Seismic Wave Velocity Research Articles

Analysis on propagation law of shallow underground chemical explosion seismic waves

Introduction: Seismic waves generated by shallow underground explosions propagate differently from those generated by surface explosions. Thus, an accurate understanding of the propagation laws of seismic waves generated by explosions at various burial depths and TNT equivalent amounts is significant in assessing the destructive power of munitions and establishing guidelines for their application.Methods: In this study, we conducted several ground vibration velocity tests of shallow underground chemical explosion seismic waves for various TNT equivalent amounts and burial depths in a shooting range and analyzed the propagation of the seismic waves. Using the explosion similarity theory and dimensional analysis, we derived an equation for the estimation of the particle vibration velocity of shallow underground chemical explosion seismic waves. This equation calculation results have a very high degree of agreement with the measured data, measured data verify that the accuracy of the calculation model is better than 90.2%.Results and discussion: This equation calculation results have a very high degree of agreement with the measured data, measured data verify that the accuracy of the calculation model is better than 90.2%, which greatly improves the calculation accuracy of the shallow underground chemical explosion seismic wave particle vibration velocity, and thus provide effective theoretical support for analyzing explosion seismic waves in engineering tests.

Preliminary Results on Receiver Function Study in Mt Merapi, Central Java, Indonesia

Mount Merapi, a stratovolcano, is the world’s most active volcano, with a relatively short eruption period. Mount Merapi formed in the Java region as a result of regional tectonics dominated by the Sunda Arc, resulting in a large earthquake. Many earth scientists are interested in studying the volcano’s subsurface conditions due to its relatively short eruption period and interesting geological features. The Receiver Function method was used in this study to determine the crust’s depth and assess the presence of a LVZ (low velocity zone) by reprocessing receiver function data. The Receiver function is used to identify the Moho discontinuity area by converting P to S waves. A total of 100 earthquake data from 8 teleseismic stations were successfully downloaded from the IRIS website, that was distributed into sections A-A′ (west side of Mount Merapi) and B-B’ (east side of Mount Merapi). The processing of the receiver function data, as shown by the stacking align results, shows that the closest teleseismic station at west side of Mount Merapi has a very strong negative amplitude response, which is represented as a LVZ or magma reservoir after the arrival of P wave. To estimate the zone for LVZ, a forward modeling receiver function technique was used to find the best correlation between the Synthetic Receiver Function curve and the Receiver Function observation curve. A forward modeling receiver function technique was used to find the best correlation between the Synthetic RFcurve and the RF observation curve to estimate the zone for the LVZ. The correlation between the synthetic RF curve from Ramdhan et al’s (2019) tomographic velocity model and the observed RF curve is poor. To improve the correlation, include the main signal source that affects the receiver function curve in the form of seismic wave velocity particularly Vs, LVZ Zone, thin sedimen layer or shallow reservoir, and depth of discontinuity by Suhardja et al (2019). The estimated depth of the LVZ at 10 - 17 km is thinning towards the south or towards Mount Merapi, according to the results of the synthetic receiver function curve modelling at the closest station to Mount Merapi.

ANALYSIS OF FREQUENCY CONTENT AND STATISTICAL RELATIONSHIP AMONG EARTHQUAKE PARAMETERS OF SEISMIC DATA

The frequency content of the strong-motion seismic data collected from seismic stations by the Bangladesh Meteorological Department (BMD) using GL-S60/120 broadband seismometers of earthquakes in and around Bangladesh is examined. In addition, the statistical relationships among various earthquake parameters, such as the peak ground velocity (PGV), magnitude, epicentral distance, and time of arrival of p-and s-waves of the collected data, are analyzed. Approximate seismic wave velocities are also obtained. The Fourier and wavelet analysis results reveal delicate differences in the frequency content of the p-and s-waves occurring during earthquakes. These results are compared to those generated from the STEAD dataset, which contains seismic waveforms collected in the U.S., France, and Greece regions. Regression analysis on the BMD data derives relationships among the aforementioned parameters. Collected data from some stations show perfect linear relationships among PGV and the travel time of seismic waves with magnitude and epicentral distance, whereas, in other stations, such relationships are not significant. Plausible explanations for these disparities are provided along with similar regression analysis using the STEAD data. The findings are useful for earthquake early-warning systems, geology research, seismic risk zone delineation, and seismic hazard forecasts.

Electronic Structure and Mechanical Properties of Solvated Montmorillonite Clay Using Large-Scale DFT Method

Montmorillonite clay (MMT) has been widely used in engineering and environmental applications as a landfill barrier and toxic waste repository due to its unique property as an expandable clay mineral that can absorb water easily. This absorption process rendered MMT to be highly exothermic due to electrostatic interactions among molecules and hydrogen bonds between surface atoms. A detailed study of a large supercell model of structural clay enables us to predict long-term nuclear waste storage. Herein, a large solvent MMT model with 4071 atoms is studied using ab initio density functional theory. The DFT calculation and analysis clarify the important issues, such as bond strength, solvation effect, elasticity, and seismic wave velocities. These results are compared to our previous study on crystalline MMT (dry). The solvated MMT has reduced shear modulus (G), bulk modulus (K), and Young’s modulus (E). We observe that the conduction band (CB) in the density of states (DOS) of solvated MMT model has a single, conspicuous peak at −8.5 eV. Moreover, the atom-resolved partial density of states (PDOS) summarizes the roles played by each atom in the DOS. These findings illuminate numerous potential sophisticated applications of MMT clay.

Fluid identification by nonlinear frequency‐dependent amplitude variation with offset inversion based on scattering theory

AbstractPre‐stack seismic amplitude variation with offset inversion is a crucial technique in seismic exploration, employed to estimate reservoir elastic parameters and thus reservoir fluid properties. However, traditional amplitude variation with offset inversion methods are based on elastic theory and linear approximation, neglecting the inelasticity of medium and nonlinear theory. To overcome this limitation, a quadratic scattering coefficient equation of the viscoelastic fluid factor is derived, which provides the basis for the equation for amplitude variation with offset inversion. Traditional amplitude variation with offset inversion methods typically neglect seismic dispersion and attenuation, failing to account for the influence of the seismic wave velocity attenuation and frequency variation. Quality factors of P‐ and S‐waves represent the degree of attenuation of seismic waves. To comprehensively address the effects of seismic wave dispersion and attenuation, a novel method called pre‐stack seismic nonlinear frequency‐dependent amplitude variation with offset inversion has been developed. This method builds upon the new quadratic scattering coefficient and is utilized for reservoir fluid prediction. The reliability and stability of the method are verified through synthetic and filed data examples. Further analysis reveals that the method is more reasonable and accurate compared to the traditional linear amplitude variation with offset inversion method. The results demonstrate that the proposed pre‐stack seismic nonlinear frequency‐dependent amplitude variation with offset inversion method can effectively identify reservoir fluids, providing a novel solution for reservoir fluid identification.

Compressibility of ferropericlase at high-temperature: Evidence for the iron spin crossover in seismic tomography

The iron spin crossover in ferropericlase, the second most abundant mineral in Earth's lower mantle, causes changes in a range of physical properties, including seismic wave velocities. Understanding the effect of temperature on the spin crossover is essential to detect its signature in seismic observations and constrain its occurrence in the mantle. Here, we report the first experimental results on the spin crossover-induced bulk modulus softening at high temperatures, derived directly from time-resolved x-ray diffraction measurements during continuous compression of (Mg0.8Fe0.2)O in a resistive-heated dynamic diamond-anvil cell. We present new theoretical calculations of the spin crossover at mantle temperatures benchmarked by the experiments. Based on our results, we create synthetic seismic tomography models to investigate the signature of the spin crossover in global seismic tomography. A tomographic filter is applied to allow for meaningful comparisons between the synthetic models and data-based seismic tomography models, like SP12RTS. A negative anomaly in the correlation between Vs variations and Vc variations (S-C correlation) is found to be the most suitable measure to detect the presence of the spin crossover in tomographic models. When including the effects of the spin crossover, the misfit between the synthetic model and SP12RTS is reduced by 63%, providing strong evidence for the presence of the spin crossover, and hence ferropericlase, in the lower mantle. Future improvement of seismic resolution may facilitate a detailed mapping of spin state using the S-C correlation, providing constraints on mantle temperatures by taking advantage of the temperature sensitivity of the spin crossover.

Airfield suitability assessment from geophysical methods

The construction of new airfields on semi-prepared terrain and the repair of existing airfield requires a quick and accurate suitability assessment of the subgrade soil strength and stability. The suitability of an airfield for regular operations is a function of the stiffness of the subgrade soil under small deflections. Stiffness is characterized by the elastic modulus of the soil. In-situ soil modulus values are commonly estimated from California Bearing Ratio (CBR) values via an empirical relationship. Currently, the dynamic cone penetration (DCP) testing method is the most widely used technique for determining the in-situ CBR. For airfield design, a DCP value is used to estimate a CBR value, which in turn, is used to estimate a modulus value. When these individual empirical equations are combined, the errors inherent to each empirical equation are compounded. Geophysical measurements such as seismic wave velocity and electrical resistivity can directly quantify modulus and eliminate a need for a multistep empirical process.This paper presents the results of an effort to use seismic wave velocity and electrical resistivity data to determine airfield design parameters. For the reported study, CBR values estimated from DCP penetration resistance were compared to equivalent CBR values estimated from shear wave velocity and electrical resistivity values. Relationships linking the geophysical measurements to CBR estimates were established using laboratory data. These relationships were then applied to field in-situ measurements. The field in-situ measurements were further used to calculate airfield design parameters such as allowable aircraft load and the number of aircraft passes. The results of this study show that CBR values estimated from shear wave velocity measurements well matched DCP-derived CBR values. Thus, establishing the viability of utilizing geophysical methods to assess airfield suitability.

Geoelectric Model of the Central Part of the Northern Caucasus and Its Fluid Saturation

A series of magnetotelluric and seismic studies have been carried out on profiles covering more than two thousand kilometers within the North Caucasus region. The earlier interpretation of the magnetotelluric observations by means of one– and two–dimensional inversion and three–dimensional mathematical modeling software has helped to construct a series of sections and models which are viewed as test and starting ones for the construction of a three–dimensional geoelectric model of the region. The test models have been used to test how well the software for three–dimensional inversion of the impedance tensor components in the magnetotelluric sounding method can estimate the parameters of conducting blocks in the structures of the Greater Caucasus and the Scythian plate. In the resulting geoelectric model, constructed from the results of three–dimensional inversion of all impedance tensor components, the position of low–resistance blocks correlates with deep faults, volcanoes of various genesis, and seismically active zones characterized by the reduced velocity of seismic waves and their increased absorption. The electrical resistivity of low–resistance anomalies is explained by the degree of their saturation with the fluid water fraction. Its maximum concentration is found within the intersections of fault systems, flexural–rupture zones, and deep faults activated by tectonic processes.

Analytic formula for the group velocity and its derivatives with respect to elastic moduli for a general anisotropic medium

Studying the anisotropy of seismic wave velocity can provide a theoretical basis for understanding the characteristics of seismic wave propagation in anisotropic media, such as forward modeling of seismic wavefield and simultaneous inversion of anisotropic parameters. It is an important work to calculate the group velocities of three kinds of seismic waves (qP, qS1, and qS2) and the analytical expressions of the partial derivatives of the group velocities with respect to 21 elastic parameters in general anisotropic media. Therefore, a new relationship between the phase and group velocity in the general anisotropic medium is introduced first, and then the analytical expressions of the group velocity of three kinds of waves are deduced. Then, the analytical formulas of partial derivatives of the group (or phase) velocity with respect to 21 elastic parameters are derived. Finally, the distribution of partial derivatives of group slowness with respect to 21 elastic parameters with varied ray angles is analyzed and discussed. The final analytical expressions of group velocity and its partial derivatives are relatively concise and can deal with the singular points and multivalued problems of qS waves. By drawing comparison to the numerical solution of the eigenvector method, the accuracy of the analytical formula of group velocity and its partial derivatives with respect to elastic parameters are verified. The numerical simulation results indicate that the algorithm can accurately obtain the partial derivatives of group slowness with respect to 21 elastic parameters and would provide a theoretical basis for seismic ray tracing and traveltime inversion in general anisotropic media.

Characterizing large rockfalls using their seismic signature: A case study of Hongya rockfall

A preliminary, yet timely characterization of rockfall hazards is essential for effective emergency response and mitigation measures. Such characterization is, however, particularly challenging for events occurring on high-mountain slopes in remote locations, for which precursory information remains often undetected. Large rockfalls are known to produce seismic signatures that, if properly interpreted, provide key information on the magnitude and destructiveness of the event. To achieve this, we establish a seismic signal-based assessment scheme and demonstrate its capability by taking a large event – the 5 April 2021 Hongya rockfall (Sichuan, China) – as a case study. First, we show how a rockfall can be distinguished from an earthquake and a rockslide by analyzing its seismic signatures. Then, we demonstrate how the kurtosis-based method can be used to rapidly detect the initiation of a rockfall and determine the seismic wave velocity accordingly, as well as how the arrival-time-based location method can be used to locate the event. The rockfall volume can be estimated from the magnitude of radiated seismic energy. Furthermore, we characterize the different phases in seismograms and link them to the typical stages of rockfall, i.e., precursory small rockfalls, impact and fragmentation, sliding and entrainment, and gravity deposition stages. Finally, a discussion and suggestions are provided for further improving the robustness of the assessment scheme. Our results show that the seismic signal-based scheme presented in this study is suitable for characterizing large rockfalls and has the potential for rapid and effective emergency management.

Along-Strike Variation in the Shallow Velocity Structure beneath the Chenghai Fault Zone, Yunnan, China, Constrained from Methane Sources and Dense Arrays

Abstract The fine structure of the fault zone and the surrounding area is the basis for understanding the process of earthquake nucleation and rupture propagation. To obtain the high-resolution structure of the Chenghai fault (CHF) and the nearby basins, we deployed two dense arrays and excited eight methane sources across the fault from October to November 2020. Based on the 611 P-wave travel times, we obtained the shallow velocity structure beneath the arrays using the simul2000 travel-time inversion program, and the results are as follows: (1) the shallow velocity structure beneath the CHF is very complex, with obvious velocity contrasts on both the sides of the regional fault; (2) low-velocity zones (LVZs) beneath the CHF show clear along-strike variations. The LVZs extend to ∼500 m in depth with widths of ∼2 km and ∼5 km beneath the Qina and Pianjiao arrays, respectively, which are consistent with the Quaternary sediments, and the velocity contrasts along the interface of the LVZ can reach 20%–50%; and (3) the distribution of shallow surface tectonic geomorphology is mainly controlled by regional fault activities that are formed under the combined action of regional near-east–west stretching and clockwise rotation of microblocks. Our results can help improve cognition and seismic hazard assessment for potential earthquakes on the CHF, as well as lay the foundation for understanding the seismic wave velocity variation mechanism in the fault zone.

Understanding slow-moving landslide triggering processes using low-cost passive seismic and inclinometer monitoring

Landslides are a major natural hazard, threatening communities and infrastructures worldwide. Mitigation of these hazards relies on understanding their causes and triggering processes, which critically depend on subsurface characteristics and their variations over time. In this study, we present a novel approach combining passive seismic and low-cost inclinometer monitoring methods to improve the understanding of landslide activation mechanisms and their controls. We evaluate the efficiency of this approach on a shallow, slow-moving landslide directly endangering a road bridge, a bridge that is part of an important emergency response route. Results show the value of combining the two approaches for observing and monitoring landslide hazards. Passive seismic monitoring captures the variation in soil properties (rigidity and density) over time by sensing the variations of the seismic wave velocity (dV/V and its associated correlation coefficient). At the same time, novel low-cost inclinometers are monitoring subsurface deformation (from millimetric to pluricentimetric scale) and temperature. Seismic precursors detected at the bottom sensor a few hours prior to the reactivation are followed by the reactivation of the landslide toe, releasing stresses in the top part that lead to the reactivation of the whole landslide. This reactivation occurs during an episode of heavy rainfall following a 7-month drought. Meanwhile, temperature monitoring enables us to track water infiltration and to highlight its role in the landslide mechanisms. Overall, the combination of the two monitoring methods shows promise for quantifying the sliding mechanisms of landslide reactivations and for designing landslide early warning systems.

Determination of effective seismic wave velocities using time gradients obtained from response and CDP reflection hodographs

Seismic wave velocities, including effective velocities, play a critical role in the kinematic processing and interpretation of 2D and 3D seismic data. Along with other parameters of elastic waves, the geological efficiency of seismic exploration also depends on the level of knowledge of the velocity model of the medium, on the accuracy of information about velocities. The article briefly lists the main methods for determining the effective velocities according to the seismic wave field, developed and applied in the practice of seismic research. The methods used to determine the effective velocities of reflected waves can be divided into two groups: methods for determining the effective velocities based on automatic or visual tracking of the in-phase axes (i.e. hodographs) of reflected waves on seismic records, then their approximation by hyperbolas constitute the first group, and the second the group consists of methods based on the application of the analysis of the seismic wave field in controlled directions on the seismograms of a common depth point (CDP). Each proposed method for determining effective speeds has advantages and disadvantages. The article focuses on the industrial method, widely used at present, based on the analysis of the wave field in controlled directions, which do not provide sufficient information to solve the main problems of kinematic interpretation. The main disadvantages of the existing methods are indicated. The article describes a new method for determining the effective velocity, which is fundamentally different from the methods that are still used in the practice of seismic exploration. The fact is that in this method, seismic survey data of single and multiple profiling are not used separately, as it was in the methods used in seismic survey practice so far, but together. Formulas have been derived for determining the effective velocity based on the time gradients of the travel time curves of the CSP and CDP of reflected waves, which makes it possible to determine the speeds even from incomplete travel time curves. A technique for determining the effective speed has been developed and a sequence of procedures has been determined for solving the problem. The results of research are given on a specific example by solving the direct and inverse problems for the Sazhdag area between the Kura and Gabyrra rivers. The influence of errors in the values of the parameters included in the formula for calculating the effective speed on the final results is studied. At the end of the article, the main advantages of the proposed method are indicated.

Internal Structure and Reactivations of a Mass Movement: The Case Study of the Jacotines Landslide (Champagne Vineyards, France)

The Jacotines landslide is representative of the large mass movements that affect the Champagne vineyards. Understanding the subsurface structure of these slopes and the mechanisms leading to sliding events is of a great interest, particularly for winegrowers who produce Champagne. This knowledge is generally used to elaborate accurate hazard assessment maps, which is an important feature in land use planning. The approach presented is based on the integration of geophysical imaging (seismic wave velocity and electrical resistivity), lithostratigraphic analysis (drilling core) and geomorphological investigations (surface landforms) to reconstruct the relations between the landslide structure, surface water flow, groundwater regime and the overall slope stability. A first phase of instability resulting in a large rotational slip probably occurred during the Late Glacial Period in morphoclimatic conditions characterized by an excess of water. A second one, still active, leading to superficial reactivations and relates to present hydrogeological conditions determined by the internal structure of the landslide.

Neotectonic Dislocations on the Barents Sea Shelf and Their Origin on the Basis of Morphometry of the Seafloor Relief, Seismic Survey, and the Deep Structure of the Mantle

A comprehensive analysis of the morphometric attribute “general curvature” for the Barents Sea bathymetry and reports on the seismic and seismoacoustic data on tectonic dislocations in a wave field, the fault network of the sedimentary cover, and seismotomographic data on the heterogeneous deep pattern of the distribution of seismic wave velocities in the upper mantle are provided. The analysis showed that mobile blocks of the upper mantle, exhibiting heterogeneous rheological properties, are associated with the consolidated part of the Earth’s crust fault network of deep-seated origin. The fault network emerges on the seafloor and, becoming a relief-forming factor, forms specific domains with different textures displayed in the morphometric attribute “general curvature.”

Tidal Response of Seismic Wave Velocity at Shallow Crust in Japan

AbstractMicrocracks in geomaterials cause variations in the elastic moduli under applied strain, thereby creating seismic wave velocity variations. These are crucial for understanding the dynamic processes of the crust, such as fault‐zone damage, healing, and volcanic activities. Solid earth tides have been used to detect seismic velocity changes responding to crustal‐scale deformations. However, no prior research has explored the characteristics of the seismic velocity variations caused by large‐scale tidal deformation. To systematically evaluate the tidal response to velocity variations, we developed a new method that utilized the flexibility of a state‐space model. The tidal response was derived from hourly stacked noise autocorrelations using a seismic interferometry method throughout Japan. In particular, large tide‐induced seismic velocity changes were observed in the low S‐wave velocity region of the shallow crust. Overall, the tidal responses of velocity variations can provide new insights into the response mechanisms of the shallow crust to applied strain.

The lunar solid inner core and the mantle overturn.

Seismological models from Apollo missions provided the first records of the Moon inner structure with a decrease in seismicwave velocities at the core-mantle boundary1-3. The resolution of these records prevents a strict detection of a putative lunar solid inner core and the impact of the lunar mantle overturn in the lowest part of the Moon is still discussed4-7. Here we combine geophysical and geodesic constraints from Monte Carlo exploration and thermodynamical simulations for different Moon internal structures toshow that only models with a lowviscosity zone enriched in ilmenite and an inner core present densities deduced from thermodynamic constraints compatible with densities deduced from tidal deformations. We thus obtain strong indications in favour of the lunar mantle overturn scenario and, in this context, demonstrate the existence of the lunar inner core with a radius of 258 ± 40 km and density 7,822 ± 1,615 kg m-3. Our results question the evolution of the Moon magnetic field thanks to its demonstration of the existence of the inner core and support a global mantle overturn scenario that brings substantial insights on the timeline of the lunar bombardment in the first billion years of the Solar System8.

Lithospheric strength and elastic properties for Mars from InSight geophysical data

Elastic moduli and unconfined compressive strength (UCS), material constants which help constrain the mechanical behaviors of rock materials, are useful for developing accurate models of geologic processes like fracturing and faulting. On Earth, UCS and elastic moduli for intact rock can be measured with uniaxial and triaxial compressive strength tests; however, when geological units are highly fractured, it is more appropriate to estimate these parameters for the rock mass, fractures included. At depth, these estimations can be obtained using seismic wave velocities where stronger more intact rock masses result in faster velocities. We use seismic wave velocities from the InSight Lander to derive the elastic moduli and UCS for the upper crust, lower crust, and mantle of Mars. These estimates could be used in developing models for lithospheric deformation on the red planet.

Porosity and permeability estimation using seismic wave velocity along Yangtze River embankment

Although porosity and permeability are essential parameters for slope stability, estimating the spatial porosity and permeability variation of slope site is difficult because of complexity of petrophysical modeling. The differential effective medium (DEM) and self-consistent approximation (SCA), which used to calculate elastic modulus of porous materials, are applied to link seismic wave velocity to porosity and permeability. The shear-wave velocity structure is gathered through a near surface Rayleigh-wave survey, and the porosity and permeability profiles are further estimated. The results are cross validated by the borehole data and poroelastic relation. The petrophysical structure of the Yangtze River embankment may further reflect hydrological properties of laminated layers, which bear relatively large porosity and permeability in some area. The results show that the porosity and permeability profiles based on SCA are more reliable with respecting to the borehole data. The relationship between seismic velocity and porosity and permeability is established and validated, favoring a sound basis for further hydrological interpretation of seismic data. Furthermore, some geotechnical suggestions are put forward during the flood seasons in correspondence to the natural hazard mitigation.

Earth’s crust and physical fields of the oceans

Some problems of the formation and development of oceanic regions with various variants of endogenic regimes (with the exception of island arcs, which, in the author’s opinion, belong to late Alpine geosynclines) are considered. Calculated geological events and anomalies of physical fields within them are determined by heat-mass-transfer schemes in the tectonosphere. The reliability and accuracy of the latter is related to the quantity and quality of information about the content of the regimes. In the oceans, such data is scarce. The article attempts to attract additional information about the formation of the Earth’s crust of a typical oceanic basin. It was presented in the form of oceanization (destruction and basification) of the continental crust with a slightly increased basicity. The process included the uplift and denudation of the upper block up to 10 km thick, the intrusion of mafic and ultrabasic rocks from the mantle in a concentration increasing with depth into the lower approximately 20—30 km of the crust. Seismic wave velocity and density in the crustal basement were almost equal to the properties of the warmed mantle rocks. The final stage of magmatism was presented in a large part of the region during the period of recent activation by the removal of partially molten matter from the shallow asthenosphere up to the surface. Similar models have also been constructed for other endogenous regimes. In all cases, significant scatter in the ages of the process stages and the order of formation of asthenolite sources rising from different depths of the upper mantle were unavoidable. The resulting thermal models were averaged effects for the considered variants of heat and mass transfer. The control of the reality of these constructions was carried out according to the correspondence of known events of geological history, allowing a quantitative description, and anomalies of physical fields. In this work, the second part is considered. The calculated velocity sections of the upper mantle regions, the heat flow distribution, and the values of mantle gravity anomalies were compared with the experimental data. In all cases, the agreement reached is satisfactory. The discrepancies can be explained by errors in observations and calculations