Local Dip Research Articles

Partial loss and significant depletion of radiation belt electrons during the April 4, 2017, geomagnetic storm

We report a specular loss event of radiation belt electrons induced by a moderate geomagnetic storm on April 4, 2017, by using Van Allen Probe observations. During the initial phase, when the solar wind dynamic pressure (Pdyn) reached 12 nPa, the radiation belt electrons at Ek > ∼200 keV experienced a partial loss, followed by noticeable energy dispersion, which pronouncedly occurred at larger pitch angles on higher L shells. During the main phase, both probes witnessed a significant electron flux depletion at all energies from 54 to 2.6 MeV on the dusk-night side (MLT = magnetic local time around 20). Moreover, the corresponding phase space density (PSD) shows a local dip within L* = 4.44–4.87 (drift shell under adiabatic coordinate), which is not the outermost of L*, lasting for one pass (semi-period) of the spacecraft and quickly disappearing. By comparing the characteristics of electron loss in response to variations of the solar wind and geomagnetic indices, the movement of the estimated magnetopause location and the last closed drift shells, as well as the distribution of the plasma waves, we find that the partial dropout was essentially induced by the magnetopause shadowing effect, while the potential effect of the subsequent local PSD dip cannot be clearly explained by the present theory as far as we know. By showing the specular dropout event in the present work, we underline that the different loss effects should draw special attention from the space physics community.

Fast computation of local dips using the one-lag-correlation method

We adapt the one-lag-correlation (OLC) method to estimate the local dips of seismic events. The resulting local dips have extensive applications in exploration geophysics, such as seismic inversion regularization, computation of seismic attributes such as coherence cube, and facilitating structural-oriented smoothing and extrapolation techniques. Compared with the widely adopted structure tensor (ST) method, our OLC algorithm exhibits notable advantages. The OLC method uses a recursive calculation process that yields significant computational efficiency, resulting in approximately 100 times faster performance for 3D scenarios. The fundamental principle of this novel approach lies in the computation of local dips by using the ratio of two inner products, i.e., OLC, performed on a 2D/3D array along the vertical and horizontal axes, respectively. Crucially, the elements of this array consist of complex numbers derived from the application of the Hilbert transform on the corresponding real-number inputs. Furthermore, the implementation of this algorithm is remarkably straightforward, as exemplified by the concise nature of the code, which requires only ten lines of programming instructions. The OLC method excels in accuracy, surpassing the performance of the ST method, and is more robust to random noise. We show these properties of the OLC approach using synthetic and field data examples.

VSP wavefields separating method based on parallel local slope scanning

Due to the detectors being distributed in the target medium, vertical seismic profile (VSP) is a seismic observation method that has the advantages of high resolution and a high signal-to-noise ratio. Separating the mixed wavefields into upgoing and downgoing waves can obtain more obvious dynamic and kinematic characteristics of seismic waves, guiding subsequent imaging and interpretation. The traditional method is mainly based on the pickup of first breaks. Flattening the global seismic data by first breaks can enhance the seismic events through techniques like median filter and singular value decomposition (SVD). However, this method relies on high-precision pickup of first breaks and is limited by zero offset. To address this limitation, we introduce an improved median filtering separation method. This method employs separations of the local dip angles into positive and negative through multi-window scanning (MWS). Due to the high accuracy and robustness of this method in 2-D VSP data, we propose to use the local dip angle of the wavefields to median filter the wavefield through positive and negative angles to obtain upgoing and downgoing waves. This method for wavefield separation is optimized by iteratively identifying the directions of the seismic data. However, this optimization comes at the cost of increased computational requirements, especially under high-precision conditions. To help alleviate this problem, we use multi-thread parallel computing technique on a multi-core central processing unit (CPU) to improve computational efficiency. Finally, we validate the proposed method by testing it on synthetic seismic data and field VSP data, respectively. The results show that this wavefield separation method has advantages in terms of accuracy and robustness compared to the median filtering method based on the first break picking.

Whistler Waves in the Quasi‐Parallel and Quasi‐Perpendicular Magnetosheath

AbstractIn the Earth's magnetosheath (MSH), several processes contribute to energy dissipation and plasma heating, one of which is wave‐particle interactions between whistler waves and electrons. However, the overall impact of whistlers on electron dynamics in the MSH remains to be quantified. We analyze 18 hr of burst‐mode measurements from the Magnetospheric Multiscale (MMS) mission, including data from the unbiased magnetosheath campaign during February‐March 2023. We present a statistical study of 34,409 whistler waves found using automatic detection. We compare wave occurrence in the different MSH geometries and find three times higher occurrence in the quasi‐perpendicular MSH compared to the quasi‐parallel case. We also study the wave properties and find that the waves propagate quasi‐parallel to the background magnetic field, have a median frequency of 0.2 times the electron cyclotron frequency, median amplitude of 0.03–0.06 nT (30–60 pT), and median duration of a few tens of wave periods. The whistler waves are preferentially observed in local magnetic dips and density peaks and are not associated with an increased temperature anisotropy. Also, almost no whistlers are observed in regions with parallel electron plasma beta lower than 0.1. Importantly, when estimating pitch‐angle diffusion times we find that the whistler waves cause significant pitch‐angle scattering of electrons in the MSH.

Geologic causatives of the stratigraphic and structural heterogeneties of Baharyia formation, based on their seismic interpretation, Razzak field, Western Desert, Egypt

Evaluation of seismic attributes and seismic reflection characteristics analysis of Razzak Field was undertaken by subdividing the study area rock units. There are four seismo-facies units of varying parameters from top to bottom. These units are comparable to the Apollonia and Khoman Formations; the Abu-Roash Formation; Baharyia Formation and Alamein Formation. The seismo-facies unit 1 of the Apollonia and Khoman Formations reveal parallel to sub-parallel layering, with thickness increases northwards. The lithological distribution consists of limestone with minor clay intercalations with facies varying from middle neritic graded to outer neritic. Unit 2 of the Abu-Roash Formation shows divergent layering, with a thickness increasing gradually northwards and eastwards. The lithological distribution shows predominance of carbonate, sandstone occurring in minor portions and laterally graded into shale with littoral facies ranging to inner and middle neritic facies. Unit 3 of the Baharyia Formation reveals chaotic and oblique layering with a time thickness increases towards northeast and southwest parts, the lithological distribution exhibited sand and shale with minor limestone streaks, with facies varied changed from continental to inner-middle neritic, unit 4 of the Alamein Formation shows variation from parallel-subparallel orientation to oblique and chaotic with thickness increasing towards northwards and eastwards, the lithological distribution exhibited dolomitic limestone with minor streaks of limestone with facies varied from middle neritic facies to outer neritic and bathyal. Finally, the results are integrated to build up a seismo-stratigraphic model of the evaluated area of the northwestern Desert of Egypt. Seismic interpretation involves the construction of structure contour maps, in terms of time and depth, on the tops of the Apollonia, Abu-Roash, Baharyia and Alamein Formations. These maps show three structural closures, due to folding, that are dissected by NW–SE faults, analysis of relevant structural and stratigraphic seismic attributes such as root-mean-square amplitude, local structural dip, variance, ISO frequency component, sweetness and acoustic impedance average energy applied on reservoir tops, to enhance the visibility of faults, geological interpretation and the physical parameters of the subsurface related to lithology and stratigraphy for reservoir characterization. Finally, the results obtained are used to construct a seismic structural model. Integration of seismic and stratigraphic data is used to build a geological model of the northwestern Desert of Egypt.

Plane-wave least-squares diffraction imaging using short-time singular spectrum analysis

Abstract Diffractions are seismic waves generated by small-scale heterogeneities in the subsurface. These are often superimposed by strong reflections so that they are not visible on the image, leading to misinterpretation and incorrect localization of the scatterers. Therefore, the separation of diffracted and reflected waves is a crucial step in identifying these small-scale diffractors. To realize the separation of diffraction and imaging, a least-squares reverse time migration method of plane waves (PLSRTM) optimized with short-time singular spectrum analysis (STSSA) was developed in this work. The proposed STSSA algorithm exploits the properties of singular spectral analysis (SSA) to separate linear signals. By establishing the Hanning window and the energy compensation function, it also compensates for the shortcomings of SSA in local dip processing and convergence of linear signals. As there is no clear boundary between reflected and diffracted waves, the energy loss during separation leads to a slow convergence rate of the diffraction wave imaging technique. We use STSSA as a constraint for PLSRTM, which greatly improves the imaging quality for diffraction waves. The tests with the Sigsbee2A model and noisy seismic data have shown that our method can effectively improve the resolution of diffraction wave imaging and that the constraint of STSSA increases the robustness to noisy data.

Whistler Wave Observations by Parker Solar Probe During Encounter 1: Counter-propagating Whistlers Collocated with Magnetic Field Inhomogeneities and their Application to Electric Field Measurement Calibration

Observations of the young solar wind by the Parker Solar Probe (PSP) mission reveal the existence of intense plasma wave bursts with frequencies between 0.05 and 0.20f ce (tens of hertz up to ∼300 Hz) in the spacecraft frame. The wave bursts are often collocated with inhomogeneities in the solar wind magnetic field, such as local dips in magnitude or sudden directional changes. The observed waves are identified as electromagnetic whistler waves that propagate either sunward, anti-sunward, or in counter-propagating configurations during different burst events. Being generated in the solar wind flow, the waves experience significant Doppler downshift and upshift of wave frequency in the spacecraft frame for sunward and anti-sunward waves, respectively. Their peak amplitudes can be larger than 2 nT, where such values represent up to 10% of the background magnetic field during the interval of study. The amplitude is maximum for propagation parallel to the background magnetic field. We (i) evaluate the properties of these waves by reconstructing their parameters in the plasma frame, (ii) estimate the effective length of the PSP electric field antennas at whistler frequencies, and (iii) discuss the generation mechanism of these waves.

Seismic Image Dip Estimation by Multiscale Principal Component Analysis

Dip estimation of geological structures plays an important role in geophysical applications. Principal component analysis (PCA) is a common approach to estimating local dips by decomposing the local gradients of a seismic migration image and obtaining its principal eigenvector. However, PCA is difficult to obtain robust and high-resolution dip estimations for low signal-to-noise ratio (SNR) migration images, while multiscale schemes in digital image processing can achieve a better compromise between noise robustness and dip resolution. Therefore, we propose to adopt a multiscale PCA (MPCA) method coupled with a propagation-weight-based fusion mechanism for seismic dip estimation of low SNR migration image. MPCA consists of three steps: 1) constructing an image pyramid by repeating the low-pass filter from fine to coarse scales; 2) estimating the dip using the PCA method at each scale of the image pyramid; and 3) fusing the multiscale dip estimations using propagation weights from coarse to fine scales. We test the MPCA method on an omnidirectional dip pattern and three seismic migration images and compare with the conventional PCA and multiscale methods. The results demonstrate that MPCA yields robust and high-resolution dip estimations for low SNR seismic migration images.

Interpretation of magnetic anomaly profiles using a decomposition in Hilbert transform pairs

ABSTRACT. We propose a simple transformation to aid the interpretation of magnetic anomalies generated by linear structures. The profile of such anomalies perpendicular to the strike can be decomposed into two signals, one symmetric and the other antisymmetric concerning the center of the source. The symmetric component serves as input data to various depth estimation techniques that often assume the anomaly is reduced to the pole. We use the fact that these components form a Hilbert transform pair to transform a skewed anomaly profile into a symmetric one. Unlike in previous works that rely on the decomposition into even and odd functions, the profile does not need to be shifted to the source's center of symmetry or limited to one isolated anomaly. Multiple effective magnetization directions presented by different dikes are modeled by a function representing the different local effective dip angles. We validate the method with synthetic data and ground magnetic survey data from a dike swarm at Ponta Grossa Arch, southern Brazil. We also illustrate the usefulness of reconstructed anomalies for depth estimation methods. The results also show that the method can handle interfering sources with distinct effective magnetization directions.

Reservoir characterization using integrated seismic attributes and petrophysical parameters in an onshore field of Niger delta basin

An integrated approach of reservoir characterization of a field was performed using seismic attributes and petrophysical parameters for the evaluation of subsurface geological features and hydrocarbon potential of an onshore field in Niger Delta Basin. Four reservoir intervals were identified within the field wells based on their position within the stratigraphic column, and the reservoir correlation, which was aided using the principle of uniform horizontality, based on the simple rule that sediments are deposited horizontally and basic understanding of sequence stratigraphy. The study revealed that, the four reservoirs were predominantly sand units intercalated with shale within the reservoir units. The petrophysical evaluation revealed the Net to Gross (NTG) values ranges from 79% to 87% within the reservoir units, while the effective porosity ranges from 17% to 21%, the permeability ranges between 1307mD to 1678mD across the reservoir units, while the water saturation ranges from the lowest of 35% (Reservoir C) to 78% in reservoir D. A total of fifteen faults were interpreted using the seismic data, while the surface maps (Time and depth surface maps) revealed the identified closures which are anticlinal structures that are fault dependent. The characterization of the reservoir was further enhanced using the seismic attributes (structural and stratigraphic) extracted such as Reflection intensity, Sweetness, Variance, Envelope, Instantaneous frequency, Time gain, Trace AGC, Local structural dip, Gradient magnitude and RMS amplitude. The results shows moderate to high sweetness (sweet spots) within the zone of interest, while the Envelope attribute show acoustic impedance contrasts indicating discontinuities, lithology changes and possible present of hydrocarbon (Bright spots). The variances and gradient magnitude enhanced the signal to map out discontinuities caused by faults and fractures which are signature that enabled delineation of the zone. The integrated approach validates the lithology discrimination of the elastic properties from the well logs and its effectiveness in optimizing and proper understanding of the subsurface, thus identifying and unmasking hidden features within the reservoir (probable bypass) in the field. The study has revealed that the integration of seismic attributes with petrophysical parameters is a better characterization method for fluid and lithology discrimination of a field in any given reservoir study.

The Impact of Genetic Surfing on Neutral Genomic Diversity.

Range expansions have been common in the history of most species. Serial founder effects and subsequent population growth at expansion fronts typically lead to a loss of genomic diversity along the expansion axis. A frequent consequence is the phenomenon of "gene surfing," where variants located near the expanding front can reach high frequencies or even fix in newly colonized territories. Although gene surfing events have been characterized thoroughly for a specific locus, their effects on linked genomic regions and the overall patterns of genomic diversity have been little investigated. In this study, we simulated the evolution of whole genomes during several types of 1D and 2D range expansions differing by the extent of migration, founder events, and recombination rates. We focused on the characterization of local dips of diversity, or "troughs," taken as a proxy for surfing events. We find that, for a given recombination rate, once we consider the amount of diversity lost since the beginning of the expansion, it is possible to predict the initial evolution of trough density and their average width irrespective of the expansion condition. Furthermore, when recombination rates vary across the genome, we find that troughs are over-represented in regions of low recombination. Therefore, range expansions can leave local and global genomic signatures often interpreted as evidence of past selective events. Given the generality of our results, they could be used as a null model for species having gone through recent expansions, and thus be helpful to correctly interpret many evolutionary biology studies.

Single and coupled Helmholtz resonators for low frequency sound manipulation

In this work, we use the finite element method to study the acoustic properties of single and coupled Helmholtz resonators (HRs). Each HR consists of a sphere drilled with one or several small openings. For a single HR, we show that the total pressure computed at the opening's edge as a function of frequency reveals the presence of a local dip in addition to the well-known resonance peak. In the case of coupled resonators, we highlight two resonance peaks at low frequencies, arising from excitation of a monopolar breathing mode, for which the twin resonators are in phase (S-peak), and a dipolar mode, where the two spheres resonate out of phase (AS-peak). In the near field, we study the influence of the number of apertures, the distance between spheres and their orientation on the frequencies, and quality factors of the two resonances. In the far field, we show that the propagation of the scattered wave is quasi-isotropic for the S-peak, while it leads to a dipolar-type pressure distribution for the AS-peak, with a directionality depending on the relative orientation of the openings in adjacent HRs. By increasing the number of coupled HRs from two to four units, we investigate the effect of additional mode coupling. Accordingly, the present study aims to manipulate the sound at targeted frequencies, by varying the distance or orientation between twin resonators, and to discuss the effect of dissipation. The demonstration of the coupling between sub-wavelength units opens the way to multi-frequency functionalities of acoustic metasurfaces.

CO Line Emission Surfaces and Vertical Structure in Midinclination Protoplanetary Disks

High spatial resolution CO observations of midinclination (≈30°–75°) protoplanetary disks offer an opportunity to study the vertical distribution of CO emission and temperature. The asymmetry of line emission relative to the disk major axis allows for a direct mapping of the emission height above the midplane, and for optically thick, spatially resolved emission in LTE, the intensity is a measure of the local gas temperature. Our analysis of Atacama Large Millimeter/submillimeter Array archival data yields CO emission surfaces, dynamically constrained stellar host masses, and disk atmosphere gas temperatures for the disks around the following: HD 142666, MY Lup, V4046 Sgr, HD 100546, GW Lup, WaOph 6, DoAr 25, Sz 91, CI Tau, and DM Tau. These sources span a wide range in stellar masses (0.50–2.10 M ⊙), ages (∼0.3–23 Myr), and CO gas radial emission extents (≈200–1000 au). This sample nearly triples the number of disks with mapped emission surfaces and confirms the wide diversity in line emitting heights (z/r ≈ 0.1 to ≳0.5) hinted at in previous studies. We compute the radial and vertical CO gas temperature distributions for each disk. A few disks show local temperature dips or enhancements, some of which correspond to dust substructures or the proposed locations of embedded planets. Several emission surfaces also show vertical substructures, which all align with rings and gaps in the millimeter dust. Combining our sample with literature sources, we find that CO line emitting heights weakly decline with stellar mass and gas temperature, which, despite large scatter, is consistent with simple scaling relations. We also observe a correlation between CO emission height and disk size, which is due to the flared structure of disks. Overall, CO emission surfaces trace ≈2–5× gas pressure scale heights (Hg) and could potentially be calibrated as empirical tracers of Hg.

Localized Excitation of Electromagnetic Ion Cyclotron Waves From Anisotropic Protons Filtered by Magnetic Dips

AbstractThe excitation of electrostatic and/or electromagnetic waves in the plasma universe is often associated with anisotropic velocity distributions of charged particles. In Earth's inner magnetosphere, this anisotropy can gradually develop as particles injected from the magnetotail drift around the Earth at different speeds depending on their energy and pitch angle. Here, we show that the perpendicular‐moving and bouncing ions can be separated more abruptly near the injection front. These pitch‐angle filters are localized magnetic dip structures formed by the diamagnetic behavior of the injected particles, which can trap perpendicular‐moving ions and allow bouncing ions to overtake. The resulting ion anisotropy facilitates the rapid generation of electromagnetic ion cyclotron (EMIC) waves, which in turn can largely reshape the Van Allen radiation belts. This scenario is examined by case and statistical observations, together with numerical simulations that reproduce most of the observational signatures, to support the causal relationship between magnetic dips, anisotropic ion distributions, and localized excitation of EMIC waves. Our study highlights the important roles of magnetic dips in the inner magnetospheric dynamics, as pitch‐angle filters of the injected ions and traveling hotspots of EMIC wave activities.

Optical characteristics and lasing spectra of a cholesteric liquid crystal with defects of different types

Spectral and laser characteristics of impurity steroidal cholesteric liquid crystals (CLC) with helical structure defects were studied. It is established that in the transmission spectra of defective CLC structures there is a local dip in the center of the selective reflection (SR) band for linear polarization of light. The spectra of laser generation in defective structures of CLC of different types have been studied and it has been shown that they are located within the dip in the transmission spectra, which allows interpreting these defects as a phase jump in the helical structure of CLC. The obtained experimental data are compared with the theoretical model of laser generation in CLC with helical structure defects.

Seismic random noise attenuation based on adaptive nonlocal median filter

Abstract The accurate image of underground medium is determined by the quality of the seismic data, which can be improved by random noise attenuation and structural continuity enhancement. We proposed an adaptive nonlocal median filter that can protect geological structure while attenuating random noise. We combine the nonlocal idea with the weighted median filter and design the appropriate weights of the nonlocal median filter based on seismic data characteristics. The local structure is represented by the neighborhood around the center point. The directional difference of spatial vectors in the neighborhood is considered when computing the similarity. According to the local dip attribute of seismic data, the anisotropic Gaussian window is adaptively adjusted to increase the constraint along the structural direction. The proposed method can search more precisely for points with similar local structure to the filtered points and effectively attenuate seismic random noise. The continuity of events is enhanced while the goal of protecting fault information is achieved. The experimental results of the theoretical model and field data show that the adaptive nonlocal median filter can strike a balance between preserving structure information and attenuating seismic random noise.

Fine Complex Geological Structure Interpretation Based on Multiscale Seismic Dip Constraint.

With the development of seismic exploration technology, geological structure interpretation has become more and more refined, whereas random noise interference, subsalt weak seismic reflection signals, and other issues are also gradually emerged at the same time, which resulted in traditional geological structure interpretation accuracy reduction only relying on single seismic data. A novel technical process integrated time-frequency decomposition of seismic data, seismic dip constraints, and geological structure interpretation is proposed in this paper which is named multiscale seismic dip constraint geological structure interpretation. The technical process contains five steps which first use the basis tracking spectrum decomposition technology to convert the seismic data into the time-frequency domain and then decompose the raw seismic data into coarse scale, fine scale, and deliberate scale through window and threshold methods. Subsequently, execute local layer dip calculation with Hilbert transform and geological structure interpretation on seismic data of different scale, respectively. At last, perform geological structure attribute fusion to obtain fine geological structure interpretation. Synthetic data test and field data test show that through multiscale time-frequency decomposition, high-frequency noise interference can be removed and the subsalt seismic weak signal can be enhanced, and then, high-precision fine complex geological structure interpretation can be obtained with seismic dip constraint. Therefore, the technical process proposed in this paper is effective and can be widely applied in the interpretation of field seismic data.

Electron magnetosonic waves and sub-ion magnetic holes in the magnetotail plasma

Recent observations of hot plasma in Earth's magnetotail and magnetosheath demonstrate nonlinear sub-ion scale magnetic holes, spatially localized dips of magnetic field intensity. These structures resemble magnetosonic solitary waves, but do not include any significant density perturbations. Instead, the magnetic field depression is balanced by hot electron pressure. This study aims to investigate linear modes of hot plasma with two electron components, hot and cold, to find a mode sharing properties (propagation direction, velocity, polarization and density/temperature perturbations) of observed sub-ion scale magnetic holes. The linear analysis of three-component plasma (ions, hot and cold electrons) shows an electromagnetic mode with slow, nearly cross field propagation and absence of density perturbations. Compressional perturbations of the magnetic field in this mode are balanced by hot electron pressure perturbations. This mode resembles the electron acoustic mode with cross field propagation in hot plasma with a significant magnetic field perturbation and can be called electron magnetosonic mode. We discuss properties of this mode in comparison with spacecraft observations.

Subsidence, not erosion: Revisiting the emplacement environment of the Giant's Causeway, Northern Ireland

For almost a century it has been recognised that the anomalous thickness of columnar-jointed tholeiite basalts at the Giant's Causeway, Northern Ireland, was due to ponding of lava in a topographic depression. For more than 80 years this feature has been ascribed to fluvial incision, yet new field observations have found no evidence for erosion of the underlying Lower Basalt Formation anywhere in the studied area. Basalt weathering and erosion rates also suggest that there was insufficient time for fluvial incision to occur on the scale required. Local dips on the Lower Basalt Formation broadly converge about a low point centred on the Giant's Causeway itself and are discordant with the regional dip of the overlying Causeway Tholeiite Member, observations consistent with a subsidence-based model. The absence of sediment and limited development of hyaloclastite beneath the Causeway Tholeiite Member here indicates that the interval between subsidence of the land surface and emplacement of tholeiite lava was insufficient for sediment, or even a significant depth of water, to accumulate. It implies that subsidence may have been directly related to draining of a relatively shallow magma reservoir from which the tholeiite lavas were erupted. The style of faulting in the Lower Basalt Formation outcrop suggests that a brief period of inflation, perhaps associated with magma injection, may have preceded subsidence caused by magma withdrawal. This study demonstrates that even at sites as well-trodden as the Giant's Causeway, new discoveries can be made from simple observations.

Localized strata-bound domino faulting offshore Espírito Santo Basin (southeastern Brazil): The case for sudden release of fluid in salt-withdrawal basins

Hydraulic-driven faults and fractures are important subsurface fluid-flow pathways, yet their seismic expressions are poorly documented. This paper uses high-quality three-dimensional seismic data to investigate curved, strata-bound domino-style faults above which a pockmark field is observed and interpreted to be associated with their formation. The faulted interval covers an area of 24 km2 and is ∼100 m thick. Faults show a concentric pattern with an average spacing of 120 m, whereas their throws approach 10 ms two-way time. Strata-bound domino faults were formed because of overpressure buildup and release in a mud-dominated succession, with their geometry responding to the local dip of the salt-withdrawal basin in which they occur. Further overpressure buildup resulted primarily from fluid migration through underlying crestal faults and secondarily through capillary permeability within permeable strata. Apart from the strata-bound domino faults and associated pockmark fields, other randomly distributed pockmarks indicate episodic fluid flow in the study area. Random pockmarks were likely formed during rapid burial of continental slope strata, resulting in the elevation of fluid pressure in underlying soft sediment. This paper concludes that strata-bound domino faults are a typical feature of fluid flow on salt-rich continental margins, such as southeastern Brazil, the Gulf of Mexico, and the western African continental margin. During their formation, strata-bound domino faults form significant conduits for migrating fluid into soft, porous strata, away from regional and local structural traps.