Analysis Of Seismic Waves Research Articles

Seismology Helps Us Understand How Material Flows in Earth's Deepest Mantle

Recent progress in the analysis of seismic waves enables us to determine where, and sometimes how, the base of the mantle deforms.

Influence of the Seabed Site and Island Structure on Seismic Response of Marine Artificial Islands

Compared with the marine structures such as sea-crossing bridges and offshore wind turbines, the marine artificial islands are bottom sitting structures and particularly sensitive to site conditions. Therefore, the study focuses on determining the effect of seabed site conditions and construction methods on the seismic performance of marine artificial islands. A seismic wave analysis model of seabed-seawater layer–artificial island coupling is developed by combining the self-programmed fluctuation analysis program and the dynamic analysis software. Firstly, the seismic response of marine artificial islands with different site conditions are analyzed by inputting P and SV waves. On that basis, the effects of incidence angles on the seismic response are explored. Then the study further explores the effects of different backfill materials and protective structures on the seismic response of the artificial island. Numerical results show that the silty soft soil layer can amplify the seismic response of seabed sites, and this amplification effect increases with the increase of the depth of silty soft soil layers. Moreover, the coral sand as backfill material can reduce the seismic response of marine artificial islands. The seismic response of marine artificial islands can also be reduced in the model with a protection structure. These results will provide some theoretical references for the site selection and construction method of marine artificial islands.

Fiber bundle model applied to slope stability assessment: co-detection multi-threshold analysis for early warning

Forecasting the imminent failure of natural slopes is crucial for effective Disaster Risk Reduction. However, the nonlinear nature of geological material failure makes predictability challenging. Recent advancements in seismic wave monitoring and analysis offer promising solutions. In this study, we investigated the co-detection method, which involves real-time processing of micro-seismic events detected concurrently by multiple sensors, to provide easy access to their initial magnitude and approximate location. By studying the Fiber Bundle Model and considering the attenuation of seismic waves, we demonstrated disparities in the statistical behavior of various rupture types before global catastrophic failure. Comparing avalanches with attenuated seismic wave amplitudes directly measured at sensor locations, we observed differences in their evolution towards catastrophic rupture. Leveraging a network of seismic wave sensors, we showed that the co-detection method was effective in detecting precursory seismic events, even with weak signals, making it a valuable tool for monitoring and predicting unstable slopes. Additionally, we demonstrated that a multi-threshold analysis of co-detection activity allowed for instantaneous capture of the seismic activity structure on unstable slopes. These findings contribute to our understanding of slope stability and offer insights for improved hazard assessment and risk management.

A real-time approach to structural seismic response analysis

This paper presents a real-time seismic response analysis method based on the Proper Orthogonal Decomposition (POD) and Proper Generalized Decomposition (PGD) theories. Initially, the damping matrix and ground motion load are incorporated using the parametric form of the solid dynamic equation. By leveraging the POD method, the computational challenge arising from the high number of parameters in the equation (one parameter for each degree of freedom of the entire model) is overcome, enabling the calculation of complex computational models. Subsequently, the proposed method's effectiveness, stability, and accuracy are demonstrated through the analysis of various seismic waves characterized by different magnitudes, durations, and frequencies. Furthermore, the method successfully achieves real-time response feedback of the structure to arbitrary seismic waves. Importantly, this approach exhibits significant potential for engineering applications.

High-resolution static corrections derived from surface-wave tomography: Application to mineral exploration

In hard-rock mineral exploration using reflection seismic imaging, standard methods to estimate the static corrections based on the analysis of seismic body waves might be ineffective due to near-surface complexities. A workflow to estimate the P-wave statics based on high-resolution surface-wave (SW) tomography is adopted. We combine the S-wave velocity model retrieved by SW tomography, a method known for its high resolution, with the Poisson’s ratio estimated by the wavelength-depth method, a technique based on the analysis of skin depth of SWs. We apply the workflow to a 2D data set recorded at a phosphate mining site in Finland and to a 2D data set acquired at an iron-oxide mining site in Sweden. The retrieved models and statics are evaluated using prior information, and the stacked sections are compared with the ones resulting after standard body-wave statics. Improvements in the continuity of deep reflectors and increase in the extent and the amplitude of the horizons associated with the orebodies are evident in the stacked sections whose statics are computed with our workflow that we call SW tomostatics.

APPLICATION OF PHASE-ENERGY ANALYSIS OF SEISMIC WAVES FOR GEOLOGICAL SECTION PREDICTION

Link for citation: Kochegurov A.I., Kochegurova E.A., Orlov O.V. Application of phase-energy analysis of seismic waves for geological section prediction. Bulletin of the Tomsk Polytechnic University. Geo Аssets Engineering, 2023, vol. 334, no. 5, рр.54-62.In Rus. Relevance. One of the main tasks in predicting a geological section is the task of determining the type of the section and mapping types over the area under study, as well as assessing the absorbing and dispersive properties of geological media. To solve these problems, specialized software-algorithmic complexes for processing and interpreting seismic data are currently widely used. In most modern complexes for forecasting a geological section, the information extracted from the kinematic and dynamic characteristics of seismic waves is used. Based on the information received and the data on the geophysical survey of wells, ideas are formed about the material composition of sediments, the presence of productive strata in the study area. This approach made it possible in a number of regions of Russia, including Western Siberia, to obtain interesting and important results related to the discovery of productive sedimentary strata and the assessment of their oil and gas content, which was confirmed by practice. At the same time, the results of practical activities have shown that when conducting studies of many areas, there are areas where the percentage of identifying false anomalies in geological environments and making erroneous decisions in the forecast is still quite large. This is due, among other things, to the fact that in the analysis of the recorded seismic field, for predicting geological section, the energy characteristics of the reflected waves are mainly used, and changes in the phase spectra are practically not taken into account. Thus, the integrated use of the characteristics of reflected seismic waves (amplitude and phase) in the prediction of a geological section is a very urgent task. The aim of the work is to carry out phase-energy analysis for various models of seismic fields based on the method of phase-frequency deconvolution for predicting the geological section. Methods: computational experiment, inverse filtering, discrete Fourier transform. Results. The authors developed the algorithm for phase-energy analysis of seismic waves, which is based on the results of phase-frequency deconvolution. The algorithm was studied on various models of geological environments, and phase-energy sections were constructed, which make it possible to identify zones with anomalously low energy values for subsequent oil and gas potential diagnostics. The paper introduces the example of constructing a phase-energy section based on real data in the interval of Upper Jurassic deposits.

A Struggled Rupture Initiation of the Mw 6.1 2009 L’Aquila Earthquake

AbstractUnderstanding under which physical conditions large earthquakes begin, is a key question in Earth science. Laboratory experiments and numerical models have shown that earthquake nucleation has distinct phases: a quasi‐static and an acceleration stage, followed by dynamic propagation. However, obtaining observations of such or similar processes in nature is complex. Here, we report on the rupture initiation of the Mw 6.1 2009 L'Aquila earthquake. From the detailed analysis of seismic waves recorded at several stations, we identify an ∼0.6‐s signal preceding the large dynamic rupture. From the geometrical characterization and rupture parameters of this initial phase, we infer that the rupture struggled to initiate exhibiting a slow rupture velocity ( km/s) and low seismic efficiency () due to a complex environment in the region where the rupture starts. We also show that the parameters of the rupture initiation are representative of scale‐dependent quantities for slip‐dependent nucleation models.

Identification of two vibration regimes of underwater fibre optic cables by distributed acoustic sensing

SUMMARYDistributed acoustic sensing (DAS) enables data acquisition for underwater Earth Science with unprecedented spatial resolution. Submarine fibre optic cables traverse sea bottom features that can lead to suspended or decoupled cable portions, and are exposed to the ocean dynamics and to high rates of marine erosion or sediment deposition, which may induce temporal variations of the cable’s mechanical coupling to the ocean floor. Although these spatio-temporal fluctuations of the mechanical coupling affect the quality of the data recorded by DAS, and determine whether a cable section is useful or not for geophysical purposes, the detection of unsuitable cable portions has not been investigated in detail. Here, we report on DAS observations of two distinct vibration regimes of seafloor fibre optic cables: a high-frequency (>2 Hz) regime we associate to cable segments pinned between seafloor features, and a low-frequency (<1 Hz) regime we associate to suspended cable sections. While the low-frequency oscillations are driven by deep ocean currents, the high-frequency oscillations are triggered by the passage of earthquake seismic waves. Using Proper Orthogonal Decomposition, we demonstrate that high-frequency oscillations excite normal modes comparable to those of a finite 1-D wave propagation structure. We further identify trapped waves propagating along cable portions featuring high-frequency oscillations. Their wave speed is consistent with that of longitudinal waves propagating across the steel armouring of the cable. The DAS data on cable sections featuring such cable waves are dominated by highly monochromatic noise. Our results suggest that the spatio-temporal evolution of the mechanical coupling between fibre optic cables exposed to the ocean dynamics and the seafloor can be monitored through the combined analysis of the two vibration regimes presented here, which provides a DAS-based method to identify underwater cable sections unsuitable for the analysis of seismic waves.

Assessment of the Impact on Steel Walls and Bracing Systems in the Analysis of Seismic Waves during a Building Moment Resistance Frame

The designs in seismic regions are for the most part vulnerable to serious harm. Alongside the gravity, loads structures need to endure the horizontal loads too which tends to foster high burdens. By and large shear walls and bracings are introduced in the design to improve their horizontal firmness and flexibility and limit their parallel relocations to give well-being to the designs. The basic issues in the seismic plans are principally story floats and sidelong relocations. Four distinct kinds of edge building models are created and assessed with the assistance of ETABS. In the present work, G+21 multi-story, second opposing edge building models are viewed as utilizing steel shear walls and two sorts of bracings. The arrangement considered for all models is 20mX20m and the strategy used for examination is the reaction range investigation technique. All individuals were planned according to IS456:2000, IS800:2007, and the load mix for seismic power was considered according to IS1893 (part-1):2016. Correlation between each of the four models was performed based on the following boundaries for example Uprooting, Stiffness, and Natural period. The outcome is communicated as charts, and figures and correlations are finished according to IS1893 (part-1):2016. The primary focal point of this study is to see the enhanced model.

S-transform application in phase extraction of spectrally resolved interferometry measuring step height.

Spectrally resolved interferometry is widely used in the measurement of distance, displacement, film thickness, and surface morphology in micro/nano-scale geometric measurement. The core of spectrally resolved white-light interferometry is phase extraction. Temporal phase shifting, Fourier transform, wavelet transform, and other methods are commonly used in phase extraction of spectrally resolved interferometry. The S-transform, providing frequency-dependent resolution and having good time-frequency characteristics, is widely used in power quality disturbance analysis, seismic wave analysis, and phase recovery in profilometry. S-transform is used to extract the phase of the spectrally resolved white-light interferometry signal measuring step height. Compared with Fourier transform and wavelet transform, it is proved that S-transform is a feasible method in phase extraction of spectrally resolved interferometry measuring step height.

Learnable Maximum Amplitude Structure for Earthquake Event Classification

Recently, most research has been conducted to minimize damage from earthquakes by establishing an early warning system through the analysis of short seismic waves. In particular, deep learning is widely used as it allows to learn complex patterns for earthquake detection from seismic data without complex physical knowledge. In this letter, we propose an improved ConvNetQuake for earthquake event classification by adding learnable features related to the maximum amplitude of the seismic waveform. Since the maximum amplitude is a major factor representing the characteristics of an earthquake, we presented a deep learning structure that can apply this factor in the process of determining whether an earthquake occurs. In the proposed structure, the maximum amplitude is transformed into a feature learned through multi-layer perceptron (MLP) and then concatenates with features extracted through a convolutional neural network (CNN). On the STanford EArthquake Dataset (STEAD) dataset, the proposed method significantly increases the performance for an earthquake event classification than the previous state-of-the-art (SOTA) method by only adding a few parameters.

Employing Remote Sensing, Data Communication Networks, AI, and Optimization Methodologies in Seismology

Seismology is among the intrinsic sciences that strictly affect human lives. Many research efforts are presented in the literature aiming at achieving risk mitigation and disaster management. More particularly, modern technologies have been employed in such a pivot. However, the day-to-day challenges and complexities of such natural science that face the stack holders still need more reliable and intelligent solutions. The solution can depend on a partial or integrated system of modern technologies. In this paper, we extensively survey the co-related modern technologies aiming to gather the major efforts exerted in this regard. It also outlines the desirability of seismology to modern technologies. Then, we present a detailed analysis of remote sensing and data communication networks (DCNs), which are considered the backend of seismic networks. Furthermore, for seismology, we depict both classical and non-classical approaches based on DCN principles, such as optical fiber-based acoustic sensors, social media, and the internet of things (IoT). Following that, a comprehensive description of the various optimization techniques utilized for seismic wave analysis and for prolonging network lifetime is offered. A description of the important functions that artificial intelligence (AI) can play in different fields of seismology is also included. Finally, we present some recommendations for stack holders to prevent natural calamities and preserve human lives.

Evaluation of the Detection Ability of New Infrasound Networks Installed by Korea Meteorological Administration

The Korea Meteorological Administration (KMA) installed infrasound networks in Cheorwon and Yanggu. These networks have been operated for detecting infrasound generated from artificial explosions, such as those due to North Korea's nuclear tests, and from natural phenomena such as the volcanic eruption of Mt. Baekdu. Currently, the KMA is simultaneously performing infrasound analysis and seismic wave analysis to discriminate between natural and artificial earthquakes. To efficiently perform the discrimination and analysis of artificial earthquakes, three infrasound networks were expanded in the West Sea and northern Gyeonggi-do Gyodong-do, Paju, and Yeoncheon. In this study, 22 cases of artificial earthquake events that occurred in North Korea in January 2020 were analyzed to test the analysis capabilities of the three newly installed infrasound networks. The results of the analysis confirmed that the newly installed infrasound networks exhibited a higher infrasound detection rate than the existing Cheorwon and Yanggu infrasound networks. The Cheorwon and Yanggu observation networks are being planned for relocation and installation due to aging and poor site conditions. The use of the new infrasound network is expected to improve the detection rate and analysis accuracy with respect to artificial earthquakes. Furthermore, it is expected to enhance the detection capability of infrasound generated from various physical phenomena such as nuclear tests performed by North Korea and volcanic eruption of Mt. Baekdu.

Ambient Noise Tomography with Short-Period Stations: Case Study in the Borborema Province

The analysis of seismic ambient noise has been recently proven a viable alternative to the analysis of seismic waves generated by earthquakes. Although seismic ambient noise had traditionally been discarded from earthquake records, it has now been shown that the cross-correlation of the seismic ambient noise allows for the recovery of the Green’s function between the receivers. Furthermore, seismic noise has the ability to propagate continuously and independently of the occurrence of earthquakes, allowing for high-resolution tomographic studies in regions of low seismicity. Over the last two decades, the cross-correlation of continuous seismic noise recordings between pairs of stations has been widely utilized in surface-wave tomography studies. For the Northeast Brazil region, tomographic studies have been exclusively performed with seismic data from broadband stations; however, in addition to those stations, there exists a large volume of short-period data that might potentially improve the resolution of existing ambient noise tomographies. Thus, the goal of this work is to utilize, in addition to broadband data, short-period data recorded by 22 short-period stations in the Borborema Province. Through cross-correlation and stacking of ambient seismic noise, the emergence of the fundamental mode of the Rayleigh waves and their dispersive character was observed. Once the empirical Green's functions were retrieved, the accuracy of (phase and group) dispersion curves for periods up to 10 s and its tomographic inversion were assessed. Our results demonstrate that short-period dispersion measurements can be successfully integrated in regional tomographic studies for improved resolution.

Analysis of Fractal Features of Blasting Vibration Signal Based on EEMD Decomposition

In order to study the propagation characteristics of blasting seismic waves by using the analysis and research of blasting vibration monitoring data of Urumqi subway tunnel excavation, the blasting vibration signal has been decomposed into several IMF components by EEMD decomposition and fractal theory has been used to calculate the correlation dimension in this paper. The results show that the IMF component can reveal the frequency characteristics in the blasting vibration signal clearly. As the measuring point is far away from the explosion source, the complexity of the frequency component of the vibration signal gradually decreases. The seismic wave interacts with the rock and soil medium in the propagation process, make it shown non-linear characteristics, which are not easily to be observed by conventional measure methods. This paper introduces fractal dimension to study the nonlinear characteristics of blasting vibration signals and achieves the purpose of analysing the law of blasting seismic wave propagation. This study achieves a quantitative description of the effects of site media on seismic waves, and at the same time, it lays a theoretical foundation for predicting the vibration effect analysis of seismic waves reaching the target position.

Oceanic crustal flow in Iceland observed using seismic anisotropy

Understanding accretion and deformation processes at mid-ocean ridges is crucial as they control the resulting oceanic crustal structure, which covers two-thirds of Earth’s surface. The most common tool for observing such dynamic processes within the Earth is seismic anisotropy. Iceland, which is uplifted by a convective mantle plume and has an active spreading ridge system exposed above sea level, offers a unique opportunity for studying this phenomenon. Here we use a high-resolution dataset of Love and Rayleigh wave speeds to constrain the seismic anisotropy in the Icelandic crust. We show that seismic anisotropy in the lower crust is controlled by crystal preferred orientation, providing a direct observation of lower crustal flow. Furthermore, since shear is needed to align the crystals, our results reveal that crustal flow cannot be a simple translation of mass and requires internal deformation. This finding suggests that crustal flow plays an important role in oceanic crustal accretion and deformation where thick, hot oceanic crust is formed, such as at volcanic rifted margins and where there are mantle plume–ridge interactions. The lower oceanic crust beneath Iceland is flowing and internally deforming, according to constraints on seismic anisotropy in the Icelandic crust from an analysis of seismic surface waves.

Static Source Properties of Slow and Fast Earthquakes

AbstractThe source characteristics of slow and fast earthquakes provide a window into the mechanical properties of faults. In particular, the average stress drop controls the evolution of friction, fault slip, and event magnitude. However, this important source property is typically inferred from the analysis of seismic waves and is subject to many epistemic uncertainties. Here, we investigate the source properties of 53 earthquakes and 17 slow‐slip events on thrust and strike‐slip faults in various tectonic settings using slip distributions constrained by geodesy in combination with other data. We determine the width, potency, and potency density of slow and fast earthquake sources based on static slip distributions. The potency density, defined conceptually as the ratio of average slip to rupture radius, is a measure of anelastic deformation with limited bias from rigidity differences across depths and tectonic settings. Strike‐slip earthquakes have the highest potency density, varying from 20 to 500 microstrain. The potency density is on average lower on continental thrust faults and megathrusts, from 10 to 200 microstrain, with an algebraic decrease with centroid depth, indicative of systematic changes in dominant rupture processes with depth. Slow slip events represent an end‐member style of rupture with low potency density and large rupture width. Significant variability in potency density of slow‐slip events affects their moment‐duration scaling. The variations of source properties across tectonic settings, depth, and rupture styles can be used to better constrain numerical simulations of seismicity and to assess the source characteristics of future earthquakes and slow slip events.

LITHOLOGY AND PALEODEPOSITIONAL ENVIRONMENT ANALYSIS OF PERMIAN SEDIMENTS IN CONNECTION WITH OIL AND GAS POTENTIAL IN THE SOUTH-KHRESTYSHCHE AREA IN THE DNIEPER-DONETS BASIN

The aim of this work to study the integration of modern geological and geophysical methods for identifying stratigraphic traps. Permian deposits of the Dnieper-Donets depression were selected for the analysis. These deposits are characterized by inconsistency of productive horizons and the sandstone bodies formation. Direct indicators of the hydrocarbons, various characteristics of the seismic wave field, lithological classification and analysis of the reservoir properties of rocks were used. The available literature data on the oil and gas development and production from the Permian deposits and geophysical data were used for a comprehensive analysis. Geophysical data was presented by well logging data and seismic data. consolidated geological section across the Dnieper-Donets depression was constructed by geophysical data. The geological section gave information about the modern occurrence of the Permian sediments. Seismic surveys was used for attribute analysis. Attribute analysis give us zones with possible hydrocarbon contents and improved reservoir properties. This method shows the role of seismic studies in determining the lithology and oil and gas content of the studied strata. The combination of lithology, seismic data and information about paleodepositional environment allowed us to identificate unconventional hydrocarbon traps.

Earthquake source properties from analysis of dynamic ruptures and far-field seismic waves in a damage-breakage model

SUMMARYWe present results on earthquake source properties using simulations of dynamic rupture and radiated seismic waves in a continuum damage-breakage rheological model. The source properties are derived by (1) calculation of source parameters directly from the simulated ruptures and (2) observational processing of the far-field radiated waves. The seismic potency, moment, damage-related source term, rupture velocity and effective rigidity are estimated directly from the simulated sources, while the radiation pattern, dominant frequency, directivity, rupture velocity and seismic potency are calculated through analysis of the radiated waves. The potencies calculated directly from the sources are used to validate those estimated by wave analysis. The effective rigidity at the rupture zone during failure is about four times smaller than that of the intact surrounding rocks. Rupture velocity can be estimated by far-field measurements for sources with unidirectional ruptures with prominent rupture directivity. The dominant frequencies for P and S waves $f_d^S/f_d^P$ reflect clearly the rupture duration and have a ratio in the range 0.87–1.12. Seismic potencies obtained through processing the P or S waves have an overall ±15 per cent difference from the source reference values. The calculated values of the coefficient ${\rm{\kappa }}$, relating rupture length to corner or dominant frequency, have strong dependency on the source geometry. Using a strain-rate dependent ${\rm{\kappa }}$, we obtain much weaker dependencies of strain-drop on the dominant frequencies, $\Delta {\rm{\varepsilon }} \propto {( {{f_d}} )^{3/4}}$, than the classical cube-dependency between stress drop and corner frequency, and corresponding weak dependency of average slip on dominant frequency, ${\rm{\bar{D}}} \propto {( {{f_d}} )^{1/2}}$. The obtained analysis procedure and relations can be used to reduce the uncertainty of source properties derived from far-field seismic waves.

Seismic Coda-Waves Imaging Based on Sensitivity Kernels Calculated Using an Heuristic Approach

In this paper we review and discuss the seismic method based on the analysis of seismic coda waves used in the last 10 years by the present authors and/or their co-workers, to produce separate images of intrinsic- and scattering attenuation in zones of peculiar geological interest (mainly volcanoes). Such separate attenuation images are considered by the scientific community as complementary to those from ordinary velocity-tomography and useful to improve the geological interpretation in volcanoes and in tectonically active zones. In this review we only list but do not discuss the most significative papers showing the images obtained, as we are focused to review the method and not the interpretation of data analysis. For sake of completeness, we anyway show also a new analysis applied to data from Stromboli volcano. We thus first introduce the physical model describing the seismogram Energy Envelope (derived from the solution of the Energy Transport integral Equation) and discuss its asymptotic approximations (Diffusion- and Single-scattering model). Then, we describe a numerical method to heuristically calculate the Sensitivity Kernels for the propagation of the scattered waves in the assumption of isotropic scattering. We attribute to these Sensitivity Kernels the physical meaning of probability that for a single source-receiver couple the measured attenuation parameters can be associated with the space coordinates. Based on this definition, the attenuation image can be obtained mapping the estimated attenuation parameters onto the zone under study weighting with the Sensitivity Kernels. We further discuss how to estimate the uncertainties associated with the results and report the list of the papers describing the (separated) scattering- and intrinsic-attenuation structures investigated using this approach.