First-arrival Traveltime Tomography Research Articles

Damped wave-equation-based first-arrival traveltime tomography using the embedded boundary method

First-arrival traveltime tomography (FATT) is used to delineate shallow velocity structures to identify static effects in oil exploration as well as to characterize the near surface for geotechnical purposes. Because FATT is generally used for land seismic data processing, it becomes necessary to consider irregular topography especially when performing wave-based tomography. However, the standard Cartesian finite-difference method cannot properly handle irregular topography. Hence, the embedded boundary method (EBM) is incorporated into the frequency-domain damped-wave equation to correctly describe irregular topography. The developed modeling algorithm is used to calculate first-arrival traveltimes and to perform FATT. The EBM-based modeling algorithm accurately describes the irregular surfaces of numerical velocity models on a regular mesh by exploiting the mirror image principle. The accuracy of the EBM-based traveltime calculation is validated by using two homogeneous velocity models with dipping and complex surfaces. The validation results demonstrate that our algorithm is unaffected by the staircase approximation. FATT is then applied to synthetic and real data to demonstrate the applicability of the developed algorithm to velocity models with complex topography. For the real data example, the inverted velocity model is used to apply static corrections. The processing results demonstrate an improvement in the continuity of seismic events, thus confirming the accuracy of the developed FATT method.

Elastic-waveform inversion and imaging of 2010 walkaway VSP data from the Raft River geothermal field

A vertical seismic profiling (VSP) survey conducted in 2010 in the original RRG-9 well at the Raft River geothermal field is to understand the subsurface geologic structures for geothermal reservoir characterization. This survey consists of 40 three-component (3C) geophones deployed in the upper 600 m of the well and 255 vibroseis sources positioned along eight walkaway lines at the surface. We perform elastic-waveform inversion and reserve-time migration of the VSP data to obtain high-resolution subsurface images. We first process the raw walkaway 3C VSP data and separate the upgoing compressional-to-compressional (PP) and compressional-to-shear (PS) wavefields. We then build an initial velocity model based on sonic logging and zero-offset VSP data, update the initial model with first-arrival traveltime tomography, and refine the model using elastic-waveform inversion to reveal high-resolution velocity variations. We finally apply reverse-time migration to the upgoing wavefields to obtain high-resolution PP and PS migration images of the lithologies encountered in the well. The refined velocity models obtained using elastic-waveform inversion improve the subsurface migration imaging results. Our elastic-waveform inversion and reverse-time migration confirm the lithology interfaces revealed from well logs and provide images of subsurface geologic layers away from well RRG-9 at the Raft River geothermal field.

A Level-Set Adjoint-State Method for Transmission Traveltime Tomography in Irregular Domains

We propose an efficient PDE based approach for solving the first-arrival traveltime tomography problem in irregular domains. We consider the mismatch functional based on the $L_1$ or $L_2$ fidelity term, respectively, and we compute both functional gradients with respect to the sound speed by the adjoint-state method. The novelty of the proposed method consists of two aspects. First, since the tomography problem is formulated in an irregular domain, we develop new efficient level-set based fast sweeping methods for solving the eikonal and adjoint-state equations in the irregular domain. Second, since the computed adjoint state is associated with a source singularity originated from the gradient of a point source eikonal solution, we propose a novel decomposition approach to remove this singularity, which just requires solving the same adjoint-state equation again but with a different boundary condition. Finally, we show the performance of the proposed algorithm on several numerical examples including a synthetic data set from ultrasound computerized tomography.

Detecting an underground tunnel by applying joint traveltime and waveform inversion

Underground tunnel and void detection is a challenging geophysical problem, and many methods have been proposed. Seismic techniques are promising because of the large seismic velocity contrasts between the air-filled void and the surrounding sediment and concrete. We apply a joint seismic traveltime and waveform inversion method to image a buried tunnel with concrete walls and a void space inside. The joint inversion images the top of the concrete tunnel as a high-velocity anomaly and the void space as a low-velocity anomaly. The location of the velocity anomalies predicted by the method agrees with the known location of the tunnel. As a comparison, the stand-alone full waveform inversion is also applied to the data. The first-arrival traveltime tomography shows weak nonlinearity but fails to image the hidden low-velocity layer. Full waveform inversion is able to image complex near-surface structures, but fitting waveforms may not honor the traveltime fit, especially when the data contain noise. Synthetic and real data tests show that the joint inversion method retains the advantages of both traveltime inversion and full waveform inversion and overcomes their respective drawbacks at the same time. The field example shows the joint inversion provides a better reconstruction of the high-velocity feature representing the top of the concrete wall in terms of its magnitude and location.

Seismic Imaging of the Mesozoic Bedrock Relief and Geological Structure under Quaternary Sediment Cover: The Bolmin Syncline (SW Holy Cross Mountains, Poland)

The clear and detailed images of geological structures that can be obtained by seismic methods are one of the main drivers of their popularity in geological research. The quality of final geophysical images and models relies strongly on the amount of data that goes into them. Analysing several complementary seismic datasets allow an improved interpretation. Responding to this challenge, this article proposed an optimal combination of geophysical methods for near-surface applications. Multi-channel analysis of surface waves, first-arrival travel-time tomography, and ground-penetrating radar were the key supports for standard reflection seismic imaging. Ease of use and fast and cheap acquisition are some of the advantages of the mentioned methods. Considering that all recorded wave fields required minimal additional processing while offering a significant improvement in the final stack, it was worth the extra effort. Thanks to that, the better-estimated velocity filed allowed high quality images to be obtained up to 200 m. The Mesozoic bedrock was a distinct and very strong reflector in the resulting reflection seismic imaging. There was also a clearly visible depression of the horizon corresponding to erosion or a structure (syncline). Deeper, it was possible to track two or even four detachments of faulting origin.

Joint refraction traveltime tomography and migration for multilayer near-surface imaging

In near-surface velocity structure estimation, first-arrival traveltime tomography tends to produce a smooth velocity model. If the shallow structures include a weathering layer over high-velocity bedrock, first-arrival traveltime tomography may fail to recover the sharp interface. However, with the same traveltime data, refraction traveltime migration proves to be an effective tool for accurately mapping the refractor. The approach downward continues the refraction traveltime curves and produces an image (position) of the refractor for a given overburden velocity model. We first assess the validity of the refraction traveltime migration method and analyze its uncertainties with a simple model. We then develop a multilayer refraction traveltime migration method and apply the migration image to constrain traveltime tomographic inversion by imposing discontinuities at the refraction interfaces in model regularization. In each subsequent iteration, the shape of the migrated refractors and the velocity model are simultaneously updated. The synthetic tests indicate that the joint inversion method performs better than the conventional first-arrival traveltime tomography method with Tikhonov regularization and the delay-time method in reconstructing near-surface models with high-velocity contrasts. In application to field data, this method produces a more accurately resolved velocity model, which improves the quality of common midpoint stacking by making long-wavelength static corrections.

Binary recovery via phase field regularization for first-arrival traveltime tomography

We propose a double obstacle phase field methodology for binary recovery of the slowness function of an Eikonal equation found in first-arrival traveltime tomography. We treat the inverse problem as an optimization problem with quadratic misfit functional added to a phase field relaxation of the perimeter penalization functional. Our approach yields solutions as we account for well posedness of the forward problem by choosing regular priors. We obtain a convergent finite difference and mixed finite element based discretization and a well defined descent scheme by accounting for the non-differentiability of the forward problem. We validate the phase field technique with a —convergence result and numerically by conducting parameter studies for the scheme, and by applying it to a variety of test problems with different geometries, boundary conditions, and source—receiver locations.

Shallow Seismic Reflection Investigation of Unstable Sedimentary Deposits in the Dăneasa Area, Romania

Results of shallow seismic reflection measurements, performed over an area with unstable sedimentary formations in the near subsurface, are presented. The investigated area is located on the Olt Valley, in the vicinity of the Dăneasa village, Romania, crossed by a railway line and a national road on which the traffic is very intense. Data were collected along a linear profile, with a length of 94 m, perpendicular to the railway line and the national road using a fixed spread of 48 vertical-component geophones with the sources rolling along the acquisition line. The surface waves generated by the intense traffic on the national road interfered with the seismic arrivals seen on most of shot gathers, especially with those seen on the traces from receiver locations greater than 48 m. The interrupted continuity of two shallow reflectors, R1 and R2, seen on the depth-converted seismic section at depth values shallower than 30 m, could be interpreted as an effect of the presence of two steep failure planes deveIoped into the ground. A P-wave velocity-depth model down to a depth of 20 m after first-arrival traveltime tomography was then created, on which four sedimentary layers with variable thicknesses and constant velocities, separated by the interfaces L1, L2 and L3, were interpreted. By comparing the depth-converted seismic section with the P-wave velocity-depth model, the reflectors R1 and R2 on the seismic section correspond pretty well with the interfaces L2 and L3 from the velocity-depth model.

Near-surface velocity estimation using source-domain full traveltime inversion and early arrival waveform inversion

Accurate estimation of near-surface velocity is a key step for imaging deeper targets. We have developed a new workflow to invert complex early arrivals in land seismic data for near-surface velocities. This workflow is composed of two methods: source-domain full traveltime inversion (FTI) and early arrival waveform inversion (EWI). Source-domain FTI automatically generates the background velocity that kinematically matches the reconstructed plane-wave sources from early arrivals with true plane-wave sources. This method does not require picking first arrivals for inversion, which is one of the most challenging and labor-intensive steps in ray-based first-arrival traveltime tomography, especially when the subsurface medium contains low-velocity zones that cause shingled multivalue arrivals. Moreover, unlike the conventional Born-based method, source-domain FTI can determine if the initial velocity is slower or faster than the true one according to the gradient sign. In addition, the computational cost is reduced considerably by using the one-way wave equation to extrapolate the plane-wave Green’s function. The source-domain FTI tomogram is then used as the starting model for EWI to obtain the short-wavelength component associated with the velocity model. We tested the workflow on two synthetic and one onshore filed data sets. The results demonstrate that source-domain FTI generates reasonable background velocities for EWI even though the first arrivals are shingled, and that this workflow can produce a high-resolution near-surface velocity model.

An efficient tomographic inversion method based on the stochastic approximation

Near-surface solutions often play a significant role in imaging subsurface structures for land or shallow marine environments. Unfortunately, the standard approach to first-arrival traveltime tomography may involve the inversion of a large number of traveltime picks and require a considerable computational effort. We have improved the efficiency of traveltime tomography by adopting a method inspired by the field of stochastic optimization. First, we verify that traveltime tomography is solvable by two methods in the field of stochastic optimization: the sample average approximation (SAA) and the stochastic approximation (SA). In SAA, random subsets of the whole data are inverted via nonlinear optimization. The final result is the average of all the inverted models. SA is similar to the SAA method. However, in the SA method, new random data subsets are used in each iteration of the nonlinear iterative inversion. The final result is also the average of multiple inversions. We found that SA performs better than the SAA method for traveltime tomography. However, these two methods do not yield substantial improvements in computational turnaround time in comparison with the classic iterative tomographic inversion that uses all data. Therefore, we adopt one realization of the SA method, and we analyze its feasibility via synthetic tests. We call this technique fast SA tomography (FSAT). We design numerical tests to understand the amount of data reduction that one can tolerate before the solution degrades. We also carry out a detailed statistical analysis to understand the impact of FSAT on the solution of the near-surface imaging problem. We apply FSAT to 2D and 3D field data sets, and the results show that FSAT method only requires a small percentage of the total traveltimes to yield a result nearly identical to the model obtained by using all the picks.

Estimation of porosity and water saturation in dual-porosity pyroclastic deposits from joint analysis of compression, shear, and electromagnetic velocities

In situ measurements of porosity and water saturation of pyroclastic deposits have the potential to improve interpretations of geology and hydrology in volcanic regions, and to provide more accurate estimates of dense rock equivalent for volcanic eruptions. However, rock-property models must consider the dual-porosity structure of pyroclastic deposits (i.e., vesicles within pumices and intergranular pores). Vesicularity, intergranular porosity, and water saturation all affect the density, elasticity, and dielectric properties of pyroclastic materials, which control seismic and electromagnetic velocities. The data from active seismic and ground-penetrating radar (GPR) techniques may improve porosity and water saturation estimation if the responses of seismic and electromagnetic velocities to porosity and water saturation variations are complementary in pyroclastic deposits. We developed a dual-porosity petrophysical model to calculate seismic and electromagnetic velocities of pyroclastic deposits with known intergranular porosity, vesicularity, and water saturation, and we tested our ability to estimate porosity and water saturation from field measurements of seismic and electromagnetic velocities in pyroclastic deposits at Mount St. Helens, Washington, USA. Our petrophysical model demonstrates that seismic velocities are more sensitive to intergranular porosity and less sensitive to vesicularity; electromagnetic velocity is primarily controlled by volumetric water content. In a multioffset GPR and active seismic case study, seismic first-arrival traveltime tomography and multichannel analysis of surface waves can resolve high-velocity anomalies caused by porosity reduction. Joint petrophysical inversion of electromagnetic and seismic velocities indicates that although intergranular porosity and water saturation are well-constrained (i.e., standard deviations of approximately 0.05), quantitative estimates of vesicularity remain less certain (i.e., standard deviation of approximately 0.21), due to weak sensitivity.

Refraction traveltime tomography based on damped wave equation for irregular topographic model

Land seismic data generally have time-static issues due to irregular topography and weathered layers at shallow depths. Unless the time static is handled appropriately, interpretation of the subsurface structures can be easily distorted. Therefore, static corrections are commonly applied to land seismic data. The near-surface velocity, which is required for static corrections, can be inferred from first-arrival traveltime tomography, which must consider the irregular topography, as the land seismic data are generally obtained in irregular topography.This paper proposes a refraction traveltime tomography technique that is applicable to an irregular topographic model. This technique uses unstructured meshes to express an irregular topography, and traveltimes calculated from the frequency-domain damped wavefields using the finite element method. The diagonal elements of the approximate Hessian matrix were adopted for preconditioning, and the principle of reciprocity was introduced to efficiently calculate the Fréchet derivative. We also included regularization to resolve the ill-posed inverse problem, and used the nonlinear conjugate gradient method to solve the inverse problem.As the damped wavefields were used, there were no issues associated with artificial reflections caused by unstructured meshes. In addition, the shadow zone problem could be circumvented because this method is based on the exact wave equation, which does not require a high-frequency assumption. Furthermore, the proposed method was both robust to an initial velocity model and efficient compared to full wavefield inversions. Through synthetic and field data examples, our method was shown to successfully reconstruct shallow velocity structures. To verify our method, static corrections were roughly applied to the field data using the estimated near-surface velocity. By comparing common shot gathers and stack sections with and without static corrections, we confirmed that the proposed tomography algorithm can be used to correct the statics of land seismic data.

3D first-arrival traveltime tomography with modified total variation regularization

3D seismic surveys have become a major tool in the exploration and exploitation of hydrocarbons. 3D seismic first-arrival traveltime tomography is a robust method for near-surface velocity estimation. A common approach for stabilizing the ill-posed inverse problem is to apply Tikhonov regularization to the inversion. However, the Tikhonov regularization method recovers smooth local structures while blurring the sharp features in the model solution. We present a 3D first-arrival traveltime tomography method with Modified Total-Variation (MTV) regularization to preserve sharp velocity contrasts and improve the accuracy of velocity inversion. To solve the minimization problem of the new traveltime tomography method, we decouple the original optimization problem into two following subproblems: a standard traveltime tomography problem with the traditional Tikhonov regularization and a L2 total-variation problem. We apply the conjugate gradient method and split-Bregman iterative method to solve these two subproblems, respectively. Our synthetic examples show that the new method produces higher resolution models than the conventional traveltime tomography with Tikhonov regularization. We apply the technique to field data. Stacking section shows significant improvements with statics corrections from the MTV traveltime tomography.

Why 3D seismic data are an asset for exploration and mine planning? Velocity tomography of weakness zones in the Kevitsa Ni-Cu-PGE mine, northern Finland

Kevitsa is a disseminated Ni-Cu-PGE (platinum group elements) ore body in northern Finland, hosted by an extremely high-velocity ([Formula: see text]) ultramafic intrusion. It is currently being mined at a depth of approximately 100 m with open-pit mining. The estimated mine life is 20 years, with the final pit reaching a depth of 500–600 m. Based on a series of 2D seismic surveys and given the expected mine life, a high-resolution 3D seismic survey was justified and conducted in the winter of 2010. We evaluate earlier 3D reflection data processing results and complement that by the results of 3D first-arrival traveltime tomography. The combined results provide insights on the nature of some of the reflectors within the intrusion. In particular, a major discontinuity, a weakness zone, is delineated in the tomography results on the northern side of the planned pit. Supported by the reflection data, we estimate the discontinuity, likely a thrust sheet, to extend down approximately 600 m and laterally 1000 m. The weakness zone terminates prominent internal reflectivity of the Kevitsa intrusion, and it is associated with the extent of the economic mineralization. Together with other weakness zones, a couple of which are also revealed by the tomography study, the discontinuity forms a major wedge block that influences the mine bench stability on the northern side of the open pit and likely will cause more issues during the extraction of the ore in this part of the mine. We argue that 3D seismic data should routinely be acquired prior to commencement of mining activities to maximize exploration efficiency at depth and also to optimize mining as it continues toward depth. Three-dimensional seismic data over mineral exploration areas are valuable and can be revisited for different purposes but are difficult to impossible to acquire after mining has commenced.

Velocity structure of the western North China basement from high-resolution wide-angle reflection/refraction profiles

Two 1420 km-long, high-resolution wide-angle reflection/refraction profiles were produced for the western part of the North China Craton. Twenty-one shots were fired along the two profiles and seismic data was collected by 700 portable three-component digital seismographers. The crust-mantle structure was investigated in different regions, including the Ordos Block, Haiyuan arcuate tectonic region, Alashan Block, and Yinchuan Basin. First-arrival Pg waves were analyzed using the finite-difference method of first-arrival traveltime tomography to construct the 2D interface morphology and velocity structure of the crystalline basement. The study identified the location and shape of major faults, and notable variations in basement depth and velocity structure in different regions. The crystalline basement in the Ordos Block is typically stable with a depth of 4.5–5.5 km and exhibits only minor fluctuations in the lateral velocity gradient. This is evidenced by Pg wave features, including stable travel time, long tracing distance and high velocity. Between the Helan Mountains and the Yinchuan Basin, notable variations in topography, basement depth, and velocity structure were identified, indicating strong divergence in vertical movement and deformation. In the Yinchuan Basin, the Pg wave traveltime curve revealed the complex structure of the crystalline basement and variations in the velocity gradient. Since the Cenozoic Era, the western North China Craton has experienced strong and frequent tectonic activity causing strong deformation on the periphery of the Alashan Block. The presence of small, low-velocity, near-surface basins, and variations in the crystalline basement interface and velocity isolines provides evidence of strong tectonic deformation of the basement near Bayan Ura Hill, on the eastern margin of the Alashan Block. The Haiyuan arcuate tectonic region is complex and interacts with the Qilian Mountains, Alashan Block, and Ordos Block. Basement depth extends to 6.0 km and varies considerably from the adjacent uplift zone, which has a depth of 2.0 km. The highly deformed and unstable basement structure at the northeastern margin of the Tibetan Plateau is probably related to the collision and squeezing of the Indian Plate and the Eurasian Plate. Seismology data indicates differences between the crystalline basement interface and the velocity structure, as well as strong transverse inhomogeneity. Differences in basement depth in the Ordos Block, together with significant lateral heterogeneity, compressional fold deformation, and the presence of fault zones in the marginal basement, block the continuous compressive movement of the Tibetan Plateau in a northeast direction.

Applying joint traveltime and waveform inversion to image the Sichuan Basin, China

ABSTRACTWe apply a joint first‐arrival traveltime and early‐arrival waveform inversion method to image complex near‐surface structures in the Sichuan Basin, China. The area includes rugged topography and large near‐surface velocity variations. Due to the near‐surface effects, it is difficult to produce high‐quality reflection images of the deep subsurface. First‐arrival traveltime tomography is often applied for near‐surface imaging, but the results may not be sufficiently accurate because of ray assumptions and the limited traveltime information. Waveform inversion should allow complex structures to be resolved; however, it may fall into local minima because of cycle skipping issues and may also produce artefacts in very shallow areas that are associated with rugged topography. Therefore, we combine the advantages of the two methods and mitigate their problems by performing joint inversion of the two types of data. We demonstrate the effectiveness of the joint inversion method using synthetic and real data from Sichuan, China. In the real data example, we compare the velocity models resolved from waveform inversion alone with those resolved from the joint inversion. We calculate long‐wavelength static corrections and apply them to the data processing. The common midpoint stacking results show that the joint inversion method produces a more effective statics solution.

Toward a robust workflow for deep crustal imaging by FWI of OBS data: The eastern Nankai Trough revisited

AbstractCrustal‐scale imaging by the full‐waveform inversion (FWI) of long‐offset seismic data is inherently difficult because the large number of wavelengths propagating through the crust makes the inversion prone to cycle skipping. Therefore, efficient crustal‐scale FWI requires an accurate starting model and a stable workflow minimizing the nonlinearity of the inversion. Here we attempt to reprocess a challenging 2‐D ocean‐bottom seismometer (OBS) data set from the eastern Nankai Trough. The starting model is built by first‐arrival traveltime tomography (FAT), which is FWI assisted for tracking cycle skipping. We iteratively refine the picked traveltimes and then reiterate the FAT until the traveltime residuals remain below the cycle‐skipping limit. Subsequently, we apply Laplace‐Fourier FWI, in which progressive relaxation of time damping is nested within frequency continuation to hierarchically inject more data into the inversion. These two multiscale levels are complemented by a layer‐stripping approach implemented through offset continuation. The reliability of the FWI velocity model is assessed by means of source wavelet estimation, synthetic seismogram modeling, ray tracing modeling, dynamic warping, and checkerboard tests. Although the viscoacoustic approximation is used for wave modeling, the synthetic seismograms reproduce most of the complexity of the data with a high traveltime accuracy. The revised FWI scheme produces a high‐resolution velocity model of the entire crust that can be jointly interpreted with migrated images derived from multichannel seismic data. This study opens a new perspective on the design of OBS crustal‐scale experiments amenable to FWI; however, a further assessment of the optimal OBS spacing is required for reliable FWI.

Alternating first-arrival traveltime tomography and waveform inversion for near-surface imaging

Near-surface seismic imaging often plays a significant role in producing quality data processing results for the deep subsurface in land and shallow marine environments. First-arrival traveltime tomography is a common approach for near-surface imaging due to its high efficiency and simplicity. However, the method faces issues of missing hidden layers and resolving the structures with low resolution. On the other hand, waveform inversion should offer better solutions for dealing with these issues, but it may suffer from the cycle-skipping problem. We intend to use the advantages and reduce the disadvantages of the two methods by developing a new strategy of alternately applying traveltime tomography and waveform inversion through iterations. First-arrival traveltime tomography applies a wavefront raytracer and a nonlinear inversion approach. Waveform inversion is a multiscale approach in which a wavelet transform is applied in the data domain to better handle the cycle-skipping problem. By alternating the two inversions rather than performing a joint inversion, we reduce the memory requirements and avoid nonphysical scaling problems between the two approaches. Using one synthetic and two real data examples, we determine that alternating inversions minimize two separate objective functions at the same time and constrain the near-surface structures fairly well compared with the waveform inversion method alone. For the field examples, the new method avoids generating the obvious artifacts and provides results consistent with the geology analysis of those areas.

Model regularization for seismic traveltime tomography with an edge-preserving smoothing operator

The solutions of the seismic first-arrival traveltime tomography are generally non-unique, and the Tikhonov model regularization for the inversion is commonly used to stabilize the inversion. However, the Tikhonov regularization for traveltime tomography often produces a low-resolution velocity model. To sharpen the velocity edges for the traveltime tomographic results and fit data at the same time, we should apply the edge-preserving concepts to regularize the inversion. In this study, we develop a new model regularization method by introducing an edge-preserving smoothing operator to detect the model edges in traveltime tomography. This edge-preserving smoothing operator is previously used in processing seismic images for enhancing resolution. We design three synthetic velocity models with sharp interfaces and with or without velocity gradients to study the performance of the regularization method with the edge-preserving smoothing operator. The new edge-preserving regularization not only sharpens the model edges but also maintains the smoothness of the velocity gradient in the layer.

Landstreamer seismics and physical property measurements in the Siilinjärvi open-pit apatite (phosphate) mine, central Finland

We tested the applicability of a newly developed broadband (0–800 Hz) digital-based seismic landstreamer for open-pit mine planning in the apatite-bearing Siilinjärvi mine in central Finland. Four seismic profiles, in total approximately 2.5 km long (2–4 m source and landstreamer receiver spacing), two inside the pit and two on its margins, were acquired in combination with wireless recorders connected to 10 Hz geophones and fixed at every 10 m spacing along the seismic profiles while the streamer data were being acquired. Downhole logging and laboratory physical property measurements on core and rock samples were carried out to not only support the seismic interpretations but also to provide information about the possible geophysical signature of these unique types of deposits. In spite of a highly noisy mining environment, seismic data of high quality were acquired; however, reflection processing and interpretations were challenged by the geologic complexities of several generations of basic and carbonatite dikes. To complement the reflection data imaging and to account for the steep elevation changes and crookedness of some of the seismic profiles, 3D first-arrival traveltime tomography and 3D swath reflection imaging were also carried out. Clear refracted arrivals from the open-pit profiles suggest the possibility of low-velocity zones associated with either blasting or several shear zones intersecting the seismic profiles. In terms of reflectivity, reflections have a different appearance from short and flat to longer and steep ones. The downhole- and borehole logging data suggest that some of these reflections are associated with diabase dikes and some are likely from zones of weaknesses in the alkaline-carbonatite complex. We determine the potential of using seismic streamers for cost- and time-effective open-pit mine planning and encourage further testing in simpler geologic settings to be established.