealed arc-shaped porphyry andesite unit that may have potential of Cu occurrences.Results prove that it extends down at depth,so exploratory drilling is highly recommended to get insights about its potential for Cu-bearing mineralization.展开更多
With the acceleration of the investigation and development of marine resources,the detection and location of submarine pipelines have become a necessary part of modern marine engineering.Submarine pipelines are a typi...With the acceleration of the investigation and development of marine resources,the detection and location of submarine pipelines have become a necessary part of modern marine engineering.Submarine pipelines are a typical weak magnetic anomaly target,and their magnetic anomaly detection can only be realized within a certain distance.At present,a towfish or an autonomous underwater vehicle(AUV)is mainly used as the platform to equip magnetometers close to the submarine pipelines for magnetic anomaly detection.However,the mother ship directly affects the towfish,thus causing control interference.The AUV cannot detect in real time,which affects the magnetic anomaly detection and creates problems regarding detection efficiency.Meanwhile,a two-part towed platform has convenient control,thus reducing the interference of the towed mother ship and real-time detection.If the platform can maintain constant altitude sailing through the controller,the data accuracy in the actual magnetic anomaly detection can be guaranteed.On the basis of a two-part towed platform,a magnetic detection system with constant altitude sailing ability for submarine pipelines was constructed in this study.In addition,experimental verification was conducted.The experimental verification research shows that the constant altitude sailing experiment of the two-part towed platform verifies that the platform has good constant altitude sailing ability in both a hydrostatic environment and the actual marine environment.Meanwhile,the offshore magnetic anomaly detection experiment of submarine pipelines verifies the stable measurement function of the magnetic field and the function of the system to detect magnetic anomaly of submarine pipelines.展开更多
There is promising indication of helium-rich natural gas in Weihe Basin.However,the lack of a detailed investigation on the origin and the spatial distribution of helium source rocks(mainly Yanshanian granites)limits ...There is promising indication of helium-rich natural gas in Weihe Basin.However,the lack of a detailed investigation on the origin and the spatial distribution of helium source rocks(mainly Yanshanian granites)limits the helium potentiality evaluation in Weihe Basin(WB).We performed three-dimensional(3 D)inversions of magnetic data in Weihe Basin and its adjacent areas to figure out the crustal thermal structure and the temporal-spatial distribution of deep granite in the basin.Based on this,we have proposed a geological model of helium accumulation and predicted the potential area of helium distribution.The results of 3 D magnetic inversion indicate that the granites in the deep Weihe Basin are mostly located at the central and southern parts of the basin,which are connected spatially with the granites in the North Qinling Orogenic Belt.These granites were all derived from largescale intra-continental orogeny in the Qinling area during the mid-Mesozoic,providing a good material basis for crust-derived helium in the basin.The local uplift of the Curie surface makes the thermal fluid more actively,which contributes to helium accumulation.The faults developed in the WB are the migration pathway of crust-derived helium and the upward migration of the mantle-derived helium.The wells with high percentage helium are mostly located near the Weihe fault and the areas on the south of it.The Wugong-Xi’an-Lantian area in the central and the Lintong-Weinan-Tongguan area in the eastern Weihe Basin are the most promising helium distribution areas.Furthermore,the region from the north of Taibai Mountain to Baoji City in the western Weihe Basin may also be another potential area of Helium resource.展开更多
The gravity and magnetic survey lines of about 13,500 km were carried out in the centraland northern parts of the South China Sea from 1977 to 1978. The results obtained showthat the Bouguer gravity and magnetic anoma...The gravity and magnetic survey lines of about 13,500 km were carried out in the centraland northern parts of the South China Sea from 1977 to 1978. The results obtained showthat the Bouguer gravity and magnetic anomalies have a tendency to increase gradually theirvalues from the northern continental shelf, through the slope, to the central abyssal basin of theSouth China Sea. The change in free-air gravity anomaly values coincides to a certain degreewith the undulation of the sea-bottom topography. The primary factor determining regionalvariation of the Bouguer gravity anomayl values is the Moho depth. The main factor deter-mining the magnetic anomly values is the nature of the basement rock. The high magnetieand Bouguer gravity anomaly values observed in some fault basin areas are inferred to becaused by draping the basic and ultrabasic magma extruding along the faults on the basementof the metamorphic rock,or by intrusion of the same magma into the basement.展开更多
The eruption of large igneous provinces usually has major geodynamic in fluence sonoverriding plates.Seamount chains indicate that the drifting direction of the Pacific Plate changed by~80°in the Early Cretaceous...The eruption of large igneous provinces usually has major geodynamic in fluence sonoverriding plates.Seamount chains indicate that the drifting direction of the Pacific Plate changed by~80°in the Early Cretaceous when the Ontong Java Plateau formed.This,however,is not fully consistent with the magnetic anomalies.Here we show that there is an angle of~25°between the magnetic anomaly lines M_(0)and 34 of both the Japanese and the Hawaiian lineations,suggesting that the orientations of both spreading ridges changed by roughly the same angle towards the same direction.The configurations of the Shatsky Rise,the Papanin Ridge and the Osbourn Trough suggest that the eruption of the Ontong Java plume head uplifted the southeastern corner of the Pacific Plate,and pushed its east part northward by~700 km within 2 Ma.Meanwhile,the west part of the Pacific Plate was subducting southwestward underneath the eastern Asian Continent.These two forces together rotated the Pacific Plate anticlockwisely by ca 50°.Consequently,the drifting direction of the Pacific Plate also changed from southwestward to northwestward,which plausibly explains the ca 80°bending of the Shatsky Rise and the Papanin Ridge.The ridge between the Pacific and the Izanagi/Kula plates was pointed towards the~300°orientation,whereas the Pacific Plate was subducting towards the~250°orientation before~125 Ma,and towards~280°afterward.展开更多
The localization of persons or objects usually refers to a position determined in a spatial reference system.Outdoors,this is usually accomplished with Global Navigation Satellite Systems(GNSS).However,the automatic p...The localization of persons or objects usually refers to a position determined in a spatial reference system.Outdoors,this is usually accomplished with Global Navigation Satellite Systems(GNSS).However,the automatic positioning of people in GNSS-free environments,especially inside of buildings(indoors)poses a huge challenge.Indoors,satellite signals are attenuated,shielded or reflected by building components(e.g.walls or ceilings).For selected applications,the automatic indoor positioning is possible based on different technologies(e.g.WiFi,RFID,or UWB).However,a standard solution is still not available.Many indoor positioning systems are only suitable for specific applications or are deployed under certain conditions,e.g.additional infrastructures or sensor technologies.Smartphones,as popular cost-effective multi-sensor systems,is a promising indoor localization platform for the mass-market and is increasingly coming into focus.Today’s devices are equipped with a variety of sensors that can be used for indoor positioning.In this contribution,an approach to smartphone-based pedestrian indoor localization is presented.The novelty of this approach refers to a holistic,real-time pedestrian localization inside of buildings based on multisensor smartphones and easy-to-install local positioning systems.For this purpose,the barometric altitude is estimated in order to derive the floor on which the user is located.The 2D position is determined subsequently using the principle of pedestrian dead reckoning based on user's movements extracted from the smartphone sensors.In order to minimize the strong error accumulation in the localization caused by various sensor errors,additional information is integrated into the position estimation.The building model is used to identify permissible(e.g.rooms,passageways)and impermissible(e.g.walls)building areas for the pedestrian.Several technologies contributing to higher precision and robustness are also included.For the fusion of different linear and non-linear data,an advanced algorithm based on the Sequential Monte Carlo method is presented.展开更多
文摘The first part of this investigation analyzes the deep earthquake occurrences in Nazca subducting under South America. The depth taken is to get information about possible influences from the unknown materials and formations under the crust. The results revealed the presence of malleable material, which is unbreakable and, therefore, unable to trigger earthquakes. The structure of those elements is diamagnetic, attracting ionized particles from the Van Allen belt region in the ionosphere. The charged particles travel towards Earth’s surface, enhanced during the geomagnetic storms. The South Atlantic Magnetic Anomaly (SAMA) found that the deformation suffered by the anomaly moving from South Africa to South America is, possibly due to a bulge of unknown flexible material buried underneath the oceanic and continental crust. The continental part is strengthening in weakness because the background also has a high amount of diamagnetic material in this region, and it would not happen over the Atlantic Ocean, where part of the deformation is placed.
文摘We use magnetic field data observed by the Swarm mission from 2014 to 2020 to construct,for the first time,a two-dimensional(2 D)lithospheric magnetic anomaly model of Egypt and its surrounding area.Nighttime data during quiet geomagnetic conditions has been expanded in terms of the Legendre polynomial in harmonic terms N=6-50.The damped least square method has been used to estimate the model coefficients based on the lithospheric magnetic data.Modeled data at two different altitudes(438-448 km and 503-511 km)were compared with the CHAOS model.Results exhibit that the 2 D model is superior to the CHAOS model in the capability of extracting more information about small-scale crustal anomaly field.At low altitudes(438-448 km),the strength of the anomaly field increases,but the noise of the external fields has greatly reduced at high altitudes(503-511 km).Besides,the magnetic anomaly field at low altitudes has illuminated short-scale anomalies that didn’t appear at high altitudes.Both the total and vertical magnetic anomaly vectors showed their ability to reveal tectonic structures compared with Moho depth map and the geological maps.
文摘The Curie point depth is the depth at which the ferromagnetic mineral loses paramagnetism,which corresponds to a temperature of 550-580 degrees Celsius.This parameter is of great significance for constraining the thermal state of the lithosphere and can be used as an important reference for the evaluation of the prospects for dry hot rock exploration.We use aeromagnetic anomaly radial power spectrum based on the fractal magnetization model to calculate the Curie depth in the Subei Basin.We use the conventional method to preprocess the aeromagnetic data and process aeromagnetic data with selecting the appropriate wave number,domain,window size and fractal parameters to calculate the depth of the bottom of the magnetic source in the Subei Basin,which is approximated as Curie depth.The Curie depth of Subei basin ranges from 18 km to 37 km,with an average Curie depth of 23 km.The Curie depth of Baoying(20 km)and Jianhu(22 km)area is relatively shallow,and that of the surrounding area is relatively deep.In most areas,the Curie depth corresponds to the terrestrial heat flow.
文摘Magnetic theory and application to a complex volcanic area located in Southern Italy are here discussed showing the example of the Gulf of Naples, located at Southern Italy Tyrrhenian margin. A magnetic anomaly map of the Gulf of Naples has been constructed aimed at highlighting new knowledge on geophysics and volcanology of this area of the Eastern Tyrrhenian margin, characterized by a complex geophysical setting, strongly depending on sea bottom topography. The theoretical aspects of marine magnetometry and multibeam bathymetry have been discussed. Magnetic data processing included the correction of the data for the diurnal variation, the correction of the data for the offset and the leveling of the data as a function of the correction at the cross-points of the navigation lines. Multibeam and single-beam bathymetric data processing has been considered. Magnetic anomaly fields in the Naples Bay have been discussed through a detailed geological interpretation and correlated with main morpho-structural features recognized through morpho- bathymetric interpretation. Details of magnetic anomalies have been selected, represented and correlated with significant seismic profiles, recorded on the same navigation lines of magnetometry. They include the continental shelf offshore the Somma-Vesuvius volcanic complex, the outer shelf of the Gulf of Pozzuoli offshore the Phlegrean Fields volcanic complex, the relict volcanic banks of Pentapalummo, Nisida and Miseno, the Gaia volcanic bank on the Naples slope, the western slope of the Dohrn canyon, the Magnaghi canyon’s head and the magnetic anomalies among the Ischia and Procida islands.
基金This work is supported by the National Natural Science Foundation of China under Grant No.41374151the Sichuan Province Applied Basic Research Project(No.2017JY0162)the Young Scholars Development Fund of SWPU(No.201599010079).
文摘When a pig mounted with permanent magnets gets stuck in the pipeline,it can be located by detecting the magnetic anomalies on the ground using a single-axis magnetic sensor.In order to collect the magnetic anomaly efficiently through single-axis magnetic sensor,a geometric detection model and calculation method for singleaxis magnetic anomaly detection is established in this paper.The distribution of magnetic inclination and declination of the measuring points is obtained.The results indicate that the magnetic inclination of all measuring points vary within a small range of 2°,and this value is highly dependent on the magnetic sensor which is configured aboveground around the geomagnetic inclination.However,the magnetic declination at different points of detection surface is subject to the geomagnetic components and the Y-axis component of the magnetic field of magnets.The magnetic declinations distribute irregularly and vary in a wide range.Therefore,to achieve a high-efficiency detection with the single-axis sensor,the sensor shall be placed in such a manner that the magnetic inclination thereof coincides with the geomagnetic inclination.The magnetic declination of the sensor can be calculated using s,the superposed Y-axis component induced by the permanent magnets,and the corresponding formula given in this paper.The article demonstrates the feasibility of locating a blocked pig in the pipeline based on the single-axis magnetic anomaly detection.It will have a practical significance in guiding the engineering detection.
基金This work is supported by the National Natural Science Foundation of China[No.41374151]the Sichuan Province Applied Basic Research Project of China[No.2017JY0162]the Young Scholars Development Fund of SWPU[No.201599010079].
文摘To aid the magnetic anomaly detection(MAD)of underground ferromagnetic pipelines,this paper proposes a geometric modeling method based on the magnetic dipole reconstruction method(MDRM).First,the numerical modeling of basic pipe components such as straight sections,bends and elbows,and tee joints are discussed and the relevant mathematical formulations for these components are derived.Next,after analyzing the function of MDRM and various element division strategies,the sectional division and blocked division methods are introduced and applied to the appropriate pipeline components to determine the volume and center coordinates of each element,establishing the general models for the three typical pipeline components considered.The resulting volume and center coordinates of each component are the fundamental parameters for determining the MAD forwarding of underground ferromagnetic pipelines using the MDRM.Finally,based on the combination and transformation of the basic pipeline components considered,the visualized geometric models of typical pipeline layouts including parallel pipelines,pipelines with elbows,and a pipeline with a tee joint are constructed.The results demonstrate the feasibility of the proposed method of geometric modeling for the MDRM,which can be further applied to the finite element modeling of these and other components when analyzing MAD data.Furthermore,the models with output parameters proposed in this paper establish a foundation for the inversion of MAD.
文摘This study focuses on the Kakobola region and its surroundings where cavities discovered in its basement may represent a major risk for the hydroelectric dam erected on the Lufuku River near the Kakobola city and the civil engineering works in the study area. In order to deepen the studies related to this understudied region and provide decision-makers with information that will enable them to make the necessary and appropriate decisions regarding the development of this area, a study based on the analysis of geomagnetic data was carried out using certain methods revealing more shallow than deep structures, and others highlighting the limits of both shallower and deeper structures. Total magnetic anomalies and reduced to equator (RTE) magnetic anomalies were used to map the subsurface of the Kakobola region and its surroundings. In order to detect the edges of magnetized structures, the horizontal gradient magnitude (HGM), the analytic signal (AS), the horizontal gradient of tilt angle (HGTA), the tilt angle (TA), the theta map (TM), the enhanced total horizontal derivative of the tilt angle (ETHDR), the tilt angle of the horizontal gradient (TAHG), and the tilt angle of analytic signal (TAAS) were used. The study area is characterized by two areas of low values of magnetic anomalies and two other sources of high magnetic anomalies located in the bed and the neighborhood of the two major rivers in the region. The shallow sources of magnetic anomalies are lying in the bed and the vicinity of the same rivers in the study area. The magnetic sources in the study area are connected and almost linear. Several magnetic lineaments identified in this region by different methods present several preferential directions, but the most predominant directions are NE-SW, NW-SE, W-E and NE-SW.
文摘Forward modelling of gravity and magnetic data was done simultaneously to show the correlation between gravity and magnetic anomalies on a measured heat flux region. The results were used to characterize the heat source structures in Eburru area. Modelling was done using Oasis montaj geosoft software which is an iteration process where the gravity and magnetic anomalies were calculated and compared to the observed residual anomaly until there was a fit. The start model was constructed based on depths from Euler deconvolution and models constrained using stratigraphy data from the existing wells in the study area. <span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">Forward modelling of gravity and magnetic data revealed intrusions within the Earth’s subsurface with depth to the top of the sources ranging from </span></span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">739 m</span></span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> to </span></span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">5811 m</span></span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">. The density of the sources ranges between </span></span></span></span><span><span><span><span style="font-family:""><span style="font-family:Verdana;">3.0 g/cm</span><sup><span style="font-family:Verdana;">3</span></sup></span></span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> and </span></span></span></span><span><span><span><span style="font-family:""><span style="font-family:Verdana;">3.2 g/cm</span><sup><span style="font-family:Verdana;">3</span></sup></span></span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> while their magnetic susceptibility was zero. This implies that intrusions from the mantle with a magnetic susceptibility of zero have temperatures exceeding the curie temperature of rocks. The density of the intrusions modelled was higher than 2.67 </span></span></span></span><span><span><span><span style="font-family:""><span style="font-family:Verdana;">g/cm</span><sup><span style="font-family:Verdana;">3</span></sup></span></span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">, the average crustal density, hence it explains the observed positive gravity anomaly. </span></span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">The results also revealed that areas with high heat flux have shallow heat sources and if the heat sources are deep, then there must be a good heat transfer mechanism to the surface.</span></span></span></span>
基金supported by the National Natural Science Foundation of China(Grant No.61174192)
文摘Generally, a magnetic target can be described with six parameters, three describing the position and three describing the magnetic moment. Due to a lack of sufficient components from one magnetometer, we need more than one magnetometer when locating the magnetic target. Thus, a magnetometer array should be designed. The baseline of the array is an important factor that affects the localization accuracy of the target. In this paper, we focus on the localization of a static target by using a scalar magnetometer array. We present the scalar magnetometer array with a cross-shaped structure.We propose a method of determining the optimal baseline according to the parameters of the magnetometer and detection requirements. In the method, we use the traditional signal-to-noise ratio(SNR) as a performance index, and obtain the optimal baseline of the array by using the Monte Carlo method. The proposed method of determining the optimal baseline is verified in simulation. The arrays with different baselines are used to locate a static magnetic target. The results show that the location performance is better when using the array with the optimal baseline determined by the proposed method.
基金This study was funded by the projects initiated by the China Geological Survey(DD20191003,DD20190236 and DD20190205).
文摘The intersection of the Kyushu-Palau Ridge(KPR)and the Central Basin Rift(CBR)of the West Philippine Basin(WPB)is a relic of a trench-trench-rift(TTR)type triple-junction,which preserves some pivotal information on the cessation of the seafloor spreading of the WPB,the emplacement and disintegration of the proto-Izu-Bonin-Mariana(IBM)Arc,and the transition from initial rifting to steady-state spreading of the Parece Vela Basin(PVB).However,the structural characteristics of this triple-junction have not been thoroughly understood.In this paper,using the newly acquired multi-beam bathymetric,gravity,and magnetic data obtained by the Qingdao Institute of Marine Geology,China Geological Survey,the authors depict the topographic,gravity,and magnetic characteristics of the triple-junction and adjacent region.Calculations including the upward continuations and total horizontal derivatives of gravity anomaly are also performed to highlight the major structural features and discontinuities.Based on these works,the morphological and structural features and their formation mechanisms are analyzed.The results show that the last episode amagmatic extension along the CBR led to the formation of a deep rift valley,which extends eastward and incised the KPR.The morphological and structural fabrics of the KPR near and to the south of the triple-junction are consistent with those of the western PVB,manifesting as a series of NNE-SSW-and N-S-trending ridges and troughs,which were produced by the extensional faults associated with the initial rifting of the PVB.The superposition of the above two reasons induced the prominent discontinuity of the KPR in deep and shallow crustal structures between 15°N‒15°30′N and 13°30′N‒14°N.Combined with previous authors’results,we propose that the stress produced by the early spreading of the PVB transmitted westward and promoted the final stage amagmatic extension of the CBR.The eastward propagation of the CBR destroyed the KPR,of which the magmatism had decayed or ceased at that time.The destruction mechanism of the KPR associated with the rifting of the PVB varies along strike the KPR.Adjacent to the triple-junction,the KPR was destroyed mainly due to the oblique intersection of the PVB rifting center.Whereas south of the triple-junction,the KPR was destroyed by the E-W-directional extensional faulting on its whole width.
基金supported by National Natural Science Foundation of China(No.41864003 and 41964004)as well as Yunnan Fundamental Research Projects(202101AT070181).
文摘The south segment of the China North-South Seismic Belt is located in the southeast margin of the Qinghai Tibet Plateau.This region is characterized by the frequent seismic activity in Chinese mainland.In this paper,the geomagnetic field model NGDC-720 and the data of terrestrial heat flow are used to investigate the distribution of crustal magnetic anomalies,the depth of Curie surface,and the characteristics of the crustal thermal structure in the south segment of the North-South Seismic Belt.The distribution characteristics of the vertical component AZ and the magnetic declination AD in the area with earthquakes over a magnitude of 6 and their aftershocks since 1970 are focused on.The results show that the earthquakes are mainly observed in the area of negative magnetic anomaly or the strong and weak transition zone.It especially shows in the AD.The Curie surface in the study area varies significantly,ranging from 20.8 to 31 km.The uplift area of the Curie surface is consistent with the high-value area of terrestrial heat flow.The high geothermal area corresponds to the strong earthquake activity area.The focal depth of most strong earthquakes is shallower than the depth of the Curie surface.The strong earthquakes mainly occur in the deep-shallow transition zones of the Curie surface.The results can be used as a reference for strong earthquake prediction in this area.
文摘One of the measurement geophysical methods to investigate kimberlite pipes is by using the magnetic method. The acquired field data in this study uses <span style="font-family:Verdana;">two proton-precession magnetometers for the mapping of magnetic anomalies</span><span style="font-family:Verdana;"> due to kimberlites. Three different magnetic maps are obtained from the result of total magnetic field data processing on Oásis Montaj software programme. These maps include magnetic anomaly maps through statistical analyses, total magnetic field intensity map and map of the analytic signal. Based on the interpretation of these maps a structure is identified with SWW-NEE directions in which magnetic signatures that indicate the presence of kimberlite pipes are observed. As the interpretation of the magnetic anomalies is a complicated process due to their dipolar nature, the analytic signal is generated, where is possible to observe the typical shape of these anomalies.</span>
基金the National Natural Science Foundation of China(grant numbers 42004051,42274214,41904134).
文摘Long-wavelength(>500 km)magnetic anomalies originating in the lithosphere were first found in satellite magnetic surveys.Compared to the striking magnetic anomalies around the world,the long-wavelength magnetic anomalies in China and surrounding regions are relatively weak.Specialized research on each of these anomalies has been quite inadequate;their geological origins remain unclear,in particular their connection to tectonic activity in the Chinese and surrounding regions.We focus on six magnetic high anomalies over the(1)Tarim Basin,(2)Sichuan Basin(3)Great Xing’an Range,(4)Barmer Basin,(5)Central Myanmar Basin,and(6)Sunda and Banda Arcs,and a striking magnetic low anomaly along the southern part of the Himalayan-Tibetan Plateau.We have analyzed their geological origins by reviewing related research and by detailed comparison with geological results.The tectonic backgrounds for these anomalies belong to two cases:either ancient basin basement,or subduction-collision zone.However,the geological origins of large-scale regional magnetic anomalies are always subject to dispute,mainly because of limited surface exposure of sources,later tectonic destruction,and superposition of multi-phase events.
基金The Scientific and Technological Project of China National Offshore Oil Corporation(CNOOC)Research Institute Co.,Ltd.,under contract No.CCL2021RCPS0167KQNthe Fundamental Research Funds for the Central Universities,CHD under contract No.300102261714。
文摘As one of the main controlling factors of oil and gas accumulation,faults are closely related to the distribution of oil and gas reservoirs.Studying how faults control petroliferous basins is particularly important.In this work,we investigated the plane positions of major faults in the China seas and its adjacent areas using the normalized vertical derivative of the total horizontal derivative(NVDR-THDR)of the Bouguer gravity anomaly,the fusion results of gravity and magnetic anomalies,and the residual Bouguer gravity anomaly.The apparent depths of major faults in the China seas and its adjacent areas were inverted using the Tilt-Euler method based on the Bouguer gravity anomaly.The results show that the strikes of the faults in the China seas and its adjacent areas are mainly NE and NW,followed by EW,and near-SN.Among them,the lengths of most ultra-crustal faults are in the range of 1000–3000 km,and their apparent depths lie between 10 km and 40 km.The lengths of crustal faults lie between 300 km and 1000 km,and their apparent depths are between 0 km and 20 km.According to the plane positions and apparent depths of the faults,we put forward the concept of fault influence factor for the first time.Based on this factor,the key areas for oil and gas exploration were found as follows:the east of South North China Basin in the intracontinental rift basins;the southeast region of East China Sea Shelf Basin,the Taixinan and Qiongdongnan basins in the continental margin rift basins;Zhongjiannan Basin in the strike-slip pull-apart basins;the Liyue,Beikang,and the Nanweixi basins in the rifted continental basins.This work provides valuable insights into oil and gas exploration,mineral resource exploration,and deep geological structure research in the China seas and its adjacent areas.
文摘This work aims to examine the functionality of a new Augmented Iteratively Re-weighted and Refined Least Squares algorithm(AIRRLS)to generate a 3D model of magnetic susceptibility property from a potential field magnetometry survey.Whereby this algorithm ameliorates an lp norm Tikhonov regularization cost function through replacing a set of weighted linear system of equations.It leads to constructing a magnetic susceptibility model that iteratively converges to an optimum solution,meanwhile the regularization parameter performs as a stopping criterion to finalize the iterations.To tackle and suppress the intrinsic tendency of a sought target responsible for generating a magnetic anomaly and to not be imaged at shallow depth in inverse modeling,a prior depth weighting function is imposed in the principle system of equations.The significance of this research lies in improvement of the performance of the inversion,where the running time of an lp norm problem after incorporating a pre-conditioner conjugate gradient solver(PCCG)in cases of large scale geophysical dataset.Forasmuch as this study attempts to image a geological target with low magnetic susceptibility property,it is assumed that there is no remanent magnetization.The applicability of the algorithm is tested for a synthetic multi-source data to demonstrate its performance in 3D modeling.Subsequently,a real case study in Semnan province of Iran,is investigated to image an embedded porphyry copper layer in a sequence of sediments.The sought target consists of a concealed arc-shaped porphyry andesite unit that may have potential of Cu occurrences.Results prove that it extends down at depth,so exploratory drilling is highly recommended to get insights about its potential for Cu-bearing mineralization.
基金the support of the Fund of State Key Laboratory of Ocean Engineering(GKZD010068,GKZD010074,GKZD010075).
文摘With the acceleration of the investigation and development of marine resources,the detection and location of submarine pipelines have become a necessary part of modern marine engineering.Submarine pipelines are a typical weak magnetic anomaly target,and their magnetic anomaly detection can only be realized within a certain distance.At present,a towfish or an autonomous underwater vehicle(AUV)is mainly used as the platform to equip magnetometers close to the submarine pipelines for magnetic anomaly detection.However,the mother ship directly affects the towfish,thus causing control interference.The AUV cannot detect in real time,which affects the magnetic anomaly detection and creates problems regarding detection efficiency.Meanwhile,a two-part towed platform has convenient control,thus reducing the interference of the towed mother ship and real-time detection.If the platform can maintain constant altitude sailing through the controller,the data accuracy in the actual magnetic anomaly detection can be guaranteed.On the basis of a two-part towed platform,a magnetic detection system with constant altitude sailing ability for submarine pipelines was constructed in this study.In addition,experimental verification was conducted.The experimental verification research shows that the constant altitude sailing experiment of the two-part towed platform verifies that the platform has good constant altitude sailing ability in both a hydrostatic environment and the actual marine environment.Meanwhile,the offshore magnetic anomaly detection experiment of submarine pipelines verifies the stable measurement function of the magnetic field and the function of the system to detect magnetic anomaly of submarine pipelines.
基金supported by the National Natural Science Foundation of China(No.41904115)the Natural Science Basic Research Plan in Shaanxi Province of China(No.2018JQ4034)。
文摘There is promising indication of helium-rich natural gas in Weihe Basin.However,the lack of a detailed investigation on the origin and the spatial distribution of helium source rocks(mainly Yanshanian granites)limits the helium potentiality evaluation in Weihe Basin(WB).We performed three-dimensional(3 D)inversions of magnetic data in Weihe Basin and its adjacent areas to figure out the crustal thermal structure and the temporal-spatial distribution of deep granite in the basin.Based on this,we have proposed a geological model of helium accumulation and predicted the potential area of helium distribution.The results of 3 D magnetic inversion indicate that the granites in the deep Weihe Basin are mostly located at the central and southern parts of the basin,which are connected spatially with the granites in the North Qinling Orogenic Belt.These granites were all derived from largescale intra-continental orogeny in the Qinling area during the mid-Mesozoic,providing a good material basis for crust-derived helium in the basin.The local uplift of the Curie surface makes the thermal fluid more actively,which contributes to helium accumulation.The faults developed in the WB are the migration pathway of crust-derived helium and the upward migration of the mantle-derived helium.The wells with high percentage helium are mostly located near the Weihe fault and the areas on the south of it.The Wugong-Xi’an-Lantian area in the central and the Lintong-Weinan-Tongguan area in the eastern Weihe Basin are the most promising helium distribution areas.Furthermore,the region from the north of Taibai Mountain to Baoji City in the western Weihe Basin may also be another potential area of Helium resource.
文摘The gravity and magnetic survey lines of about 13,500 km were carried out in the centraland northern parts of the South China Sea from 1977 to 1978. The results obtained showthat the Bouguer gravity and magnetic anomalies have a tendency to increase gradually theirvalues from the northern continental shelf, through the slope, to the central abyssal basin of theSouth China Sea. The change in free-air gravity anomaly values coincides to a certain degreewith the undulation of the sea-bottom topography. The primary factor determining regionalvariation of the Bouguer gravity anomayl values is the Moho depth. The main factor deter-mining the magnetic anomly values is the nature of the basement rock. The high magnetieand Bouguer gravity anomaly values observed in some fault basin areas are inferred to becaused by draping the basic and ultrabasic magma extruding along the faults on the basementof the metamorphic rock,or by intrusion of the same magma into the basement.
基金supported by the National Key R&D Program of China(No.2016YFC0600408)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA22050103)+1 种基金the Taishan Scholar Program of Shandong Province(No.ts201712075)the Aoshan Talents Cultivation Program supported by Pilot National Laboratory of Marine Science and Technology(No.2017ASTCP-OS07)。
文摘The eruption of large igneous provinces usually has major geodynamic in fluence sonoverriding plates.Seamount chains indicate that the drifting direction of the Pacific Plate changed by~80°in the Early Cretaceous when the Ontong Java Plateau formed.This,however,is not fully consistent with the magnetic anomalies.Here we show that there is an angle of~25°between the magnetic anomaly lines M_(0)and 34 of both the Japanese and the Hawaiian lineations,suggesting that the orientations of both spreading ridges changed by roughly the same angle towards the same direction.The configurations of the Shatsky Rise,the Papanin Ridge and the Osbourn Trough suggest that the eruption of the Ontong Java plume head uplifted the southeastern corner of the Pacific Plate,and pushed its east part northward by~700 km within 2 Ma.Meanwhile,the west part of the Pacific Plate was subducting southwestward underneath the eastern Asian Continent.These two forces together rotated the Pacific Plate anticlockwisely by ca 50°.Consequently,the drifting direction of the Pacific Plate also changed from southwestward to northwestward,which plausibly explains the ca 80°bending of the Shatsky Rise and the Papanin Ridge.The ridge between the Pacific and the Izanagi/Kula plates was pointed towards the~300°orientation,whereas the Pacific Plate was subducting towards the~250°orientation before~125 Ma,and towards~280°afterward.
文摘The localization of persons or objects usually refers to a position determined in a spatial reference system.Outdoors,this is usually accomplished with Global Navigation Satellite Systems(GNSS).However,the automatic positioning of people in GNSS-free environments,especially inside of buildings(indoors)poses a huge challenge.Indoors,satellite signals are attenuated,shielded or reflected by building components(e.g.walls or ceilings).For selected applications,the automatic indoor positioning is possible based on different technologies(e.g.WiFi,RFID,or UWB).However,a standard solution is still not available.Many indoor positioning systems are only suitable for specific applications or are deployed under certain conditions,e.g.additional infrastructures or sensor technologies.Smartphones,as popular cost-effective multi-sensor systems,is a promising indoor localization platform for the mass-market and is increasingly coming into focus.Today’s devices are equipped with a variety of sensors that can be used for indoor positioning.In this contribution,an approach to smartphone-based pedestrian indoor localization is presented.The novelty of this approach refers to a holistic,real-time pedestrian localization inside of buildings based on multisensor smartphones and easy-to-install local positioning systems.For this purpose,the barometric altitude is estimated in order to derive the floor on which the user is located.The 2D position is determined subsequently using the principle of pedestrian dead reckoning based on user's movements extracted from the smartphone sensors.In order to minimize the strong error accumulation in the localization caused by various sensor errors,additional information is integrated into the position estimation.The building model is used to identify permissible(e.g.rooms,passageways)and impermissible(e.g.walls)building areas for the pedestrian.Several technologies contributing to higher precision and robustness are also included.For the fusion of different linear and non-linear data,an advanced algorithm based on the Sequential Monte Carlo method is presented.
