Seismic Reflection Research Articles

Teleseismic virtual-source reverse time migration of upper crustal structures in the Three Gorges region, China

SUMMARY The Three Gorges (TG) in central China is an earthquake prone region that lacks active-source seismic surveys, hence requiring high-resolution passive seismic imaging to reveal crustal structures in detail. While teleseismic virtual-source reflection (TVR) profiling is effective for imaging gently dipping upper crustal structures, it is unsuitable for mapping steep structures beneath rugged topography in the TG region. Here we develop a teleseismic virtual-source reverse time migration (TV-RTM) to improve the imaging of steep structures. Synthetic tests are conducted to demonstrate the validity and resolution of the TV-RTM method. To mitigate the imaging inaccuracy due to sparse station spacing, we interpolate direct-arrival waveforms to achieve a doubling of the minimally required station spacing from 2 to 4 km. The TV-RTM images of the upper crustal structure beneath a 2-D array in the TG region reveal significant fold and thrust structures that correlate well with the surface geology and tectonic framework. The resolution of the images is assessed using 2-D and 3-D synthetic models with the station and source geometry of field data. The TV-RTM method provides a new passive seismic solution for studying upper crustal structures in regions that lack active-source seismic data.

New Estimates of the Potential Schrödinger Equation

The Schrödinger equation, a fundamental construct in quantum mechanics, plays a pivotal role in understanding the properties and behaviors of quantum systems across various scientific fields, including but not limited to physics, economics, and geophysics. This research paper delves into the exploration of novel invariants associated with the Schrödinger equation, uncovering previously unrecognized symmetries and properties that open new pathways for theoretical and applied scientific exploration. The investigation reveals that the energy of bound states remains invariant under transformations of the coordinate system, highlighting a universal symmetry embedded within the equation. This discovery, coupled with an analysis of the variation in scattering amplitudes’ phase with different coordinate systems, not only enriches the theoretical framework of quantum mechanics but also has significant practical implications across various domains such as fluid dynamics, material science, and medical imaging. Furthermore, by applying the principles of the Poincaré-Riemann-Hilbert boundary-value problem, the study offers a novel approach to estimate potentials within the Schrödinger equation, advancing the three-dimensional inverse problem of quantum scattering theory. This methodological innovation allows for a more profound understanding of the unitary scattering operator, facilitating enhanced modeling of complex systems and phenomena. The implications of these findings extend beyond theoretical physics, offering transformative insights and applications in areas ranging from fluid dynamics, where it aids in refining models for the Navier-Stokes equations, to seismic exploration, tomography, and ultrasound imaging, where it enhances phase selection and interpretation of measurement results. In essence, this research not only contributes to a deeper understanding of the Schrödinger equation’s fundamental properties but also paves the way for interdisciplinary advancements, demonstrating the profound impact of theoretical discoveries on practical applications in diverse scientific and technological domains.

Deep geophysical investigations (DERT and Seismic Reflection) to unravel the Ferrara urban area geology

Exploring the ‘fragile crust of our planet’ is crucial for human survival holding an immense social and economic significance. Therefore, innovative approaches become of utmost importance for obtaining precise subsoil models in urban areas making the latter more resilient to natural disasters. Due to logistic issues and a high level of anthropogenic disturbance and related background noise, urban areas are usually intrinsically more problematic for applying geophysical prospecting methods. This work presents the results obtained by Deep Electrical Resistivity Tomography and P wave Seismic Reflection surveys performed along the Ferrara, north Italy, city walls documenting the adaptability of the geophysical surveys and how it is possible to obtain high-quality electrical resistivity and seismic data even in complex urban settings. The joint interpretation of geoelectrical and seismic data fully integrated with tectonic, geological and hydrogeological information allowed to reconstruct the stratigraphic evolution down to a depth of about 1.5 km. These results highlight the occurrence of a syndepositional Quaternary tectonic tilting associated with the growth of a fault-propagation fold.

The study on vibrator seismic data acquisition and processing for sandstone type uranium prospecting in Erlian Basin

Abstract Seismic exploration technique has been widely used in sandstone-type uranium exploration in recent years. Aiming to the demands of sandstone type uranium prospecting in Erlian Basin, seismic geometry parameters are designed, and excitation parameters of high-precision vibrator are proved by field test. High quality raw seismic data are obtained. According to characteristics of vibrator seismic data, crucial data processing method and techniques are researched. The main processing techniques include tomographic static correction, pre-stack combination de-noising in different domain, surface consistent prediction deconvolution, surface consistent amplitude compensation, velocity analysis and residual static correction. The reasonable stack velocity model is established, and the stack section which has high signal-to-noise ratio is obtained. the stack velocity model is built as initial migration velocity model. After multiple iteration of migration velocity analysis and pre-stack Kirchhoff time migration, the underground target geological structure is reasonable imaged, and the true subsurface stratum distributing feature is obtained. Finally, the reasonable vibrator seismic data acquisition and processing techniques are built. The ultimate seismic section which has high resolution, clear wave group, reasonable stratum distribution feature is obtained, besides, the section provides reliable basis for subsequent seismic inversion, interpretation and favorable ore-forming sandstone prediction.

Range versus frequency averaging of underwater propagation loss for soundscape modelinga).

Guidance on efficient methods is needed for the practical application of modeling the sound field from broadband sources such as vessels, seismic surveys, and construction activities. These sound field models are employed for estimating how changes in the soundscape will affect marine life. For efficiency, acoustic propagation modeling is often performed in bands (decidecade or 13-octave), where propagation loss modeled for central frequency is assumed to represent an average propagation loss in the band. This shortcut comes at the expense of accuracy, which can be rectified by averaging the propagation loss across many frequencies in the band. Alternately, the equivalence of range and frequency averaging was shown by Harrison and Harrison [J. Acoust. Soc. Am. 97, 1314-1317 (1995)]. However, when and how to apply range averaging required further investigations. A simple environment with a flat sandy bottom and an isovelocity water-column sound speed profile was considered to test the agreement between the range and frequency averages for decidecade bands typically considered in soundscape modelling (10-1000 Hz). The optimal range smoothing window is a Gaussian window with a width of 10%-16% of the range from the source that switches to a width fixed beyond 20 km distance from the source.

Application of Sparsity-Enhanced Predictive Deconvolution in Offshore Wind Farm Site

Abstract The development of offshore wind power has become an integral part of the global energy transition. Geological surveys targeting the bedrock surface are indispensable in the development process of offshore wind farms, as they directly affect the site selection and design of the wind farms. Single-channel seismic surveying is a towed survey method that offers advantages in exploration efficiency and accuracy. However, strong interference from multiple reflections is a unique challenge in offshore seismic exploration. To address this issue, we propose a sparse-promoting multi-channel predictive deconvolution method. This method begins by establishing a framework for multichannel predictive deconvolution, and then leverages the high redundancy and sparsity benefits of the Shearlet transform to enhance the sparsity of seismic signals. Through the processing of field data, we have verified that our method can effectively suppress multiple reflections, improve signal-to-noise ratio, and enhance the accuracy and efficiency of seismic exploration, providing more accurate and reliable technical support for the preliminary environmental investigation of offshore wind power projects.

Comparative analysis of distributed acoustic sensing responses across different optical fiber types for engineering geological exploration

Abstract Distributed Acoustic Sensing (DAS) has emerged as a revolutionary technology in seismic exploration, offering a novel approach to data acquisition. Despite its widespread adoption, the deployment of DAS in surface engineering exploration faces significant challenges, particularly concerning signal-to-noise ratio limitations and spatial resolution constraints. We conduct a comparative analysis of DAS responses using various types of optical fibers commonly employed for sensing purposes. We evaluate fibers of type A (tight-buffered fiber and strain-sensitive fiber) and type B (communication optical fiber, loose tube optical fiber, and temperature measurement optical fiber), as well as fibers in a helical configuration with different armoring materials. The deployment of optical fibers for this comparison includes both surface layouts and borehole integrations. Conventional geophones and hydrophones serve as benchmarks to contextualize the analysis and validate the performance of the DAS system data. This comparative approach highlights the utility of DAS for engineering seismic prospecting.

Analysis of difficulties in reflection seismic data processing in the shallow-surface igneous rich areas and suggestions

Abstract The seismic geological conditions in shallow-surface igneous rich areas are poor, resulting in complex original data wave fields and low signal-to-noise ratios, making seismic processing challenging. Although the research at home and abroad has made some progress over the years, the seismic imaging in this area is still poor, which affects the effect of seismic exploration. This paper analyzes the main factors influencing processing imaging, further examines the signal-to-noise ratio and static correction, and proposes targeted processing strategies and suggestions for data acquisition.

A quantitative analysis of acoustic field directionality from a seismic airgun array

Marine seismic reflection surveys generate high-amplitude impulsive acoustic events using airgun arrays to study the geophysical characteristics of the seabed. These data can be used beyond seismic imaging, including for modeling short-range propagation, considering impacts on marine mammals, and extracting seabed properties and their effect on the acoustic field. Knowledge of the source characteristics is necessary to use these data, and proper modeling of sound propagation from these arrays requires characterization of the array beam pattern. Complex simulations of airgun arrays have been used in the past to model airgun array spectra, but beam patterns have not been thoroughly considered in the literature. Delay-and-sum combinations of these airgun signatures provide a simple beam pattern estimate, but this approach ignores variability in airgun position, timing, amplitude, interactions between airguns, and so on. The use of more complex notional airgun signatures can yield more accurate estimates, but these are more challenging to model and still ignore shot-to-shot variability. Experimentally determined beam patterns are evaluated here, and the variability in the results are considered, showing both similarities and notable differences from simulated results. The experimental results indicate that the source array depth impacts the ghost-free array beam pattern and that variability between shots is enough to significantly alter beam patterns. Overall, the observations suggest that accurate simulation of array beam patterns may require more complexity than is currently considered and that inclusion of uncertainty due to environmental and airgun shot variability is essential.

The Influence of Using a Seismically Inferred Magma Reservoir Geometry in a Volcano Deformation Model for Soufrière Hills Volcano, Montserrat

AbstractVolcano deformation models contribute to hazard assessment by simulating magma system dynamics. Traditional magma reservoir pressure source shape assumptions often fail to replicate irregular, geophysically identified geometries. Uncertainties regarding the influence of reservoir geometry can limit the effectiveness of using deformation models to decipher unrest signals. Here, we aim to determine the feasibility of using a magma reservoir geometry directly derived from a seismic tomography survey in a volcano deformation model for Soufrière Hills Volcano, Montserrat. Three‐dimensional deformation models are created to simulate displacement using a pressure source geometry constrained from a low seismic velocity anomaly, inferred to be a region of partial melt, and contrasted against a traditional ellipsoid reservoir geometry. We also test a “hybrid” model combining a seismically inferred reservoir upper geometry and ellipsoidal base. Results of each model are evaluated against ground displacement observed on Montserrat from 2010 to 2022. Our results show that different reservoir geometries change the horizontal and vertical displacement fields across the island: the ellipsoid reservoir best reproduces vertical displacement magnitude, while the hybrid reservoirs best simulate horizontal displacement vectors and the region of maximum uplift. Overall, the ellipsoid‐shaped reservoir provides our best‐fit to the observed data, but we note this result could be biased due to prior years of optimization helping constrain the ellipsoid shape, size, and location. Our results show the potential for further use of geophysically constrained reservoir geometries in deformation modeling, and our methods could be applied to other deforming volcanoes worldwide.

3‐D Subsurface Geophysical Modeling of the Charity Shoal Structure: A Probable Late Proterozoic‐Early Paleozoic Simple Impact Structure in Eastern Lake Ontario

AbstractThe Charity Shoal structure is a circular, ∼1.2‐km‐diameter, bedrock‐rimmed shoal in eastern Lake Ontario with a ∼20‐m‐deep central basin. The structure has been proposed as a possible Middle Ordovician impact crater or volcanic intrusion. We conducted marine seismic and magnetic surveys (9‐km2) and 3‐D geophysical modeling to better resolve the Charity Shoal subsurface geology and possible origins. Three models were evaluated: (a) a buried (>450 m) impact structure in Mesoproterozoic basement, (b) a maar‐diatreme, (c) a cylindrical, zoned volcanic plug. Seismic profiles and multi‐beam bathymetry revealed >30 m of Quaternary sediments overlying Middle Ordovician (Trenton Group) carbonate bedrock and complex, 3‐dimensional folding and faulting of the structure rim. Magnetic surveys recorded an annular magnetic high (>600 nT) over the structure rim and a central magnetic low (∼500–600 nT) coincident with a ∼−1.7 mGal Bouguer gravity anomaly. The continuity of Trenton Group strata in seismic profiles rules out a previously proposed Mesozoic maar‐diatreme intruded into Paleozoic strata. The zoned volcanic plug model reproduced the annular magnetic anomaly but was incompatible with Bouguer gravity profiles. The magnetic anomaly was best reproduced by a simple impact structure seated in Mesoproterozoic basement at 450–500 m depth with a rim‐to‐rim diameter of ∼1.2 km and rim height of ∼10–20 m. A 100‐m wide and 50‐m‐deep channel in the Mesoproterozoic basement may record fluvial dissection of the southwestern rim. A buried (>450 m), simple impact crater is most compatible with all available geophysical data at Charity Shoal.

USCNet: Seismic P-wave arrival time pickup based on deep learning

Abstract The accurate pickup of seismic P-waves has important application value for real-time seismic data processing such as earthquake activity monitoring and earthquake disaster warning. However, existing low signal-to-noise ratio seismic data pickup algorithms often face problems of low accuracy and poor robustness. To address these issues, we designed a seismic P-wave picking network called USCNet. This network combines the advantages of U-Net and SegNet networks. The U-Net network performs well in picking accuracy, but requires a large number of learning parameters; SegNet networks are trained with fewer learning parameters, but have lower picking accuracy. The USCNet network integrates the CBAM attention mechanism, which can deeply extract key information from seismic data, thereby significantly improving the picking accuracy. We use the Stanford Earthquake Dataset (STEAD) as the data source. The experimental results show that USCNet performs significantly better than U-Net and SegNet networks on this dataset, with significant improvements in metrics such as Mean (μ), Variance (δ), Precision (P), and Recall (R), as well as significantly improved picking performance.

Subsurface Imaging in Urban Areas With Ambient Noise Using DAS and Seismometer Data Sets: Granada, Spain

AbstractDistributed acoustic sensing (DAS) is an innovative technology with great potential for acquiring seismic data sets in urban areas. In this work, we check the suitability of a DAS data set acquired in Granada (Spain) for retrieving subsurface reflectivity from ambient noise. The fiber‐optic is a pre‐existing underground telecommunication cable that crosses the city from Northwest to Southeast. We use a 10 hr recording of strain rate from a 2020 experiment to obtain seismic reflections using the autocorrelation method. We compare the DAS results with reflections obtained from seismic ambient noise recorded in nine seismometers deployed close to the fiber‐cable for 7 days in November 2022. The novel approach proposed in this study for the identification of the reflections is to use autocorrelations after bandpass filtering for specific central frequencies and to check the stability of the signals over a broad frequency band. Microtremor Horizontal to Vertical Spectral Ratio (MHVSR) measurements at a total of 14 stations, five of them outside the city, help to constrain the reflection interpretation. These include one station at the borehole that reaches the basement in the Granada Basin crossing all the Cenozoic units. We use the legacy sonic log to obtain a relationship between frequencies of MHVSR peaks and depth. Autocorrelation and MHVSR methods give consistent results delineating bedrock depth deeper than 1,000 m in Granada. These results confirm that DAS can provide valuable subsurface information in urban areas.

The Lomonosov Ridge, central Arctic Ocean - the world's longest submarine ridge of continental origin: outline of the history of exploration, morphology, sediment deposition, and exhumation of the North American and Central ridge segments

We have accessed the North American segment of the Lomonosov Ridge in the central Arctic Ocean by a 12-month hovercraft expedition on drifting sea ice and revisit legacy seismic data to explore the geological history of the ridge. Seismic reflection images on the North American segment resemble the acoustic reflection sequence calibrated by scientific drilling at the ACEX site on the Central ridge segment, although the thickness of the Cenozoic sediment section is reduced to 70%. A base-Cenozoic unconformity is present north of about 88 o 30’ N and older sediments dip towards the Makarov Basin along the entire ridge segment. During the Eocene, sediment drifts were deposited along the flanks on top of the North American segment north of 87 o N as well as next to the ACEX drill site on the Central segment of the ridge. Two local sediment lenses deposited at the Canadian end of the Lomonosov Ridge document local ridge-uplift events at about 56 Ma and 48 Ma during the Eurekan Orogeny. Compressional velocity gradients derived from published seismic reflection/refraction measurements are consistent with 1-3 km of Cretaceous/early Cenozoic exhumation of an up to 500 km wide swath of continental crust along the polar continental margin including the Lomonosov Ridge, Svalbard and Franz Josef Land .

Industry-First Deployment of Simultaneous Source Acquisition Using a Dispersed Source Array with Tuned Pulse Source and Conventional Airgun for a Shallow Water Seismic Survey Offshore Malaysia

Industry-First Deployment of Simultaneous Source Acquisition Using a Dispersed Source Array with Tuned Pulse Source and Conventional Airgun for a Shallow Water Seismic Survey Offshore Malaysia

Evaluating distributed acoustic sensing for crosswell seismic surveys with helical and linear fibers using conventional P-, SH-, and SV-wave sources

Evaluating distributed acoustic sensing for crosswell seismic surveys with helical and linear fibers using conventional P-, SH-, and SV-wave sources

Monitoring Salt Domes Used for Energy Storage With Microseismicity: Insights for a Carbon‐Neutral Future

AbstractUnderground storage in geologic formations will play a key role in the energy transition by providing low‐cost storage of renewable fuels such as hydrogen. The sealing qualities of caverns leached in salt and availability of domal salt bodies make them ideal for energy storage. However, unstable boundary shear zones of anomalous friable salt can enhance internal shearing and pose a structural hazard to storage operations. Considering the indistinct nature of internal salt heterogeneities when imaged with conventional techniques such as reflection seismic surveys, we develop a method to map shear zones using seismicity patterns in the US Gulf Coast, the region with the world's largest underground crude oil emergency supply. We developed and finetuned a machine learning algorithm using tectonic and local microearthquakes. The finetuned model was applied to detect microearthquakes in a 12‐month long nodal seismic dataset from the Sorrento salt dome. Clustered microearthquake locations reveal the three‐dimensional geometry of two anomalous salt shear zones and their orientations were determined using probabilistic hypocenter imaging. The seismicity pattern, combined with borehole pressure measurements, and cavern sonar surveys, shows the spatiotemporal evolution of cavern shapes within the salt dome. We describe how shear zone seismicity contributed to a cavern well failure and gas release incident that occurred during monitoring. Our findings show that caverns placed close to shear zones are more susceptible to structural damage. We propose a non‐invasive technique for mapping hazards related to internal salt dome deformation that can be employed in high‐noise industrial settings to characterize storage facilities.

Transforming Seismic Surveys with OBN and Autonomous Technology

Transforming Seismic Surveys with OBN and Autonomous Technology

Application of Integrated Directional and Guide Drilling Technology in Deep Coalbed Methane

Abstract Deep coalbed methane is characterized by deep burial, complex and diverse microstructures, significant lateral variations in reservoirs, and the development of internal interlayers. Current seismic exploration methods suffer from severe high-frequency signal attenuation in coal layers, resulting in low seismic resolution, which severely limits the precision of geological models for coalbed methane and the encounter rate of reservoirs in horizontal wells. Based on this, this paper introduces an integrated directional and guide drilling technology and applies it to horizontal well operation, achieving excellent results. Firstly, in the pre-drilling phase, we utilize well-seismic integrated reservoir and structural prediction techniques to meticulously characterize coal seam distribution patterns and subtle geological structures. This enables the construction of a geo-steering model specifically for horizontal wells, optimizing the locations of target points, designing well trajectories, and selecting the optimal configuration of geological steering tools. Secondly, in the drilling operation stage, this system iteratively refines the depth-domain seismic section based on real-time measure while drilling (for short MWD). This process reconstructs the geological steering model, precisely predicts the position of coal seams at the bottom of the well, continuously optimizes the well trajectory design in real-time, and ultimately generates geo-steering instructions. Finally, after the completion of drilling operations, the system evaluates the coal seam area and iteratively refines the three-dimensional geological model. This process provides technical support for the deployment of the next well and the design of the target trajectory. After verification through multiple horizontal wells targeting deep coalbed methane, the guiding model reconstructed by this technology has achieved a fitting rate of over 95%, significantly enhancing the reservoir encounter rate to above 90%. This remarkable achievement underscores the technology’s precision and effectiveness in accurately guiding drilling operations toward targeted coal seam reservoirs.

Design and implementation of seismic and electric joint detection system

Abstract Single geophysical method faces challenges in accurately depicting water-bearing anomalies due to complex factors in underground spaces. In response to this issue, our design innovatively proposes a combined approach, integrating seismic exploration with parallel electrical method. We have developed a complete joint acquisition instrument for seismic and parallel electrical method using a multi-channel acquisition board based on INTEL and FPGA. This instrument enables simultaneous data collection for both methods within the same timeframe. With high integration, it allows convenient deployment and can be controlled through visualization software on the upper computer. Laboratory tests confirm its ability to meet the basic design requirements. Once fully implemented, it is poised to offer innovative and effective technical support for the development of urban underground spaces, demonstrating broad application potential.