JGR–Solid Earth

Aqueous fluids are extensively present in the middle to lower crust, as revealed by seismic and magnetotelluric soundings. The α−β quartz phase transition significantly affects many physical properties and leads to substantial microcracks that can provide pathways for the migration of crustal fluids. A systematic investigation of macroscopic physical properties and microstructure of quartz is crucial to elucidate their correlation. In the present study, the effects of water content, trace elements, orientations, and phase transition on the electrical conductivity of quartz were thoroughly evaluated at 400−900°C and 1 GPa. Individual annealing experiments were simultaneously conducted on quartz single crystals at different peak temperatures and 1 GPa to investigate the evolution and spatial distribution of microcracks using X-ray microtomography (CT) and backscattered electron imaging. We found that trace element content and orientations, rather than H2O, are the dominant factors controlling the conductivity of quartz. The distinct changes in conductivity of single crystals at around α−β phase transition temperature are attributed to the transformation of microcracks from isolated to interconnected networks, as confirmed by two-dimensional (2-D) and three-dimensional (3-D) microstructure images. Based on the variation in electrical conductivity and microstructure across the transition, it thus is proposed that the intragranular microcracks caused by quartz phase transition can serve as fluid or melt pathways within highly conductive zones present in the middle to lower crust, while α-quartz acts as an impermeable cap.

Distributed acoustic sensing (DAS) has emerged as a promising seismic technology for monitoring microearthquakes (MEQs) with high spatial resolution. Efficient algorithms are needed for processing large DAS data volumes. This study introduces a deep learning (DL) model based on a Residual Convolutional Neural Network (ResNet) for detecting MEQs using DAS data, named as DASEventNet. The test data were collected from the Utah FORGE 16A (78)-32 hydraulic stimulation experiments conducted in April 2022. The DASEventNet model achieves a remarkable accuracy of 100% when discriminating MEQs from noise in the raw test set of 260 examples. Surprisingly, the model identified weak MEQ signatures that have been manually categorized as noise. The decision-making process with the model is decoded by the classic activation map, which illuminates learning features of the DASEventNet model. These features provide clear illustrations of weak MEQs and varied noise types. Finally, we apply the trained model to the entire period (∼7 days) of continuous DAS recordings and find that it discovers >5,700 new MEQs, previously unregistered in the public Silixa DAS catalog. The DASEventNet model significantly outperforms the traditional seismic method Short-Term Average/Long-Term Average (STA/LTA), which detected only 1,307 MEQs. The DASEventNet detection threshold is M w −1.80 compared to the minimum magnitude of M w −1.14 detected by STA/LTA. The spatiotemporal distribution of the newly identified MEQs defines an extensive stimulation zone and more accurately characterizes fracture geometry. Our results highlight the potential of DL for long-term, real-time microseismic monitoring that can improve enhanced geothermal systems and other activities that include subsurface hydraulic fracturing.

We study how the normal stiffness and the permeability of a realistic rough fracture at the field scale are linked and evolve during its closure up to the percolation threshold. We base our approach on a well-established self-affine geometric model for fracture roughness, which has proven to be a relevant proxy from laboratory to multi-kilometer scales. We explore its implications for fracture apertures in reservoir-scale open channels. We build our approach on a finite element model using the MOOSE/GOLEM framework and conduct numerical flow-through experiments in a 256×256× $256\times 256\times $ 256 m3 ${\mathrm{m}}^{3}$ granite reservoir hosting a single, partially sealed fracture under variable normal loading conditions and undrained conditions. Navier-Stokes flow is solved in the embedded 3-dimensional rough fracture, and Darcy flow is solved in the surrounding poroelastic matrix. We study the evolution of the mechanical stiffness and fluid permeability of the fracture-rock system during fracture closure including mechanisms that impact the contact surface geometry like asperity yield and deposit of fracture-filling material in the open space of the rough fracture. The largely observed stiffness characteristic is shown to be related to the self-affine property of the fracture surface. A strong anisotropy of the fracture permeability is evidenced when the fluid percolation thresholds are exceeded in two orthogonal directions of the imposed pressure gradient. We propose a unifying physically based law for the evolution of stiffness and permeability in the form of an exponential increase in stiffness as permeability decreases.

We develop a 3D full waveform inversion (FWI) method based on dynamic time warping (DTW) to address the issue of cycle-skipping, which can prohibit the convergence of conventional FWI methods. DTW globally compares data samples at different time steps in 2D matrices against the time shifts of waveforms. We introduce the concept of shape descriptors into softDTW, creating a soft-shapeDTW objective function within our waveform inversion process to improve alignment accuracy. Additionally, including constraints from Sakoe-Chiba bands in the inversion further enhances efficiency and overall performance. A synthetic test has shown that the soft-shapeDTW inversion outperforms conventional waveform inversions in overcoming the cycle-skipping challenges that arise from poor initial models. This method was applied to fit observed seismograms to reveal western Yunnan's crustal structure. Seismic waveforms were recorded by 88 broadband stations from 10 local earthquakes, which were then denoised using a continuous wavelet transform method. Generalized cut and paste waveform inversions were used to determine the source parameters of these seismic events. Our inversion well-aligned various seismic phases in the selected time windows of seismograms, and the resolved velocity models well associate with local geological structure. Results suggest that the soft-shapeDTW inversion offers a robust alternative to FWI, reducing the reliance on accurate starting models.

The 2022 eruption at Mauna Loa, Hawai'i, marked the first extrusive activity from the volcano after 38 years of quiescence. The eruption was preceded by several years of seismic unrest in the vicinity of the volcano's summit. Characterizing the structure and dynamics of seismogenic features within Mauna Loa during this pre-eruptive interval may provide insights into how pre- and co-eruptive processes manifest seismically at the volcano. In particular, the extent to which seismicity may be used to forecast the location and timing of future eruptions is unclear. To address these questions, we construct a catalog of relocated seismicity on Mauna Loa spanning 2011–2023. Our earthquake locations image complex, sub-kilometer-scale seismogenic structures in the caldera and southwest rift zone. We additionally identify a set of streaks of seismicity in the volcano's northwest flank that are radially oriented about the summit. Using a rate-and-state friction model for earthquake occurrences, we demonstrate that the seismicity rate in this region can be modeled as a function of the stressing history caused by magma accumulation beneath the summit. Finally, we observe a mid-2019 step change in the seismicity rate in the Ka'oiki region that may have altered the stress state of the northeast rift zone in the three years before the eruption. Our observations provide a framework for interpreting future seismic unrest at Mauna Loa.

The understanding of the velocity structure and basement morphology within the basin is crucial for seismic hazard mitigation and the study of basin evolution. To explore the intricate structure of the Binchuan Basin in western Yunnan, China, we deployed a linear dense array in the northern region of the Binchuan Basin, with inter-station distance ranging from 50 to 100 m. We propose a novel receiver function processing workflow. Initially, we extracted coherent receiver functions based on the dense array, followed by a inversion of basement morphology, S-wave velocities, and sedimentary layer's average V p /V s ratio jointly with frequency-dependent teleseismic apparent shear velocity and receiver function waveforms. The results show that S-wave velocity anomalies correspond to the unconsolidated sediments. The thickness of the sedimentary layer ranges from ∼0.5 to ∼0.75 km. The basement morphology suggests the basin is controlled by normal faults. Additionally, intra-basin faults displayed higher fault displacement to length ratios (∼0.27) than most isolated normal faults (10−3–10−1), which may result from accumulated fault displacement due to interactions between fault segments. These results emphasize the significant role of N–S trending intra-basin faults in basin evolution, suggesting that micro-block rotations and transitional movements within the Northwestern Yunnan Rift Zone are primary mechanisms shaping the Binchuan Basin. We further proposed a multi-stage model for the evolution of the Binchuan Basin. The robustness testing validates that the proposed processing flow is an effective approach to comprehensively image the basin velocity structure and the basement morphology.

Earth possesses a Poincaré mode called Free Core Nutation (FCN) due to the misalignment of the rotation axes of the mantle and fluid outer core. FCN is the primary signal in the observations of Celestial Pole Offsets (CPO) and maintained by geophysical mechanisms that are yet to be understood. Earlier studies suggested an origin in Atmospheric Angular Momentum (AAM)—and to a lesser degree Oceanic Angular Momentum (OAM)—but discrepancies between these geophysical excitations and the geodetic (CPO-based) excitation were too large to reach definite conclusions. Here we use newly calculated, 3-hourly AAM and OAM series for the 1994–2022 period, in conjunction with the latest CPO series from the International Earth Rotation and Reference Systems Service (IERS 20 C04 series), to demonstrate a markedly lower power ratio (∼ ${\sim} $4.6) of geophysical over geodetic excitation at the FCN frequency compared to previous works (ratio ∼ ${\sim} $10). Among all excitation sources, the AAM pressure term exhibits the highest coherence (0.56) and correlation (0.48) with the geodetic excitation, whereas the coherence with OAM is smaller by a factor of 3. Similar analyses using existing angular momentum series give comparable, albeit smaller coherence and correlation results. We attribute the relevant AAM pressure term signal to Northern Hemispheric landmasses and further show consistent temporal variations in the amplitude of geophysical and geodetic excitations around the FCN band. Our results thus corroborate evidence for large-scale atmospheric mass redistribution to be the main cause of continuous FCN excitation.

At ultra-slow spreading ridges, with full spreading rates less than ∼20 mm/yr, spreading is accommodated both by highly spatially and temporally segmented magmatism, and tectonic extension along large-scale detachment faults that exhume ultramafic material to the seafloor. In the most magma-poor regions, detachment faulting alternates in polarity over time, producing a “flip-flopping” effect of subsequent detachment dips. The resulting seafloor in these regions displays a morphology termed “smooth seafloor” comprising elongate, broad ridges with peridotite/serpentinite lithologies. We conducted tomographic travel-time inversion of a 3-D wide-angle seismic data set acquired over a region of smooth seafloor around 64°30′E along the Southwest Indian Ridge (SISMOSMOOTH; Cruise MD199), to produce a seismic velocity volume through the crustal section and into the uppermost mantle. We observe patterns of velocity anomalies that correspond with variations in the bathymetry arising from the mode of spreading and are interpreted as changes in the degree of alteration with depth resulting from spatial and temporal variations in fluid-rock interaction, controlled by faulting and tectonic damage processes. The detachment faults do not show simple planar structures at depth but instead mirror the shapes of the bathymetric ridges that they exhume. Magmatic input is overall highly limited, but there is one region on the lower part of an exhumed detachment footwall where a thickness of volcanic material is observed that suggests a component of syn-tectonic volcanism, which could contribute to detachment abandonment.

Body waves traversing the Earth's interior from a seismic source to receivers on the surface carry rich information about its internal structures. Their travel time measurements have been widely used in seismology to constrain Earth's interior at the global scale by mapping the time anomaly along their ray paths. However, picking the travel time of global seismic waves, suitable for studying Earth's fine-scale structures, requires highly skilled personnel and is often fairly subjective. Here, we report the development of an automatic picker for PKIKP waves traveling through the inner core (IC), especially nearly along Earth's diameters, based on the latest advances in supervised deep learning. A convolutional neural network (CNN) we develop automatically determines the PKIKP onset on vertical seismograms near its theoretical prediction of cataloged earthquakes. As high-quality manual onset picks of global seismic phases are limited, we employ a scheme to generate a synthetic supervised training data set containing 300,000 waveforms. The PKIKP onsets picked by our trained CNN automatic picker exhibit a mean absolute error of ∼0.5 s compared to 1,503 manual picks, comparable to the estimated human-picking error. In an integration test, the automatic picks obtained from an extended waveform data set yield a cylindrically anisotropic IC model that agrees well with the models inferred from manual picks, which illustrates the success of this pilot model. This is a significant step closer to harvesting an unprecedented volume of travel time measurements for studying the IC or other regions of the Earth's deep interior.

Models of active deformation of the Earth's crust are predominantly represented with dislocations having a downdip continuation into the lower crust, where the fault slips continuously. This model predicts surface strain accumulation concentrated near the fault during the interseismic period. In an alternative model, faults do not extend beneath the elastic portion of the crust and are accompanied by a wide zone of distributed shear underneath, predicting a more constant strain rate lacking concentrations at the faults. We use high-precision GPS data collected across the northern and central Walker Lane, USA— a region of complex faulting near the western edge of the Basin and Range Province to evaluate which model is appropriate. Despite the existence of dense continuous and semi-continuous geodetic networks that have been surveyed for ∼20 years, the horizontal velocities reveal no evidence of localized strain accumulation across the fault surface expressions. Instead, deformation within the Walker Lane is uniformly linear, suggesting that the surface deformation reflects distributed shear within the ductile crust rather than focused deformation at faults. This suggests no downdip extension of the faults below the seismogenic layer. The shear zone is 172 ± 6 km wide in the northernmost Walker Lane narrowing to 116 ± 4 km in the central Walker Lane. The total velocity budget across the shear zone is 7.2 ± 0.1 mm/yr in the north, increasing to 10.1 ± 0.1 mm/yr in the central Walker Lane. We conclude that assuming the presence of lower crustal dislocations when estimating geodetic faults slip rates may be inappropriate.

The eastward extrusion of the Tibetan Plateau materials has caused intricate tectonic deformations and frequent seismic activities in the Sanjiang lateral collision zone (SLCZ). To reveal crust structures and deformation mechanisms, we investigate high-resolution structural features of crustal depth (≤40 km). A 3-D S-wave velocity and azimuthal anisotropy model is constructed by the direct tomography method with Rayleigh phase velocity at periods of 2–40 s from multiple temporary seismic arrays and regional permanent network. In the middle-to-lower crust, an obvious low-velocity zone is confined by the large-scale fault systems of Jinhe-Qinghe fault and Chenhai fault (CHF) to the northeast and east, Lancangjiang fault (LCJF) and Red River fault (RRF) to the west, with strong N-S-oriented anisotropy, which evident differs from the ENE-WSW-oriented weak anisotropy in the high-velocity zone on the northeastern side. We consider that the weak material may be obstructed by large faults and the high-velocity zone, resulting in complex crustal deformation and tectonic boundary. The crustal low-velocity materials beneath the Tengchong volcano (TCV) are probably separated with those from the Tibetan Plateau. The low-velocity beneath the Chuxiong basin (CXB) may be combinations of partial melts and fluid derived from shear deformation and deep material upwelling. The segmented anisotropy at the NW end of the RRF suggests complex deformation by crustal flow, emphasizing the important influence of faults on anisotropic pattern. The complex anisotropy in the fault intersection of the Lijiang-Xiaojinhe fault and RRF also highlights the important role of these faults in shaping crustal deformation.

Oceanic plates are doubly curved spherical shells, which influences how they respond to loading during subduction. Here we study a viscous fluid model for gravity-driven subduction of a shell comprising a spherical plate and an attached slab. The shell is 100–1,000 times more viscous than the upper mantle. We use the boundary-element method to solve for the flow. Solutions of an axisymmetric model show that the effect of sphericity on the flexure of shells is greater for smaller shells that are more nearly flat (the “sphericity paradox”). Both axisymmetric and three-dimensional models predict that the deviatoric membrane stress in the slab should be dominated by the longitudinal normal stress (hoop stress), which is typically about twice as large as the downdip stress and of opposite sign. Our models also predict that concave-landward slabs can exhibit both compressive and tensile hoop stress depending on the depth, whereas the hoop stress in convex slabs is always compressive. We test these two predictions against slab shape and earthquake focal mechanism data from the Mariana subduction zone, assuming that the deviatoric stress in our flow models corresponds to that implied by centroid moment tensors. The magnitude of the hoop stress exceeds that of the downdip stress for about half the earthquakes surveyed, partially verifying our first prediction. Our second prediction is supported by the near-absence of earthquakes under tensile hoop stress in the portion of the slab having convex geometry.

South-central Alaska features a history of massive volcanic activity. How the Denali volcanic gap (DVG) formed and why the Wrangell volcanoes are clustered remain vigorously debated. Investigating the crustal thermal structure can be crucial for understanding subsurface magmatic activity. We present a high-resolution broadband Lg-wave attenuation model to constrain crustal thermal anomalies beneath Alaska. Strong Lg attenuation is observed beneath the volcanoes in south-central Alaska, indicating thermal anomalies and possible melting in the crust. In contrast, the central Yakutat terrane (YT) and DVG are characterized by weak Lg attenuation, suggesting the existence of a cool crust that prevents hot mantle materials from invading the crust. This cool crust is likely the reason for the DVG. Quarter-toroidal crustal melting with strong attenuation is revealed around the YT. This curved zone of crustal melting, possibly driven by toroidal mantle flow, weakly connects the Wrangell and Buzzard Creek-Jumbo Dome magmatic chambers.

During the last 20 kyr, the Etna volcano has been characterized by almost continuous summit eruptions and by less frequent—yet definitely more destructive—flank eruptions issuing at <1,000 m asl altitudes and reaching the Ionian Sea. The chronological framework of pre-historic (pre-2,750 yr BP) flank eruptions is supported only by few radiometric and paleomagnetic ages. Here we paleomagnetically investigated 15 Holocene lava flows from SE Etna lower slopes and dated 12 of them. Paleomagnetic dating at Etna relies on best method pre-requisites: European location where reference geomagnetic models are well defined, and detailed stratigraphic evidence is available. We sampled 45 sites (450 oriented cores) from lavas loosely constrained in the 19,000–2,000 yr BP age window. Ten eruptions yielded a minimum 40% refinement with respect to initial age constraints, with four lava flows achieving refinement up to 90%. We obtained 620–1,398 yr (998 yr on average) dating accuracy for three flows bracketed in relatively short (1,398–1,644 yr) independent age constraints. By contrast, five flows characterized by longer 6,567–7,439 yr initial age windows yielded multiple age solutions. Finally, four lava flows with 1,644–6,567 yr-long initial age windows were tightly dated with 120–680 yr age ranges. We conclude that at volcanoes where best paleomagnetic dating pre-requisite are fulfilled, singular solutions are expected for 30% of the analyzed flows and, significant refinements for the others. Seven kyr seems to represent an independent age window threshold length to get or not significant dating refinements.

Fault activity and structure are important factors for the assessment of seismic hazards. The Anninghe fault is one of the most active strike-slip faults in southwestern China but has been experiencing seismic quiescence for M > 4 earthquakes since the 1970s. To understand better the characteristics of its highly locked southern segment, we investigate seismicity and ground motion variability using recently deployed multi-scale dense arrays. Assisted by machine learning (ML) seismic phase picking and event discrimination models, we first compile a high-resolution catalog of local seismic events. We find limited earthquakes that occurred on the Anninghe fault, consistent with its generally acknowledged high locking degree. Whereas, most newly detected events appear within off-fault clusters, among which four are closely related to anthropogenic activities (e.g., mining blasts), and two neighboring faults host the remaining ones. We further apply an ML-based first-motion polarity (FMP) classifier and successfully obtain a reliable small earthquake focal mechanism, which agrees well with the geologically inferred north-south trending and eastward dipping of the Anninghe fault. Analyses of ground motion variations along two across-fault linear arrays show abrupt changes in FMPs and obvious frequency-dependent site amplifications near the mapped fault traces. It further suggests that, at finer scales, the damaged Anninghe fault zone may have split into two smaller damaged zones at shallower depths, resulting in a typical “flower-type” fault structure. The efficient workflow developed in this study can be well applied for the longer-term monitoring and better characterization of the southern Anninghe fault, or other similar regions.

Understanding preferential flow in porous media holds substantial theoretical significance on the design and optimization of hydrocarbon exploitation in shale reservoir. Previous researches discussed the competition of imbibition front in layered porous media while the underlining mechanism for interfacial dynamics and induced displacement efficiency of multiphase flow remains ambiguous. In this paper, we investigate the spontaneous imbibition in dual permeable media and analyze the flux exchange between the neighboring porous zones with permeability contrast using dynamic pore network model. The impact of fluid viscosity ratio and permeability contrast on the spontaneous imbibition preference have been addressed, and finally a phase diagram for displacement efficiency has been obtained. The results reveal that the dual permeable structure enhances the invasion rate of wetting fluid in the low-permeable zone and induces unstable displacement patterns, leading to reduction of the long-term displacement efficiency. The interfacial pattern transition from stable displacement to unstable pattern in dual permeable media could be ascribed into the flux exchange between dual permeable zones, which shows a contrary impact on the fluid flow within the low-permeable zone under favorable and unfavorable viscosity ratios. The permeability contrast in dual permeable media intensifies this impact during spontaneous imbibition. These results help us to understand the occurrence and mutual interaction of multiphase flow in layered porous media, and provide a theoretical guidance for the hydrocarbon exploitation in shale reservoir.

Open-vent volcanoes continuously emit magmatic products and frequently feature multiple adjacent craters. Temporal shifts of thermal emissions between craters are especially detectable by InfraRed satellites. Here, SENTINEL-2 and LANDSAT-8/9 Short Wave InfraRed (SWIR) high-spatial resolution satellite data, are combined to investigate 10 years (2013–2023) of thermal activity at Stromboli volcano (Italy). The correlation between Volcanic Radiative Power (VRP, in Watts) and Volcanic Radiative Energy (VRE, in Joules), retrieved by moderate MODIS and VIIRS Middle InfraRed (MIR) data, with the Thermal Index SWIR (TISWIR) data, allows us to quantify long-term series of heat fluxes (VRPSWIR) and energy (VRESWIR). Combining moderate and higher spatial resolution data and fitting cumulative trends of TISWIR with VREMIR allows to measure thermal activity sourced by single craters during Strombolian activity. Long-term results highlight that thermal emissions are clustered in the northern and southern parts of the crater terrace, with total energy emitted (∼12 × 1014 J) equally distributed. The thermal increase since April 2017 marked a reactivation of shallow magma transportation and an intensification of the activity after the 2014 eruption. Distinct thermal behaviors are shown by the NE, C, and SW craters, related to mechanisms of explosions. We found that short-term thermal variations match well those resolved by ground-based signals, and the NE crater as the most sensitive to the transition to higher-intensity activity. Our multispatial/multisensory investigation allows, for the first time, the long-term quantification of heat flux from Stromboli's craters, with an improved understanding of open-vent dynamics and a new approach to monitor multiple active craters.

We investigate the continent-size lithospheric structures of paleo rift around the central Korean Peninsula using ambient noise tomography and earthquake-based Eikonal tomography based on dense seismic networks. We determine Rayleigh-wave group velocities at periods of 1–15 s from ambient noise tomography and Rayleigh-wave phase velocities at periods of 20–80 s from earthquake-based Eikonal tomography. We determine a 3-D shear-wave velocity model in the lithosphere from the Rayleigh wave velocities. The model exhibits high lateral variations ranging from ∼ ${\sim} $‒9% to ∼ ${\sim} $8%, depending on depth. The shear-wave velocities at shallow depths (≤ ${\le} $2 km) are relatively high in mountain regions and low in coastal and basin regions. Strong velocity contrasts are observed around major earthquake hypocenters at depths of 3–20 km, which may be due to the presence of seismogenic faults. Shear-wave velocities at depths of ∼ ${\sim} $30–40 km are high along the east coast, suggesting uplifted mantle that is responsible for the opening of the East Sea (Sea of Japan). High velocity structures beneath Moho around the coast may suggest solidified underplated magma caused by the paleo rifting. The root of coast-parallel high-mountain range (Taebaek Mountain Range) is bounded by the uplifted mantle, presenting mountain range development in rift flank along paleo-rift axis. Low shear-wave velocities along the coast at depths ≥60 ${\ge} 60$ km may imply elevated temperature beneath the solidified underplated magma. The continent-side paleo rift affects the geological, thermal, and seismological properties around the continental margin at present.

We apply a template matching method on GNSS data for stations located in Honshu, Japan, to detect slow slip events associated with the subducting Philippine Sea and Pacific plates during the period from 1997 to 2020. A measure of the minimum detectable moment magnitude is proposed, from which we infer that the method could potentially detect SSEs as small as M w 5.2 on the westernmost part of the Philippine Sea plate and M w 6 on the Pacific plate below Honshu eastern coastline. We find 12 slow slip events on the Philippine Sea plate, among which eight are located on the known Boso slow slip event asperity and the four others are located offshore north-east relative to the Boso SSEs, at the transition with the Pacific plate. We find 9 SSEs on the Pacific plate, mainly on the northern section, offshore Iwate prefecture. A clear gap with no SSEs coincides with the main asperity that broke during the 2011 Tohoku earthquake. Most event locations correlate with low locking areas. We do not find any clear temporal pattern apart from the regular occurrence of the largest Boso SSEs.

We perform a joint analysis of gravity and magnetic data sets in the Tyrrhenian Sea region to infer the rock physical properties of several volcanic seamounts. We propose a moving-window application using Poisson's theorem, which relates the total gradient of the magnetic field to the total gradient of the first-order vertical derivative of the gravity field data. In volcanic environments, where strong intensity of remanent magnetization is expected, the total gradient of the magnetic field is particularly useful since it is almost independent on the direction of the total-magnetization. The moving-window approach resulted necessary due to the heterogeneous magnetization distribution of the volcanoes. First, we perform synthetic tests based on realistic seamount models which exhibit inhomogeneous magnetization intensity and orientation. Using the total gradients, we demonstrate that our approach can provide an appropriate magnetization-to-density ratio in different subareas of seamounts. The results of the correlation analysis for the Palinuro, Marsili, Vavilov, and Magnaghi seamounts provide interesting information on the variability of magnetization associated with different epochs of formation and demagnetization effects due to hydrothermal alteration processes.