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Intermediate‐depth intraslab earthquakes in the Philippine Sea Plate occur at depths of 100–200 km beneath the Ryukyu Arc and are widely interpreted as manifestations of slab dehydration; however, the spatial variability in continuity of the volcanic front and the asymmetric distribution of volcanic activity are poorly explained by existing models. We demonstrate that spatial variations in the intraslab stress field control anisotropy in the permeability of the subducted slab, influencing the up‐dip migration of fluids and therefore the distribution of arc volcanism. By inverting the stress tensors of 184 focal mechanism solutions (Mw > 3.3) of earthquakes between 1997 and 2007, we identified heterogeneous intraslab stress regimes and evaluated how their mechanical expression, particularly the orientation of the intermediate principal stress axis (σ2), influences the direction of fluid flow. Our results show that regions characterized by down‐dip extensional stress regimes, in which σ2 is oriented approximately perpendicular to the slab dip, coincide with enhanced permeability and efficient dehydration pathways toward the mantle wedge. These results highlight the pivotal role of intraslab stress in shaping fluid migration pathways and arc magmatism in the Ryukyu subduction zone.

The Zhugongtang lead-zinc deposit is a super-large lead-zinc deposit controlled by the fault-fold structure in the Western Guizhou, China. In this paper, the complex migration process of ore-bearing fluid in fault-fold structures is reproduced by numerical simulation based on a multi-field coupled framework combining thermodynamics and fluid mechanics. The results show that ore-bearing fluid first migrates vertically rapidly along the fault and then transfers horizontally along the stratum to the SE flank of the fold. Negative pressure anomalies appear at the narrowing position in the deep part of the fault and at the intersection of faults and folds. The spatial distribution of Zn 2+ is related to the known mineralization distribution. Under the influence of heat flow field and pressure, ore-bearing fluid tends to the abnormal area of negative stress. Comparative experiments with different interlimb angle show that for smaller interlimb angle, mineralization tends to occur in faults, and conversely, mineralization tends to occur in strata. This is consistent with the structural control of mineralization observed in other deposits in northwestern Guizhou. This research provides a new insight into the understanding of fault ore control model.

To investigate the three-dimensional spatial distribution characteristics of fluids during the combined production of coalbed methane from multi-coal reservoirs (MCR), a physical simulation test platform was established, and a quantitative characterization parameter calculation principle for fluid migration was developed. The influence of fluid pressure difference and in situ stress difference on the three-dimensional spatial distribution of fluids and their quantitative characterization parameters was analyzed. The results indicate that the dynamic pressure equilibrium between the coal reservoir and the wellbore forces fluids from high-pressure reservoirs to intrude into low-pressure reservoirs, altering the flow state of fluids in the latter. Consequently, the relative flow velocity in the low-pressure reservoir becomes negative, with the relative deflection angle approaching 180°, while the relative flow velocity in the high-pressure reservoir remains positive. An increase in the relative flow rate of 0.08 and 0.007 corresponds to a 1 MPa increase in fluid pressure difference and geostress difference, respectively. During the co-production of coalbed methane from MCR, the existing pressure difference and in situ stress difference between reservoirs modify the fluid migration patterns, leading to fluid interaction and interference effects. This results in centrifugal flow patterns in low-pressure reservoirs and centripetal flow patterns in high-pressure reservoirs. Compared to in situ stress difference, the fluid pressure difference exerts a more significant influence on the fluid migration patterns.

After the subsidence phase that followed the 1982–1984 bradyseismic crisis, a gradual ground uplift at Campi Flegrei caldera resumed in 2005, while volcanic-tectonic earthquakes have steadily increased in frequency and intensity since 2018, with a significant intensification observed since 2023. This rise in seismic activity enabled a new tomographic study using data collected from 2020 to June 2024. In this work, 4161 local earthquakes (41,272 P-phases and 14,683 S-phases) were processed with the tomoDDPS code, considering 388,166 P and 107,281 S differential times to improve earthquake locations and velocity models. Compared to previous tomographic studies, the 3D velocity models provided higher-resolution images of the central caldera’s structure down to ~4 km depth. Additionally, separate inversions of the two 2020–2022 (moderate seismicity) and 2023–2024 (intense seismicity) datasets identified velocity variations ranging from 5% to 10% between these periods. These changes observed in 2023–2024 support the existence of two pressurized sources at different depths. The first, located at 3.0–4.0 km depth beneath Pozzuoli and offshore, may represent either a magma intrusion enriched in supercritical fluids or an accumulation of pressurized, high-density fluids—a finding that aligns with recent ground deformation studies and modeled source depths. Additionally, the upward migration of magmatic fluids interacting with the geothermal system generated a secondary, shallower pressurized source at approximately 2.0 km depth beneath the Solfatara-Pisciarelli area. Overall, these processes are responsible for the recent acceleration in uplift, increased seismicity and gases from the fumarolic field, and changes in crustal elastic properties through stress variations and fluid/gas migration.

The hierarchies of the stratigraphic discontinuity surfaces observed in ancient tidalites are qualitatively assessed, aiming to evaluate their role as possible preferential conduits for fluid migration. Three outcrop examples are presented from microtidal settings of southern Italy: (i) siliciclastic tidalites consisting of quartz‐rich cross‐stratified sandstones generated by strong two‐directional tidal currents flowing along a tidal strait; (ii) carbonate tidalites, which accumulated in a Cretaceous lagoon and tidal flat where peritidal cycles formed vertically‐stacked sequences of biopeloidal and fenestral packstones, wackestones and bindstones during repeated phases of Milankovitch‐scale sea‐level changes; (iii) mixed, siliciclastic‐bioclastic tidalites, deposited in a bay and recording offshore‐transition, to shoreface wave‐dominated and tide‐influenced environments. Observations made during this study suggest that fluid movement can be controlled by the presence of main bounding surfaces that occur at different dimensions, from large (hectometre)‐scale, to medium (decametre)‐scale, to smaller (metre)‐scales. These surfaces produced either by depositional or erosional processes, are characterised by different features and geometries in siliciclastic, carbonate and mixed siliciclastic‐bioclastic tidalites arguably revealing complex internal pathways for fluid flows. These results suggest that fluids propagating along the main discontinuities follow a dominant sub‐horizontal direction of propagation, associated with minor sub‐vertical movements, due to local internal surface geometries and interconnections and a general lack of fractures. This surface‐based approach to the study of fluid‐flow transmission within stratified rocks represents a conceptual attempt to predict fluid mobility and reservoir potential in tidalite‐bearing siliciclastic, carbonate and mixed reservoir rocks. The hierarchies of the stratigraphic discontinuity surfaces observed in ancient tidalites are qualitatively assessed, aiming to evaluate their role as possible preferential conduits for fluid migration. Three outcrop examples are presented from microtidal settings of southern Italy: (i) siliciclastic tidalites accumulated in a strait; (ii) carbonate tidalites, accumulated in a lagoon and tidal flat; and (iii) mixed siliciclastic‐bioclastic tidalites deposited in a bay.

Slow earthquakes play a crucial role in understanding stress accumulation and release along plate interfaces in subduction zones. The northern Ryukyu Trench, where the Philippine Sea Plate subducts northwestward beneath the Eurasian Plate, experienced a major earthquake in 1911 and is currently regarded as a low-seismicity area (LSA). Understanding the seismic activity in this region, particularly the relationship between very-low-frequency earthquakes (VLFEs) and regular seismic events, is crucial for understanding subduction zone dynamics. We investigated the spatial and temporal distribution of VLFE activity in the northern Ryukyu Trench using broadband ocean-bottom seismometers deployed around Amami Island between September 2018 and June 2019. Our analysis, employing the envelope correlation method, revealed that VLFE activity is primarily concentrated northeast of Amami Island, an area characterized by low regular earthquake activity, with the distribution of VLFEs spatially segregated from that of regular earthquakes. Furthermore, we observed earthquake swarm activity at the edges of the LSA in the northern Ryukyu Trench following VLFE activity. In November 2018, intense VLFE activity northeast of Amami Island migrated northeastward, which was followed by a regular earthquake swarm at the edge of this LSA. Following VLFE activity in January 2019, additional seismic activity, including foreshocks, occurred at the edges of this LSA approximately 1 month later. The spatial segregation of VLFEs and regular earthquakes suggests that VLFE activity may be influenced by the migration of high-pressure fluids within the subducted slab. This migration appears to trigger related time-delayed seismic activity, similar to mechanisms observed in other subduction zones such as Hikurangi. Understanding these dynamics is essential for assessing the coupling state of subduction zones and associated fluid behaviors, which play a critical role in evaluating seismic hazards in LSAs. Graphical Abstract

It is difficult to exploit low-permeability reservoirs, and CO2 flooding is an effective method to improve oil recovery from low permeability reservoirs. However, in the process of CO2 flooding, acidic fluids dissolved in formation water will react with rock to cause dissolution and precipitation, resulting in pores and precipitates, changing the evolution law of seepage channels, destroying formation integrity, and affecting the effect of CO2 oil displacement. The change in rock’s physical properties and the mass transfer law between CO2-water-rock are unclear. This paper considers the coupling effects of seepage, mechanics, and chemistry when CO2 is injected into the formation. The mass transfer model of CO2-water-rock in the geochemical reaction process is established on this basis. The physical properties of the reservoir after CO2 injection are quantitatively studied based on the microscopic mechanism of chemical reaction, and the migration law of solute in the reservoir rock during CO2 flooding under the coupling effects of multiple fields is clarified. The experimental results show that with the increase in reaction time, the initial dissolution reaction of formation rocks will be transformed into a precipitation reaction of calcite, magnesite, and clay minerals. The porosity and permeability of the rocks near the well first increase and then decrease. The far well end is still dominated by dissolution reactions, and the average values of formation porosity and permeability show an upward trend. Although the dissolution reaction of CO2-water-rock can improve the physical properties of reservoir rocks to a certain extent, the mutual transformation of the dissolution reaction and precipitation reaction further exacerbates the heterogeneity of formation pore structure, leading to the instability of CO2 migration, uneven displacement, and destruction of formation stability. The research results of this paper solve the problem of quantitative calculation of physical parameters under the coupling effect of multiple fields after CO2 injection into reservoirs and can predict the changes in formation physical properties, which can provide a certain theoretical basis for evaluating formation integrity and adjusting CO2 injection under the condition of CO2 flooding.

Most of the developing oil and gas fields in Russia are located in Arctic regions and constructed on permafrost, where recent environmental changes cause multiple hazards for their infrastructure. The blowing-up of pingos, resulting in the formation of gas emission craters, is one of the disastrous processes associated both with these external changes and, likely, with deep sources of hydrocarbons. We traced the channels of fluid migration which link a gas features reservoirs with periglacial phenomena associated with such craters with the set of geophysical methods, including common depth point and shallow transient electromagnetic methods, on an area of a prospected gas field. We found correlated vertical anomalies of acoustic coherence and electrical resistivity associated with gas chimneys in the upper 500–600 m of the section. The thickness of the ice-bonded permafrost acting as a seal for fluids decreased in the chimney zone, forming 25–50 m deep pockets in the permafrost base. Three pingos out of six were located above chimneys in the study area of 200 km2. Two lakes with parapets typical for craters were found. We conclude that the combination of applied methods is efficacious in terms of identifying this type of hazard and locating potentially hazardous objects in the given territory.

Brittle‐failure earthquakes in the lower crust, where high pressures and temperatures would typically promote ductile deformation, are relatively rare but occasionally observed beneath active volcanic centers. Where they occur, these earthquakes provide a rare opportunity to observe volcanic processes in the lower crust, such as fluid injection and migration, which may induce brittle faulting under these conditions. Here, we examine recent short‐duration earthquake swarms deep beneath the southwestern margin of Long Valley Caldera, near Mammoth Mountain. We focus in particular on a swarm that occurred September 29–30, 2009. To maximally illuminate the spatial‐temporal progression, we supplement catalog events by detecting additional small events with similar waveforms in the continuous data, achieving up to a 10‐fold increase in the number of locatable events. We then relocate all events, using cross‐correlation and a double‐difference algorithm. We find that the 2009 swarm exhibits systematically decelerating upward migration, with hypocenters shallowing from 21 to 19 km depth over approximately 12 hours. This relatively high migration rate, combined with a modest maximum magnitude of 1.4 in this swarm, suggests the trigger might be ascending CO2 released from underlying magma. Key Points Brief earthquake swarms occur in the lower crust beneath Mammoth Mtn We observe systematically decelerating upward migration of earthquake sources Migration of high pressure CO2 may have triggered the 2009 swarm

The Hikurangi Margin off the east coast of the North Island (Te Ika-a-Māui) is a tectonically active subduction zone and the location of New Zealand’s largest gas hydrate province. Faults are internally complex volumetric zones that may play a significant role in the migration of fluids beneath the seafloor. The combined processes of deformation and fluid migration result in the formation of concentrated hydrate accumulations along accretionary ridges. It is not fully understood to what extent faults control fluid migration along the Hikurangi Margin, and whether deep-seated thrust faults provide a pathway for thermogenic gas to migrate up from sources at depth. Using 2D models based on seismic data from the region we investigated the role of thrust faults in facilitating fluid migration and contributing to the formation of concentrated gas hydrates. By altering permeability properties of the fault zones in these transient state models we can determine whether faults are required to act as fluid flow pathways. In this study we focus on two study sites offshore southern Wairarapa, using realistic yet simplified fault geometries derived from 2D seismic lines. The results of these models allow us to start to disentangle the complex relationship between fault zone structure, permeability, geometry, fluid migration and gas hydrate formation. Based on the model outputs we propose that faults act as primary pathways facilitating fluid migration and are critical in the formation of concentrated gas hydrate deposits.