Earth's Interior Research Articles

Rupture phases reveal geometry-related rupture propagation in a natural earthquake.

Understanding and deciphering wiggles from seismograms has been a long endeavor to understand the internal structure of the Earth and to explore earthquake source properties. Here, we make an attempt to decipher the continuous rupture phases as large near-fault velocity pulses along the East Anatolian Fault in the 2023 moment magnitude (Mw) 7.8 Kahramanmaraş, Türkiye, earthquake. Through data analysis and dynamic rupture simulations, we robustly identify the transient supershear rupture on a segment with flat fault trace and rupture deceleration at fault bends. Our study highlights the complexity and superior application of near-fault data for understanding earthquake dynamics.

Detection of Earth’s free oscillation and analysis of the non-synchronous oscillation phenomenon of normal modes

Earth’s free oscillation can provide essential constraints for refining Earth models, inverting seismic source mechanisms, and studying the deep internal structure of the Earth. Large earthquakes can simultaneously excite numerous normal modes. Due to the Earth’s ellipticity, rotation, and internal heterogeneities, these normal modes undergo splitting, with the frequencies of singlets of normal modes becoming very close (only a few µHz apart). This imposes greater demands on the detection of normal modes. This paper introduces a novel method for normal mode detection based on the normal time–frequency transform (NTFT). Compared to classical FT spectrum methods and recent optimal sequence estimation (OSE), the proposed method not only detects more weak normal modes but also reveals the spatial distribution of the phase of each normal mode. Taking the detection of 0S2 as an example, the phase measurements of each singlet are spatially inconsistent. This phenomenon can provide prior information for other methods, such as product spectrum analysis (PSA), spherical harmonic stacking (SHS), multistation experiments (MSE), and OSE. Additionally, understanding the phase distribution patterns contributes to further study of geological structures, offering crucial foundational data and observational support.

Analysis of Science Literacy Profile and Development of E-Book Interactive Learning Media for Junior High School Students on Earth Structure Material

This study aims to evaluate students' science literacy profile and implement earth structure and disaster mitigation materials to improve junior high school students' science literacy. This research uses a type of introductory research that applies analysis techniques in the form of descriptive research design (DPD). The research instruments used include science literacy tests, student learning experience questionnaires, and teacher performance observations in delivering the material. This indicates that the science literacy skills of junior high school students can be further improved by using appropriate learning. Based on the results of the research obtained, the science literacy indicator ‘Designing Scientific Investigations’ received the highest score with an average of 3.275, while ‘Critically Evaluating Scientific Information’ received the lowest score of 3.206. Based on the results of the research data that has been obtained, it is concluded that students' science literacy skills still need to be improved. However, female students tend to have better science literacy skills than male students, which indicates a challenge in achieving science literacy skills at an adequate level. The indicator with the lowest level of science literacy was critically evaluate scientific information. Therefore, the study recommends the development of contextualized inquiry-based learning media and technology integration to support more effective learning, as well as training for teachers to facilitate learning that trains students' critical thinking skills.

Recent ice melt above a mantle plume track is accelerating the uplift of Southeast Greenland

Around the periphery of the Greenland ice sheet, satellite-based observations of ground uplift record Earth’s response to past and recent unloading of Greenland’s ice mass. On the southeast coast, near the Kangerlussuaq glacier, rapid uplift exceeding 12 mm/yr cannot be explained using current layered Earth deformation models. Here we find that 3D models with a weakened Earth structure, consistent with the passage of Greenland over the Iceland plume, can explain the rapid uplift of Southeast Greenland. This uplift is dominated by a viscous response that is accelerated by the low viscosities of the hot plume track. Recent mass loss, occurring during the last millennium and especially within the past few decades, drives most of the uplift. Holocene indicators recorded similarly rapid uplift following deglaciation that ended the last ice age. Such rapid uplift, occurring beneath marine terminating glaciers, can affect the future stability of entire ice catchment areas and will become increasingly important in the near future as deglaciation accelerates.

Optical remote spectral acquisition of elemental stoichiometry

Optical remote sensing (RS) enables the study of the elemental composition of Earth’s surface over broad spatial extents by detecting reflected electromagnetic radiation. Covalent bonds of macromolecular structures often reflect electromagnetic radiation at specific wavelengths, and in some cases relate to bonds of specific elemental identity. In other cases, interfering optical properties greatly impact the ability of RS to measure elements directly, but advances in statistical methods and the theoretical understanding of optical properties expand the capacity to quantify diverse elements in many systems. When applied under the framework of ecological stoichiometry, spatially and temporally explicit measurements of elemental composition permit understanding of the drivers of ecological processes and variation over space and through time. However, the multitude of available technologies and techniques present a large barrier of entry into RS. In this paper we summarize the capabilities and limitations of RS to quantify elements in terrestrial and aquatic systems. We provide a practical guide for researchers interested in using RS to quantify elemental ratios and discuss RS as an emerging tool in ecological stoichiometry. Finally, we pose a set of emerging questions which integrating RS and ecological stoichiometry is uniquely poised to address.

Gravitational waves derived from the elastic energy

The Adams‐Williamson equations adeptly characterize the pressure distribution within Earth's interior, highlighting the role of pressure in storing elastic energy. This stored energy forms the basis for deriving the Newtonian gravitational field. The variability of the dielectric constant and electric charge (alongside magnetic permeability and magnetic charge) in response to gravitational field strength renders Maxwell's equations applicable within the context of a strong gravitational field. Intriguingly, the wave equation satisfied by the gravitational field can be derived from Maxwell's equations.

Transformations of the bottom pressure variations, generated by marine infragravity waves into displacements of the upper layer of the earth’s crust. Quantitative assessment

A quantitative assessment of the transformation of the bottom pressure variations, generated by infragravity waves into displacements of the upper layer of the Earth's crust has been made on the basis of experimental data, obtained with a laser meter of hydrosphere pressure variations and two laser strainmeters. The dependence of the coefficient of transformation of bottom pressure into elastic vibrations of the Earth's crust on the periods of infragravity waves was determined.

Crustal properties beneath the northeastern United States shaped by past tectonic processes

Constraints on the thickness, transitional boundaries, and composition of Earth's crust are pivotal in studying its formation and evolution. We use data from 132 seismic installations throughout northeastern U.S. to explore how tectonic events, such as orogenesis and rifting, have altered the crust of the northeastern U.S. and southeastern Canada, and to distinguish differences between Laurentia and the Appalachian terranes. We include data from seismic installations from the NEST and SEISConn experiments, spanning the Laurentia-Appalachian boundary, and present estimates of crustal thickness, Vp/Vs, and thickness of the transition between crustal and mantle rocks using Ps receiver functions. We find some first-order differences between Laurentia and Appalachian terranes, with Laurentia exhibiting thicker crust (∼39 km vs. ∼33 km) and a broader crust-mantle transition thickness (∼3 km vs. <1.5 km). Average Vp/Vs values are similar between Laurentia (∼1.77) and Appalachian terranes (∼1.74); however, we identify anomalous Vp/Vs in a few regions, including high Vp/Vs around the Adirondack Mountains and low Vp/Vs in southern New England. The southern New England region is also anomalous in terms of its systematically thinner crust and sharper crust-mantle transition, which may be a consequence of the formation and collapse of the Acadian altiplano during the mid-to-late Paleozoic.

Structures of the Earth: Metageographies of Early Medieval China, by D. Jonathan Felt

Structures of the Earth: Metageographies of Early Medieval China, by D. Jonathan Felt

Dispersive and attenuation behavior of Love wave in a non-local highly heterogeneous media with imperfect contact condition

Abstract The primary aim of this study is to explore the impact of different physical parameters on the propagation of Love waves in non-local media. This study considers heterogeneous orthotropic viscoelastic properties within a layer and the variation of sandy medium properties with exponential depth, representing the half-space. Furthermore, the interface between the layer and the half-space is considered mechanically imperfect and perfect. The solutions of mechanical displacement of the layer and half-space are derived separately by solving the second-order hyperbolic type differential equation with the help of a variable-separable technique. A closed form of the dispersion relation is obtained using appropriate boundary conditions involving the medium's non-local elasticity and inhomogeneity parameters. Verification of the dispersion relation is shown by deriving some particular cases and comparing them with the classical dispersion relation of Love wave. The effects of physical parameters (like viscoelasticity, inhomogeneity, interfacial imperfection, sandy, non-locality, and \textcolor{blue}{thickness of the layer}) on the phase and attenuation phenomena of Love wave are investigated through numerical calculations and graphical representation. Furthermore, it is observed that the particle displacement in the layer decreases with depth, while in the half-space, the amplitude decreases oscillatory with depth, and the displacement gradually converges towards zero. A comparative graphical analysis of these parameters on the phase and attenuation characteristics of Love wave through the stratified Earth's structure with imperfect and perfect interfaces has been accomplished.

The integrate geomorphological, morphotectonics investigations using remote sensing data from space as the basis for the efficiency increasing of geological works

The underestimation of the integrated application of geomorphological, morphotectonic information and materials of space remote data during a geological research, the geological survey and predictive-prospecting work significantly reduces their effectiveness. The imperfection of the geomorphological researches methodology focused on the study of territories relief as a collection of surfaces of geological bodies is one of the possible reasons for this. Perspectives opens the transition to the research of landforms and geological structures, bodies in their unity, as three-dimensional, volumetric objects. Fundamentally new opportunities for studying the geology of the seas and oceans bottom are associated, in particular, with the visualization of digital 3D relief models created on the basis of the global bathymetric database GEBCO 2014 (http ://Ocean3dproects...), regional echo-depth-sounder metering’s maps, altimetry materials and remote sensing of the Earth from space. The topicality of such investigations is also due to the fact determined that plate tectonics cannot explain many features of the structure of the Earth and individual regions relief. A number of examples show that modern geomorphology combined with methods of remote sensing from space and computerization should be considered as one of the necessary disciplines for geological mapping and work aimed at solving various geological problems. The further common development of the planet relief sciences (geomorphology + morphotectonics) determines the need to train geomorphologists at both geographical and geological faculties of universities.

Parameters of graphite shock compression at the initial stages of Popigai astrobleme formation

A numerical modeling of the process of a high-speed impact of a massive asteroid with the Earth’s surface was carried out to study the hypothesis of the meteoritic origin of the impact diamond deposit located in the Popigai River basin. A normal collision of a chondritic asteroid with a layered structure of the Earth’s soil at a speed of 25 km/s is simulated in 2D axisymmetric formulation. The natural carbon deposit layer is located in the near-surface zone of the loaded area. The calculations were carried out using a multidimensional parallel implementation of the finite-size particle-in-cell method. Models of the equations of state of chondrite, quartz and carbon are used to describe the properties of the meteorite and soil material. Thermodynamic parameters of impact compression of soil materials at the initial stages of loading and crater formation processes are obtained.

Accuracy and Precision of Earthquake Location Programs: Insights from a Synthetic Controlled Experiment

Abstract Earthquake location programs employ diverse approaches to address the challenges posed by incomplete knowledge and simplified representation of complex Earth structures. Assessing their reliability in location and uncertainty characterization remains challenging as benchmark datasets with known event locations are rare, and usually confined to particular sources, such as quarry blasts. This study evaluates eight earthquake location methods (GrowClust, HypoDD, Hypoinverse, HypoSVI, NonLinLoc, NonLinLoc_SSST, VELEST, and XCORLOC) through a controlled synthetic computational experiment on 1000 clustered earthquakes based on the setting of the 2019 Ridgecrest, California, earthquake sequence. We construct a travel-time dataset using the fast-marching method and a 3D velocity model extracted from the Community Velocity Model, supplemented with a von Karman perturbation to represent small-scale heterogeneity, and including elevation effects. Picking errors, phase availability, and outliers are introduced to mimic difficulties encountered in seismic network monitoring. We compare the location results from eight programs applied to the same travel-time dataset and 1D velocity structure against the ground-truth locations. For this aftershock sequence, our results reveal the superior accuracy and precision of differential time-based location methods compared to single-event location methods. The results validate the significance of compensating for deviations from assumed 1D velocity structure either by path or site correction modeling or by cancellation of unmodeled structure using differential arrival times. We also evaluate the uncertainty quantification of each program and find that most of the programs underestimate the errors.

The mysterious, massive structures in Earth’s deep mantle

Seismic waves traversing the interior of the planet reveal continent-sized regions with distinct physical properties. Researchers are investigating what they are, how they got there, and what their role is in Earth’s dynamic convecting interior.

The Effect of Southern Ocean Topography on the Global MOC and Abyssal Water Mass Distribution

Abstract We investigate the role of Southern Ocean topography and wind stress in the deep and abyssal ocean overturning and water mass composition using a suite of idealized global ocean circulation models. Specifically, we address how the presence of a meridional ridge in the vicinity of Drake Passage and the formation of an associated Southern Ocean gyre influence the water mass composition of the abyssal cell. Our experiments are carried out using a numerical representation of the global ocean circulation in an idealized two-basin geometry under varying wind stress and Drake Passage ridge height. In the presence of a low Drake Passage ridge, the overall strength of the meridional overturning circulation is primarily influenced by wind stress, with a topographically induced weakening of the middepth cell and concurrent strengthening of the abyssal cell occurring only after ridge height passes 2500 m. Passive tracer experiments show that a strengthening middepth cell leads to increased abyssal ventilation by North Atlantic water masses, as more North Atlantic Deep Water (NADW) enters the Southern Ocean and then spreads into the Indo-Pacific. We repeat our tracer experiments without restoring in the high-latitude Southern Ocean in order to identify the origin of water masses that circulate through the Southern Ocean before sinking into the abyss as Antarctic Bottom Water. Our results from these “exchange” tracer experiments show that an increasing ridge height in Drake Passage and the concurrent gyre spinup lead to substantially decreased NADW-origin waters in the abyssal ocean, as more surface waters from north of the Antarctic Circumpolar Current (ACC) are transferred into the Antarctic Bottom Water formation region. Significance Statement The objective of this study is to investigate how topographic features in the Southern Ocean can affect the overall structure of Earth’s large-scale ocean circulation and the distribution of water masses in the abyssal ocean. We focus on the Southern Ocean because the region is of central importance for exchange between the Atlantic and Indo-Pacific Ocean basins and for CO2 and heat uptake into the abyssal ocean. Our results indicate that Southern Ocean topography plays a major role in the overall circulation by 1) controlling the direct transfer of abyssal waters from the Atlantic to the Indo-Pacific via its influence on the Atlantic meridional overturning circulation and 2) controlling the coupling between the abyssal ocean and surface waters north of the Antarctic Circumpolar Current via the Southern Ocean gyre.

Teleseismic Full‐Waveform Tomography Based on a 3D FK‐LTSOS Hybrid Method for Local Imaging

AbstractTeleseismic waveforms contain abundant interpretable information about Earth's properties. They can be used to explore the refined structure of Earth's interior, especially in the regions with imbalanced spatial distribution of seismic activity. However, it's technically infeasible to numerically simulate high‐frequency (>1 Hz) teleseismic wave propagation within a whole domain iteratively in full‐waveform inversion due to its vast computational costs. We develop a 3D FK‐LTSOS (Frequency‐Wavenumber, Layered Time‐Space Optimized Symplectic) hybrid method and then apply it to teleseismic full‐waveform tomography to tackle this computational challenge. The 3D FK‐LTSOS hybrid method combines the semi‐analytical solution computed by the FK method rapidly in a 1D background model and the numerical solution calculated by the 3D LTSOS method accurately in 3D localized heterogeneous media with topography to simulate teleseismic wave propagation efficiently and accurately. The comparison of synthetic seismograms shows its accuracy and stability when simulating wave propagation in the topographic model. Based on this hybrid method, the teleseismic full‐waveform tomographic method is developed to efficiently resolve the detailed structure of the local research domain utilizing high‐frequency teleseismic data. The essential contents of full‐waveform tomography are presented, including misfit function, Fréchet kernels, smoothing strategy, and nonlinear conjugate gradient method. Synthetic data application for spherical anomaly models with planer surface and Gaussian topography, and observed data application for the crust‐upper mantle structure beneath eastern Tibet confirm the validity of the teleseismic full‐waveform tomography and demonstrate that our tomographic method can image the localized structures speedily from full‐waveform information.

Utilizing the Gravity Method to Detect the Potential Effect of the Salt Dome in the Nahr Omar Oilfield, Southern Iraq

Geophysics is one of the branches of Earth sciences and deals with studying the Earth's interior by studying the variation of physical properties within rock layers. Applied geophysics depends on procedures that involve the measurements of potential fields, such as the gravitational method. One of the significant oil fields in southern Iraq is represented by the Nahr Omar structure. A power spectrum analysis (SPA) technique was used to collect gravity data within the chosen oil field area in order to confirm the salt dome in the subsurface layers. The analysis of SPA resulted from six surfaces representing the gravity variation values of the depths (m)14300, 3780, 3290, 2170, 810, and 93.5. Gravity surfaces have been converted to density surfaces to determine density and velocity models from these six depth slices. The inverted data were consistent with the Nafe and Drake standard curves of converting densities to average velocities. The current study illustrated the benefit/assist of the inversion technique of gravity data to average velocity, to a large extent, in detecting the salt dome effects on the subsurface strata for the Nahr Omar oilfield. In comparison, the decrease in the average velocity of the salt dome area is related to this effect. The acquired inversion results were supported by available seismic data within the Nahr Omar area and utilized the seismic attributes processing technique.

CONSTRUCTION OF EARTH CRUST SECTIONS DOWN TO THE MOHO BOUNDARY BASED ON LOW AMPLITUDE REFLECTED WAVES OF RIVER SEISMIC SURVEY USING CPD-2D METHOD (Vitim River, junction zone of the Angara-Lena monocline of the Siberian platform and the Bodaibo-Patom folded system)

In 2019, employees of the Research and Production Enterprise Luch jointly with specialists of the Seismological Branch of the Geophysical Survey of the Russian Academy of Sciences (GS RAS) carried out river seismic exploration works using the common depth point method (CDP-2D) along a 170 km long profile in the lower reaches of the Vitim River. The research was carried out according to the original methodology developed in the Siberian branches of the GS RAS, using the “Baikal” equipment recording seismic signals continuously (in contrast to traditional cable bottom or ground-based systems with time-limited recording). In this case, patented air guns “Malysh” were used in the water for the excitation of elastic waves, which have been recorded by ground registration method on the riverbank. To this day, the archives store primary materials from each receiving point (about 7000, with a distance of 25 m between them) in the form of a continuous hours-long digital recording of seismic signals and noise. These materials make it possible to generate seismograms of significant duration – up to 23 s, equal to the time interval between wave generations, in contrast to 6–10 second seismograms traditionally used to construct sections of the upper part of the Earth’s crust. In addition, the 24-bit Baikal recorder makes it possible to record signals with an amplitude two orders of magnitude lower than the amplitude of seismic noise. On the seismic sections constructed by the processor at arrival times of up to 13–14 sec, due to an increase in the stack fold of signals up to 1000–2000, we can select low-amplitude waves, reflected from boundaries in the middle and lower parts of the Earth’s crust to the Moho boundary. High fold is achieved by increasing the size of the stacking site (bin) by several times. By processing seismograms, generated from archival materials, for the first time, we have a complete vertical section of the Earth’s crust along a 170 km long profile, using low-amplitude signals. The profile passes through the junction zone of the Angara–Lena monocline and the Bodaibo-Patom folded system. The proposed approach can be used to obtain preliminary (and relatively cheap) information about the deep structure of the Earth’s crust along profiles performed using the CDP-2D river seismic exploration method.

Efficient Trans-Dimensional Bayesian Inversion of C-Response Data from Geomagnetic Observatory and Satellite Magnetic Data

To investigate deep Earth information, researchers often utilize geomagnetic observatories and satellite data to obtain the conversion function of geomagnetic sounding, C-response data, and employ traditional inversion techniques to reconstruct subsurface structures. However, the traditional gradient-based inversion produces geophysical models with artificial structure constraint enforced subjectively to guarantee a unique solution. This method typically requires the model parameterization knowledge a priori (e.g., based on personal preference) without uncertainty estimation. In this paper, we apply an efficient trans-dimensional (trans-D) Bayesian algorithm to invert C-response data from observatory and satellite geomagnetic data for the electrical conductivity structure of the Earth’s mantle, with the model parameterization treated as unknown and determined by the data. In trans-D Bayesian inversion, the posterior probability density (PPD) represents a complete inversion solution, based on which useful inversion inferences about the model can be made with the requirement of high-dimensional integration of PPD. This is realized by an efficient reversible-jump Markov-chain Monte Carlo (rjMcMC) sampling algorithm based on the birth/death scheme. Within the trans-D Bayesian algorithm, the model parameter is perturbated in the principal-component parameter space to minimize the effect of inter-parameter correlations and improve the sampling efficiency. A parallel tempering scheme is applied to guarantee the complete sampling of the multiple model space. Firstly, the trans-D Bayesian inversion is applied to invert C-response data from two synthetic models to examine the resolution of the model structure constrained by the data. Then, C-response data from geomagnetic satellites and observatories are inverted to recover the global averaged mantle conductivity structure and the local mantle structure with quantitative uncertainty estimation, which is consistent with the data.

Assemblr Edu Learning Media Based on Augmented Reality to Improve Learning Outcomes of Grade V Elementary School Students

Based on the results of observations made by researchers in class V elementary school which proves that there are problems in the learning process, the lack of types and kinds of learning media used, one of which is on the learning content of Natural and Social Sciences (IPAS) on the content of the structure of the earth's layers. The reason researchers conducted this study was to develop learning media with creative and innovative to foster higher student interest in learning. This research not only aims to develop learning media but also to determine the feasibility of the media and the effectiveness of Augmented Reality-based Assemblr Edu learning media. Research that used by researchers using the Research and Development (R&D) method, and the method used uses the ADDIE method. Then, for data collection conducted by researchers through observation, interviews, and student learning outcomes. The subjects in this study were students, teachers, and a team of experts (media experts and material experts). The use of qualitative descriptive techniques, quantitative descriptive, and also iferential statistics are techniques in analyzing data on the development of this learning media. The results obtained in this study from the media expert test 87.5%, material expert test 70.8%, teacher test 91.25%, learner test 95%, as well as the results of the pretest and postest to test the effectiveness of the media developed which has very decent results from small and large groups. The N-gain results which state that the Augmented Reality-based Assemblr Edu learning media has a decent category in the use of the learning process. So, it can be concluded that the Augmented Reality-based Assemblr Edu learning media on the material of the structure of the earth's layers is well used, effective, and feasible to use in the learning process.