Gravity Profiles Research Articles

Preliminary Gravity Study of Pre-Tertiary and Tertiary Rock in Northern Kebumen, Central Java, Indonesia

Luk Ulo Melange Complex is a Pre-Tertiary rock formation consisting of various lithological background and complicated geological structure. Located in Northern Kebumen Regency, this rock is originally interpreted as products of tectonic process caused by paleo-subduction between Indian Oceanic Plate beneath Eurasian Plate in Cretaceous age. According to previous study on geological surface investigation shows that the melange complex is tectonically overlain by Tertiary sedimentary formation. On the contrary, geophysical study of the subsurface condition of the area is still under discussion due to limited of measured data. In order to obtain detailed subsurface image, gravity profiling was measured and interpreted across both Tertiary and pre-Tertiary rock. Frequency domain filter and designed moving average filter were used to separate residual and regional anomaly. The results denote gravity value of residual anomaly varying from -5 to +5 mGal, while regional anomaly is ranging from 150-180 mGal respectively. The preliminary interpretation was developed by taking into account the geological information and also the data that was collected during field campaign. Overall, high gravity anomaly is interpreted as diabase intrusion in the middle of research area. Meanwhile, low gravity anomaly indicated clay rich rock material related to matrix content of Luk-Ulo Melange Complex in the northern area.

Seismic investigation of an active ocean–continent transform margin: the interaction between the Swan Islands Fault Zone and the ultraslow-spreading Mid-Cayman Spreading Centre

SUMMARY The Swan Islands Transform Fault (SITF) marks the southern boundary of the Cayman Trough and the ocean–continent transition of the North American–Caribbean Plate boundary offshore Honduras. The CAYSEIS experiment acquired a 180-km-long seismic refraction and gravity profile across this transform margin, ∼70 km to the west of the Mid-Cayman Spreading Centre (MCSC). This profile shows the crustal structure across a transform fault system that juxtaposes Mesozoic-age continental crust to the south against the ∼10-Myr-old ultraslow spread oceanic crust to the north. Ocean-bottom seismographs were deployed along-profile, and inverse and forward traveltime modelling, supported by gravity analysis, reveals ∼23-km-thick continental crust that has been thinned over a distance of ∼70 km to ∼10 km-thick at the SITF, juxtaposed against ∼4-km-thick oceanic crust. This thinning is primarily accommodated within the lower crust. Since Moho reflections are not widely observed, the 7.0 km s−1 velocity contour is used to define the Moho along-profile. The apparent lack of reflections to the north of the SITF suggests that the Moho is more likely a transition zone between crust and mantle. Where the profile traverses bathymetric highs in the off-axis oceanic crust, higher P-wave velocity is observed at shallow crustal depths. S-wave arrival modelling also reveals elevated velocities at shallow depths, except for crust adjacent to the SITF that would have occupied the inside corner high of the ridge-transform intersection when on axis. We use a Vp/Vs ratio of 1.9 to mark where lithologies of the lower crust and uppermost mantle may be exhumed, and also to locate the upper-to-lower crustal transition, identify relict oceanic core complexes and regions of magmatically formed crust. An elevated Vp/Vs ratio suggests not only that serpentinized peridotite may be exposed at the seafloor in places, but also that seawater has been able to flow deep into the crust and upper mantle over 20–30-km-wide regions which may explain the lack of a distinct Moho. The SITF has higher velocities at shallower depths than observed in the oceanic crust to the north and, at the seabed, it is a relatively wide feature. However, the velocity–depth model subseabed suggests a fault zone no wider than ∼5–10 km, that is mirrored by a narrow seabed depression ∼7500 m deep. Gravity modelling shows that the SITF is also underlain, at >2 km subseabed, by a ∼20-km-wide region of density >3000 kg m−3 that may reflect a broad region of metamorphism. The residual mantle Bouguer anomaly across the survey region, when compared with the bathymetry, suggests that the transform may also have a component of left-lateral trans-tensional displacement that accounts for its apparently broad seabed appearance, and that the focus of magma supply may currently be displaced to the north of the MCSC segment centre. Our results suggest that Swan Islands margin development caused thinning of the adjacent continental crust, and that the adjacent oceanic crust formed in a cool ridge setting, either as a result of reduced mantle upwelling and/or due to fracture enhanced fluid flow.

The Geothermal Potential of Büyük Menderes Graben Obtained by Combined 2.5-D Normalized Full Gradient Results

In this study, the normalized full gradient (NFG) method was applied to the Bouguer gravity data for western Anatolia to identify the locations of the structures and the variations within the mediums. The NFG values were calculated for different harmonics using Bouguer gravity profile values, and the locations of possible structures were determined. In the next step, for analyzing the continuity of these structures in detail, 2.5-D NFG maps were created by combining the NFG results of the profiles for the same harmonics. Additionally, the relationship between the structures obtained in this study and the geothermal sources was examined. Based on the study results, the geothermal capacity of the region was estimated using the locations and the depths of the wells at the surroundings of Kizildere-Saraykoy. Thus, the possible fields with higher geothermal potential were identified throughout the region. The structure borders obtained in this study were also evaluated with respect to the earthquakes that have occurred in Aydin and Denizli cities that contain high-temperature geothermal basins, and it was found that the regions, which feed the geothermal sources, are either non-seismic or represent low seismicity.

Cinder cone morphometry in relation to gravity anomaly zones in the Harrat al Birk and Asir foreland, SW Saudi Arabia

The Harrat al Birk (HAB) of the alkali basalts of the post-Miocene age erupted through a thick Precambrian crust along the Red Sea coast. The 200 cinder cones scatter within HAB and three distinct Bouguer anomaly zones are identified as the coastal gravity high (CGH), axial gravity low (AGL) and a gravity high further east Jabal As-Sawda gravity high (JSGH). Interpreted satellite imagery for 150 sizeable cinder cones in three gravity anomaly zones (134 (90%) in CGH, 10 (6%) in AGL and 6 (4%) in JSGH) are morphologically analysed. The juvenile cinder cones (age \({<}{1}\hbox {Ma}\)) are characterised by sub-vertical slope angles (\({<}{40}^{\circ }\)) with a variable average geomorphic slope, 27\(^{\circ }\)–40\(^{\circ }\) in JSGH, \(25^{\circ }\) in AGL and 2\(^{\circ }\)–15\(^{\circ }\) in CGH. The oldest cones of JSGH display a high \(H_{\mathrm{co}}/W_{\mathrm{co}}\) ratio with angular asymmetry at their base angles. The major feeder lineaments/faults are oriented NNW–SSE to NW–SE, and they supply volcanic material to cinder cones within a distance of 2 km. The results, when integrated with geological maps and gravity profiles, provide a probable root-plumbing system of the volcano edifice. HAB is the produce of the volcanic process from the source area in JSGH that hosts the major cinders, where the tertiary gabbroic dyke zone acts as a vertical magma sheet for the cinders.

High-precision local gravity survey along planned motorway tunnel in the Slovak Karst

Abstract Results from a detailed gravity survey realized along the planned highway tunnel in the karstic area of Slovak Karst in the eastern Slovakia are presented. Detailed gravity profiles crossed an area of rugged topography, therefore the terrain corrections played a crucial role in the gravity data processing. The airborne laser scanning technique (LiDAR) was used in order to compile a high-resolution digital terrain model (DTM) of the surrounding area and to calculate terrain corrections properly. The difference between the Bouguer anomalies calculated with an available nationwide DTM and those with new LiDAR-based model can be significant in some places as it is presented in the paper. A new method for Bouguer correction density analysis based on surface data is presented. Special underground gravity measurements in the existing nearby railway tunnel were also conducted in order to determine the mean density of the topographic rocks. The Bouguer anomalies were used to interpret lithological contacts and tectonic/karstic discontinuities.

ỨNG DỤNG PHƯƠNG PHÁP CỰC ĐẠI WAVELET VÀ SỰ CHUẨN HÓA THAM SỐ TỈ LỆ ĐỂ XÁC ĐỊNH CÁC NGUỒN DỊ THƯỜNG TRỌNG LỰC LIỀN KỀ

Nowadays, the wavelet transform is frequently used in processing and interpretaion of potential field data, to detect accurately the location of the anomaly sources and their properties. For gravity anomalies of adjacent sources, they always superimpose upon each other not only in the spatial domain but also in the frequency domain, making the identification of these sources significantly problematic. In this paper, a new mother wavelet for effective analysis of the locations of the close potential field sources was introduced. By theoretical modeling, using the wavelet transform modulus maxima (WTMM) method, we set up a correlative function between the scale parameter and gravity source depth. Moreover, a scale normalization on the wavelet coefficients was applied to enhance resolution for the separation of these sources in the scalograms, thereby determining their depth. After verifying the reliability of the proposed method on the modeling data, we proposed a process for the location of the gravity anomalies of adjacent sources using the wavelet transform, and then application for analysing some of the gravity profiles in the Mekong Delta. The results of this interpretation were consistent with previously published results, but the level of resolution for this technique was quite coincidental with other methods using different geological data.

Guiding teacher talk in the Content and Language Integrated Learning classroom using Semantics from Legitimation Code Theory

ABSTRACT The paper seeks to demonstrate how academic Content Obligatory Language can be potentially organized in teacher talk applying semantic gravity waving from Legitimation Code Theory. The questions asked are: Which concepts do I teach from my discipline in this session? How do I teach these to ensure effective comprehension? Research was conducted for a Content and Language Integrated Learning academic English language programme for undergraduates at a leading Asian University. Three texts as theoretical planning for a teacher input session were composed and provided to students to read. Each text represented different semantic gravity profiles. Students reported which of these texts, if any, was most effectively explaining key concepts from the course. They then provided qualitative comments to substantiate their decisions. Findings indicate that knowledge and use of semantic graving waving can theoretically facilitate student comprehension more effectively and could be a useful tool for planning teacher talk.

Dark Matter: An Unforeseen Gravitational Property of Relativistic Space-Time?

If the wave functions of matter expanded with time dilation for an outside observer in the same way as photons do in gravitational redshift; with some modifications the general relativity might alone explain dark matter, galaxy rotation curves, and part of the energy released in supernova explosions. Also, the event horizons of black holes couldn’t be formed when packing matter more and more densely together. Essentially, if the time dilation increases enough, the particles turn less localized to outside observers and the mass distribution of the same particles would expand into larger volume of space. Small particles deep inside a black hole might seem like dark matter instead by their gravitational influence if the time dilation alters their size enough for outside observers. At the same time, the surface particles of the black hole would be less dispersed, creating the Newtonian gravitational potential we see closer to black holes. The following research doesn’t attempt to reformulate the general relativity itself, but only proposes the idea while approximating the Milky way gravity profile to compare the hypothesis with measurements. Therefore, actually proving the hypothesis is still far off while the idea is sound at its core.

Interpretation of gravity anomalies over the eighty-five East Ridge in the Bay of Bengal

Several profiles of the negative gravity anomaly over the submerged 85o E ridge in the Bay of Bengal of the Indian Ocean have been interpreted in two dimension and results are combined together to give a detailed picture of its morphology and thickness of surrounding sediments. The observed negative gravity anomaly has been explained as the combined effect due to the positive mass anomaly caused by the replacement of sediments by high dense igneous rocks of the ridge, and the negative mass anomaly caused by replacing the high dense upper mantle material by the oceanic crust, which has been bended and sunk into the upper mantle due to the pressure exerted by the ridge. Downward migration of the oceanic crust has been also calculated assuming that the oceanic crust is behaving as a thin infinite elastic plate resting on inviscid fluid half space and is found to closely agree with the results of the gravity study. Both studies indicate that the thickness of the ridge vary from 11 km to 16 km while the oceanic crust has undergone a depression of 9 km to 14 km.

Contribution of gravity and Bristow methods for Karez (aqueduct) detection

Karez (aqueduct or Qanat) is a water supply system used for hundreds of years in a number of different regions across the world. Due to the extension of constructions close to old networks of Karezes, the detection of path and depth of the Karez is very important. The Karez network understudy is embedded in the alluvial environment in which mostly clay material surrounds the channel. Further, the ceiling of Karez in the survey area has a frequent depth of 1–2 m. to the surface. Initially, to identify the path and boundaries of the Karez's network, three gravity profiles were carried out. After processing, a derived residual map of Bouguer anomaly revealed the path of the Karez. Applying the relatively recent method of Euler deconvolution in a radial coordinate system yields the depth of 1.4 m. from the surface to the center of Karez. In addition to this, a successful technique in determining the depth of underground cavities, the Bristow method was carried out. Actually, soft and low resistivity soil around the Karez channel was the biggest challenge in the interpretation of conducted pole-dipole electrical arrays. Therefore, a forward modeling based on the finite difference method was used in order to model pole-dipole resistivity array for a round-shaped object with two various diameters in several depths which looks the same as a Karez. The results of the models were used in Bristow graphical interpretation. The average of measurement error for depth estimation obtained by this method is about 7%. Further, the interpreted field data obviously revealed the depth of 1.8 m. from the center to the top of Karez, which agrees well with gravity results.

Satellite-Derived Regional Apparent Thermal Inertia and Gravity for Mapping Different Rock Types in Parts of Banswara, Rajasthan

In this study, utility of satellite derived Apparent Thermal Inertia (ATI) and residual gravity data have been analyzed for delineating the major rock types of Aravalli Supergroup. Density is a common contributing factor responsible for ATI and gravity variations of rock types. In addition to density, thermal inertia is also controlled by specific heat and thermal conductivity. In the present study, MODIS (Moderate resolution imaging spectrometer) day and consecutive night time land surface temperature (LST), albedo data have been processed to derive ATI image for the study area. On the other hand, Bouguer gravity generated from EIGEN6C4 gravity model data is processed to derive the residual gravity over the study area. It has been observed that ATI values of different rock types are influenced by the variations in weathering pattern and forest cover developed over the rock in addition to the thermophysical parameters of rocks. Forest cover and agricultural activity are responsible for shifting the ATI values to higher side for any rocks due to evapotranspiration; which is responsible for reducing day and night land surface temperature difference. ATI pixels( collected from large rock pavements) of different rocks can however, be used to discriminate them from each other. Conjugate analysis of residual gravity and ATI has been proved useful to discriminate different rock types of spatially well distributed rock exposures. It is found that ATI and gravity values are well correlated for the spatially large surface exposures of rocks. In regional scale, low frequency changes of ATI broadly matches with the changes observed on the corresponding spatial profiles of residual gravity with some localized variations. This is due to the fact that shallow surface gravity anomaly is cumulative effect of vertical and horizontal variations of density in contrast to ATI which is more sensitive to near surface density, conductivity and specific heat variations of rocks. Moreover, high frequency variations imprinted on regional ATI spatial profiles are due to the cumulative effect of complex thermophysical properties of surface elements (weathering residuum, surface moisture variations) density variation and intrinsic thermophysical properties of rocks measured at regional scale. High frequency changes of ATI do not correspond well with residual gravity variation.

Quaternary structural and paleo-environmental evolution of the Alpine Fault near Haast, New Zealand, from 2D seismic reflection and gravity data

ABSTRACTThe geometry of the upper-crustal portion of the Alpine Fault plate boundary on New Zealand’s South Island, is poorly constrained where it cuts through the sedimentary units of the Westland coastal plain. Two seismic reflection and gravity lines are presented here to better image the upper km of the fault beneath the most recent fault rupture scarps south of the Haast River. Analysis of the seismic lines suggests that multiple fault strands have cut across post-glacial sedimentary strata that overlie the glacially eroded basement. Total combined fault offsets of 39 m at the Haast River and 33 m at the Turnbull River over <17 ka is consistent with previously determined uplift rates. Dip on the fault strands is interpreted to be between ∼53 and ∼76° SE. 2D gravity profiles constrain the interpretation of the interface between sedimentary units and basement, which has considerable 3D variability resulting from glacial erosion processes.

Measurements and Accuracy Evaluation of a Strapdown Marine Gravimeter Based on Inertial Navigation.

The strapdown gravimetry system uses the combination of an Inertial Measuring Unit (IMU) and a Global Navigation Satellite System (GNSS) to measure the Earth’s gravity field. Due to limited accuracies of IMU and GNSS, early strapdown gravimetry systems were more often used in airborne surveys, but less used in marine surveys. We developed a strapdown inertial navigation system (SINS), the Sea-Air Gravimeter-2Marine (SAG-2M), using novel IMU components, whose accuracy was further improved with the application of Precise Point Positioning (PPP) and enhanced algorithm, making it possible to be used in marine gravity survey. The testing results of the SAG-2M were compared to those of the Lacoste and Romberg S-129 gravimeter on the same ship in the South China Sea basin. The cruise lasted for 50 days, during which 134 effective gravity profiles were measured, resulting in 174 crossover points. The results showed that, for the SAG-2M, the root mean square (RMS) crossover points were 1.35 mGal before difference adjustment and 0.69 mGal after difference adjustment; for the S-129 gravimeter, they were 5.62 mGal and 0.95 mGal, correspondingly. In calm sea conditions, the results of the two systems were relatively consistent at all wavelengths. However, in rough sea conditions, since the SAG-2M was not affected by the cross-coupling effect, its data demonstrated less high-frequency jump. A physical platform adopted in SAG-2M can further make the transition data effective when the ship is turning around. Therefore, SAG-2M was able to improve the proportion of valid data and the efficiency of data post-processing for measurements taken during the cruise. The testing results indicate that in terms of accuracy and efficiency in the marine gravity survey, SAG-2M is better than S-129. In addition, as the miniaturization and precision of inertial components are developing continuously, SAG-2M also shows great potential in miniaturization.

Helicopter Test of a Strapdown Airborne Gravimetry System.

Airborne gravimetry from a helicopter has been a feasible tool since the 1990s, with gravimeters mounted on a gyro-stabilised platform. In contrast to fixed-wing aircrafts, the helicopter allows for a higher spatial resolution, since it can move slower and closer to the ground. In August 2016, a strapdown gravimetry test was carried out over the Jakobshavn Glacier in Greenland. To our knowledge, this was the first time that a strapdown system was used in a helicopter. The strapdown configuration is appealing because it is easily installed and requires no operation during flight. While providing additional information over the thickest part of the glacier, the survey was designed to assess repeatability both within the survey and with respect to profiles flown previously using a gyro-stabilised gravimeter. The system’s ability to fly at an altitude following the terrain, i.e., draped flying, was also tested. The accuracy of the gravity profiles was estimated to 2 mGal and a method for inferring the spatial resolution was investigated, yielding a half-wavelength spatial resolution of 4.5 km at normal cruise speed.

Wood Variability in Mature Longleaf Pine: Differences Related to Cardinal Direction for a Softwood in a Humid Subtropical Climate

Mature longleaf pine ( Pinus palustris Mill .) trees were harvested to compare wood property data for opposing bark-to-pith wood strips representing the northern and southern cardinal (or compass) directions. For each of the ten 70-yr-old trees used in the study,wood property datawere compared at breast height (BH) and three relative heights: one-quarter height (1Q), midheight (MID), and three-quarter height (3Q). Scanning of the specimens by X-ray densitometry gave specific gravity (SG) profiles that were used to determine wood properties for comparison. No significant differences were determined for wood property data at BH, MID, or 3Q. However, data at 1Q showed higher ring SG (p . 0.043) and percent latewood (p . 0.018) for the northern side, although no differences were observed in the earlywood or latewood SG. This indicated that the higher ring SG for the northern direction results from a greater proportion of latewood. Partitioning the data into estimated juvenile-transition wood and mature wood zones demonstrated that the greater ring SGand percent latewood values in the northern direction occurredwithin the mature wood zone. Findings presented herein appear to provide the first demonstration of variation in wood properties with respect to cardinal direction for a pine species growing in a humid subtropical climate.

Tectonic structure of Central-Western Attica (Greece) based on geophysical in vestigations-Preliminary results

In an effort to investigate the deep geological structure in the broader area of central-western Attica, that suffered severe damage during the destructive Athens earthquake of September 7th, 1999, the Department of Geophysics-Geothermics of the Faculty of Geology and Geoenvironment of Athens University, in collaboration with the Geodynamic Institute of National Observatory of Athens and the Department of Geological Sciences of Durham University, carried out a combined geophysical survey. For the first time in Attica, seismic and gravity geophysical methods were applied along profiles, in such an extensive scale. Within the framework of this investigation the following tasL· were accomplished: a) Three (3) seismic lines of about 30 kilometres of total length, two (2) in the area of Thriassion plain and one (1) along the Parnitha-Krioneri-Drosia-Ekali-Dionysos axis (Attica plain) and b) 338 gravity measurements distributed along eight (8) gravity profiles, four (4) of which in Thriassion plain, three (3) in Petroupoli-Aharnes-Thrakomakedones region (Attica plain) and one (1) along Parnitha-Krioneri-Drosia-Ekali-Dionysos axis (Attica plain). Preliminary results of the geophysical investigation combined with existing geological and tectonic data are presented in this paper. Significant variation in the elevation of the alpine basement has been detected, expressed by manifestation of low and high subsurface areas which are well correlated with existing fault zones. In the area of Thriassion plain the thickness of post-alpine sediments is estimated of a few hundred meters (&lt;500 meters) and huge thickness of several hundred meters (-800 meters) of post-alpine sediments were detected in Thrakemakedones and Krioneri areas. The relief of alpine basement is more intense in fault zones areas, such as Thriassion plain (WNW-ESE), Pathitha and Kifissos (NE-SW) as well as along the fault zone outline the Fili and Aharnes graben and is covered by postalpine formations

Regional and residual gravity anomaly separation using the singular spectrum analysis-based low pass filtering: a case study from Nagpur, Maharashtra, India

We present here a singular spectrum analysis (SSA)-based low pass filtering algorithm for regional and residual gravity anomaly separation. The data adaptive decomposition in SSA frequency filtering algorithm facilitates reduction of the artefacts in the filtering of the non-linear and non-stationary gravity data. Initially, the method was tested on synthetic gravity data representing combined response of regional and residual components derived from the geological structures like infinite horizontal layers, intrusive dykes, deep-seated faults and volcanic intrusive bodies and compared with fast Fourier transform (FFT) wavenumber and wavelet-based filtering techniques. The results show that SSA-based filtered output exhibits a better match with pure synthetic data than the output generated from the FFT and wavelet filtering methods. The underlying method was then applied to two parallel gravity profiles of real data from the Umred coalfield, Nagpur, Maharashtra, India. Further, the SSA-based filtered regional anomaly was modelled using Geosoft GM-SYS software to construct the model of crustal structure of the study region. In essence, the modelling results suggest the following: (i) a basin-type graben structure with variable trap and sedimentary thicknesses and (ii) deep seated faults on either sides of the basin. These results correlate fairly well with known regional geology attesting the authenticity of the regional models generated from the two gravity profiles, which also agree well with each other. We, therefore, conclude that the SSA-based filtering technique is robust for regional gravity anomaly separation and could be effectively exploited for filtering other geophysical data.

Geophysical Investigation of the Pb–Zn Deposit of Lontzen–Poppelsberg, Belgium

The drillhole information from the Lontzen–Poppelsberg site has demonstrated three orebodies and has allowed the estimation of the extension of the lodes, their dip, and the location at the ground surface. The localisation of the lodes makes them excellent targets for further exploration with geophysics. This deposit is classified as a Mississippi Valley Type (MVT) deposit. It consists mainly of Pb–Zn–Fe sulphides that display contrasting values in resistivity, chargeability, density, and magnetic susceptibility, with regards to the sedimentary host rocks. The dipole–dipole direct current (DC) resistivity and induce polarization (IP) profiles have been collected and inverted to successfully delineate the Pb–Zn mineralization and the geological structures. Short-spacing EM34 electromagnetic conductivity data were collected mainly on the top of Poppelsberg East lode and have revealed a conductive body matching with the geologically modelled mineralization. Gravity profiles have been carried out perpendicularly to the lode orientation; they show a strong structural anomaly. High resolution ground magnetic data were collected over the study area, but they showed no anomaly over the ore deposits. The geophysical inversion results are complementary to the model based on drill information, and allow us to refine the delineation of the mineralization. The identification of the geophysical signatures of this deposit permits targeting new possible mineralization in the area.

Quantitative Interpretation of Gravity and Magnetic Anomalies in West of Tikrit City and Surroundings, Iraq

A quantitative interpretation of gravity and magnetic anomalies in west of Tikrit city and surroundings, has been completed utilizing Grav2dc and Mag2dc (2D, 2.5D) forward techniques. The modeling has been carried out along four profiles, two NW-SE profiles along the distinct gravity residual anomalies and two NE-SW profiles along the magnetic residual anomalies. The most geologic plausible model that matches the data was picked. The model along the gravity profile (A-A') reveal faulting of the basement, whereas along the profiles B-B', C-C' and D-D' did not present faulting. The models comprise of two rock units, the first is the sedimentary cover and the second unit is the basement rock. According to the results of modeling, thickness of the sedimentary cover and basement depth values are in good agreement with the results of previous studies. The upper part of sedimentary cover exhibited different density and susceptibility contrasts. These contrasts may be interpreted in term of lithological lateral variation.

Crustal structure of the southeastern Tibetan Plateau from gravity data: New evidence for clockwise movement of the Chuan–Dian rhombic block

The crustal deformation beneath the Chuan–Dian rhombic block (CDB) and surrounding regions has been studied in geological and geodetic methods, and provide important insights into the kinematics and dynamics about the clockwise movement of this tectonic block. In this work, we present images of the normalized full gradient (NFG) of the Bouguer gravity anomalies from five gravity profiles across the boundary faults of the CDB measured in recent years, and investigate the distribution characteristics of the crustal anomalous bodies along the profiles. Firstly, an anomalous body with eastward dipping exist beneath the Xianshuihe fault, suggesting that crustal mass move to east. Secondly, near the Xiaojiang fault, two anomalous bodies dip westward with depth increasing. The inferred movement direction of the north one is from west to east, and the south one is from east to west. Thirdly, anomalous bodies on the northeast and southwest sides of the Red River fault suggest the directions of crustal movement is from northeast to southwest. These results are also consistent with GPS solutions, and provide gravity evidence for crustal deformation of the CDB with clockwise rotation.