Physics of the Earth and Planetary Interiors最新文献

{"title":"Strength, plasticity, and spin transition of Fe-N compounds in planetary cores","authors":"Allison Pease ,&nbsp;Jiachao Liu ,&nbsp;Mingda Lv ,&nbsp;Yuming Xiao ,&nbsp;Katherine Armstrong ,&nbsp;Dmitry Popov ,&nbsp;Lowell Miyagi ,&nbsp;Susannah M. Dorfman","doi":"10.1016/j.pepi.2024.107236","DOIUrl":"10.1016/j.pepi.2024.107236","url":null,"abstract":"<div><p>Elastic and plastic properties of Fe-light element alloys and compounds are needed to determine the compositions and dynamics of planetary cores. Elastic strength and plastic deformation mechanisms and their relationship to electronic properties of ε-Fe₇N₃ and γ'-Fe₄N mixture were investigated by x-ray diffraction and x-ray emission spectroscopy in the diamond anvil cell from 1 bar up to 60 GPa. X-ray diffraction shows that ε-Fe₇N₃ reaches a pressure of 15–20 GPa before undergoing bulk plasticity at a differential stress of 4.4–10.4 GPa. ε-Fe₇N₃ is stronger than γ'-Fe₄N and hcp-Fe which achieve a flow stress of 1.5–3.6 GPa at 10–15 GPa and 2–3 GPa at ∼20 GPa, respectively. X-ray emission spectroscopy shows that a decrease in electronic spin moment begins before and completes after plastic flow onset for each nitride, suggesting that pressure-driven changes in electronic arrangement do not trigger a plastic response although they may modify the strength and plastic behavior of Fe-N compounds. Plastic deformation in ε-Fe₇N₃ and hcp-Fe results in a preferred orientation of (0001) normal to maximum compression, while γ'-Fe₄N develops a maximum in the (110). These observations may be combined with measurements of elasticity to model seismic properties of cores of small planetary bodies such as Mars, Mercury, and the Moon.</p></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"355 ","pages":"Article 107236"},"PeriodicalIF":2.4,"publicationDate":"2024-07-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141848168","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":"Source parameter and tectonic implications of small earthquakes originating in South India","authors":"Utpal Saikia,&nbsp;Davin Mathews David","doi":"10.1016/j.pepi.2024.107235","DOIUrl":"10.1016/j.pepi.2024.107235","url":null,"abstract":"<div><p>A data collection of 80 local earthquakes (1.8 &lt; M_L &lt; 3.5) recorded by several seismic stations beneath South India from February 2009 to October 2012 was studied to estimate the source parameter characteristics. The result shows that the seismic moments (<span><math><msub><mi>M</mi><mn>0</mn></msub></math></span>) vary from 8.95<span><math><mo>×</mo><msup><mn>10</mn><mn>11</mn></msup></math></span>to 6.56<span><math><mo>×</mo><msup><mn>10</mn><mn>13</mn></msup></math></span> Nm, while source radii (r) are between 120 and 150 m. The source radius seems to be independent of magnitude and smaller within a major part of the region. This can be due to local earthquakes that may originate in the region from either the brittle shear-failure mechanism on faults or the presence of weakened zones in this region. The estimated stress drops values range from 0.20 to 3 MPa for most of the events and shows an increasing trend with the seismic moment, indicating a wide range of strength of crustal rocks. Few lower crustal event exhibits slightly elevated stress drop (4–10 MPa) values, and these cannot be solely attributed to a single model; instead, it appears that the potential contributing factors vary area wise. The corner (<span><math><msub><mi>f</mi><mi>c</mi></msub></math></span>) and high cut (<span><math><msub><mi>f</mi><mi>max</mi></msub></math></span>) frequency values are bit scattered with the seismic moment, and the possible explanation would be either a complex rupture process or the involvement of a long period spectrum in the component. Both <span><math><msub><mi>f</mi><mi>max</mi></msub></math></span> and <span><math><msub><mi>f</mi><mi>c</mi></msub></math></span> show a decreasing trend against seismic moments, indicating that both are caused by a source process and independent of epicentral distances and focal depths. However, source displacement <span><math><mfenced><mi>D</mi></mfenced></math></span>(0.006 and 0.04 m) and radiated seismic energy (<span><math><msub><mi>E</mi><mi>s</mi></msub></math></span>) increases linearly with the seismic moment and is an indication of the size dependency feature. We established various empirical relationships between source parameters, including M_W - M_L and log(M₀) - M_L and proposed the M_L- M_W relationship for the study region, which is M_W <span><math><mo>∝</mo></math></span> 0.62M_L. Overall, the present study indicates that most source parameters tend to vary with the size of the earthquake and generally follow the global model of small magnitude earthquakes. The information, we gained through this study provides insight into earthquake size, source physics, and that can help the scientific community significantly, to better understand, mitigate, and respond to the seismic hazards posed by earthquakes in the studied area.</p></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"354 ","pages":"Article 107235"},"PeriodicalIF":2.4,"publicationDate":"2024-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141839986","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":"Simulation of microtextural evolution in omphacite: Ordering transformation kinetics as unexplored archives of slab eclogitization","authors":"Ryo Fukushima ,&nbsp;Tatsuki Tsujimori ,&nbsp;Nobuyoshi Miyajima","doi":"10.1016/j.pepi.2024.107227","DOIUrl":"https://doi.org/10.1016/j.pepi.2024.107227","url":null,"abstract":"<div><p>Earth's subduction zone processes and surface environments are intricately governed by mass transfer phenomena at plate convergent boundaries. The determination of their rates and timings from high-pressure metamorphic rocks (e.g., eclogite), or remnants of ancient convergent boundaries, remains an ongoing challenge. Here, we proposed the potential and versatility of ordering transformation kinetics of omphacite, an essential mineral found in eclogite, as a dynamic recorder of the metamorphic history. Through macroscopic phase-field simulation, we explored the growth of antiphase domains (APDs) in metastable disordered omphacite, discussing the feasibility of constraining metamorphic reaction kinetics based on the size and morphology of omphacite APDs in eclogitized oceanic crust. Our simulation corroborated that omphacite nucleating later during the prograde metamorphism can exhibit an incompletely ordered state with sparsely distributed ordered domains, which suggests their usefulness in estimating the recrystallization timing of the omphacite. Additionally, we confirmed that the APD formation dynamics are significantly influenced by the initial cation configuration of the disordered matrix. This implies the APD morphology in natural omphacite under slab-surface conditions may reflect their precipitation kinetics. These findings provide valuable insights into the microtextural evolution of omphacite due to its ordering transformation, thereby enhancing our ability to interpret morphological features.</p></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"354 ","pages":"Article 107227"},"PeriodicalIF":2.4,"publicationDate":"2024-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0031920124000852/pdfft?md5=31ed937b8cd6e1e8eac118ea2de63b58&pid=1-s2.0-S0031920124000852-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141604873","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":"Hydrogenation of calcite and change in chemical bonding at high pressure: Diamond formation above 100 GPa","authors":"Alexander F. Goncharov ,&nbsp;Huiyao Kuang ,&nbsp;John S. Tse ,&nbsp;Eric Edmund ,&nbsp;Maxim Bykov ,&nbsp;Elena Bykova ,&nbsp;Stella Chariton ,&nbsp;Vitali B. Prakapenka ,&nbsp;Timofey Fedotenko ,&nbsp;Nico Giordano ,&nbsp;Mohamed Mezouar ,&nbsp;Jesse S. Smith","doi":"10.1016/j.pepi.2024.107228","DOIUrl":"https://doi.org/10.1016/j.pepi.2024.107228","url":null,"abstract":"<div><p>Synchrotron X-ray diffraction (XRD) and Raman spectroscopy in laser heated diamond anvil cells and first principles molecular dynamics (FPMD) calculations have been used to investigate the reactivity of calcite and molecular hydrogen (H₂) at high pressures up to 120 GPa. We find that hydrogen reacts with calcite starting below 0.5 GPa at room temperature forming chemical bonds with carbon and oxygen. This results in the unit cell volume expansion; the hydrogenation level is much higher for powdered samples. Single-crystal XRD measurements at 8–24 GPa reveal the presence of previously reported III, IIIb, and VI calcite phases; some crystallites show up to 4% expansion, which is consistent with the incorporation of ≤ 1 hydrogen atom per formula unit. At 40–102 GPa XRD patterns of hydrogenated calcite demonstrate broadened features consistent with the calcite VI structure with incorporated hydrogen atoms. Above 80 GPa, the C<img>O stretching mode of calcite splits suggesting a change in the coordination of C<img>O bonds. Laser heating at 110 GPa results in the formation of C<img>C bonds manifested in the crystallization of diamond recorded by in situ XRD at 300 K and 110 GPa and by Raman spectroscopy on recovered samples commenced with C¹³ calcite. We explored several theoretical models, which show that incorporation of atomic hydrogen results in local distortions of CO₃ groups, formation of corner-shared C<img>O polyhedra, and chemical bonding of H to C and O, which leads to the lattice expansion and vibrational features consistent with the experiments. The experimental and theoretical results support recent reports on tetrahedral C coordination in high-pressure carbonate glasses and suggest a possible source of the origin of ultradeep diamonds.</p></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"354 ","pages":"Article 107228"},"PeriodicalIF":2.4,"publicationDate":"2024-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141604878","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":"Electrical conductivity model for transversely isotropic rocks with interconnected cracks","authors":"Yoshiya Usui","doi":"10.1016/j.pepi.2024.107226","DOIUrl":"https://doi.org/10.1016/j.pepi.2024.107226","url":null,"abstract":"<div><p>The electrical conductivity of subsurface rocks is generally anisotropic. The anisotropy of the subsurface electrical conductivity provides important information on the stress-strain state and geodynamics. To quantitatively interpret anisotropic conductivity structures revealed by electromagnetic surveys, it is essential to use a mixing model considering the anisotropy. Although there exists a mixing model for transversely isotropic rocks with crack-shaped pores, the previous model seems inappropriate in interpreting conductive anomalies revealed by electromagnetic exploration because cracks are assumed to be isolated in the model. Therefore, this study develops a theoretical mixing model for transversely isotropic rocks with mutually interconnected cracks by a statistical approach. The derived mixing model considers the macroscopic tortuosity of a collection of cracks as well as the tortuosity of each crack. The derived model can represent general transverse isotropy and includes the isotropic and parallel models as special cases. I compare the developed model to previously proposed mixing models, showing that the developed model can reproduce a much wider range of anisotropy than the already-existing anisotropic mixing model. By applying the developed model to an example of the anisotropic conductivity in the oceanic upper crust inferred by electromagnetic exploration, I demonstrate that the developed mixing model enables us to quantitatively infer the crack orientation and fluid volume fraction that reproduce significant anisotropic conductivity found by field observations. Furthermore, I compare the developed model to the anisotropic seismic velocity model for fluid-filled cracks.</p></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"354 ","pages":"Article 107226"},"PeriodicalIF":2.4,"publicationDate":"2024-06-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0031920124000840/pdfft?md5=97fe02e6169550ae880f6fa4076adefe&pid=1-s2.0-S0031920124000840-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141543749","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":"Thermal instability from rock magnetic measurements confirms the underestimates of absolute paleointensity records during the Santa Rosa geomagnetic excursion","authors":"Junxiang Miao ,&nbsp;Huapei Wang","doi":"10.1016/j.pepi.2024.107225","DOIUrl":"https://doi.org/10.1016/j.pepi.2024.107225","url":null,"abstract":"<div><p>Geomagnetic excursion events have been widely studied in recent years as a key process for understanding the evolution of the Earth's magnetic field. The Santa Rosa geomagnetic excursion (SRE) event during the Matuyama chron has been globally recorded in sediment sequences and lava flows. Galapagos lavas distributed in near-equatorial with an ⁴⁰Ar/³⁹Ar age of 925.7 ± 4.6 ka display absolute paleointensity values of about 14% of the modern magnetic field, which is a valuable record of the Earth's magnetic field strength during the SRE event. However, the above extremely low estimates of paleointensities during the SRE were fitting from higher temperature segments (400 °C–575 °C) from previous paleointensity experiments, which is biased by the thermal instability of Galapagos lava samples during high-temperature heating treatments. From our comprehensive rock magnetic experiments in this study, Galapagos lava samples exhibit thermal instability after heating treatments higher than 400 °C. The severe thermal alteration occurred after the heating temperature reached 500 °C, mainly manifested as an increase in remanence-carrying capacities, such as the enhanced ability of paleointensity specimens to record partial thermoremanent magnetization, resulting in underestimated paleointensities during the SRE. In-depth experiments on rock magnetism and hysteresis parameters analysis provide a powerful method to detect the thermal instability of lava samples, which can help us confirm the biased geomagnetic field strength during this short-lived excursion period and prevent misinterpretations of the Earth's magnetic field evolution through erroneous low paleointensity records.</p></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"354 ","pages":"Article 107225"},"PeriodicalIF":2.4,"publicationDate":"2024-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141543750","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":"Inversion of fluid-release rates from episodic tremor and slip signals in subduction zones via a coarse-grained reaction diffusion model","authors":"Qingpei Sun ,&nbsp;Klaus Regenauer-Lieb ,&nbsp;Manman Hu","doi":"10.1016/j.pepi.2024.107223","DOIUrl":"https://doi.org/10.1016/j.pepi.2024.107223","url":null,"abstract":"<div><p>Episodic Tremor and Slip (ETS) events showcase dynamic interactions of oscillatory slow slips and tremors deep within subduction zones and offer a window into Earth's internal dynamics. However, the exact mechanisms driving these events remain unresolved. This study proposes a novel approach that goes beyond traditional explanations focused on fluid pressure from mineral dehydration. Existing models often neglect the intricate interplay between fluid and rock pressures across various depths and potential fluid sources. This calls for a more comprehensive understanding of how fluid release from reactions interacts with rock deformation. The present formulation captures the interplay between fluid and solid pressures providing a more rigorous picture of ETS events. It employs a minimalistic and efficient approach based on integrating dehydration reactions. The model thereby develops a generic framework for mineral dehydration, offering an enhanced perspective of the underlying processes without the need to trace down to specific minerals. It allows a refined fit to GPS data by including high-frequency components from linear and nonlinear stability analyses, giving rise to improved correlation coefficients. Through the inclusion of the dynamic interplay between fluid and rock pressure diffusion within subduction zones, we propose a unified model of ETS events.</p></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"353 ","pages":"Article 107223"},"PeriodicalIF":2.4,"publicationDate":"2024-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141486911","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":"Strain localization by diffusion creep of Bridgmanite-Ferropericlase mixture: Application of self-consistent method","authors":"H.E. Cho ,&nbsp;Shun-ichiro Karato","doi":"10.1016/j.pepi.2024.107224","DOIUrl":"https://doi.org/10.1016/j.pepi.2024.107224","url":null,"abstract":"<div><p>In this study, we investigate the finite deformation of a polycrystalline mixture of bridgmanite (Br) and ferropericlase (Fp) by diffusion creep at the lower mantle-like temperature and pressure by using the self-consistent approach. We explore the influence of volume fraction of Fp, viscosity contrast, and strain dependence (effect of shape change) under both axial (coaxial deformation) and simple shear (non-coaxial deformation). Our present study shows: i) the strength (viscosity) contrast between Fp and Br increases with strain since the viscosity of Fp significantly decreases as Fp grain elongates, and (ii) deformation starts from nearly homogeneous strain to finally nearly homogeneous stress under simple shear whereas deformation behavior remains nearly homogeneous strain under axial deformation. A more substantial creep rate partitioning occurs in simple shear than in axial deformation. These results imply that strain localization <em>via</em> diffusion creep might occur in the lower mantle, particularly in regions where the simple shear is dominated (<em>i.e.</em>, in the boundary layers (<em>e.g.</em>, the D″ layer)).</p></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"353 ","pages":"Article 107224"},"PeriodicalIF":2.4,"publicationDate":"2024-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141483834","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":"Enigmatic mixture of magnetite magnetofossils and diagenetic greigite as the magnetic carriers of the Early Miocene lacustrine sediments from the Most Basin in Central Europe","authors":"Hakan Ucar ,&nbsp;Gunther Kletetschka ,&nbsp;Ramon Egli ,&nbsp;Karel Mach ,&nbsp;Michael S. Petronis ,&nbsp;Hana Grison ,&nbsp;Stephanie Scheidt ,&nbsp;Petr Schnabl ,&nbsp;Simon Kdyr","doi":"10.1016/j.pepi.2024.107216","DOIUrl":"10.1016/j.pepi.2024.107216","url":null,"abstract":"<div><p>The Early Miocene lacustrine sediments of the Most Basin in the Czech Republic preserve a European continental paleoenvironmental archive. A number of paleoenvironmental and magnetostratigraphic studies have been carried out on sediment cores from boreholes due to ongoing coal mining in the basin. However, the magnetic carriers of the studied sediments have not been identified clearly. Here, we present a detailed paleo-rock magnetic study from the Burdigalian sediments near the Bilina mining area, Most Basin. The studied clay sediments cover the period of local lakes and a basin-wide lake above the main coal seam. Our results suggest that the magnetic carriers of the studied section in the Most Basin are mixtures of authigenic greigite and magnetite magnetofossils with overlapping magnetic signatures. Greigite is formed by migration of pore water through the sediment column, where iron from siderite grains reacts with these fluids with limited H₂S, which then favors greigite precipitation. The co-existence of greigite and magnetite indicates a partial dissolution of magnetofossils due to H₂S deficiency. Diagenetic greigite has been problematic in paleomagnetic studies due to an unknown time lag between the depositional remanence and the chemical remanent magnetization (CRM). A ghost polarity interval reveals that greigite acquired at least ∼45 kyr delayed CRM. The revealed timing of remanence acquisition brings a new perspective to the chronostratigraphic structure of the Most Basin.</p></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"353 ","pages":"Article 107216"},"PeriodicalIF":2.4,"publicationDate":"2024-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141393963","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":"Quantifying the features of earthquake clusters in north-Central Iran, based on nearest-neighbor distances and network analysis","authors":"Mohammad Talebi ,&nbsp;Mehdi Zare ,&nbsp;Antonella Peresan","doi":"10.1016/j.pepi.2024.107215","DOIUrl":"10.1016/j.pepi.2024.107215","url":null,"abstract":"<div><p>The statistical features of earthquake clusters in North-Central Iran (Tehran Region) are investigated, with the aim of quantitatively characterizing the properties of earthquake triggering and allow exploring their possible relations with the tectonic setting of the study area.</p><p>The nearest-neighbor approach is used for the identification of the earthquake clusters in the space-time-energy domain. This approach permits for a data-driven identification of clusters so that, within multi-event clusters, the features of secondary and higher orders dependent events can be explored. The study is based on a revised dataset that is extracted from the catalog compiled by the Iranian Seismological Center (IRSC) for the period of 1996–2022. In order to exclude the effect of non-tectonic events, which turn out quite numerous within the study region, explosions within quarry-rich areas are removed; the identification of non-tectonic events is performed by considering the normalized ratios of daytime to nighttime events in an iterative removal procedure. According to preliminary analysis of the resulting catalog, an area is selected, within which a satisfactory completeness level is assessed for events with magnitude &gt;2.0. Robust values of the scaling parameters, namely the b-value and the fractal dimension of epicenters, are also computed and are used to calculate the nearest-neighbor distances and to identify the earthquake clusters.</p><p>The nearest-neighbor method also permits to investigate the internal structure of earthquake sequences, and to differentiate the spatial properties of seismicity according to the different topological features of the clusters structure. The obtained results allow us identifying two macro-areas, approximately separated by the 52°E meridian, which are characterized by different clustering features, namely: high complexity indexes, indicating simple (burst-like) structure of clusters, to the East; low complexity index, corresponding to complex multi-level (swarm-like) structure of clusters, to the West. The complexity measures, borrowed from network theory (i.e. the Closeness and Outdegree Centralization indexes), consistently capture the complexity of the identified clusters, and confirm that the cluster structures have distinct preferred geographic locations. The territorial heterogeneity of the examined clustering properties can be related with the spatial variability of tectonic, structural and geophysical features of the Alborz region, in good agreement with findings from the Alps-Dinarides junction (Northeastern Italy), a region also characterized by a contractional structural setting, mainly including reverse and strike-slip faulting systems, and by moderate to high seismic activity.</p></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"353 ","pages":"Article 107215"},"PeriodicalIF":2.3,"publicationDate":"2024-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141282201","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}