Pub Date : 2025-02-07DOI: 10.1016/j.pepi.2025.107316
K. Miyazaki, J. Nakajima
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.
{"title":"Flat 410 and 660 discontinuities beneath northeastern Japan: Implication for a sub-slab wet plume hypothesis","authors":"K. Miyazaki, 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}
Pub Date : 2025-02-05DOI: 10.1016/j.pepi.2025.107322
John Somiah , Sidao Ni , Xiaohui He
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.
{"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 , Sidao Ni , 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}
Pub Date : 2025-02-04DOI: 10.1016/j.pepi.2025.107321
Takashi Nakagawa
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.
{"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}
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.
{"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 , Khaled Roubeche , Hichem Bendjama , El-Mahdi Tikhamarine , Oualid Boulahia , Radia Kherchouche , Sofiane Taki-Eddine Rahmani , 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}
Pub Date : 2025-02-01DOI: 10.1016/j.pepi.2024.107305
Lili Feng , Weiling Zhu , Yiliang Guan , Wenjie Fan , Yingfeng Ji
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.
{"title":"A new method for extracting geomagnetic perturbation anomalies preceding the M7.4 Maduo earthquake","authors":"Lili Feng , Weiling Zhu , Yiliang Guan , Wenjie Fan , 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 km<sup>2</sup> and 112 × 104 km<sup>2</sup>, 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}
Pub Date : 2025-02-01DOI: 10.1016/j.pepi.2024.107304
Dargilan Oliveira Amorim , Tamara Gudkova
<div><div>We use estimates of Earth's tidal response at 12 frequencies (M2, Mqm, Msqm, Mtm, Mstm, SN, Mf, Msf, Mm, Msm, Ssa, Sa) to constrain the values of the Andrade parameters in Earth's mantle. The viscoelasticity and anelasticity of the planet are modeled using the Andrade rheology which depends on the frequency of the tidal forcing, the viscosity profile of Earth's interior, and two parameters (<span><math><mi>α</mi></math></span> and <span><math><mi>ζ</mi></math></span> that are unknown for planetary interiors. We compute Earth's tidal deformation and its Love numbers for the 12 mentioned frequencies, for 3 viscosity profiles, and for a total of 2850 different combinations of values of <span><math><mi>α</mi></math></span> and <span><math><mi>ζ</mi></math></span> in the ranges <span><math><mi>α</mi><mo>∈</mo><mfenced><mn>0.13,0.37</mn></mfenced></math></span> and <span><math><mi>ζ</mi><mo>∈</mo><mfenced><msup><mn>10</mn><mrow><mo>−</mo><mn>2</mn></mrow></msup><msup><mn>10</mn><mn>5</mn></msup></mfenced></math></span>.</div><div>By comparing the computed complex Love numbers <em>k</em><sub>2</sub>, <em>h</em><sub>2</sub> and <em>l</em><sub>2</sub> at each tidal frequency with their available estimates, we obtained the values of the Andrade parameters <span><math><mi>α</mi></math></span> and <span><math><mi>ζ</mi></math></span> that successfully reproduce Earth's observed anelastic behavior. Our best estimates for these parameters in Earth's interior are <span><math><mi>α</mi><mo>∈</mo><mfenced><mn>0.218</mn><mn>0.238</mn></mfenced></math></span> and <span><math><mi>ζ</mi><mo>∈</mo><mfenced><mn>0.5</mn><mn>133</mn></mfenced></math></span>. However, values within the broader ranges of <span><math><mi>α</mi><mo>∈</mo><mfenced><mn>0.200</mn><mn>0.256</mn></mfenced></math></span> and <span><math><mi>ζ</mi><mo>∈</mo><mfenced><mn>0.2</mn><mn>485</mn></mfenced></math></span> may also be suitable, with the majority of the variability stemming from uncertainties in Earth's viscosity profile. Not all combinations of <span><math><mi>α</mi></math></span> and <span><math><mi>ζ</mi></math></span> within these ranges are acceptable and every value of <span><math><mi>α</mi></math></span> has its own appropriate range of <span><math><mi>ζ</mi><mo>:</mo><mi>α</mi></math></span> values closer to the upper bound 0.256 are only suitable if 0.2<span><math><mo><</mo><mi>ζ</mi><mo><</mo><mn>20</mn></math></span>, while <span><math><mi>α</mi></math></span> values closer to the lower bound 0.2 must be accompanied by 3<span><math><mo><</mo><mi>ζ</mi><mo><</mo><mn>485</mn></math></span>.</div><div>Here we emphasize the importance of using an Andrade rheology with two free parameters when modeling planetary interiors, instead of the common practice of always setting <span><math><mi>ζ</mi><mo>=</mo><mn>1</mn></math></span>. Depending on the used viscosity profile, <span><math><mi>ζ</mi><mo>=</mo><mn>1</mn></math></span> may not adequately explain the observed
{"title":"Constraining the parameters of the Andrade rheology in Earth's mantle with Love numbers of 12 tidal constituents","authors":"Dargilan Oliveira Amorim , Tamara Gudkova","doi":"10.1016/j.pepi.2024.107304","DOIUrl":"10.1016/j.pepi.2024.107304","url":null,"abstract":"<div><div>We use estimates of Earth's tidal response at 12 frequencies (M2, Mqm, Msqm, Mtm, Mstm, SN, Mf, Msf, Mm, Msm, Ssa, Sa) to constrain the values of the Andrade parameters in Earth's mantle. The viscoelasticity and anelasticity of the planet are modeled using the Andrade rheology which depends on the frequency of the tidal forcing, the viscosity profile of Earth's interior, and two parameters (<span><math><mi>α</mi></math></span> and <span><math><mi>ζ</mi></math></span> that are unknown for planetary interiors. We compute Earth's tidal deformation and its Love numbers for the 12 mentioned frequencies, for 3 viscosity profiles, and for a total of 2850 different combinations of values of <span><math><mi>α</mi></math></span> and <span><math><mi>ζ</mi></math></span> in the ranges <span><math><mi>α</mi><mo>∈</mo><mfenced><mn>0.13,0.37</mn></mfenced></math></span> and <span><math><mi>ζ</mi><mo>∈</mo><mfenced><msup><mn>10</mn><mrow><mo>−</mo><mn>2</mn></mrow></msup><msup><mn>10</mn><mn>5</mn></msup></mfenced></math></span>.</div><div>By comparing the computed complex Love numbers <em>k</em><sub>2</sub>, <em>h</em><sub>2</sub> and <em>l</em><sub>2</sub> at each tidal frequency with their available estimates, we obtained the values of the Andrade parameters <span><math><mi>α</mi></math></span> and <span><math><mi>ζ</mi></math></span> that successfully reproduce Earth's observed anelastic behavior. Our best estimates for these parameters in Earth's interior are <span><math><mi>α</mi><mo>∈</mo><mfenced><mn>0.218</mn><mn>0.238</mn></mfenced></math></span> and <span><math><mi>ζ</mi><mo>∈</mo><mfenced><mn>0.5</mn><mn>133</mn></mfenced></math></span>. However, values within the broader ranges of <span><math><mi>α</mi><mo>∈</mo><mfenced><mn>0.200</mn><mn>0.256</mn></mfenced></math></span> and <span><math><mi>ζ</mi><mo>∈</mo><mfenced><mn>0.2</mn><mn>485</mn></mfenced></math></span> may also be suitable, with the majority of the variability stemming from uncertainties in Earth's viscosity profile. Not all combinations of <span><math><mi>α</mi></math></span> and <span><math><mi>ζ</mi></math></span> within these ranges are acceptable and every value of <span><math><mi>α</mi></math></span> has its own appropriate range of <span><math><mi>ζ</mi><mo>:</mo><mi>α</mi></math></span> values closer to the upper bound 0.256 are only suitable if 0.2<span><math><mo><</mo><mi>ζ</mi><mo><</mo><mn>20</mn></math></span>, while <span><math><mi>α</mi></math></span> values closer to the lower bound 0.2 must be accompanied by 3<span><math><mo><</mo><mi>ζ</mi><mo><</mo><mn>485</mn></math></span>.</div><div>Here we emphasize the importance of using an Andrade rheology with two free parameters when modeling planetary interiors, instead of the common practice of always setting <span><math><mi>ζ</mi><mo>=</mo><mn>1</mn></math></span>. Depending on the used viscosity profile, <span><math><mi>ζ</mi><mo>=</mo><mn>1</mn></math></span> may not adequately explain the observed ","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"359 ","pages":"Article 107304"},"PeriodicalIF":2.4,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143135235","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}
Pub Date : 2025-02-01DOI: 10.1016/j.pepi.2024.107306
Wenlong Zhou , Xiangyun Hu , Meihua Wei , Weiyang Liao , Xin Yang
Tianyang Basin, situated in Northern China, is one of the most significant geothermal fields in the region. While high-temperature geothermal resources within the basin are predominantly concentrated in its northern part, the southern region's potential remained largely unexplored. To investigate the geothermal potential in the southern part of the basin, we conducted a comprehensive magnetotelluric (MT) survey comprising 460 sites across this region. Based on the 3D MT inversion result, we constructed a detailed electrical conductivity model to reveal the deep subsurface electrical structure. The crustal structure of the study area exhibits three distinct layers: the uppermost layer comprises a low-resistance Quaternary sedimentary sequence with conductive anomalies associated characterized by clay alteration zones; the middle layer comprises a high-resistivity Archean metamorphic rock containing several low- resistivity regions (< 20 Ω·m), which are interpreted as geothermal reservoirs at depths of 1–4 km; the bottom layer, extending from 8 to 16 km depth, features a widespread low-resistance zone, potentially attributed to partial melts associated with the Datong volcanic activity, with melt content estimated ranging from 2 % to 7 %. Our investigation revealed distinct heat transfer channels between the heat source and the geothermal reservoirs, characterized by relatively low resistivity and closely correlated with concealed faults in the area. This study not only delineates the spatial distribution of the geothermal system in the southern part of the Tianyang Basin but also provides a scientific foundation for the comprehensive development and utilization of the geothermal resources in the region.
{"title":"Geothermal potential of the southern Tianyang basin, northern China, revealed by 3D inversion of magnetotelluric data","authors":"Wenlong Zhou , Xiangyun Hu , Meihua Wei , Weiyang Liao , Xin Yang","doi":"10.1016/j.pepi.2024.107306","DOIUrl":"10.1016/j.pepi.2024.107306","url":null,"abstract":"<div><div>Tianyang Basin, situated in Northern China, is one of the most significant geothermal fields in the region. While high-temperature geothermal resources within the basin are predominantly concentrated in its northern part, the southern region's potential remained largely unexplored. To investigate the geothermal potential in the southern part of the basin, we conducted a comprehensive magnetotelluric (MT) survey comprising 460 sites across this region. Based on the 3D MT inversion result, we constructed a detailed electrical conductivity model to reveal the deep subsurface electrical structure. The crustal structure of the study area exhibits three distinct layers: the uppermost layer comprises a low-resistance Quaternary sedimentary sequence with conductive anomalies associated characterized by clay alteration zones; the middle layer comprises a high-resistivity Archean metamorphic rock containing several low- resistivity regions (< 20 Ω·m), which are interpreted as geothermal reservoirs at depths of 1–4 km; the bottom layer, extending from 8 to 16 km depth, features a widespread low-resistance zone, potentially attributed to partial melts associated with the Datong volcanic activity, with melt content estimated ranging from 2 % to 7 %. Our investigation revealed distinct heat transfer channels between the heat source and the geothermal reservoirs, characterized by relatively low resistivity and closely correlated with concealed faults in the area. This study not only delineates the spatial distribution of the geothermal system in the southern part of the Tianyang Basin but also provides a scientific foundation for the comprehensive development and utilization of the geothermal resources in the region.</div></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"359 ","pages":"Article 107306"},"PeriodicalIF":2.4,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143135236","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}
Pub Date : 2025-01-31DOI: 10.1016/j.pepi.2025.107314
Emilio Herrero-Bervera , Brian R. Jicha
New paleomagnetic measurements, coupled with 40Ar/39Ar dating of terrestrial lava sequences, are revolutionizing our understanding of the geodynamo by providing high resolution records of the paleomagnetic field. As part of an investigation of the short-term behavior of the geomagnetic field, we performed detailed sampling of ten cooling units of the Kaupo vent belonging to the Honolulu Volcanic series of the Koolau Volcano, Oahu Hawaii. At least eight samples, collected from each of 10 successive cooling units at Kaupo, were stepwise demagnetized by both alternating field (5 mT to 100 mT) and thermal (from 28 °C to 575–650 °C) methods. Mean directions were obtained by principal component analysis. All samples yielded a strong and stable ChRM trending towards the origin of vector demagnetization diagrams based on seven or more demagnetization steps, with thermal and AF results differing insignificantly. Low-field susceptibility vs. temperature (k–T) analysis conducted on individual lava flows indicated approximately half with reversible curves. Curie point determinations from these analyses revealed a temperature close to or equal to 580 °C, indicative of almost pure magnetite ranging from single domain (SD) to pseudo-single domain (PSD) grain sizes for most of the flows. The mean directions of magnetization of the entire section sampled indicate a normal polarity, with ∼10 m of the section characterized by excursional directions (∼6 cooling units). Paleomagnetic investigations revealed a series of excursional directions. Absolute paleointensity determinations were performed by means of the modified Thellier-Coe protocol, the most salient results indicate absolute P.I. as low as ∼26.9 μ-Teslas (VADM 5.887 × 1022 Am2) (i.e. 22° Lat. North) and as high as ∼87.2 μ-Teslas (VADM 19.082 × 1022 Am2) at high latitudes (i.e. 87° Lat. North). The results of both the directional results (i.e. Declination, Inclination and VGPs) of the 10 cooling units in question in general terms correlate well to the GAD (i.e. +38°). The Kaupo flow VGPs are located over the eastern part of Asia (i.e. over Japan and Korea) 40Ar/39Ar ages from multiple flows give a weighted mean of 64.2±2.7 ka, which correlates well with the Norwegian-Greenland Sea excursion recorded in sediments.
{"title":"First terrestrial geomagnetic record of the Norwegian-Greenland Sea excursion in the Kaupo flow, Koolau volcano, Oahu, Hawaii: Insights from 40Ar/39Ar, NRM and absolute paleointensity determinations","authors":"Emilio Herrero-Bervera , Brian R. Jicha","doi":"10.1016/j.pepi.2025.107314","DOIUrl":"10.1016/j.pepi.2025.107314","url":null,"abstract":"<div><div>New paleomagnetic measurements, coupled with <sup>40</sup>Ar/<sup>39</sup>Ar dating of terrestrial lava sequences, are revolutionizing our understanding of the geodynamo by providing high resolution records of the paleomagnetic field. As part of an investigation of the short-term behavior of the geomagnetic field, we performed detailed sampling of ten cooling units of the Kaupo vent belonging to the Honolulu Volcanic series of the Koolau Volcano, Oahu Hawaii. At least eight samples, collected from each of 10 successive cooling units at Kaupo, were stepwise demagnetized by both alternating field (5 mT to 100 mT) and thermal (from 28 °C to 575–650 °C) methods. Mean directions were obtained by principal component analysis. All samples yielded a strong and stable ChRM trending towards the origin of vector demagnetization diagrams based on seven or more demagnetization steps, with thermal and AF results differing insignificantly. Low-field susceptibility vs. temperature (k–T) analysis conducted on individual lava flows indicated approximately half with reversible curves. Curie point determinations from these analyses revealed a temperature close to or equal to 580 °C, indicative of almost pure magnetite ranging from single domain (SD) to pseudo-single domain (PSD) grain sizes for most of the flows. The mean directions of magnetization of the entire section sampled indicate a normal polarity, with ∼10 m of the section characterized by excursional directions (∼6 cooling units). Paleomagnetic investigations revealed a series of excursional directions. Absolute paleointensity determinations were performed by means of the modified Thellier-Coe protocol, the most salient results indicate absolute P.I. as low as ∼26.9 μ-Teslas (VADM 5.887 × 10<sup>22</sup> Am<sup>2</sup>) (i.e. 22° Lat. North) and as high as ∼87.2 μ-Teslas (VADM 19.082 × 10<sup>22</sup> Am<sup>2</sup>) at high latitudes (i.e. 87° Lat. North). The results of both the directional results (i.e. Declination, Inclination and VGPs) of the 10 cooling units in question in general terms correlate well to the GAD (i.e. +38°). The Kaupo flow VGPs are located over the eastern part of Asia (i.e. over Japan and Korea) <sup>40</sup>Ar/<sup>39</sup>Ar ages from multiple flows give a weighted mean of 64.2±2.7 ka, which correlates well with the Norwegian-Greenland Sea excursion recorded in sediments.</div></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"362 ","pages":"Article 107314"},"PeriodicalIF":2.4,"publicationDate":"2025-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143642227","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}
Pub Date : 2025-01-25DOI: 10.1016/j.pepi.2025.107315
D. Andrault, L. Pison Pacynski, J. Monteux, E. Gardés, A. Mathieu
We do not know precisely whether powering a planetary magnetic field is a common or rare feature of Earth-like planets, and for how many billion years it should likely be operating. If planetary dynamos should be driven by internal heat flow essentially (i.e. thermally driven dynamo, TDD), the answer relies on the energy budget of the planetary interior. On Earth, the Moon-forming impact provided a lot of energy ∼4.5 billion years ago and the magnetic field remains strong until present. Despite extensive work on this subject, the controversial nature of the outer-core's thermal conductivity (kCond) makes the energy budget of the core open to discussions. Here we present new experimental constraints on the evolution of kCond with pressure from 22 to 150 GPa and temperature from 1050 to 2700 K. kCond is obtained by numerical modeling of the mechanism of propagation of a short heat pulse through a thin foil of iron loaded, compressed and heated in the laser-heated diamond anvil cell. With good coverage of large P-T domains, the accuracy of our measurements enables an accurate modeling of kCond as a function of the molar volume of Fe and temperature. We refine a value of 37(5) W/m/K at P-T conditions found at the Earth core-mantle boundary (CMB). If the geodynamo should be TDD essentially, this implies CMB cooling by 380–450 K over the entire Earth history and an inner core 1.9(4) billion years old. By comparing the mantle efficiency to extract heat at the CMB with the power requirement to sustain a TDD, we show that the geodynamo is unlikely to stop until the Earth's core is solidified. This effect comes from a decreasing power requirement to generate the dynamo with decreasing the temperature at the CMB. Now applying our P-T dependent kCond model to terrestrial planets with various external radii and fractions of silicate and metal, we show that the core size is a critical parameter. For a core smaller than a critical size, mantle convection induces a sufficient CMB heat flow to enable a TDD. This can explain absence of dynamo on Mars and possibly on Venus also if its core would be relatively large. Calculations show that exoplanets 1.5 times heavier than the Earth are unlikely to present an alive TDD, especially if they present large bulk densities. In contrast, the small exoplanets reported to date could host a TDD.
{"title":"Long-lived magnetic field in earth-like terrestrial planets","authors":"D. Andrault, L. Pison Pacynski, J. Monteux, E. Gardés, A. Mathieu","doi":"10.1016/j.pepi.2025.107315","DOIUrl":"10.1016/j.pepi.2025.107315","url":null,"abstract":"<div><div>We do not know precisely whether powering a planetary magnetic field is a common or rare feature of Earth-like planets, and for how many billion years it should likely be operating. If planetary dynamos should be driven by internal heat flow essentially (i.e. thermally driven dynamo, TDD), the answer relies on the energy budget of the planetary interior. On Earth, the Moon-forming impact provided a lot of energy ∼4.5 billion years ago and the magnetic field remains strong until present. Despite extensive work on this subject, the controversial nature of the outer-core's thermal conductivity (<em>k</em><sub><em>Cond</em></sub>) makes the energy budget of the core open to discussions. Here we present new experimental constraints on the evolution of <em>k</em><sub><em>Cond</em></sub> with pressure from 22 to 150 GPa and temperature from 1050 to 2700 K. <em>k</em><sub><em>Cond</em></sub> is obtained by numerical modeling of the mechanism of propagation of a short heat pulse through a thin foil of iron loaded, compressed and heated in the laser-heated diamond anvil cell. With good coverage of large P-T domains, the accuracy of our measurements enables an accurate modeling of <em>k</em><sub><em>Cond</em></sub> as a function of the molar volume of Fe and temperature. We refine a value of 37(5) W/m/K at P-T conditions found at the Earth core-mantle boundary (CMB). If the geodynamo should be TDD essentially, this implies CMB cooling by 380–450 K over the entire Earth history and an inner core 1.9(4) billion years old. By comparing the mantle efficiency to extract heat at the CMB with the power requirement to sustain a TDD, we show that the geodynamo is unlikely to stop until the Earth's core is solidified. This effect comes from a decreasing power requirement to generate the dynamo with decreasing the temperature at the CMB. Now applying our P-T dependent <em>k</em><sub><em>Cond</em></sub> model to terrestrial planets with various external radii and fractions of silicate and metal, we show that the core size is a critical parameter. For a core smaller than a critical size, mantle convection induces a sufficient CMB heat flow to enable a TDD. This can explain absence of dynamo on Mars and possibly on Venus also if its core would be relatively large. Calculations show that exoplanets 1.5 times heavier than the Earth are unlikely to present an alive TDD, especially if they present large bulk densities. In contrast, the small exoplanets reported to date could host a TDD.</div></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"360 ","pages":"Article 107315"},"PeriodicalIF":2.4,"publicationDate":"2025-01-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143150396","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}
Pub Date : 2025-01-07DOI: 10.1016/j.pepi.2024.107303
Chris A. Jones , Yue-Kin Tsang
Convection driven geodynamo models in rotating spherical geometry have regimes in which reversals occur. However, reversing dynamo models are usually found in regimes where the kinetic and magnetic energy is comparable, so that inertia is playing a significant role in the core dynamics. In the Earth's core, the Rossby number is very small, and the magnetic energy is much larger than the kinetic energy. Here we investigate dynamo models in the strong-field regime, where magnetic forces have a significant effect on convection. In the core, the strong field is achieved by having the magnetic Prandtl number small, but the Ekman number extremely small. In simulations, very small is not possible, but the strong-field regime can be reached by increasing . However, if is raised while the fluid Prandtl number is fixed at unity, the most common choice, the Péclet number becomes small, so that the linear terms in the heat (or composition) equation dominate, which is also far from Earth-like behaviour. Here we increase and together, so that nonlinearity is important in the heat equation and the dynamo is strong-field. We find that Earth-like reversals are possible at numerically achievable parameter values, and the simulations have Earth-like magnetic fields away from the times at which it reverses. The magnetic energy is much greater than the kinetic energy except close to the reversal times.
{"title":"Low inertia reversing geodynamos","authors":"Chris A. Jones , Yue-Kin Tsang","doi":"10.1016/j.pepi.2024.107303","DOIUrl":"10.1016/j.pepi.2024.107303","url":null,"abstract":"<div><div>Convection driven geodynamo models in rotating spherical geometry have regimes in which reversals occur. However, reversing dynamo models are usually found in regimes where the kinetic and magnetic energy is comparable, so that inertia is playing a significant role in the core dynamics. In the Earth's core, the Rossby number is very small, and the magnetic energy is much larger than the kinetic energy. Here we investigate dynamo models in the strong-field regime, where magnetic forces have a significant effect on convection. In the core, the strong field is achieved by having the magnetic Prandtl number <span><math><mi>Pm</mi></math></span> small, but the Ekman number <span><math><mi>E</mi></math></span> extremely small. In simulations, very small <span><math><mi>E</mi></math></span> is not possible, but the strong-field regime can be reached by increasing <span><math><mi>Pm</mi></math></span>. However, if <span><math><mi>Pm</mi></math></span> is raised while the fluid Prandtl number <span><math><mo>Pr</mo></math></span> is fixed at unity, the most common choice, the Péclet number becomes small, so that the linear terms in the heat (or composition) equation dominate, which is also far from Earth-like behaviour. Here we increase <span><math><mo>Pr</mo></math></span> and <span><math><mi>Pm</mi></math></span> together, so that nonlinearity is important in the heat equation and the dynamo is strong-field. We find that Earth-like reversals are possible at numerically achievable parameter values, and the simulations have Earth-like magnetic fields away from the times at which it reverses. The magnetic energy is much greater than the kinetic energy except close to the reversal times.</div></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"360 ","pages":"Article 107303"},"PeriodicalIF":2.4,"publicationDate":"2025-01-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143150397","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}
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