Physics of the Earth and Planetary Interiors最新文献

{"title":"Effect of chemistry on the compressibility and high-pressure structural evolution of the CaFe2O4-type aluminous silicate phase","authors":"Giacomo Criniti ,&nbsp;Tiziana Boffa Ballaran ,&nbsp;Alexander Kurnosov ,&nbsp;Takayuki Ishii ,&nbsp;Elena-Marie Rogmann ,&nbsp;Konstantin Glazyrin ,&nbsp;Timofey Fedotenko ,&nbsp;Daniel J. Frost","doi":"10.1016/j.pepi.2025.107331","DOIUrl":"10.1016/j.pepi.2025.107331","url":null,"abstract":"<div><div>Approximately 22–26 vol% of a basaltic phase assemblage at lower mantle conditions is comprised of a (Na,Mg,Fe²⁺)(Al,Si,Fe³⁺)₂O₄ phase with CaFe₂O₄-type (CF-type) structure. Previous experimental studies attempted to determine the equation of state of the CF-type phase but reported contrasting compressibility values, even for samples with the same composition. Therefore, the elastic properties of the CF-type phase remain, to date, largely unconstrained. Here, we conducted single-crystal X-ray diffraction (SCXRD) measurements in the diamond anvil cell (DAC) at high pressure and room temperature on three samples of CF-type phase with compositions Na_0.90(1)Al_1.03(2)Si_1.00(2)O₄ (NaCF), Na_0.66(4)Mg_0.28(4)Al_1.22(3)Si_0.78(3)O₄ (MgCF) and Na_0.62(2)Mg_0.19(1)Fe²⁺_0.17(1)Fe³⁺_0.080(4)Al_1.20(3)Si_0.70(1)O₄ (FeCF). A multi-sample loading approach was employed for most DAC runs, where two samples were loaded in the same sample chamber to reduce possible systematic deviations between datasets, thus enhancing internal consistency and corroborating data reproducibility. Experiments on the NaCF and MgCF samples were conducted up to ∼50 GPa, while the FeCF sample was compressed to ∼72 GPa to better characterize the effect of the spin crossover of octahedrally coordinated Fe³⁺. We found the isothermal bulk modulus (<em>K</em>_T0) to increase with decreasing NaAlSiO₄ content, accompanied by only a slight decrease in its pressure derivative (<em>K'</em>_T0). Analysis of the crystal structures of the three samples at high pressure allowed compositional trends to be determined also for the interatomic bonds and polyhedral compressibility, as well as the distortion indices. These suggest an overall stiffening of the A site with increasing Mg²⁺ and Fe²⁺ content, as well of the two B sites with increasing Al³⁺ and Fe³⁺ content. Enhanced compressibility of the unit cell and octahedral B sites was observed between ∼26–42 GPa in the FeCF sample, suggesting a pressure-induced spin crossover of Fe³⁺, in agreement with some previous observations. Finally, trends in the elastic properties from experimental studies conducted along the NaAlSiO₄-MgAl₂O₄ join are discussed and used as a proxy to evaluate the reliability of end-member properties for the CF-type phase employed in most recent mineral physical and thermodynamic databases. Our analysis suggests current mineral physical models might underestimate densities and overestimate bulk sound velocities of NaAlSiO₄-rich CF-type phases with basaltic composition.</div></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"361 ","pages":"Article 107331"},"PeriodicalIF":2.4,"publicationDate":"2025-02-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143512264","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A 6-year quasi-periodicity in the geomagnetic secular acceleration pulses over 1932–2022","authors":"R. Sidorov ,&nbsp;A. Soloviev ,&nbsp;Sh. Bogoutdinov","doi":"10.1016/j.pepi.2025.107330","DOIUrl":"10.1016/j.pepi.2025.107330","url":null,"abstract":"<div><div>Recent studies suggest that the secular variation dynamics of the geomagnetic field exhibits periodic patterns that indicate underlying wave processes in the Earth's core. However, analytical models of the core geomagnetic field based on geographically sparse and noisy observatory data have apparent limitations for studying fine structure of its spatiotemporal variations. The advent of satellite measurements of the full geomagnetic field vector in 1999 removed this limitation and made it possible to produce reliable and highly accurate models of the secular variation that allow downward continuation to the core-mantle boundary. These models have revealed rapid core field variations on a time scale of the order of 10 years. In particular, the 6-year quasi-periodicity in the second time derivative of the geomagnetic field has been discovered. In this research, we build on our previous works to extract the secular variation and secular acceleration signal from the magnetic observatory datasets over a longer period. As a result, our approach to data analysis has made it possible to confirm the existence of a 3-year quasi-periodicity of secular acceleration pulses of alternating polarity over 90-year period (1932–2022), i.e. far before the advent of the space era. The proposed methodology does not imply an intermediate production of a core field model, as done according to classical approaches.</div></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"361 ","pages":"Article 107330"},"PeriodicalIF":2.4,"publicationDate":"2025-02-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143465133","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"SeisTeC: A neural network tool to constrain mantle thermal and chemical properties from seismic observables","authors":"Ashim Rijal,&nbsp;Laura Cobden,&nbsp;Jeannot Trampert","doi":"10.1016/j.pepi.2025.107317","DOIUrl":"10.1016/j.pepi.2025.107317","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Three-dimensional variations of wave speeds and density have identified the presence of seismically distinct structures in the Earth's mantle. To determine the thermochemical properties and dynamic relevance of these structures, it is crucial to understand the relationship between seismic properties and temperature and composition. However, multiple thermochemical parameters influence seismic wave speeds simultaneously. A given wave speed pair (compressional and shear) and density can be generated by many possible combinations of thermochemical parameters, which makes the inversion of wave speeds and density for thermochemical parameters a non-unique problem. We have developed a tool which efficiently captures the mapping between seismic wave speeds (and density) and thermochemical properties, with the capacity to represent both the inherent trade-offs between parameters as well as data uncertainties. These trade-offs and uncertainties are represented by the posterior probability density function provided by a neural network. We demonstrate the concept for seismic wave speeds and density, but the same tool can also be adapted for other parameters such as attenuation or properties of seismic discontinuities. SeisTeC is available to the wider community and is intended to facilitate interpretations of seismic structures inside the Earth, or in general, any planetary bodies.&lt;/div&gt;&lt;div&gt;Our tool is based on a neural network, which implicitly learns the non-linear mapping between temperature and bulk composition. We chose the example of the lower mantle and expressed composition in terms of six end-member oxides (&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mi&gt;SiO&lt;/mi&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/msub&gt;&lt;mo&gt;,&lt;/mo&gt;&lt;mi&gt;MgO&lt;/mi&gt;&lt;mo&gt;,&lt;/mo&gt;&lt;msub&gt;&lt;mi&gt;Al&lt;/mi&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/msub&gt;&lt;msub&gt;&lt;mi&gt;O&lt;/mi&gt;&lt;mn&gt;3&lt;/mn&gt;&lt;/msub&gt;&lt;mo&gt;,&lt;/mo&gt;&lt;mi&gt;FeO&lt;/mi&gt;&lt;mo&gt;,&lt;/mo&gt;&lt;msub&gt;&lt;mi&gt;Na&lt;/mi&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/msub&gt;&lt;mi&gt;O&lt;/mi&gt;&lt;mo&gt;,&lt;/mo&gt;&lt;mi&gt;CaO&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt;) and modelled seismic wave speeds and density at appropriate temperature and pressure conditions. Wave speeds and density are calculated for 750,000 thermochemical models, whose temperature and composition are selected at random from pre-defined ranges, using thermodynamic modelling. We train neural networks with wave speeds plus or minus density as the input, and temperature and bulk composition as target outputs. The networks then approximate a probability density function for each output, which allows us to interpret seismic observables in terms of physical parameters, crucially, with uncertainties. When working with wave speeds (&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mi&gt;V&lt;/mi&gt;&lt;mi&gt;P&lt;/mi&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; and &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mi&gt;V&lt;/mi&gt;&lt;mi&gt;S&lt;/mi&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;) only, we find trade-offs between pairs of parameters such as temperature - &lt;span&gt;&lt;math&gt;&lt;mi&gt;FeO&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt;, &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mi&gt;SiO&lt;/mi&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; - &lt;span&gt;&lt;math&gt;&lt;mi&gt;MgO&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt;, &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mi&gt;SiO&lt;/mi&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; - &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mi&gt;Na&lt;/mi&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/msub&gt;&lt;m","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"361 ","pages":"Article 107317"},"PeriodicalIF":2.4,"publicationDate":"2025-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143465132","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Radial structure of the Earth: (I) Model concepts and data","authors":"Pritwiraj Moulik ,&nbsp;Göran Ekström","doi":"10.1016/j.pepi.2025.107319","DOIUrl":"10.1016/j.pepi.2025.107319","url":null,"abstract":"&lt;div&gt;&lt;div&gt;A framework is introduced for developing a radial reference model that incorporates diverse observations and techniques for improving the constraints on bulk Earth structure. This study describes new modeling concepts and reference datasets while features of the reference Earth model REM1D and geological interpretations are discussed in a companion manuscript. Recent measurements from various techniques have improved in precision and are broadly consistent, and are summarized as best estimates with uncertainties. We construct a reference dataset comprising normal-mode eigenfrequencies and quality factors, surface-wave dispersion curves, impedance constraints and travel-time curves from body waves, and astronomic-geodetic observations. Classical radial reference models do not account for the theoretical effects and observational biases resulting from heterogeneity in the crust and mantle. We address three issues that account for lateral variations in the modeling of average elastic, anelastic and density structure. First, current ray coverage of traveling waves is biased towards structure in the northern hemisphere, leading to faster velocities especially in the lower mantle. Second, horizontal wavelength of the heterogeneity that a traveling wave encounters is assumed to be much greater than that of the corresponding normal mode in most ray-theoretical and finite-frequency formulations of wave propagation. Effects of the full volumetric sensitivity on local eigenfrequencies and phase velocities that are ignored with this approximation exceed the data uncertainty for both fundamental spheroidal (Rayleigh waves, T &lt;span&gt;&lt;math&gt;&lt;mo&gt;≥&lt;/mo&gt;&lt;/math&gt;&lt;/span&gt; 220 s) and toroidal modes (Love waves, T &lt;span&gt;&lt;math&gt;&lt;mo&gt;≥&lt;/mo&gt;&lt;/math&gt;&lt;/span&gt; 120 s); waves at these longer periods cannot be modeled solely in terms of radial variations along the ray path. Third, non-linear effects from the strongly heterogeneous crustal structure are substantial for shorter-period waves (T &lt;span&gt;&lt;math&gt;&lt;mo&gt;≤&lt;/mo&gt;&lt;/math&gt;&lt;/span&gt; 100 s) and need to be accounted for while deriving radial models. After accounting for these issues on heterogeneity, rapid convergence for average structure is facilitated by utilizing &lt;em&gt;a priori&lt;/em&gt; constraints from recent literature, analytical sensitivity kernels that account for physical dispersion, and a flexible parameterization comprising polynomial functions and cubic B-splines. By adopting a higher order polynomial for density than the elastic structure, artifacts that imply strong inhomogeneity and non-adiabaticity are avoided in potentially well-mixed regions like the outer core. Derivative properties like the gradient of bulk modulus with pressure (&lt;span&gt;&lt;math&gt;&lt;msup&gt;&lt;mi&gt;κ&lt;/mi&gt;&lt;mo&gt;′&lt;/mo&gt;&lt;/msup&gt;&lt;/math&gt;&lt;/span&gt; = &lt;span&gt;&lt;math&gt;&lt;mi&gt;dκ&lt;/mi&gt;&lt;mo&gt;/&lt;/mo&gt;&lt;mi&gt;dp&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt;) and the Bullen's stratification parameter &lt;span&gt;&lt;math&gt;&lt;mfenced&gt;&lt;msub&gt;&lt;mi&gt;η&lt;/mi&gt;&lt;mi&gt;B&lt;/mi&gt;&lt;/msub&gt;&lt;/mfenced&gt;&lt;/math&gt;&lt;/span&gt; are adjusted in the core to match expectations fr","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"361 ","pages":"Article 107319"},"PeriodicalIF":2.4,"publicationDate":"2025-02-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143551095","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Radial structure of the Earth: (II) Model features and interpretations","authors":"Pritwiraj Moulik ,&nbsp;Göran Ekström","doi":"10.1016/j.pepi.2025.107320","DOIUrl":"10.1016/j.pepi.2025.107320","url":null,"abstract":"&lt;div&gt;&lt;div&gt;A new reference model is presented for the spherically-averaged profiles of elasticity, density and attenuation, which reflect the bulk composition, temperature profile and dominant processes of the Earth's heterogeneous interior. This study discusses the features of REM1D and geological interpretations while the underlying modeling concepts and reference datasets are described in a companion manuscript. All physical parameters in REM1D vary smoothly between the Mohorovičić and 410-km discontinuity, thereby excluding the 220-km discontinuity in earlier models. REM1D predicts arrival times of major body-wave phases in agreement (±0.8 s, normalized misfit &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mi&gt;ψ&lt;/mi&gt;&lt;mi&gt;pb&lt;/mi&gt;&lt;/msub&gt;&lt;mo&gt;≤&lt;/mo&gt;&lt;/math&gt;&lt;/span&gt; 0.25 s) with widely used but theoretically incomplete isotropic models optimized for earthquake location. Substantial radial anisotropy is present only in the shallowest mantle (∼250 km) with peak values of shear-wave (&lt;em&gt;a&lt;/em&gt;&lt;sub&gt;&lt;em&gt;S&lt;/em&gt;&lt;/sub&gt; = 3.90 %, &lt;span&gt;&lt;math&gt;&lt;mi&gt;ξ&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt; = 1.08) and compressional-wave anisotropy (&lt;em&gt;a&lt;/em&gt;&lt;sub&gt;&lt;em&gt;P&lt;/em&gt;&lt;/sub&gt; = 3.78 %, &lt;span&gt;&lt;math&gt;&lt;mi&gt;ϕ&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt; = 0.93) between ∼125–150 km, consistent with textures that can form by the alignment of intrinsically anisotropic minerals in this deforming region. The upper mantle (24.4–410 km) is the most dissipative region with a finite bulk attenuation (&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mi&gt;Q&lt;/mi&gt;&lt;mi&gt;κ&lt;/mi&gt;&lt;/msub&gt;&lt;mo&gt;∼&lt;/mo&gt;&lt;/math&gt;&lt;/span&gt; 386) and strong shear attenuation (&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mi&gt;Q&lt;/mi&gt;&lt;mi&gt;μ&lt;/mi&gt;&lt;/msub&gt;&lt;mo&gt;∼&lt;/mo&gt;&lt;/math&gt;&lt;/span&gt; 60–80) that peaks at a depth of ∼150–175 km in the mechanically weak asthenosphere. An olivine-rich pyrolitic composition is broadly consistent with REM1D structure in the upper mantle and extended transition zone (&lt;span&gt;&lt;math&gt;&lt;mo&gt;≲&lt;/mo&gt;&lt;/math&gt;&lt;/span&gt; 800 km) with step changes across the 410-km and 650-km discontinuities. Features of the lower mantle can be reconciled with: (i) effects of thermally driven convection throughout the central lower mantle (771–2741 km) leading to an apparent subadiabaticity in the stratification parameter &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mi&gt;η&lt;/mi&gt;&lt;mi&gt;B&lt;/mi&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;, (ii) effects of spin transitions in iron-bearing minerals that manifest as distinct linear segments in modulus and Poisson's ratios (&lt;span&gt;&lt;math&gt;&lt;mi&gt;μ&lt;/mi&gt;&lt;mo&gt;/&lt;/mo&gt;&lt;mi&gt;κ&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt;, &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mi&gt;σ&lt;/mi&gt;&lt;mi&gt;P&lt;/mi&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;) on either side of a complex transition region (∼1300–1700 km, 52–73 GPa), (iii) a thermal boundary layer with steeper superadiabatic gradients than near the surface, which ultimately exceed the critical gradients for both &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mi&gt;v&lt;/mi&gt;&lt;mi&gt;P&lt;/mi&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; and &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mi&gt;v&lt;/mi&gt;&lt;mi&gt;S&lt;/mi&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; (but not for density &lt;span&gt;&lt;math&gt;&lt;mi&gt;ρ&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt;) at a depth of 2741 km, and (iv) chemical stratification in the bottom ∼500–750 km of the mantle that acts to suppress the thermal effects. Signatures of this th","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"361 ","pages":"Article 107320"},"PeriodicalIF":2.4,"publicationDate":"2025-02-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143479207","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Flat 410 and 660 discontinuities beneath northeastern Japan: Implication for a sub-slab wet plume hypothesis","authors":"K. Miyazaki,&nbsp;J. Nakajima","doi":"10.1016/j.pepi.2025.107316","DOIUrl":"10.1016/j.pepi.2025.107316","url":null,"abstract":"<div><div>Recent seismic tomography studies have shown that distinct low-velocity anomalies exist below subducting slabs in many subduction zones and these anomalies are interpreted as a hot plume from the lower mantle. However, it is still unclear how high are the temperatures in the sub-slab low-velocity anomaly regions. Here, we conduct receiver function analysis and estimate the horizontal temperature variation in the mantle transition zone by determining the depth variation of 410 and 660 discontinuities beneath northeastern Japan. The obtained results show that the depth of the two discontinuities changes little, which suggests no distinct thermal heterogeneities over the study area. Therefore, we infer that the major cause of the sub-slab low-velocity anomaly is attributable not to high-temperature anomaly but to the presence of a small amount (∼0.2 wt%) of hydrous minerals, which can explain the sub-slab low-velocity anomalies and the flat 410 and 660 discontinuities.</div></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"361 ","pages":"Article 107316"},"PeriodicalIF":2.4,"publicationDate":"2025-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143394579","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Reassessment of focal depth estimates of small-to-moderate magnitude continental earthquakes in Western to Central Africa with the optimal period of Rayleigh wave amplitude spectra using sparse regional seismic data","authors":"John Somiah ,&nbsp;Sidao Ni ,&nbsp;Xiaohui He","doi":"10.1016/j.pepi.2025.107322","DOIUrl":"10.1016/j.pepi.2025.107322","url":null,"abstract":"<div><div>We investigate the focal depths of earthquakes in West and Central Africa using regional seismic data collected over the past two decades. Due to limited seismic network coverage, reliable source depth estimates are sparse in global earthquake catalogs for this region. To address this gap, we exploit the sensitivity of short-period (0.5–20 s) Rayleigh waves to source depths. Using the optimal period of Rayleigh wave amplitude spectra, we used an automated method to estimate earthquake focal depths. This method enabled us to resolve the depths of fifteen small-to-moderate earthquakes (mb 4.0–5.0) occurring in the region between 2000 and 2023. The focal depths ranged from approximately 3.3 km to 16 km, indicating that seismicity in the region is primarily confined to the upper crust. This finding is consistent with previous studies suggesting shallow crustal seismicity in the area. We conclude that the shallow stress regime in West and Central Africa reflects a localized weakness zone in the upper crust. Our study demonstrates the effectiveness of using the optimal Rayleigh wave period method to accurately determine focal depths of small-to-moderate earthquakes, particularly in regions with sparse seismic station coverage.</div></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"360 ","pages":"Article 107322"},"PeriodicalIF":2.4,"publicationDate":"2025-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143372154","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"On the deep carbon cycle in numerical modelling of mantle convection: Implications for the long-term climate evolution","authors":"Takashi Nakagawa","doi":"10.1016/j.pepi.2025.107321","DOIUrl":"10.1016/j.pepi.2025.107321","url":null,"abstract":"<div><div>A model of deep-water and carbon cycles was developed to elucidate the mechanisms governing the carbon cycle in Earth's deep interior. This model integrates the solubility limit of carbon in mantle rocks into numerical simulations of mantle convection. To account for the total carbon released from the deep interior, I considered both the carbon release flux through metamorphic decarbonization during subduction and the outgassing fluxes at mid-ocean ridges and hotspots. Additionally, the model assumes a carbon solubility of 1.0 wt% at the top of the mantle transition zone. The carbon budget within Earth's deep interior appears nearly balanced by the carbon uptake during subduction and the decarbonization of the subducting slab through metamorphic reactions. This study also suggests that a warmer climate is likely if the carbon release flux from the deep interior comprises both decarbonization and volcanic outgassing. Therefore, an Earth-like climate may be sustained by the carbon release associated with plate subductions. It is acknowledged that this study presents a case study of carbon cycle modelling in mantle convection simulations, with a specific emphasis on the integration of carbon solubility limits in mantle rocks based on the carbon solubility model in mantle minerals.</div></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"360 ","pages":"Article 107321"},"PeriodicalIF":2.4,"publicationDate":"2025-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143348580","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Exploring the structural components of the Bejaia-Babors shear zone (BBSZ) in NE Algeria: Evidence from local earthquake tomography using recent seismic events (2012−2022)","authors":"Issam Abacha ,&nbsp;Khaled Roubeche ,&nbsp;Hichem Bendjama ,&nbsp;El-Mahdi Tikhamarine ,&nbsp;Oualid Boulahia ,&nbsp;Radia Kherchouche ,&nbsp;Sofiane Taki-Eddine Rahmani ,&nbsp;Hamoud Beldjoudi","doi":"10.1016/j.pepi.2025.107318","DOIUrl":"10.1016/j.pepi.2025.107318","url":null,"abstract":"<div><div>In recent years, the Algerian region of Bejaia-Babors (BB) has experienced significant seismic activity, including the Bejaia-Babors seismic sequence in 2012–2013, the Jijel earthquake in 2019, the El Aouana earthquake in 2020, and Bejaia subsequent earthquakes in 2021 and 2022. These seismic events have not only brought to light the existence of the Bejaia-Babors Shear Zone (BBSZ) but have also emphasized the importance of discerning its structural components, depth, and extent. Our study focuses on the analysis of seismological data from 2012 to 2022, with a particular emphasis on elucidating the intricacies of this geological structure. Using the LOTOS (local tomography software) algorithm, we conducted three iterations of tomographic inversion, successfully obtaining horizontal and vertical sections that facilitated the identification and characterization of subsurface anomalies. The resulting 3D velocity models unveiled key tectonic structures within the BBSZ, including the Offshore Faults System of Jijel (OFSJ), South Greater Kabylia Fault (SGKF), Transversal Fault 1 (TF1), and the collision between the Lesser Kabylia Block (LKB) and the Babors (THF-1). Futhermore, brittle-ductile shears were identified along the Aftis Fault (AF) in the east and brittle shears along the Babors Transverse Fault (BTF) in the west. P-wave velocity analysis indicated the presence of rigid blocks. The observed high Vp/Vs ratio near segment 3 of the BTF fault suggests the presence of a fluid reservoir, likely involved in the Bejaia-Babors seismic sequence (2012−2013), as previously documented. These findings provide valuable insights into the tectonic framework of the BBSZ, highlighting major fault systems and the interaction between different tectonic blocks. The presence of brittle-ductile shears along the AF suggests complex deformation processes in this region. Overall, by identifying key fault systems, characterizing subsurface anomalies, and unveiling the presence of fluid reservoirs, our research not only contributes significantly to geodynamic knowledge but also holds immense significance for seismic hazard assessment, resource exploration, and future research in this field.</div></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"360 ","pages":"Article 107318"},"PeriodicalIF":2.4,"publicationDate":"2025-02-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143150395","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A new method for extracting geomagnetic perturbation anomalies preceding the M7.4 Maduo earthquake","authors":"Lili Feng ,&nbsp;Weiling Zhu ,&nbsp;Yiliang Guan ,&nbsp;Wenjie Fan ,&nbsp;Yingfeng Ji","doi":"10.1016/j.pepi.2024.107305","DOIUrl":"10.1016/j.pepi.2024.107305","url":null,"abstract":"<div><div>Although the single-station geomagnetic polarization method is typically used for predicting impending earthquakes, newly constructed multiple-station geomagnetic networks exhibit more advantages in predicting the exact times and epicenters of events. In this study, the polarization method for extracting geomagnetic radiation anomalies before the M7.4 Maduo earthquake was greatly improved, and mathematical treatments such as normalization and interpolation were carried out via second-sampled observations from multiple geomagnetic stations in western China. In addition, the spatial polarization map was upgraded from the original single-station map to a multiple-station map. The improved spatiotemporal G'-value method can intuitively determine the distribution of anomalies preceding strong earthquakes. Our results showed that (1) two polarization highs occurred near the epicenter 7 months and 15 days before the M7.4 earthquake, and the epicenter was near the core of the high anomaly; (2) the two G\" maximum stations are both Qinghai Dulan (DUL) stations, within an epicenter distance of 191 km; the areas of high G\"-value zones greater than 0.2 are 58 × 104 km² and 112 × 104 km², respectively. This method provides new insights into identifying seismomagnetic anomalies preceding large earthquake epicenters, which is helpful for in-depth research on characterizing electromagnetic radiation from earthquakes.</div></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"359 ","pages":"Article 107305"},"PeriodicalIF":2.4,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143135233","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}