Physics of the Earth and Planetary Interiors最新文献

{"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}

{"title":"Geothermal potential of the southern Tianyang basin, northern China, revealed by 3D inversion of magnetotelluric data","authors":"Wenlong Zhou ,&nbsp;Xiangyun Hu ,&nbsp;Meihua Wei ,&nbsp;Weiyang Liao ,&nbsp;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 (&lt; 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}

{"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 ,&nbsp;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 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.</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}

{"title":"Long-lived magnetic field in earth-like terrestrial planets","authors":"D. Andrault,&nbsp;L. Pison Pacynski,&nbsp;J. Monteux,&nbsp;E. Gardés,&nbsp;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>_{<em>Cond</em>}) makes the energy budget of the core open to discussions. Here we present new experimental constraints on the evolution of <em>k</em>_{<em>Cond</em>} with pressure from 22 to 150 GPa and temperature from 1050 to 2700 K. <em>k</em>_{<em>Cond</em>} 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>_{<em>Cond</em>} 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>_{<em>Cond</em>} 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}

{"title":"Low inertia reversing geodynamos","authors":"Chris A. Jones ,&nbsp;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}

{"title":"Physics-informed neural networks for the improvement of platform magnetometer measurements","authors":"Kevin Styp-Rekowski ,&nbsp;Ingo Michaelis ,&nbsp;Monika Korte ,&nbsp;Claudia Stolle","doi":"10.1016/j.pepi.2024.107283","DOIUrl":"10.1016/j.pepi.2024.107283","url":null,"abstract":"<div><div>High-precision space-based measurements of the Earth's magnetic field with a good spatiotemporal coverage are needed to analyze the complex system of our surrounding geomagnetic field. Dedicated magnetic field satellite missions like the Swarm mission form the backbone of research, providing high-precision data with limited coverage. Many satellites carry so-called platform magnetometers that are part of their attitude and orbit control systems. These can be re-calibrated by considering different behaviors of the satellite system, hence reducing their relatively high initial noise originating from their rough calibration. These platform magnetometer data obtained from satellite missions not dedicated to geomagnetic fields complement high-precision data from the Swarm mission by additional coverage in space, time, and magnetic local times. In this work, we present an extension to a previous machine learning approach for automatic in-situ calibration of platform magnetometers. We introduce a new physics-informed layer incorporating the Biot-Savart formula for dipoles that can efficiently correct artificial disturbances due to electric current-induced magnetic fields evoked by the satellite itself. We demonstrate how magnetic dipoles can be co-estimated in a neural network for the calibration of platform magnetometers and thus enhance the machine learning-based approach to follow known physical principles. Here, we describe the derivation and assessment of re-calibrated datasets for two satellite missions, GOCE and GRACE-FO, which are made publicly available. Compared to the reference model, we achieved an average residual of about 7 nT for the GOCE mission and 4 nT for the GRACE-FO mission across all three components combined in the low- and mid-latitudes.</div></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"358 ","pages":"Article 107283"},"PeriodicalIF":2.4,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143161727","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":"Pebble accretion and siderophile element partitioning between Earth's mantle and core","authors":"Peter L. Olson,&nbsp;Zachary D. Sharp,&nbsp;Susmita Garai","doi":"10.1016/j.pepi.2024.107295","DOIUrl":"10.1016/j.pepi.2024.107295","url":null,"abstract":"<div><div>Pebble accretion is an efficient mechanism for early terrestrial protoplanet growth and differentiation. Metal-silicate partitioning of moderately siderophile elements offers constraints on the role of pebble accretion in Earth's formation and the segregation of its core. Here, we determine pebble accretion properties of the proto-Earth that are consistent with metal-silicate partitioning measurements and siderophile abundances in the mantle and core. We combine a pebble accretion model that includes mass balances for siderophile abundances in the mantle and core of a growing terrestrial protoplanet with experimentally-determined partition functions for seven moderately siderophile elements: Ni, Co, V, Cr, Mo, Mn, and W. Mantle and core abundances of these elements during pebble accretion are calculated, as well as changes to their abundances following the addition of large and giant impactors built with pebbles. Model results are compared to the estimated abundances of these elements in Earth's primitive mantle and core. We find that metal-silicate partitioning of these elements is especially sensitive to the total mass of accreted pebbles. Best fits to primitive mantle and core siderophile abundances are found in cases where the proto-Earth accreted with pebbles to approximately 0.6 times its present mass under slightly reducing conditions, then added the remaining mass via one or more impactors with the same composition. We also find that pebbles consisting of chondritic components (chondrules, metal grains, AOAs, and CAIs) generally yield better partitioning results compared to pebbles made from chondrites.</div></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"358 ","pages":"Article 107295"},"PeriodicalIF":2.4,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143161726","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 method for simultaneously determining Earth's magnetic field and mantle conductivity models using MSS-1 and Swarm satellite magnetic data","authors":"Hongbo Yao,&nbsp;Juyuan Xu,&nbsp;Keke Zhang","doi":"10.1016/j.pepi.2024.107296","DOIUrl":"10.1016/j.pepi.2024.107296","url":null,"abstract":"<div><div>The magnetospheric primary and its Earth mantle-induced fields are essential components of geomagnetic field models. Previous geomagnetic field modeling methods typically use a fixed <em>a priori</em> Earth's mantle conductivity model to account for the induced field. This treatment may reduce accuracy, as electromagnetic induction depends on conductivity models. Here, we propose a new method that simultaneously determines the mantle conductivity model during geomagnetic field modeling. This method has the advantages of (i) self-consistently accounting for the induced field in geomagnetic field modeling, and (ii) simultaneously providing valuable information on Earth's internal structure. We implement the method into a new computationally parallel field modeling framework, which scales nearly linearly up to a large number of MPI cores. The Macau Science Satellite-1 (MSS-1), primarily aiming to accurately measure the Earth's magnetic field, was successfully launched on May 21, 2023. We apply our method to the magnetic data from MSS-1 as well as Swarm satellites and obtain the first self-consistent models of Earth's magnetic field and mantle conductivity. We also investigate how different conductivity models affect geomagnetic field modeling. Our results show that a fixed <em>a priori</em> conductivity model introduces field differences of about 2–4 nT in magnetic field models. These field differences, which are larger than the measuring accuracy of modern geomagnetic satellites, can be avoided by our method.</div></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"358 ","pages":"Article 107296"},"PeriodicalIF":2.4,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143161725","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":"Late-stage Deccan eruption from multiple shallow magma chambers through vertical flow along fissures: Insights from magnetic fabric analysis of the Pachmarhi dyke swarm","authors":"Garima Shukla ,&nbsp;Jyotirmoy Mallik ,&nbsp;Yadav Krishna ,&nbsp;Sayandeep Banerjee","doi":"10.1016/j.pepi.2024.107285","DOIUrl":"10.1016/j.pepi.2024.107285","url":null,"abstract":"<div><div>The Pachmarhi dyke swarm, located in the eastern part of the Narmada-Satpura-Tapi dykes belonging to the Deccan Continental Flood Basalt, are studied using the Anisotropy of Magnetic Susceptibility (AMS) technique. This research aims to determine the direction and sense of magma flow within the dykes, providing insights into the depth, number, and location of magma chambers, as well as the geodynamics of their plumbing system. Petrography and rock magnetism analyses revealed a mixture of high- and low-titanium magnetite particles, predominantly of pseudo-single domain nature (with a smaller proportion of multi-domain dominated) grains are primary remanence carriers. We identified four distinct types of magnetic fabric (I-IV) within the Pachmarhi dykes. The K₁-axis being parallel to the dyke plane, and the intersection of the imbrication angle of magnetic foliation (for oblate fabric) and magnetic lineation (for prolate fabric) was used to discern the direction of magma flow. This analysis revealed multiple trends of magma flow, ranging from vertical/sub-vertical to inclined. The flow fabric provides valuable information about the presence of multiple shallow sub-crustal magma chambers. This interpretation aligns with prior independent gravity and 3-D density modelling studies, which indicates the presence of dense mafic magma bodies at depths of 4 to 8 km along the Narmada-Tapi intraplate rift zone. These findings are similar to those observed in the Nandurbar-Dhule dyke swarms in the western region of the Narmada-Satpura-Tapi dykes. Consequently, we can infer that the emplacement of dykes in the Pachmarhi region of the Narmada-Son-Lineament, which likely served as feeders for the late-stage Deccan volcanism, was primarily facilitated by a “polycentric flow” mechanism. In this process, magma was injected vertically from multiple shallow magma chambers through crustal fissures, potentially feeding into the late-stage Deccan flow units, such as the Ambenali or Mahabaleshwar Formations.</div></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"357 ","pages":"Article 107285"},"PeriodicalIF":2.4,"publicationDate":"2024-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142746542","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":"Mechanisms of seismic attenuation beneath Bhutan Himalaya","authors":"Abhisek Dutta ,&nbsp;Rahul Biswas ,&nbsp;Chandrani Singh","doi":"10.1016/j.pepi.2024.107279","DOIUrl":"10.1016/j.pepi.2024.107279","url":null,"abstract":"<div><div>We have analyzed 614 high quality local earthquake (1.5 <span><math><mo>≤</mo></math></span><span><math><msub><mi>M</mi><mi>l</mi></msub></math></span> (local magnitude) <span><math><mo>≤</mo></math></span> 5.5) data recorded by temporary GANSSER network of 44 broadband stations to investigate the attenuation mechanism of Bhutan Himalaya. Initially, the single isotropic scattering model is applied to study the coda wave attenuation (<span><math><msubsup><mi>Q</mi><mi>c</mi><mrow><mo>−</mo><mn>1</mn></mrow></msubsup></math></span>). Subsequently, we have used the Multiple Lapse Time Window Analysis (MLTWA) to estimate the relative contribution of scattering (<span><math><msubsup><mi>Q</mi><mi>sc</mi><mrow><mo>−</mo><mn>1</mn></mrow></msubsup></math></span>) and intrinsic (<span><math><msubsup><mi>Q</mi><mi>i</mi><mrow><mo>−</mo><mn>1</mn></mrow></msubsup></math></span>) attenuation to the total attenuation (<span><math><msubsup><mi>Q</mi><mi>t</mi><mrow><mo>−</mo><mn>1</mn></mrow></msubsup></math></span>) under the assumption of multiple isotropic scattering with uniform half space medium. The analysis has been carried out for five different central frequencies within the range of 1.5 to 18 Hz. All the estimated values of <span><math><mi>Q</mi></math></span> exhibit high frequency dependent nature. Interestingly, scattering attenuation is found to be the dominant factor attenuating the seismic waves in the crust of Bhutan Himalaya which is different from the rest of the Himalayas except Garwhal–Kumaun Himalaya and the adjacent Sikkim Himalaya. This strongly suggests that the relative role of both scattering and intrinsic attenuation varies across the Himalaya and is likely to be associated with the structural variabilities among different segments. The role of Main Himalayan Thrust (<span><math><mi>MHT</mi></math></span>) in changing the differential stress regime across the region could be the major cause of the intra-crustal deformation which resulted in the predominance of scattering attenuation in the crust of Bhutan Himalaya.</div></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"357 ","pages":"Article 107279"},"PeriodicalIF":2.4,"publicationDate":"2024-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142705628","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}