Inversion Of Dispersion Curves Research Articles

A MATLAB Package for Calculating Partial Derivatives of Surface-Wave Dispersion Curves by a Reduced Delta Matrix Method

Various surface-wave exploration methods have become increasingly important tools in investigating the properties of subsurface structures. Inversion of the experimental dispersion curves is generally an indispensable component of these methods. Accurate and reliable calculation of partial derivatives of surface-wave dispersion curves with respect to parameters of subsurface layers is critical to the success of these approaches if the linearized inversion strategies are adopted. Here we present an open-source MATLAB package, named SWPD (Surface Wave Partial Derivative), for modeling surface-wave (both Rayleigh- and Love-wave) dispersion curves (both phase and group velocity) and particularly for computing their partial derivatives with high precision. The package is able to compute partial derivatives of phase velocity and of Love-wave group velocity analytically based on the combined use of the reduced delta matrix theory and the implicit function theorem. For partial derivatives of Rayleigh-wave group velocity, a hemi-analytical method is presented, which analytically calculates all the first-order partial differentiations and approximates the mixed second-order partial differentiation term with a central difference scheme. We provide examples to demonstrate the effectiveness of this package, and demo scripts are also provided for users to reproduce all results of this paper and thus to become familiar with the package as quickly as possible.

Wave-equation dispersion inversion of Love waves

We present a theory for wave-equation inversion of Love-wave dispersion curves, in which the misfit function is the sum of the squared differences between the wavenumbers along the predicted and observed dispersion curves. Similar to inversion of Rayleigh-wave dispersion curves, the complicated Love-wave arrivals in traces are skeletonized as simpler data, namely, the picked dispersion curves in the [Formula: see text] domain. Numerical solutions to the SH-wave equation and an iterative optimization method are then used to invert these dispersion curves for the S-wave velocity model. This procedure, denoted as wave-equation dispersion inversion of Love waves (LWD), does not require the assumption of a layered model or smooth velocity variations, and it is less prone to the cycle-skipping problems of full-waveform inversion. We demonstrate with synthetic and field data examples that LWD can accurately reconstruct the S-wave velocity distribution in a laterally heterogeneous medium. Compared with Rayleigh waves, inversion of the Love-wave dispersion curves empirically exhibits better convergence properties because they are completely insensitive to the P-velocity variations. In addition, Love-wave dispersion curves for our examples are simpler than those for Rayleigh waves, and they are easier to pick in our field data with a low signal-to-noise ratio.

Delineating a low velocity zone using joint inversion of rayleigh-wave dispersion curve

Seismic methods widely used to study the shallow subsurface for different purposes. Analysis of P-wave refraction cannot uniquely determine the seismic velocities as a function of depth when a low velocity layer is present. It is situation commonly encountered in geotechnical site investigation. Utilization of Rayleigh wave dispersion can be uses to determine the structure with existence of low velocity zone. In this study, we discuss efficiency and effectiveness of a joint inversion of Rayleigh wave dispersion curve which combining the genetic algorithm and the Occam’s algorithm to delineate a low velocity zone. Numerical test is presented. The shear wave velocity and thickness errors which is the difference between the true and inverted model parameters is used to appraise the value accuracy inversion model. The result provides accurate solution models with is 2.3 % and is 13.4%. Finally, we demonstrates the joint inversion scheme to invert Rayleigh wave dispersion curve which calculated by phase-shift method from a real example data.

Near-surface S-wave Estimation base on Inversion of Rayleigh Wave Dispersion Curve Using Genetic Algorithm

Multi-channel analysis of surface wave (MASW) is a suitable technique to infer shallow structure of vertical shear-wave velocity profile from seismic record data. The processing stage is focused on obtaining the reliable dispersion curves, and the final stage of the method is that to obtain the shear velocity model that can explain the observation. The genetic algorithm (GA) method, one of the global optimization approaches, has been implemented to obtain shear wave model from Rayleigh wave dispersion curve. The GA method mimic biological evolution in order to obtain the optimum solution. Application of GA method to two synthetic models for normal velocity profile and low velocity anomaly give good results indicated with small misfit. Finally, we demonstrate the GA to Rayleigh dispersion curve for real data which calculated by using phase-shift method.

Shallow and in depth seismic testing in urban environment: A case study in Lisbon Miocene stiff soils using joint inversion of active and passive Rayleigh wave measurements

The use of Surface Wave Methods for the characterization of the shear wave velocity profile of the soil has become increasingly attractive due to its non-invasive nature and its ability to provide information at a larger scale. Their main drawbacks are the non-uniqueness of the solution and high uncertainty of the results at higher depths. Its application in dense urban areas can be challenging due to the proximity to underground structures, high background noise level and space limitations. This paper describes a case study on the use of surface wave based methods on stiff soil in urban environment within a confined area located in Lisbon city, Portugal, surrounded by buildings and between an underground car park and the subway tunnel. The old building, built in the study area, was demolished for the construction of a new building with five basement floors. During this process, passive and active linear array and passive three-component single-station measurements were made at the surface level, before the works started, and at 2 deeper excavation levels. The results obtained using shallow and in depth measurements were compared, including HVSR and Rayleigh wave ellipticity curves and Vs profiles obtained through the conventional MASW method and through the joint inversion of both Rayleigh wave dispersion and ellipticity curves. A deeper Vs profile with low uncertainty was obtained through the joint analysis of Rayleigh wave dispersion and ellipticity curves, compatible with Vs profile obtained in depth.

Nonlinear Inversion of Ultrasonic Dispersion Curves for Cortical Bone Thickness and Elastic Velocities.

In this study, a nonlinear grid-search inversion has been developed to estimate the thickness and elastic velocities of long cortical bones, which are important determinants of bone strength, from axially-transmitted ultrasonic data. The inversion scheme is formulated in the dispersive frequency-phase velocity domain to recover bone properties. The method uses ultrasonic guided waves to retrieve overlying soft tissue thickness, cortical thickness, compressional, and shear-wave velocities of the cortex. The inversion strategy requires systematic examination of a large set of trial dispersion-curve solutions within a pre-defined model space to match the data with minimum cost in a least-squares sense. The theoretical dispersion curves required to solve the inverse problem are computed for bilayered bone models using a semi-analytical finite-element method. The feasibility of the proposed approach was demonstrated by the numerically simulated data for a 1 mm soft tissue-5 mm bone bilayer and ex-vivo data from a bovine femur plate with an overlying 2 mm-thick soft-tissue mimic. The bootstrap method was employed to evaluate the inversion uncertainty and stability. Our results have shown that the cortical thickness and wave speeds could be recovered with fair accuracy.

An Interactive Integrated Interpretation of GPR and Rayleigh Wave Data Based on the Genetic Algorithm

Ground-penetrating radar (GPR) and the seismic surface wave method are two geophysical techniques commonly used in near-surface surveys up to a depth of tens of meters. GPR can be utilized to clearly distinguish lithologic interfaces, while the seismic surface wave method (hereby referred to as the Rayleigh wave) is employed for its high sensitivity to the shear (S) wave velocity. However, the propagation velocity of the electromagnetic (EM) wave which is both initiated and tracked by GPR is difficult to determine within the stratum. Unfortunately, this can affect the time–depth conversion and interpretation of the radargram. Moreover, both the horizontal resolution and the detectability of the properties of the shallow stratum are limited by the seismic geometry of the Rayleigh wave data. It is important to note that the non-uniqueness of geophysical inversion problem also generates additional biases. To overcome the problems mentioned above, we put forward an interactive integrated geophysical system that utilizes the thickness as a bridge to connect GPR and the Rayleigh wave data in the data processing and inversion. In this study, we employed the velocity of a radagram and the Rayleigh wave dispersion curve inversion based on a genetic algorithm to reconstruct the near-surface distribution. Then, we set the thickness derived from the GPR data as limit of the Rayleigh wave dispersion curve inversion. Hence, we applied the constrained inversion result to determine the most accurate EM wave velocity. As expected, both the constrained inversion of the Rayleigh wave dispersion curve and the velocity correction of the radargram performed better than did the geophysical method alone, both in the numerical models and in the field. Finally, we found the interactive integrated geophysical system to be more conducive for geological interpretation in near-surface surveys.

Using a vibratory source at Mt. Etna (Italy) to investigate the wavefield polarization at Pernicana Fault

ABSTRACTThe paper presents the results of a controlled‐source seismic experiment performed using a vibratory source capable of producing harmonic vibrations. The survey aimed at investigating the horizontal directional amplification mechanism observed at the Pernicana Fault (Mt. Etna in Sicily, Italy) along an N150°/N330° orientation. With the vibratory source (a shaker truck) working in shear‐wave mode in the frequency range 5–40 Hz, we recorded seismic data using both three‐component velocimeters and 4.5 Hz geophones. These two types of receivers were arranged in linear configuration along two orthogonal orientations: radial and transverse to the direction of the main polarization observed within the fault zone. The two lines of seismic stations allowed us to investigate the polarization evolution as a function of the distance from the source. Results show that when the shear excitation induced by the source is parallel to the direction of observed polarization of the ground motion, the seismic signal propagates efficiently, maintaining the same horizontal polarization induced by the active source. This polarization is well recorded up to distances as large as 300 m from the source. On the contrary, when the shear excitation is orthogonal to the predominant site polarization, the ground excitation loses its initial polarization in less than 50 m away from the source position. At larger distances, the transmitted energy propagates with the natural site polarization independently from the original source polarization. The observations in terms of polarization were combined with surface‐wave analysis, aimed at investigating the dispersion characteristics of the wavefield on the geophone lines. The data suggest that the experimental Rayleigh‐wave dispersion spectra show a more coherent signal over the frequency range along the same orientation of the observed site polarization, supporting a preferential direction in the propagation of surface waves. From inversion of the Rayleigh dispersion curves, we inferred the shear‐wave velocity (Vs) to be in the range of 120–450 m/s in the first 30 m deep of Quaternary volcanic sediments. The dispersion curves are not constant along transverse and radial directions, suggesting the presence of fracture‐induced seismic anisotropy in the near surface.

Subglacial sediment distribution from constrained seismic inversion, using MuLTI software: examples from Midtdalsbreen, Norway

ABSTRACTFast ice flow is associated with the deformation of subglacial sediment. Seismic shear velocities, Vs, increase with the rigidity of material and hence can be used to distinguish soft sediment from hard bedrock substrates. Depth profiles of Vs can be obtained from inversions of Rayleigh wave dispersion curves, from passive or active-sources, but these can be highly ambiguous and lack depth sensitivity. Our novel Bayesian transdimensional algorithm, MuLTI, circumvents these issues by adding independent depth constraints to the inversion, also allowing comprehensive uncertainty analysis. We apply MuLTI to the inversion of a Rayleigh wave dataset, acquired using active-source (Multichannel Analysis of Surface Waves) techniques, to characterise sediment distribution beneath the frontal margin of Midtdalsbreen, an outlet of Norway's Hardangerjøkulen ice cap. Ice thickness (0–20 m) is constrained using co-located GPR data. Outputs from MuLTI suggest that partly-frozen sediment (Vs 500–1000 m s−1), overlying bedrock (Vs 2000–2500 m s−1), is present in patches with a thickness of ~4 m, although this approaches the resolvable limit of our Rayleigh wave frequencies (14–100 Hz). Uncertainties immediately beneath the glacier bed are <280 m s−1, implying that MuLTI cannot only distinguish bedrock and sediment substrates but does so with an accuracy sufficient for resolving variations in sediment properties.

Inversion of Rayleigh wave dispersion curves via adaptive GA and nested DLS

Inversion of Rayleigh wave dispersion curves via adaptive GA and nested DLS

Vs30 Mapping and Site Classification in Surakarta City Based on Multichannel Analysis of Surface Waves Method

The Multichannel Analysis of Surface Waves (MASW) method is one of the noninvasive methods that can be used to determine the shear wave velocity. The shear wave velocity can be obtained from the inversion of dispersion curve of the Rayleigh wave. The surveys have done at 10 sites in Surakarta city. Active MASW measurements are performed by using the P.A.S.I. Seismograph Mod. 16S24-P. Geophone used as many as 24 channels with threshold frequency is 4.5 Hz of the vertical component and 8 lbs hammer as an active source. Each spread is given once shot point at 5 to 10 meters from the near geophone. The measurement data as a time domain is transformed to frequency domain. The average shear wave velocity up to 30 meters depth is referred as Vs30. The results show that the distribution Vs30 of Surakarta between 250 − 450 m/s. Based on the National Earthquake Hazard Reduction Program (NEHRP) classification, these values are classified as C and D class. The highest Vs30 values at the southwest part (Laweyan site) is 435.7 m/s and the northern part (Banjarsari site) is 411.7 m/s classified as site class C. Meanwhile, the lowest Vs30 values at the northwest and southeast part (Serengan and Pasar Kliwon sites) classified as D class.

Joint analysis of Rayleigh-wave dispersion curves and diffuse-field HVSR for site characterization: The case of El Ejido town (SE Spain)

The location of El Ejido town over a deep sedimentary basin in a zone of high seismicity in the Spanish context has motivated research on its seismic response characterization. To this aim, S-wave velocity models have been obtained from joint inversion of Rayleigh wave dispersion curves and full-wavefield modelling of the horizontal-to-vertical spectral ratio of ambient noise (HVSR) under the diffuse field assumption (DFA). Combination of spatial autocorrelation surveys (SPAC) with array apertures of several hundred metres and HVSRs displaying low-frequency peaks allowed to characterize deep ground features down to the Triassic bedrock. Predominant periods in the town ranged from 0.8 to 2.3 s, growing towards the SE, with few secondary peaks at higher frequencies.The shallow structure has been explored by means of geotechnical surveys, Multichannel Analysis of Surface Waves (MASW) and SPAC analysis in small-aperture arrays. Resulting models support a general classification of the ground as stiff soil.

Novel depiction of love wave dispersion and inversion for inversely dispersive medium by full SH-wavefield reflectivity method – part I: numerical example

Recently, Love wave applications on geological and geophysical problems have been frequently reported by numerous authors. Unlike Rayleigh wave, Love wave modelling has a simpler algorithm since depends only on three earth properties: SH-wave velocity, density, and thickness of layers. The fewer the parameters more stable the inversion result. There are several tasks, however, that have not been reported related to the modelling and inversion of Love wave data. The tasks are to give answer to several following questions: (a) can Love wave propagate in an inversely dispersive medium of the earth? (b) what is the method recommended to use for explaining appropriate Love wave dispersion curve for the inversely dispersive medium? (c) is that possible to have ‘effective’ Love wave dispersion curve for the inversely dispersive medium and to utilize it in the inversion process? Numerical simulations show that modal matrix method cannot prepare appropriate Love wave dispersion for such a medium. The resulting Love wave dispersion curve still shows high phase velocities at low frequencies, which is not as desired. Full SH-waveform method, in the other hand, successful simulates appropriate Love wave dispersion for such a medium. By this method, an effective Love wave dispersion curve is also introduced. Inversion of the effective dispersion curve can excellently estimate the shear-wave velocity.

Multimodal Layered Transdimensional Inversion of Seismic Dispersion Curves With Depth Constraints

AbstractMuLTI (Multimodal Layered Transdimensional Inversion) is a Markov chain Monte Carlo implementation of Bayesian inversion for the probability distribution of shear wave velocity (Vs) as a function of depth. Based on Multichannel Analysis of Surface Wave methods, it requires as data (i) a Rayleigh‐wave dispersion curve and (ii) additional layer depth constraints, the latter we show significantly improve resolution compared to conventional unconstrained inversions. Such depth constraints may be drawn from any source (e.g., boreholes, complementary geophysical data) provided they also represent a seismic interface. We apply MuLTI to a Norwegian glacier, Midtdalsbreen, in which ground‐penetrating radar was used to constrain internal layers of snow, ice, and subglacial sediments, with transitions at 2 and 25.5 m, and whose Vs is assumed to be in the range 500–1,700, 1,700–1,950, and 200–2,800 m/s, respectively. Synthetic modeling demonstrates that MuLTI recovers the true model of Vs variation with depth. Significantly, compared to inversions without depth constraints, in this synthetic case MuLTI not only reduces by about a factor of 10 the error between the true and the best fitting model, but also reduces by a factor of 2 the vertically averaged spread of the distribution of Vs based on the 95% credible intervals. We further show that using frequencies above about 100 Hz lead to unconverged solutions due to mode ambiguities associated with fine spatial structures. For our acquired data on Midtdalsbreen, we use 14‐100 Hz data for which MuLTI produces a large‐scale converged inversion.

Retrieving shallow shear-wave velocity profiles from 2D seismic-reflection data with severely aliased surface waves

The inversion of surface-wave phase-velocity dispersion curves provides a reliable method to derive near-surface shear-wave velocity profiles. In this work, we invert phase-velocity dispersion curves estimated from 2D seismic-reflection data. These data cannot be used to image the first 50 m with seismic-reflection processing techniques due to the presence of indistinct first breaks and significant NMO-stretching of the shallow reflections. A surface-wave analysis was proposed to derive information about the near surface in order to complement the seismic-reflection stacked sections, which are satisfactory for depths between 50 and 700 m. In order to perform the analysis, we had to overcome some problems, such as the short acquisition time and the large receiver spacing, which resulted in severe spatial aliasing. The analysis consists of spatial partitioning of each line in segments, picking of the phase-velocity dispersion curves for each segment in the f-k domain, and inversion of the picked curves using the neighborhood algorithm. The spatial aliasing is successfully circumvented by continuously tracking the surface-wave modal curves in the f-k domain. This enables us to sample the curves up to a frequency of 40 Hz, even though most components beyond 10 Hz are spatially aliased. The inverted 2D VS sections feature smooth horizontal layers, and a sensitivity analysis yields a penetration depth of 20–25 m. The results suggest that long profiles may be more efficiently surveyed by using a large receiver separation and dealing with the spatial aliasing in the described way, rather than ensuring that no spatially aliased surface waves are acquired.

Crevasse-induced Rayleigh-wave azimuthal anisotropy on Glacier de la Plaine Morte, Switzerland

AbstractCrevasses and englacial fracture networks route meltwater from a glacier's surface to the subglacial drainage system and thus influence glacial hydraulics. However, rapid fracture growth may also lead to sudden and potentially hazardous structural failure of unstable glaciers and ice dams, rifting of ice shelves, or iceberg calving. Here, we use passive seismic recordings to investigate the englacial fracture network on Glacier de la Plaine Morte, Switzerland. Glacier dynamics and the drainage of an ice-marginal lake give rise to numerous icequakes, the majority of which generate dispersed, high-frequency Rayleigh waves. A wide distribution of events allows us to study azimuthal anisotropy between 10 and 30 Hz in order to extract englacial seismic velocities in regions of preferentially oriented crevasses. Beamforming applied to a 100-m-aperture array reveals azimuthal anisotropy of Rayleigh-wave phase velocities reaching a strength of 8% at high frequencies. In addition, we find that the fast direction of wave propagation coincides with the observed surface strike of the narrow crevasses. Forward modeling and inversion of dispersion curves suggest that the azimuthal anisotropy is induced by a 40-m-thick crevassed layer at the surface of the glacier with 8% anisotropy in shear-wave velocity.

Shear velocity structural characterization around the Lonar crater using joint inversion of ambient noise HVSR and Rayleigh wave dispersion

The Lonar crater in India is the only known hyper-velocity impact crater formed in basalt target on the Earth formed by an extra-terrestrial meteorite impact, with a distinct shock-induced metamorphosed signature. To understand the effects of impact deformation, fracturing, emplacement of the shock-metamorphosed ejecta material and sedimentation structure in the target basalt around the crater, we investigate the sub-surface shear velocity structure around the Lonar crater region. We use three components, 24-hour records of ambient noise (or microtremor) H/V spectral ratio (HVSR) and Rayleigh wave dispersion data through cross-correlation of ambient noise, obtained from 20 broadband seismic stations around the Lonar crater. The HVSR pattern across the Lonar crater does not present common frequency peaks, suggesting a laterally varying lithological arrangement around the crater. We observe that the HVSR curves at the stations show one or more peaks, below 1 Hz and above 2 Hz. To obtain the average sub-surface shear velocity models, we use the joint inversion of the phase dispersion curves of fundamental and higher mode Rayleigh wave with HVSR data sets, using neighborhood algorithm, in the frequency range 0.2–20 Hz and explored up to 750 m depth. As a reliability-check for the shear velocity models, we compute the theoretical HVSR by forward modeling. The theoretical and observed HVSR peaks match fairly well at each broadband station spread across the Lonar crater. The results show the existence of the fractured/weathered and sedimentary layers and also of the fundamental and higher modes of Rayleigh waves altering the shape of the HVSR and the Rayleigh wave dispersion curves. A pattern of the multiple layers in the sediment–package is visible in the shallow and deeper parts up to 600 m depths across the Lonar crater, but with spatial variations, which may be due to variations in the extent of the fractured zone. This spatial asymmetry of shear velocity profiles might also be the effect of an obliquity impact at the Lonar crater. The significance of such a joint analysis of different datasets of surface waves and HVSR is intended to reduce non-uniqueness involved in the non-linear inversions and present more acceptable sub-surface models to enhance the near-surface geophysical understanding of the impacted structure around the Lonar Crater.

Two robust imaging methodologies for challenging environments: Wave-equation dispersion inversion of surface waves and guided waves and supervirtual interferometry + tomography for far-offset refractions

Two robust imaging technologies are reviewed that provide subsurface geologic information in challenging environments. The first one is wave-equation dispersion (WD) inversion of surface waves and guided waves (GW) for the shear-velocity (S-wave) and compressional-velocity (P-wave) models, respectively. The other method is traveltime inversion for the velocity model, in which supervirtual refraction interferometry (SVI) is used to enhance the signal-to-noise ratio of far-offset refractions. We have determined the benefits and liabilities of both methods with synthetic seismograms and field data. The benefits of WD are that (1) there is no layered-medium assumption, as there is in conventional inversion of dispersion curves. This means that 2D or 3D velocity models can be accurately estimated from data recorded by seismic surveys over rugged topography, and (2) WD mostly avoids getting stuck in local minima. The liability is that WD for surface waves is almost as expensive as full-waveform inversion (FWI) and, for Rayleigh waves, only recovers the S-velocity distribution to a depth no deeper than approximately 1/2 to 1/3 wavelength of the lowest-frequency surface wave. The limitation for GW is that, for now, it can estimate the P-velocity model by inverting the dispersion curves from GW propagating in near-surface low-velocity zones. Also, WD often requires user intervention to pick reliable dispersion curves. For SVI, the offset of usable refractions can be more than doubled, so that traveltime tomography can be used to estimate a much deeper model of the P-velocity distribution. This can provide a more effective starting velocity model for FWI. The liability is that SVI assumes head-wave first arrivals, not those from strong diving waves.

The Seismic Potential in the Seismic Gap Between the Wenchuan and Lushan Earthquakes Revealed by the Joint Inversion of Receiver Functions and Ambient Noise Data

AbstractBased on a dense seismic array deployed to monitor the seismic gap between the Wenchuan and Lushan earthquakes, a joint inversion of dispersion curves and receiver functions yielded a fine velocity structure in this region with the highest resolution of approximately 20 km. The results show that the upper crust of the Songpan‐Ganzi terrane overthrusted onto the basement of the Sichuan Basin, indicating that the crustal shortening model may be the major mechanism that accounts for the growth of the Longmenshan. The results also show a low‐velocity zone (Vs < 3.5 km/s) and thickened crust (>67 km) beneath the seismic gap, which could be associated with partial melting. The heat transferred from the partial melting at the base of the seismic gap may increase the temperature of the faults to as high as 300–400 °C and cause the segment of the Longmenshan Fault in the seismic gap to become “aseismic.” In contrast, the Shuangshi‐Dachuan Fault, Dayi Fault, and other blind faults to the east‐southeast of the seismic gap are located above a high‐velocity body. The seismogenic environment of these faults is similar to the segments ruptured during the Wenchuan and Lushan earthquakes, both of which occurred above the westward extension of the strong Sichuan Basin. Higher seismic activity was also observed along these faults than that above the low‐velocity zone. Therefore, we deduce that a major earthquake on these faults is possible and that the magnitude could be larger than that of the Dayi earthquake (M 6.2).

Crustal and upper mantle structures of Makran subduction zone, SE Iran by combined surface wave velocity analysis and gravity modeling

The inversion of Rayleigh wave group velocity dispersion curves is challenging, because it is non-linear and multimodal. In this study, we develop and test a new Rayleigh wave dispersion curve inversion scheme using the Shuffled Complex Evolution (SCE) algorithm. Incorporating this optimization algorithm into the inverse procedure not only can effectively locate the promising areas in the solution space for a global minimum but also avoids its wandering near the global minimum in the final stage of search. In addition, our approach differs from others in the model parameterization: Instead of subdividing the model into a large number of thin layers, we invert for thickness, velocities and densities and their vertical gradients of four layers, sediments, upper-crust, lower-crust and upper mantle. The proposed inverse procedure is applied to non-linear inversion of fundamental mode Rayleigh wave group dispersion curves for shear and compressional wave velocities. At first, to determine the efficiency and stability of the SCE method, two noise-free and two noisy synthetic data sets are inverted. Then real data for Makran region in SE Iran are inverted to examine the usage and robustness of the proposed approach on real surface wave data. In a second step, we applied 3D Gravity Modeling based on surface wave analysis results to obtain the density structure and thickness of each layer. The reason for using both types of data sets, is that gravity anomaly has a bad vertical resolution and surface wave group velocities are good for placing layer limits at depth, but they are not very sensitive to densities. Therefore, using gravity data increases the overall resolution of density distribution. In a final step, we used again the SCE method to invert the fundamental mode Rayleigh wave group dispersion curves based on the gravity results. Gravity results like thicknesses and sediment densities have been used to constrain the limit of search space in the SCE method. Results show a high shear and compressional velocity under the Gulf of Oman which reduce to the North of the Makran region. The Moho depth of the Oman Gulf is about 18–28 km and it increases to 46–48 km under the Taftan-Bazman volcanic-arc. The density image shows an average crustal density with maximum values under the Gulf of Oman decreasing northward to the Makran.