Journal of Geophysical Research: Solid Earth最新文献

Ongoing climate change is leading to an increase in prolonged droughts and severe weather events, which are particularly pronounced in semi-arid regions, such as the western United States. These extremes could have lasting social and environmental impacts. Continuous monitoring of near-surface hydrological processes and groundwater resources provides helpful information for effective water resource management. The seismological signature of groundwater fluctuations is clear in the temporal variations in seismic velocities, dv/v. To this end, developing a proxy for groundwater level using dv/v represents an opportunity, but further understanding of the relation between dv/v and subsurface hydrology is required. In this study, we apply single-station cross-component correlation analysis to 28 broadband seismic stations in Utah between January 2006 and March 2023 and analyze the dv/v in the 2–4 Hz frequency band. To explain dv/v, we linearly superimpose thermoelastic stresses, soil moisture estimated from remote sensing data products, and a long-term deep water table pore pressure. We find that the relative contributions of each depend on the location. Still, adding a long-term water table decline, which is not systematically observed in soil moisture, better fits our data. We conclude that soil moisture alone does not explain the variations in total water storage when subsurface moisture is decoupled from the deep-water table. We also conclude that dv/v can be used as a proxy for water storage.

Basalt mineralization storage is widely recognized as a secure, permanent method for large-scale CO₂ sequestration. At present, the majority of research endeavors are centered around the investigation of reaction mechanisms and microscopic properties. However, research on standard basalt rock samples (before/after storage) and the quantification of CO₂ consumption during reactions remains limited. This study explored CO₂-water-rock interactions, focusing on how mineral carbonation alters rock physical/mechanical properties and how to characterize CO₂ consumption rate. Experiments were conducted using a self-designed rock reactor on standard cylindrical basalt samples (from Wenchang, Hainan) under 12 MPa and 70°C for 0, 10, 20, 30, and 60 d. A theoretical CO₂ consumption calculation method (based on pressure drop, accounting for gas-liquid-solid three-phase systems) was proposed. Validated against actual consumption data (from water and rock weigh changes in the reactor), it showed an average absolute deviation (AAD) <5%, confirming high reliability. CO₂ consumption data were fitted with a double exponential function to derive the reaction rate curve, which peaked initially, then decreased continuously, and finally flattened. Changes in uniaxial compressive strength, tensile strength, Poisson's ratio, elastic modulus, porosity, T₂ and mineral composition were observed at different reaction times. Though siderite and calcite precipitated on sample surfaces, rock dissolution dominated—increasing porosity, reducing mechanical properties and leaving yellowish-brown precipitates (more pronounced with longer reactions). These findings support safety evaluation of basalt reservoirs.

Myanmar is located on the eastern margin of the India-Eurasia collision zone, where the Indian sub-continent is subducting beneath the Burma microplate. Magmatic processes during subduction and collision in orogenic belts are significant and well-studied for oceanic subduction; however, the magmatism associated with continental subduction remains poorly understood. Seismic attenuation is highly sensitive to changes in lithospheric thermodynamics and fluid content. Understanding arc volcanism is vital for comprehending a key manifestation of subduction-related processes. However, there is still no high-resolution 3D attenuation model for this region. Here, we use the coda-normalized method to image the lithospheric-scale 3D attenuation structure in the Indo-Burma subduction zone. Our results reveal high attenuation in major sedimentary basins. The prominent high-attenuation anomalies in the mid-to-lower crust of the Indo-Burma Ranges (IBR) may represent thick, fluid-rich sediments scraped off from the subducting Indian Plate and accumulated beneath the IBR. Low-attenuation anomalies at depths of 30–50 km beneath the Monywa volcano are a clear signature of a cooled mantle wedge, which currently overlies strong attenuation anomalies deeper than 50 km, likely associated with the upwelling of hot asthenospheric material. Compared to oceanic subduction systems, the insufficient water content of the continental subduction plate, coupled with the compressional regime induced by oblique subduction, leads to weak attenuation within the mantle wedge.

We present elemental geochemistry and multiple isotopic systematics (Re-Os, Lu-Hf, Sm-Nd and Sr) for mantle peridotite xenoliths from Lashaine in northern Tanzania. We use the data to examine how the major Proterozoic tectono-thermal events that affected the crust of the western Tanzanian craton are imprinted on the lithospheric mantle in the Mozambique belt adjacent to the eastern margin of the Tanzanian craton. Whole-rock and mineral compositions together with ¹⁸⁷Os/¹⁸⁸Os ratios of Lashaine peridotites are consistent with Archean-aged cratonic mantle assembled to create the root beneath the Tanzanian cratonic nucleus. Highly radiogenic ⁸⁷Sr/⁸⁶Sr ratios (0.70411−0.83604), unradiogenic Nd (ɛNd = −14 − +2) and variable Hf isotope ratios (ɛHf = +4 − +2,912) of minerals combined with the other geochemical features in Lashaine peridotites reflect extensive melt extraction followed by metasomatic enrichment of the lithospheric mantle by subduction-related melts/fluids. Mineral Lu-Hf isotopic compositions define a 1.4 Ga isochron and, together with the distinctive, robust Lu-Hf model age (1.4 Ga) of one garnet with very high ¹⁷⁶Lu/¹⁷⁷Hf ratio (3.182), indicate that a major Mesoproterozoic subduction-related metasomatic event reset Lu-Hf isotope systematics of the Lashaine peridotites. This over-printing of the mantle lithosphere indicates a clear link to the Mesoproterozoic Kibaran event along the western margin of the Tanzanian craton. We invoke a flat-slab subduction model during the Kibaran event to introduce subduction-related components in a pervasive Mesoproterozoic metasomatic event beneath Lashaine.

The global distribution of the Earth's lithospheric induced magnetization is examined through an inverse modeling approach that integrates constraints from both petrological data and satellite magnetic observations. The distribution of induced magnetization is characterized by the Vertical Integrated Susceptibility (VIS) of a spherical equivalent source layer. To reconstruct the long-wavelength structures of the lithospheric magnetic field, a prior petrologically derived VIS model (SM3-SI) is utilized to provide constraints at spherical harmonic degrees 0–16, while finer structures are constrained by satellite magnetic data. The resultant VIS model furnishes a higher-resolution and more accurate depiction of lithospheric induced magnetization. Significant variations in the resultant VIS model across different crustal types and basement ages are confirmed through a comprehensive analysis. High lithospheric magnetization is generally observed in Precambrian provinces characterized by cold and thick lithospheres, whereas orogenic belts and extended crustal regions exhibit lower magnetization due to reduced magnetic materials from crustal thinning. In oceanic regions, elevated lithospheric magnetization is mainly concentrated in oceanic plateaus which are associated with Cretaceous magmatic activity. Mantle-derived magnetic sources, which are related to an increased Curie depth caused by the cold subducted slabs and the serpentinization within the mantle wedge, are inferred to underlie the strong magnetization observed in island arcs and subduction zones.

Subduction initiation often begins with slow, forced convergence, switches “on” catastrophically as the slab collapses into the mantle, and then evolves to steady-state, self-sustained sinking that drives global plate movements. Numerical models suggest that the collapse phase implies sudden weakening of the plate interface. However, geological records of subduction infancy preserved as metamorphosed oceanic crust accreted beneath ophiolites (i.e., metamorphic soles) present a paradox. During the pre-collapse period that may last 2–15 million years, the nascent plate interface is hot, whereas during collapse, shear zone temperatures plummet, which typically strengthens rocks. So, how could cooling cause weakening? Here, we show microstructures of metamorphic sole rocks from Mont Albert (Québec, Canada) that demonstrate that upon cooling, metamorphic mineralogy became more heterogeneous, average grain size decreased, and deformation mechanisms shifted from dislocation-accommodated to fluid-assisted and grain size sensitive, which culminated in drastic rheological weakening. Quartz piezometry indicates that flow stress increased with cooling, but flow laws indicate that the colder rocks exhibited lower viscosity and therefore could localize strain. Interface viscosity initially rose with cooling, but upon reaching a threshold where major metamorphic minerals changed, dropped from >10¹⁸ to <10¹⁷ Pa-s. Cooling-induced mineral-mechanical changes thus drove rheological weakening, and provide a general mechanism explaining slab collapse and the transition to self-sustaining subduction. This implies that strain localization is inherent to modern metamorphosed oceanic lithosphere and does not require a “stress drop.” The next step to understanding subduction initiation is identifying causes of high temperatures and incipient cooling during the pre-collapse phase.

We perform Rayleigh wave ambient noise tomography to investigate crustal seismic velocity structure and sources of volcanism in Armenia. Armenia, a key part of the tectonically and volcanically active Caucasus-Anatolia region, is actively being deformed by the ongoing Arabian-Eurasian continental collision. Unlike typical intracontinental settings, Armenia exhibits exceptional diversity of volcanic compositions and eruption styles: large stratovolcanoes are interspersed among more broadly distributed monogenetic cones and extensive lava flows. This study presents the first seismic tomography model of Armenia with sufficient resolution to infer potential magma sources. We analyze ∼19 months of continuous ambient noise data recorded by 32 seismic stations, extracting Green's functions and Rayleigh wave dispersion curves. A two-step tomographic inversion first yields 2D group velocity maps, followed by a 3D shear-wave velocity model. Synthetic tests confirm the model's resolution and ability to detect lateral and vertical velocity anomalies. Our results reveal prominent low-velocity anomalies down to 25 km beneath monogenetic cones, likely indicating magma transport zones. At greater depths, velocity anomalies reverse sign. A high-velocity zone at 40 km depth beneath dispersed cones suggests crustal thinning and asthenosphere upwelling. Beneath Lake Sevan, we identify two distinct structures: a low-velocity anomaly in the NW linked to fault-related fracturing and fluid saturation, and a high-velocity anomaly in the SE that may represent a rigid block, possibly remnant oceanic crust. This study provides new insights into crustal structure beneath Armenia, shedding light on its magmatic and tectonic evolution.

Deep-origin carbonatite melts are considered to be the products of partial-melting of the oceanic crust in the subduction zones. In this study, we conducted electrical conductivity (EC) measurements on two samples, the composition of which resemble the partial-melting products atop the 410-km discontinuity and in the lower part of the transition zone. The EC of carbonatite melts was investigated using impedance spectroscopy combined with a multi-anvil press up to 20 GPa. Pressure has a great effect on the EC of the carbonatite melts. While the EC dropped overall by 0.6 log unit from 3 to 20 GPa for varying compositions, the pressure effect becomes weaker above 10 GPa. The Hashin-Shtrikman mixing model indicates that melt fraction of 0–0.3 vol% is necessary to account for the EC atop the 410-km discontinuity beneath NE China, north Philippine Sea, north Pacific, and Australian craton. However, this value soars to 1–4.5 vol% for the lower part of the transition zone in the same regions, and further increases to 3.7–7.3 vol% for cold subduction regions if the slab surface temperature is 300 K lower. The difference in the needed melt fraction at different depths implies that the magnitude of partial melting is much larger in the lower part of the mantle transition zone, and it is thus likely to be the main barrier to the recycled carbonates towards the deep interior.

Paleomagnetic data are usually retrieved by subjecting bulk samples, for example lavas, to laboratory measurement protocols. In many instances, the data related to these protocols yield uninterpretable results caused by the presence of particles with adverse magnetic properties that blur the signal of the reliable magnetic particles. With Micromagnetic Tomography (MMT) we focus on identifying the signal of particles with reliable properties. Their individual magnetic moments are computed by scanning the surface of a $��\sim �$3 $��{\text{mm}}^2�$ thin section with a quantum diamond microscope (QDM) and locating the magnetic recorders with computed tomography. Currently, the largest portion of all resolved magnetic moments is discarded due to numerical instability, making it difficult to obtain statistically relevant paleointensities and paleodirections based on the remaining magnetic moments. We improve the number of reliable magnetic moments from MMT experiments by making a QDM scan of both sides of the sample. Here, we conduct a combined numerical and empirical study to investigate the benefits and difficulties of adding this double-sided scanning (DSS) protocol to MMT. By investigating the theoretical gain of DSS for varying sample thicknesses, we show that DSS returns twice more numerically stable magnetic moments compared to single sided scanning for a sample thickness of 60 $��\mu �$m. By overcoming practical difficulties related to sample preparation and scanning, DSS will provide a significant boost in retrieved stable magnetic moments.

At the northern Hikurangi margin, Aotearoa New Zealand, slow slip events (SSEs) recur every 6–24 months to $��\sim �$30 km depth. Although shallow SSEs (0–10 km) are well-studied offshore, the deeper portion (10–30 km) remains poorly understood, limiting insight into SSE initiation. Here we investigate this deeper region and examine relationships between newly resolved SSEs and seismicity. Using time-dependent inversions, we resolve two small SSEs ($��M_W�$ 6.2 and 6.4), including one that extends from 15 to 30 km depth. Using data from a dense onshore seismograph network deployed directly above this deeper portion from December 2017 to October 2018, we construct a catalog of 3,071 high-quality earthquakes with hypocentral uncertainties $��\le �$5 km, located using a 3-D velocity model and a new 1-D model. Earthquake magnitudes range from −0.84 to 4.40, with a completeness magnitude of 1.7 and a b-value of 1.06. Focal mechanisms reveal numerous normal-faulting earthquakes, including some within the slab mantle. Vertically-aligned seismicity and normal-faulting earthquakes outline pathways linking the slab mantle to surface seeps of mantle-derived fluids. We infer that normal faults form due to slab bending and localized uplift of subducting seamounts, which roughen the plate interface, damage the upper plate, and promote fluid migration. Landward of $��\sim �$100 km from the trench, both surface seeps and normal-faulting mechanisms cease, coinciding with the downdip limit of shallow SSEs. Together, these results suggest that the Hikurangi margin's rough subducting plate interface exerts strong control on forearc dewatering and SSE genesis.