Seismic Tool Research Articles

No globally detectable seismic interfaces within Earth's mantle transition zone: Evidence for basalt enrichment

Earth's mantle transition zone (MTZ) is characterized by multiple mineral phase changes. The MTZ is bounded seismically by the 410- and 660-km elastic discontinuities, which are interpreted as phase changes from olivine to wadsleyite and from ringwoodite to bridgmanite, respectively. Within the transition zone, the wadsleyite-to-ringwoodite phase change has been assigned to a seismic feature at 520-km depth. Here we show that SS precursors, the most common seismic tool for imaging MTZ structure at global scale, are susceptible to signal-processing artifacts within the transition zone. Owing to the narrow frequency range in which the SS wave is typically examined, S waves scattered by the bounding MTZ discontinuities generate Gibbs-effect overshoots that map into features within the transition zone, including at 520-km depth. These results suggest that inferences of global interfaces at 520-km depth and, in some studies, at 560-km depth, are problematic. If such interfaces are not detectable, Earth's mantle transition zone may depart significantly from the pyrolite composition, enriched in a subducted basalt component that contributes a high proportion of garnet. A basalt fraction (f = ∼0.4) in the MTZ, consistent with some estimates, can render the 520-km discontinuity indistinguishable from signal-processing artifacts.

Development of a numerical simulator for modeling seismic EOR

Natural earthquakes, culture noise, and artificially induced mechanical waves have been reported to affect the productivity of oil wells. Sources emitting waves in the seismic frequency range, between 1 and 1000 Hz, have been used as an enhanced oil recovery (EOR) tool for improving oil production rates. Theories suggest several mechanisms for the increased oil production rate including (AbuZaid et al., 2021): overcoming the capillary forces holding the oil phase in place (Alzahrani and Abbas, 2020), improving the relative permeability of oil, and (Ariadji, 2005) decreasing viscosity as temperature rises from waves attenuation. In this work, a fully implicit modified black oil simulator has been developed. The fluid flow simulator is coupled with a ray tracing module for simulating waves propagation in the model. Wave simulation is used to calculate the effect of seismic waves on capillary pressure, oil relative permeability, and reservoir temperature. It is also used to investigate the applicability of the proposed mechanisms for explaining the observed enhancement in oil recovery due to seismic waves. This seismic stimulation simulator can provide insights on the response of wells’ production rates at various field characteristics and seismic tool(s) operation conditions, explain field results, and design field implementation of seismic EOR.

Mapping the Fizzy Brines and Fluid-Filled Fractures Below a Volcano

Seismic tools reveal where hydrothermal fluids lie beneath the Uturuncu volcano in Bolivia and hint at their composition.

Seepage-Induced Pore Pressure Variations Beneath an Earthen Levee Measured with a Novel Seismic Tool

Shear-wave seismic reflection velocity-versus-depth models can complement our understanding of seepage pore pressure variations beneath earthen levees at locations between geotechnical sites. The seasonal variations of water level in the Mississippi River create pore pressure changes in the adjacent hydraulically connected aquifer on the protected side of artificial levees. Time-lapse shear-wave velocity analysis or repetition of seismic acquisition over an area is a non-invasive method that can detect seasonal pore pressure variations in shallow (<40 m) aquifers. The seismic reflection patterns during the seasonal pore pressure variations of the river show a distinctive change in the velocity semblance analysis, which is translated as a change in the average stress carried by the grain-to-grain contact, or simply the effective pressure. The seismic data show a greater variation of up to +140/−40 m/s or +700/−150 kPa in the confined aquifer zone, compared with the leaky confined aquifer zone of up to +46/−48 m/s or +140/−80 kPa. These relative effective pressure characteristics allow us to distinguish between confined and leaky aquifers and can be an optional approach for pressure prediction in floodplains along levees without the need to drill borings in the area to measure piezometric data.

Development of 4D Seismic Monitoring Tool Considering Anisotropic Media based on Pseudo-acoustic Wave Equation

Development of 4D Seismic Monitoring Tool Considering Anisotropic Media based on Pseudo-acoustic Wave Equation

Comparing Hysteretic Energy and Ductility Uniform Annual Failure Rate Spectra for Traditional and a Spectral Shape-Based Intensity Measure

In this study, with the objective to develop a reliability-based seismic design tool, ductility and dissipated hysteretic energy uniform annual failure rate (UAFR) spectra are obtained and compared using the spectral acceleration at first mode of vibration of the structure Sa(T1) and the well-known spectral shape-based intensity measure INp. Notice that this is the first time in the literature that UAFR spectra are obtained for the advanced spectral shape intensity measure INp. For this aim, 110 simulated ground motions recorded from the soft soil of Mexico City were selected due to their large energy amount demanded to the structures; moreover, four elastoplastic hysteretic behavior models are considered for the dynamic analyses with post-yielding stiffness of 0, 3, 5, and 10%. It is observed that the use of elasto-perfectly plastic models provided similar UAFR spectra in comparison with hysteretic models with different post-yielding stiffness. This conclusion is valid for the two selected intensity measures. In addition, the lateral resistance required to achieve similar structural reliability levels is larger when the INp intensity measure is used, especially for buildings with vibration periods equal or larger than the soil period, in such a way that the traditional use of Sa(T1) could provide structures with less structural reliability levels.

Application of Neural Network Analysis for Seismic Data to Differentiate Reservoir Units of Yamama Formation in Nasiriya Oilfield A Case Study in Southern Iraq

The EMERGE application from Hampsson-Russell suite programs was used in the present study. It is an interesting domain for seismic attributes that predict some of reservoir three dimensional or two dimensional properties, as well as their combination. The objective of this study is to differentiate reservoir/non reservoir units with well data in the Yamama Formation by using seismic tools. P-impedance volume (density x velocity of P-wave) was used in this research to perform a three dimensional seismic model on the oilfield of Nasiriya by using post-stack data of 5 wells. The data (training and application) were utilized in the EMERGE analysis for estimating the reservoir properties of P-wave velocity, in addition to the neural network analysis and deriving relations between them at well locations. P- wave velocity slices of reservoir units (Yb1, Yb2, and Yc) of Yamama Formation were prepared to determine the enhancement trends within these units. From a general economic point of view, due to good prospecting in Cretaceous rocks, especially in Nasiriya oilfield, , Yamama Formation was found to contain hydrocarbon accumulation and can be considered as one of the most important reservoirs in southern Iraq.

Asteroseismic analysis of variable hot subdwarf stars observed with TESS

Context. We present photometric and spectroscopic analyses of gravity (g-mode) long-period pulsating hot subdwarf B (sdB) stars, also called V1093 Her stars, observed by the TESS space telescope in both 120 s short-cadence and 20 s ultra-short-cadence mode during the survey observation and the extended mission of the southern ecliptic hemisphere. Aims. We performed a detailed asteroseismic and spectroscopic analysis of five pulsating sdB stars observed with TESS in order to compare the observations with model predictions based on our stellar evolution computations coupled with adiabatic pulsation computations. Methods. We processed and analyzed TESS observations of long-period pulsating hot subdwarf B stars. We used standard pre-whitening techniques on the datasets to extract the pulsation periods from the TESS light curves. We applied standard seismic tools for mode identification, including asymptotic period spacings and rotational frequency multiplets. Based on the values obtained from Kolmogorov-Smirnov and Inverse Variance tests, we searched for a constant period spacing for dipole (l = 1) and quadrupole (l = 2) modes. We calculated the mean period spacing for l = 1 and l = 2 modes and estimated the errors by means of a statistical resampling analysis. For all stars, atmospheric parameters were derived by fitting synthetic spectra to the newly obtained low-resolution spectra. We computed stellar evolution models using the LPCODE stellar evolution code, and computed l = 1 g-mode frequencies with the adiabatic nonradial pulsation code LP-PUL. Derived observational mean period spacings were then compared to the mean period spacings from detailed stellar evolution computations coupled with the adiabatic pulsation computations of g-modes. Results. We detect 73 frequencies, most of which are identified as dipole and quadrupole g-modes with periods spanning from ∼3000 s to ∼14 500 s. The derived mean period spacing of dipole modes is concentrated in a narrow region ranging from 251 s to 256 s, while the mean period spacing for quadrupole modes spans from 145 s to 154 s. The atmospheric parameters derived from spectroscopic data are typical of long-period pulsating sdB stars with an effective temperature ranging from 23 700 K to 27 600 K and surface gravity spanning from 5.3 dex to 5.5 dex. In agreement with the expectations from theoretical arguments and previous asteroseismological works, we find that the mean period spacings obtained for models with small convective cores, as predicted by a pure Schwarzschild criterion, are incompatible with the observations. We find that models with a standard, modest convective boundary mixing at the boundary of the convective core are in better agreement with the observed mean period spacings and are therefore more realistic. Conclusions. Using high-quality space-based photometry collected by the TESS mission coupled with low-resolution spectroscopy from the ground, we provide a global comparison of the observations with model predictions by means of a robust indicator such as the mean period spacing. All five objects that we analyze in this work show remarkable homogeneity in both seismic and spectroscopic properties.

Introduction to this special section: Basin exploration

Originally, explorers relied on hydrocarbon seeps and 2D seismic lines to define a basin's petroleum potential and to identify its best part. Due to dramatic improvements in seismic technology, today's explorers have access to a vast seismic tool kit, from basin-scale regional 3D seismic surveys to neural network techniques that directly derive reservoir properties from seismic volumes. However, in frontier or mature exploration, geoscientists are often limited by the amount of well data and rock properties information available, and they may deal with poor(er) seismic that makes seismic calibration difficult. Successful explorers will require a lot of knowledge-based creativity to derive meaningful geologic and reservoir properties models to reduce exploration risk. By embracing uncertainties, explorers develop “outside-the-box” thinking to help them chase the hydrocarbon molecules and unlock the prize. With their knowledge in rock physics, subsurface deformation, and wave propagation, geoscientists are deploying new methodologies and tools to fill the data gap and produce an improved description of the subsurface.

Huang-Hilbert transform and application in signal processing of seismic detection tools

Huang-Hilbert transform and application in signal processing of seismic detection tools

“Seismic attributes and reservoir simulation’ application to image the shallow-marine reservoirs of Middle-Eocene carbonates, SW Pakistan”

Carbonates form brilliant stratigraphic traps. The execution of traditional seismic data interpretation using time and depth mapping generates ambiguities in the discrimination of porous and non-porous reservoir beds. In these stratigraphic circumstances, placement of development wells within the unproven prospects is a trial for exploration geophysicist. The 3D post-stack seismic attributes and quantitative seismo-petrophysical simulation (QSPS) are applied on Habib Rahi Limestone (HRL) Member from a gas field, SW Pakistan. 45 Hz spectral magnitude delineates the lithology, fractures, and geomorphology of gas-bearing shoal reservoir facies than full-spectrum seismic tools. 45 Hz predicts a north-east oriented gas-bearing stratigraphic lead, which covers an area of 105 km2. The QSPS reveals a very low-density (2–2.1 g/c.c.) and low-velocity (~2500–3000 m/s) of shoal reservoir. The high-quality shoal limestone reservoirs of HRL with ~30% porosity are deposited during the regression phase of sea-level fall in the east. The low-quality fine-grained seal facies with <9% porosity are deposited during the substantial transgression phase of sea-level rise in the west. The cross plots of seismic-based porosity (%) versus inverted velocity (m/s), inverted density (g/c.c), and reservoir thickness (m) show correlation coefficients of (R)2>0.92, (R)2>0.97, and (R)2>0.89. The coarse-grained gas-bearing reservoirs experience 31.8 m thickness and least density (2–2.1 g/c.c.) are deposited during sea-level fall. The 31.3 m thick and high-density (2.2–2.3 g/c.c.) fine-grained seal facies are deposited during sea-level rise. This workflow can serve as an analogue for the development of carbonate fairways within Asia and similar world basins.

Identifikasi Lapisan Akuifer Menggunakan Metode Seismik Refraksi di Desa Jatimulyo, Kecamatan Jati Agung, Kabupaten Lampung Selatan

An initial subsurface survey to predict the aquifer is important to avoid the unprospect drill location and getting groundwater with the right discharge. In this study, prediction of the aquifer was carried out using the seismic refraction method in Jatimulyo Village, Jati Agung District, South Lampung Regency. The data was collected on October 6, 2019 using the SUMMIT X One seismic tool with 24 Geophones. The first break data from p-wave travel time is processed and interpreted using the Hagiwara method. Interpretation results show that there are three layers of subsurface lithology in the study area. The weathering layer was found at 2 m to 3.5 m depth with average velocity of 360 m/s. The second layer is dry sand with a velocity of 890 m/s at a depth of 2 m to 8 m. The third layer with a 2300 m/s velocity is a mixture of clay rock and saturated sand at depths of more than 8 m. As a comparison there is resistivity distribution data on the same measurement line in the study area. The overall interpretation shows that at a depth of 12 m with saturated clay sedimentary rock as a prospect of aquifer in this study area.

Factors impacting post-earthquake damage repair cost estimations

Purpose Reconstruction processes after an earthquake require estimating repair costs to decide on whether to repair or rebuild. This requires an accurate post-earthquake cost estimation tool. Currently, there are no post-earthquake loss estimation models to estimate repair costs accurately. There are loss assessment tools available, namely, HAZUS, performance assessment calculation tool (PACT), seismic performance and loss assessment tool (SLAT) and seismic performance prediction tool, which have not been specifically used for post-earthquake repair cost estimation. This paper aims to focus on identifying factors that need to be considered when upgrading these tools for post-earthquake repair cost estimation. Design/methodology/approach The research was conducted as an exploratory study using a literature review, document analysis of the PACT, SLAT and HAZUS software and 18 semi-structured interviews. Findings The research identified information sources available for estimation and factors to be considered when developing estimations based on the information sources. Research limitations/implications The data was collected from professionals who were involved mostly in housing repair work in New Zealand. Therefore, impact of these repair work factors might vary in other forms of structures such as civil structures include bridges and the country as a result of varying construction details and standards. Practical implications The identified factors will be used to improve the loss estimation tools are such as PACT and HAZUS, as well as to develop a post-earthquake repair cost estimation tool. Originality/value Currently, the identified factors impacting post-earthquake damage repair cost estimations are not considered in loss estimation tools. Factors identified in this research will help to develop a more accurate cost estimation tool for post-earthquake repair work.

High mantle seismic P-wave speeds as a signature for gravitational spreading of superplumes.

New passive- and active-source seismic experiments reveal unusually high mantle P-wave speeds that extend beneath the remnants of the world's largest known large igneous province, making up the 120-million-year-old Ontong-Java-Manihiki-Hikurangi Plateau. Sub-Moho Pn phases of ~8.8 ± 0.2 km/s are resolved with negligible azimuthal seismic anisotropy, but with strong radial anisotropy (~10%), characteristic of aggregates of olivine with an AG crystallographic fabric. These seismic results are the first in situ evidence for this fabric in the upper mantle. We show that its presence can be explained by isotropic horizontal dilation and vertical flattening due to late-stage gravitational collapse and spreading in the top 10 to 20 km of a depleted, mushroom-shaped, superplume head on a horizontal length scale of 1000 km or more. This way, it provides a seismic tool to track plumes long after the thermal effects have ceased.

Spectroscopic and Asteroseismic Analysis of the Secondary Clump Red Giant HD 226808*

Abstract In order to clarify the properties of the secondary clump star HD 226808 (KIC 5307747), we combined four years of data from Kepler space photometry with high-resolution spectroscopy of the High Efficiency and Resolution Mercator Échelle Spectrograph mounted on the Mercator telescope. The fundamental atmospheric parameters, radial velocities, rotation velocities, and elemental abundance for Fe and Li were determined by analyzing line strengths and fitting-line profiles, based on a 1D local thermodynamic equilibrium model atmosphere. Second, we analyzed a photometric light curve obtained by Kepler and we extracted asteroseismic data of this target using Lets Analysis, Use and Report of Asteroseismology, a new seismic tool developed for the study of evolved FGK solar-like stars. We determined the evolutionary status and effective temperature, surface gravity, metallicity, microturbulence, and chemical abundances for Li, Ti, Fe, and Ni for HD 226808, by employing spectroscopy, asteroseismic scaling relations, and evolutionary structure models built in order to match observed data. Our results also show that an accurate synergy between good spectroscopic analysis and asteroseismology can provide a jump toward understanding evolved stars.

A diagnostic diagram for γ Doradus variables and slowly pulsating B-type stars

Pulsating variables of γ Doradus type (γ Dor) and slowly pulsating B-type (SPB) stars are found on and near the main sequence with typical periods varying between one and several days, making them rather hard to detect from the ground. It is only with space missions such as CoRoT and Kepler that we became truly capable of determining their oscillation frequencies with enough precision to perform in-depth analyses. Here we present an efficient and easy-to-implement seismic tool, in which the frequency (ν) and the square root of the frequency difference ($ \sqrt{\Delta \nu} $) are plotted against each other as the abscissa and the ordinate, respectively. This allows us to immediately (1) perform mode identification; (2) estimate the average rotation rate and the characteristic period of gravity modes; and (3) recognise certain physical effects, including buoyancy glitches and avoided crossings. This diagnostic tool can only be applied to prograde sectoral g modes. To validate the tool presented here, we used stellar models and also applied it to three γ Dor (KIC 12066947, KIC 5608334 and KIC 4846809) and one SPB star (KIC 3459297), all observed with Kepler. Furthermore, we show that the rotation rates determined using this new tool are consistent with the results of previous studies.

State-of-the-art Seismic Tools for Subsurface Imaging

State-of-the-art Seismic Tools for Subsurface Imaging

Сейсмостойкие конструкции крупнопанельных зданий

В статье рассматривается опыт применения крупнопа­нельных зданий в сейсмических районах. Приводится анализ причин, по которым такой тип зданий является одним из наи­более перспективных конструктивных систем в этих районах строительства. Отмечается, что среди крупнопанельных зда­ний наиболее предпочтительным вариантом конструктивного решения являются здания с узким шагом поперечных несущих стен, который позволяет создать жёсткую пространственную систему здания. Освящаются вопросы повышения сейсмо­стойкости крупнопанельных зданий. Эффективность работы крупнопанельных зданий при сейсмических воздействиях различного частотного состава можно существенно повысить путём устройства в фундаментной части специальных средств сейсмозащиты в виде сейсмоизоляции и сейсмогашения. При­ведены примеры реализации различных систем сейсмозащи­ты в конструкциях крупнопанельных зданий различных серий. Особое внимание уделено конструктивным решениям 122-ой серии, которая получила название «Крупнопанельные здания с "сухими" стыками». Представлены результаты изучения и уточнения моделей крупнопанельных зданий этой серии, а также методов их расчётов, что имеет большое практическое значение. Дан анализ расчётно-теоретических исследований крупнопанельных зданий с «сухими» стыками, который под­твердил их высокую сейсмостойкость. Показано, что при­менение дополнительных элементов сухого трения в стыках панелей позволяет на 30% снизить сейсмические нагрузки на здания и, соответственно, усилия в сборных элементах крупнопанельного здания. При этом резерв несущей способ­ности «сухих» горизонтальных стыков обеспечивается за счёт упругопластических свойств применяемых в них прокладок.

Comprehensive Correlations Between the Geotechnical and Seismic Data Conducted via Bender Element

Bender element (BE) is a useful seismic tool to predict the geotechnical soil properties using empirical correlations. However, there were uncertainties in the correlation equations which were not discussed in detail. In this study, the seismic data was thoroughly investigated to improve the correlations with the physical soil properties. Several proportions of sand–kaolin mixtures were compacted, sheared, as well as BE tested. The results showed curve relationships whereas the highest seismic wave velocity and the highest shear strength were attained at the proportion of 40% fine content. At this point, the void ratio, intergranular void ratio, maximum dry density, and specific gravity were 0.43, 1.43, 1.79 g/cm3, and 2.585 respectively. In addition, a direct positive linear relationship between the seismic wave velocity with cohesion (c) and shear strength (τ) provided highest values of seismic velocities at 53.7 kPa and 81.7 kPa of c and τ respectively. However, the seismic wave velocity less significant effected by the friction angle. The paper presented 68 empirical correlation equations between the previous parameters. The comparison with previous researchers indicated that the application of the empirical correlation equations was limited to the material type (clay and sand), fine content range (20–70%), void ratio range (> 0.43), and condition of the samples.

Characterization of Microseismic Noise in Cape Verde

The authors thank projects CVPLUME (Ref. PTDC/CTE-GIN/64330/2006) and Cape Verde Mantle Structure (YW network) for providing the broadband seismic data they used in this research. This study was partially supported by projects Atmosphere-Ocean-Solid Earth Coupling: Seismic Tools to Explore and Monitor the Oceans (STORM) (Ref. UTAP-EXPL/EAC/0056/2017) and Transnational cooperation-Pessoa Program (PHC-PESSOA) (Ref. 4318/40851YL). This is a contribution to project Fogo Island volcano: multi disciplinary Research on 2014 Eruption (FIRE) (Ref. PTDC/GEO-GEO/1123/2014). Fundacao para a Ciencia e Tecnologia (FCT) Ph.D. Grant Ref. PD/BD/114480/2016 supported Joana Carvalho. Publication supported by FCT-project UID/GEO/50019/2019-Instituto Dom Luiz. The authors are grateful to the European COST action TIDES (ES1401) for all the discussions and for supporting Short-term scientific mission (STSM) of the authors.