Synthetic Seismic Response Research Articles

Fast diagnosis of reservoir simulation models based on 4D seismic similarity indicators

In the last ten years, 4D seismic (4DS) data acquisition is evolving to permanent reservoir monitoring (PRM) systems where sensors are installed at the ocean-bottom, collecting seismic data according to the project's monitoring demand. Simultaneously, reservoir management workflows evolved to include uncertainties, where multiple reservoir models may be considered. Model-based approaches for developing and managing a field rely on error minimizations between modelled and measured data, traditionally from well production data, and eventually adapted to 4DS data. This study presents a fast, robust and unsupervised workflow to provide a comprehensive diagnosis of multiple reservoir simulation models using similarity indicators with observed 4DS. The methodology comprises a seismic forward modelling to convert hundreds of models from the reservoir engineering domain to the seismic domain. The diagnosis includes a novel region-by-region approach to compare the predicted synthetic seismic response with the observed 4DS anomalies using ternary maps generated from Gaussian mixture models (GMM), in addition to a magnitude metric. The methodology is tested in an ultra-deep turbidite field from the Campos basin in Brazil with a PRM system that captured various 4DS anomalies of different polarity, magnitude, shapes and sizes over several production and injection years. The contributions of this work are demonstrated in four applications: (1) feedback on various iterations of geomodelling, (2) feedback on well and seismic data assimilation, (3) quick evaluation of a new seismic monitor, and (4) ranking models for further decision-making studies. The workflow advantages are proved along the model-based reservoir management outline. For application (1), we successfully flagged which 4DS anomalies were being honored in the simulation models and quantified the impact of introducing features interpreted from seismic monitors in the geomodelling. For application (2), we quantified simulation model improvements provided by data assimilation. For application (3), we rapidly evaluated the quality of the seismic monitor against the existing simulation models as soon as the new seismic acquisition and processing was complete, validating the requirement to re-visit the simulation models. Finally, the workflow was crucial to select best models, out of hundreds, for the decision-making process, in application (4).

Assessing the impact of regional geology on the ground motion model variability at the Kashiwazaki-Kariwa Nuclear Power Plant (Japan) via physics-based numerical simulation

This study investigates the sensitivity of physics-based earthquake prediction to the choice of the regional geological model. The generally poor information on the mechanical properties of the Earth’s crust induces large uncertainty margins on the synthetic seismic response. Therefore, uncertainty quantification must be associated with high-fidelity numerical simulation, especially when verging on broad-band simulations (i.e., numerical theoretical accuracy higher than the conventional 1 Hz limit). In this paper, the synthetic seismic response of the Niigata region (Japan), during the Chūetsu offshore earthquake (MW6.6) serves as representative case study. Three plausible three-dimensional (3-D) geological structures are compared for two point-wise aftershock numerical simulations, duly validated. The framework of comparison targets the Ground Motion Prediction Equation (GMPE) for pseudo-spectral acceleration at the surface. The impact of the geology on the variability of between-event and the within-event residuals is inferred from synthetic simulations and related to common parameters representing site-specific conditions.

High-fidelity broadband prediction of regional seismic response: a hybrid coupling of physics-based synthetic simulation and empirical Green functions

The prediction of the seismic response of critical structures is highly sensitive to many aspects, among which the earthquake source and the geological setting are prominent. The related uncertainty issues must be taken into account in seismic risk mitigation studies, for example through the evaluation of several realizations of a future earthquake scenario. This aspect is crucial when addressing vulnerability studies at a regional scale. When opting for physical-based numerical simulations (PBS), however, the computational burden increases along with the expected degree of fidelity, making it difficult to evaluate more than a few dozens of alternatives. To cope with this disadvantage, in this work an alternative method is proposed, which exploits a rather low number of synthetic earthquake simulations and combines them with the empirical Green function (EGF) method, to finally generate thousands of alternative yet realistic seismic response of the site of interest. This hybrid strong motion predictions benefit of both (i) PBS high fidelity and (ii) data assimilation of strong ground motion records in the seismic area of interest, via EGF method, producing broadband synthetics at a relative cheap computational price. The power of the hybrid method is tested on a real case scenario, embodied by the ground-shaking prediction at the nuclear site of Cadarache, in the surroundings of the fault of Middle Durance, in South-Eastern France. Thousands of broadband (0–15 Hz) hybrid synthetic seismic response are generated, associated with different fault parameters (EGF method) and based upon a few key physics-based simulations, accurate up to 5 Hz.

Assessing the value of seismic monitoring of CO2 storage using simulations and statistical analysis

Successful storage of CO2 in underground aquifers requires robust monitoring schemes for detecting potential leakage. To aid in this challenge we propose to use statistical approaches to gauge the value of seismic monitoring schemes in decision support systems. The new framework is based on geostatistical uncertainty modeling, reservoir simulations of the CO2 plume in the aquifer, and the associated synthetic seismic response for both leak and seal scenarios. From a large set of simulations we assess the leak and seal conditional probabilities given seismic data over time, and build on this to compute the value of information of the seismic monitoring schemes. The Smeaheia aquifer west of Norway is used to exemplify the approach for early leakage detection and decision support regarding CO2 storage projects. For this case study, we find that the optimal monitoring time is about 10 years after injection starts.

Machine learning and geophysical inversion — A numerical study

As geophysicists, we are trained to conceptualize geophysical problems in detail. However, machine learning algorithms are more difficult to understand and are often thought of as simply “black boxes.” A numerical example is used here to illustrate the difference between geophysical inversion and inversion by machine learning. In doing so, an attempt is made to demystify machine learning algorithms and show that, like inverse problems, they have a definite mathematical structure that can be written down and understood. The example used is the extraction of the underlying reflection coefficients from a synthetic seismic response that was created by convolving a reflection coefficient dipole with a symmetric wavelet. Because the dipole is below the seismic tuning frequency, the overlapping wavelets create both an amplitude increase and extra nonphysical reflection coefficients in the synthetic seismic data. This is a common problem in real seismic data. In discussing the solution to this problem, the topics of deconvolution, recursive inversion, linear regression, and nonlinear regression using a feedforward neural network are covered. It is shown that if the inputs to the deconvolution problem are fully understood, this is the optimal way to extract the true reflection coefficients. However, if the geophysics is not fully understood and large amounts of data are available, machine learning can provide a viable alternative to geophysical inversion.

Assessment of Frequency versus Time Domain enhanced technique for response-only modal dynamic identification under seismic excitation

In the present study, response-only system identification is explored towards estimating modal dynamic properties of buildings under earthquake excitation. Seismic structural response signals are adopted with two different implemented Operational Modal Analysis (OMA) techniques, namely a refined Frequency Domain Decomposition algorithm and an improved data-driven Stochastic Subspace Identification (SSI-DATA) procedure, working in the Frequency Domain and in the Time Domain, respectively. These algorithms are specifically conceived to operate with seismic structural responses and at simultaneous heavy damping (in terms of identification challenge), towards achieving consistent estimations of natural frequencies, mode shapes and modal damping ratios. Classical OMA assumptions shall not contemplate short-duration, non-stationary earthquake-induced response signals. Nevertheless, the present enhanced output-only algorithms allow for estimating all strong ground motion modal parameters. First, a linear three-storey frame structure under ten selected earthquake base-excitations is considered, in order to assess the two OMA techniques at synthetic seismic response input. Comprehensive results are presented, by comparing the two developed methods, between achieved modal estimates and sought target values. Second, an existing instrumented building (CESMD database) is analyzed, by adopting real seismic response signals, reaching again effective modal estimates and corroborating the previous necessary condition analysis. According to this investigation, best up-to-date, re-interpreted, output-only techniques may effectively be used for potential Structural Health Monitoring purposes in the Earthquake Engineering range.

Seismic FDD modal identification and monitoring of building properties from real strong-motion structural response signals

In the present study, output-only modal dynamic identification and monitoring of building properties is attempted successfully by processing real earthquake-induced structural response signals. This is achieved through an enhanced version of a recently-developed refined Frequency Domain Decomposition (rFDD) approach, which in the earlier implementation was adopted to analyse synthetic seismic response signals only. Despite that short duration, nonstationary seismic response data and heavy structural damping shall not fulfil traditional Operational Modal Analysis assumptions, the present rFDD response-only algorithm allows for the effective estimation of strong-motion natural frequencies, mode shapes, and modal damping ratios, with real seismic response signals. The present rFDD enhancement derives from a preprocessing time-frequency analysis and from an integrated approach for Power Spectral Density matrix computation, which constitute crucial innovative issues for the treatment of real earthquake response data. A monitoring case study is analysed by taking the real strong-motion response records from a seven-storey reinforced concrete building in Van Nuys, California, from 1987 to the latest 2014 events (Center of Engineering Strong Motion Data database), as recorded before, during and after the 1994 Northridge earthquake, which severely damaged the building (then retrofitted). This paper proves the effectiveness of the proposed enhanced rFDD algorithm as a robust method for monitoring current structural modal properties under real earthquake excitations. This shall allow for identifying possible variations of structural features along experienced seismic histories, providing then a fundamental tool towards Earthquake Engineering and Structural Health Monitoring purposes.

Seismic Properties of Rocks from the Flin Flon Volcanogenic Massive Sulfide Camp

Seismic properties of rocks from the Flin Flon volcanogenic massive sulfide (VMS) camp were determined to evaluate the suitability of seismic reflection imaging for mineral exploration and have subsequently aided interpretation of 2-D and 3-D seismic data acquired in the camp. Seismic impedances of Flin Flon rocks were determined from laboratory measurements of compressional and shear wave velocity (Vp, Vs) and density for 61 core samples. Complementary in situ measurements of Vp and density provided by sonic and density logs acquired in nine drill holes allow calculation of synthetic seismic responses. Sandstones of the Missi Group show low reflectivity with sparse strong internal reflections resulting from intrusions or thrust-interleaved mafic rocks. Basaltic sequences are generally moderately reflective due to variability in their composition, alteration, and the effects of foliation and shearing. The mine horizon, which hosts the known orebodies, should be reflective, based on the impedance contrast of constituent rhyolite and mafic igneous rocks and the presence of sulfide mineralization. However, reflectivity of this horizon should be variable due to the significant alteration of the footwall basalt. Ore zones (solid sulfide) should range from moderately to very highly reflective, depending on their sulfide compositions. Vertical seismic profiles demonstrate that contacts between major stratigraphic units (e.g., Missi Group contact with Hidden Formation volcanic rocks or felsic igneous rocks within the basalts) should produce significant reflections, whereas some of the internal reflectivity predicted for the basaltic sequences will not be as prevalent.

Seismic petrophysics focused case study for AVA modelling and pre-stack seismic inversion

Hydrocarbon reservoirs are characterised by integrating seismic, well-log and petrophysical information, which are dissimilar in spatial distribution, scale and relationship to reservoir properties. Well logs are essential for amplitude versus offset (AVO) modelling and seismic inversion. The usability of well logs can be determined during wavelet estimation, seismic-to-well ties, background model building, property distribution for inversion, deriving probability density functions and variograms, offset-to-angle conversion of seismic data, and many other processes. For the implementation of seismic inversion workflows, accurate and geologically corrected compressional-sonic, shear-sonic and density logs are necessary. Preparing the logs for quantitative interpretation becomes challenging in a real-field environment because of bad borehole conditions including washouts, uncalibrated and variability of logging tools, invasion effects, missing shear logs and change of borehole size. Conventional petrophysical analysis is usually restricted to the reservoir interval, the calculation of reservoir versus non-reservoir (including sands or shales), and log corrections for smaller intervals; in contrast, seismic petrophysics encompasses the entire geological interval, calculates the volume of multi-minerals, incorporates boundaries between non-reservoir and reservoir, and often includes the prediction of missing compressional and shear-sonic for AVO analysis. A detailed seismic petrophysics analysis was performed for amplitude versus angle (AVA) modelling and attributes analysis. To perform the AVA modelling, a series of forward models in association with rock physics modelled fluid-substituted logs were developed, and associated seismic responses for various pore fluids and rock types studied. The results reveal that synthetic seismic responses together with the AVA analysis show changes for various lithologies. AVA attributes analysis show trends in generated synthetic seismic responses for various fluid-substituted and porosity logs. Reservoir modelling and fluid substitution increases understanding of the observed seismic response. This paper describes detailed data analysis using various techniques to confirm the rock model for petrophysical evaluation, rock physics modelling, AVA analysis, pre-stack seismic inversion, and the scenario modelling applied to the study of an oil field in Australia.

Analysis of frequency shifting in seismic signals using Gabor-Wigner transform

A hybrid time-frequency method known as Gabor-Wigner transform (GWT) is introduced in this paper for examining the time-frequency patterns of earthquake damaged buildings. GWT is developed by combining the Gabor transform (GT) and Wigner-Ville distribution (WVD). GT and WVD have been used separately on synthetic and recorded earthquake data to identify frequency shifting due to earthquake damages, but GT is prone to windowing effect and WVD involves ambiguity function. Hence to obtain better clarity and to remove the cross terms (frequency interference), GT and WVD are judiciously combined and the resultant GWT used to identify frequency shifting. Synthetic seismic response of an instrumented building and real-time earthquake data recorded on the building were investigated using GWT. It is found that GWT offers good accuracy for even slow variations in frequency, good time-frequency resolution, and localized response. Presented results confirm the efficacy of GWT when compared with GT and WVD used separately. Simulation results were quantified by the Renyi entropy measures and GWT shown to be an adequate technique in identifying localized response for structural damage detection.

Soil damping influence on seismic ground response: A parametric analysis for weak to moderate ground motion

Small-strain stiffness and damping ratio are the key parameters for modeling the dynamic behavior of soils, but they are often problematic and onerous to obtain under field conditions. This is particularly true for the attenuation characteristics. As an alternative to classical laboratory tests, that are costly and prone to inaccuracies due to scale and sampling issues, recent studies stress the opportunity of using in situ measurements, and particularly surface-wave methods. However, while these methods are often used to provide shear wave velocities, they are more rarely used to give in situ estimates of damping parameters. Similarly, it is uncommon to extract attenuation information from down-hole tests. In practice, the usual anti-earthquake design is confronted with a scarcity of laboratory test measurements and with the intricacies of obtaining reliable in situ attenuation measurements. Consequently, shaking simulations commonly use literature values of the damping coefficient. This choice is often motivated by the assumption that damping does not have a critical role in ground shaking evaluations, especially for weak-moderate motion cases. The purpose of this work is to provide, for these conditions, an analysis of when an accurate characterization of the damping coefficient is needed to produce reliable shaking predictions. We performed a stochastic analysis of synthetic seismic response for different realistic subsoil conditions using as input several real ground motion records. For completeness, we also compared linear-equivalent to fully non-linear shaking simulations, showing that, for the moderate-strain conditions we consider, the linear-equivalent approach is adequate. In our simulations we fixed the subsoil structures and material deformation properties while we adopted a Monte Carlo approach to explore the effects of randomly variable damping coefficient values. Our results show how an accurate knowledge of the attenuation coefficient is of minor importance in absence of strong impedance contrasts in the shallow subsurface.

A preliminary study on sensitivity of seismic responses to changes in reservoir parameters using various RPM-constructing strategies

Rock physics model (RPM) transforms reservoir characteristics into elastic seismic properties which control generation of seismic responses through synthetic seismic simulation. The changes in fluid saturation or pressure lead to corresponding changes in seismic responses based on constructed RPM. The different RPMs are first constructed based on four different strategies of Gassmann's equation, Krief's formulation, Duffy–Mindlin's method, and Wyllie's equation. Differences among these RPMs are analyzed before performing sensitivity analysis of changes in seismic responses with respect to changes in reservoir parameters. The synthetic seismic responses used for the analysis are generated from the seismic simulation, which algorithm is developed by using a finite difference method based on staggered grid with convolutional perfect match layer and free surface.

Pre-Stack Seismic Inversion and Amplitude Versus Angle Modeling Reduces the Risk in Hydrocarbon Prospect Evaluation

Pre-Stack seismic inversion and Amplitude versus Angle (AVA) techniques were used in for direct hydrocarbon identification (DHI) and to understand better the risk during hydrocarbon prospecting. In order to understand and predict the seismic response for different fluid type and lithologies pre-stack seismic inversion and AVA modeling based on existing well logs information were performed. An optimized seismic inversion workflow that includes conditioning of seismic data followed by seismic petrophysics and rock physics modeling in combination with fluid substituted logs was used to predict the seismic response for different fluid types. Inverted rock properties of a wedge model were then correlated with seismic response for DHI. Another hydrocarbon prospect was studied based on AVA modeling response. AVA effects on angle gathers provide basic information on the lithology and pore fill contents of the rocks under investigation. To perform the AVA modeling, a series of forward models in association with rock physics-modeled fluid-substituted logs have been developed and associated seismic responses for different pore fluids and rock types studied. The results reveal that synthetic seismic responses together with the AVA analysis show changes for different lithologies. AVA attributes analysis show trends in generated synthetic seismic responses for different fluid-substituted and porosity logs. Reservoir modeling and fluid substitution increases understanding of the observed seismic response. It ultimately leads to a better reservoir prediction with delineation of sweet spots and improved volumetric prognosis. Assessing the effect of fluid-substituted logs for different lithologies and associated AVA seismic response can improve the prediction in reservoir characterization. Truly integrated studies of seismic, geology and well data will reduce the drilling and development risks even further. Key Words: Pre-stack seismic inversion; Wedge model; Amplitude versus angle (AVA); Fluid substitution; Intercept (I); Gradient (G); Rock physics; Derisking and forward modeling

Global sensitivity analysis for crosswell seismic and neutron-capture measurements in CO2 storage projects

Quantification of reservoir uncertainty is an essential part of a monitoring design. A systematic approach that quantitatively links predicted uncertainties in a monitoring program to the underlying reservoir variability is, however, needed. We developed a methodology for quantifying uncertainty in crosswell seismic monitoring combined with neutron-capture logging and applied global sensitivity analysis (GSA) to compute and rank contributions of uncertain reservoir parameters to the predicted uncertainty of the measurements. The workflow is illustrated by a numerical study using a simplified model of a [Formula: see text] storage site where crosswell measurements have not actually been taken. Synthetic seismic responses are computed through the integration of multiphase flow, a new thermodynamically consistent fluid substitution model, and a fast marching eikonal solver. We quantified uncertainty in first-arrival times to illustrate the potential utility of crosswell seismic surveys and their limitation. Consistent with these calculations, uncertainties in neutron capture cross-section logs are also computed and related to predicted [Formula: see text] migration. The predicted uncertainty range for neutron-capture measurements indicated significant sensitivity to the uncertainty of the reservoir properties (standard deviations [STDs] of up to 6 c.u. in the injector and up to 3.5 c.u. in the monitoring well). However, the STD of predicted time-lapse crosswell seismic responses for two different source locations did not exceed 0.75 ms during the life of the project, suggesting limited value of first-arrival measurements for reservoir-parameter inversion in this case. With the time-dependent uncertainty of the predicted measurements, calculated GSA indices provided a quantitative basis for the monitoring program design. Practical implications of GSA results for model reduction and subsequent inversion were also evaluated.

Simulation of CO2 Injection into a Baltic Sea Saline Aquifer and Seismic Monitoring of the Plume

TOUGH2/ECO2N was used to simulate CO2 injection into a saline aquifer in the Baltic Sea and the effect of different amounts of CO2 injection on the seismic response. The Biot-Gassmann model was used to convert the simulated saturation and densities to seismic velocities and synthetic seismic responses before and after injection were compared. The results show that the amplitude changes in the seismic response are detectable even for small amounts of injected CO2, while noticeable signs of velocity pushdown, as a signature of the CO2 substitution, could only be observed if the injection rate is high enough.

Integration of the life of field seismic data with the reservoir model at the Valhall Field‡

ABSTRACTThe frequent time‐lapse observations from the life of field seismic system across the Valhall field provide a wealth of information. The responses from the production and injection wells can be observed through time‐shift and amplitude changes. These observations can be compared to modelled synthetic seismic responses from a reservoir simulation model of the Valhall Field. The observed differences between the observations and the modelling are used to update and improve the history match of the reservoir model. The uncertainty of the resulting model is reduced and a more confident prediction of future reservoir performance is provided.A workflow is presented to convert the reservoir model to a synthetic seismic response and compare the results to the observed time‐lapse responses for any time range and area of interest. Correlation based match quality factors are calculated to quantify the visual differences. This match quality factor allows us to quantitatively compare alternative reservoir models to help identify the parameters that best match the seismic observations.Three different case studies are shown where this workflow has helped to reduce the uncertainty range associated with specific reservoir parameters. By updating various reservoir model parameters we have been able to improve the match to the observations and thereby improve the overall reservoir model predictability. The examples show positive results in a range of different reservoir modelling issues, which indicates the flexibility of this workflow and the ability to have an impact in most reservoir modelling challenges.

An exact solution of the conversion point for the converted waves from a dipping reflector with homogeneous (isotropic) overburden

For converted waves, stacking traces with a common reflection point, forming gathers, and performing dip moveout (DMO) all require accurately calculating the location of conversion points. Because of the asymmetrical paths of converted waves, even for horizontally layered media, the calculation of a conversion point for converted waves is complicated. Previous authors have obtained analytic solutions for the conversion point for converted waves in a horizontally layered media. We extend those results to the more general case of converted waves from a dipping reflector with a homogeneous, isotropic overburden. By using Snell's law, we derive a quartic equation and solve it uniquely for the conversion point. The resultant analytic expression is a function of offset, compressional-, and shear-wave velocities; normal reflector depth; and dip angle at the conversion point. This solution can be readily used to generate accurate synthetic seismic responses for converted waves based on ray theory. It also can be extended to operators for stacking converted waves and applying DMO correction.

4D seismic for oil‐rim monitoring

ABSTRACTIn the central North Sea ‘Gannet‐A’ field, a 50 ft oil rim is overlain by a gas cap of variable thickness. Oil is produced from horizontal wells which initially produced dry oil, but as the field became more mature, a significant water cut was seen in several wells. A dedicated 4D seismic monitor survey was acquired in order to assess the remaining distribution of oil reserves. By forward modelling the synthetic seismic response to parameters such as contact movement and residual saturations (using 2D and 3D wedge models), and comparing the results with real seismic data, we are able to decipher the contact movements across the field. It is shown that, in one part of the field, the increased water cut is caused primarily by the vertical displacement of the entire oil rim into the initial gas cap. This oil‐rim displacement produces a very different 4D seismic response from the case of a static gas–oil contact and rising oil–water contact (normal production). As a result of these observations, we are able to optimize field production by both re‐perforation of existing wells and by drilling sidetracks into the displaced rim: a brown‐field development opportunity that might otherwise be missed.

4D Seismic Monitoring of Water Influx at Bay Marchand: The Practical Use of 4D in an Imperfect World

SummaryMany waterflooded or aquifer influx reservoirs are old or marginal and thus do not have ideal data conditions, either historic or current, for 4D seismic. We modeled the synthetic seismic response for the 7100 Sand in the Bay Marchand field and found it suitable for 4D. To determine the noise level in modeling, we derived relations for calculating the appropriate level of noise from differences in the field data. We also developed relations between measured noise and the quantitativeness of calculated saturation changes. These methods, as applied to the Bay Marchand, showed that useful saturation predictions could be made from the seismic data shot 30 years after initial production with a recent, nonexclusive survey. From these data, both downdip and updip wells were drilled successfully.Multiple seismic surveys over time that were not intentionally designed for 4D evaluation can be used for imaging fluid and pressure changes and locating bypassed reserves. Bay Marchand is a mature Gulf of Mexico field with a series of stacked reservoirs separated by shale. The first 3D seismic survey was acquired after first production, and the second seismic survey was a nonexclusive survey having very different acquisition parameters. These circumstances make interpreting 4D results difficult but not impossible. We were able to make a reasonable interpretation of the "A" fault block on the original data before cross-equalization (XEQ), although XEQ reduced the acquisition and processing differences between the cubes. We were able to identify areas of water influx and areas not yet invaded by water, even though we were prevented from following the typical steps in 4D. Reliability estimates were derived for estimates of saturation change as a function of signal-to-noise ratio and scatter in the rock physics relationships. This paper discusses these steps in contrasting the ideal case with Bay Marchand and shows where a 4D project can still be successful even with compromises forced by lack of early data or current budget.

Seismic reflectivity of detachment faults of the Iberian and Tethyan distal continental margins based on geological and petrophysical data

Low-angle detachment faults are key to our understanding of the tectonic evolution of magma-poor rifted continental margins. In seismic images of present-day rifted margins the identification and interpretation of such features is, however, notoriously difficult and ambiguous. We address this problem by studying the structure and seismic response of such faults through a synoptic interpretation of petrophysical data and geological evidence from the distal segments of the present-day West Iberian and the ancient Tethyan margins. On the basis of the geologically well-constrained remnants of the Tethyan margins, which are spectacularly preserved and exposed in the Alps of Eastern Switzerland, vertical profiles at four key geological settings of a typical magma-poor rifted margin are constructed and their synthetic seismic responses are compared to the observed seismic data from corresponding locations in the present-day Iberian margin. The seismic structure of these profiles is considered as the sum of deterministic large-scale and the stochastic small-scale components. Both components are analyzed for all pertinent lithologies. The large-scale structures are derived from laboratory measurements on samples from both, the West Iberian and Tethyan margins, whereas the small-scale fluctuations are constrained predominantly on the basis of well-log data from the Iberian margin. Different realizations of the simulated stochastic small-scale velocity fluctuations illustrate the potential variability of impedance contrasts and its impact on the seismic response from lithological interfaces and fault structures. Our results indicate that the nature of the seismic response from low-angle detachment faults is largely determined through the fracture-healing behavior of the surrounding rocks. Geological evidence from the exposed fragments of the Tethyan margins indicate that fracture-healing is generally well developed in crustal lithologies, but largely absent in mantle lithologies. It is for this reason that low-angle, intra-crustal detachment faults tend to be seismically undetectable. Conversely, crust–mantle detachments have a complex and variable seismic response, depending on the nature of the damaged zone and on the frequency content of the seismic data. These model-based inferences are consistent with the available evidence from the present-day Iberian passive margin and thus open new perspectives for the interpretation of the corresponding seismic images.