This study investigates the dissolution behaviour of different gases (O₂, O3, CO₂, H₂, N₂, and air) in nanobubble (NB) form in pure water. The experiment was conducted in a pure water-filled tank equipped with sensors to monitor pH, dissolved CO2 (DCO2), dissolved O2 (DO), dissolved H2 (DH), dissolved O3 (DO₃), oxidation-reduction potential (ORP), and electrical conductivity. The influence of the NBs in pure water was continuously monitored by measuring the parameters throughout the experiment. The findings highlight that NBs play a crucial role in rapid gas dissolution in water and change the water chemistry. For instance, CO2 NBs reduced the pH of water from 6.8 ± 0.2 to 4.2 ± 0.2 within 20 min of CO2-NBs generation, and DCO2 concentration reached >1500 mg/L in 30 min. DO concentration was noted as 31.6 ± 3.0 mg/L and 51.8 ± 5.0 mg/L, with O2 and O3 NBs infusion, respectively. H₂ and N₂ gases were easily able to replace the inherent DO saturated with air and reduced the DO concentration to 2.3 ± 0.1 and 1.8 ± 0.1 mg/L. The study suggests the potential industrial applications of NB technology in processes like wastewater treatment, enhanced gas solubility, and disinfection because of the unique physicochemical properties of NBs. This report might provide valuable insights for further investigations about physicochemical properties and performances of various gas NBs on water chemistry and their potential usage in environmental sustainability.

This paper investigates the combustion dynamics of interacting lazy multi-component gas plumes (i.e., buoyancy-dominated gas releases with a low initial momentum flux), a configuration relevant to coal mining waste emissions. By coupling a three-dimensional large eddy simulation (mesh size of 10−2 m; paralleling with 2048 processors) with detailed chemical kinetics (GRI-Mech 3.0), we analyzed the sensitivity of the flow structure and plume stabilization to the vent spacing of twin hydrogen-rich multi-component gas plumes (H2-CO-CH4-air). The results identified a distinct topological transition. While gas plumes from vents spaced at δ/D=5 (δ and D are the spacing and width of gas vents, respectively) evolve independently, those at closely spaced sources (δ/D=5/4) exhibit rapid coalescence driven by hydrodynamic shielding. This hydrodynamic merging results in a unified column with an effective hydraulic diameter of Deff≈2D. This leads to a significant reduction in the surface-to-volume ratio available for ambient air entrainment, maintaining a coherent combustible-rich core to higher altitudes than isolated-source correlations would predict. However, despite this mass retention, the rapid vertical acceleration of buoyancy-dominated flows induces high strain rates, significantly disrupting the reaction zone structure. These findings establish that, for clustered emission sources, the dispersion hazard is governed by a coupling between hydrodynamic coalescence, which maintains reactant concentration, and finite-rate chemistry, restricting oxidation efficiency. This paper provides critical insights for designing gas capture infrastructure and assessing flammability limits in multi-vent systems.

Submarine slope failures and turbidity currents triggered by earthquakes play critical roles in sediment transport, subsea infrastructure damage, and tsunami generation. While extensive case studies exist for large-magnitude events (Mw > 7), the thresholds for triggering such processes under moderate earthquakes (Mw < 6) remain poorly constrained. This study investigates seafloor response to a moderate Mw 5.7 earthquake that occurred off northeast Kikai Island, Japan, on March 15, 2024. Seafloor observations were conducted within 24 h of the earthquake using the research vessel Shinsei-maru by employing multibeam bathymetric surveys, sediment coring, in-situ video monitoring, and CTD measurements to detect signs of seafloor instability and sediment remobilization. Peak ground acceleration (PGA) across the studied area was estimated from multiple ground motion prediction equations (GMPEs), evaluated by observed land-based strong motion records in the Ryukyu arc. The estimated PGA of 0.15-0.19 g, considering shear-wave velocities, is at or slightly larger than the typical threshold for triggering slope failures. However, despite these ground motions and the steep (10-25 degrees), silty-to-fine-sandy slopes, we observed no significant morphological changes or recent deposition indicative of slope failure or turbidity current. These findings suggest that the threshold for surface failure was not exceeded under the studied conditions, advancing our understanding of seafloor slope stability under moderate earthquake shaking.

Controlling and reducing dissolved gas levels is vital for process quality, equipment integrity, and product stability. However, current techniques for dissolved gas removal are generally limited by high costs, process inefficiencies, the potential to introduce undesirable solids, and the requirement for extreme pressures and temperatures. Here, we experimentally demonstrate that environmental-friendly nanobubbles (NBs), with a mean bubble size <= 50 nm and number density <= 2 & times; 10(10) bubbles/mL, can efficiently remove dissolved oxygen (DO) from water under standard atmospheric pressure and temperature conditions. Notably, N-2 NBs readily reduce DO concentrations to near-zero levels (<5 ppb, or effectively "below detection limit"), achieving a > 99.9% DO removal, a level unattainable by conventional N-2 gas bubbling. The NBs-driven DO removal is highly effective across a broad range of initial DO levels, up to similar to 49 mg/L. While CO2 NBs can reduce DO levels to <= 0.03 mg/L, the results indicate N-2 NBs are superior due to the inherent physicochemical properties of the gas. Mechanistically, NBs significantly alter gas exchange dynamics by enhancing gas transfer and Ostwald ripening, leading to O-2 outgassing as NB gas dissolves into the water. The experimentally observed DO removal efficiency aligns closely with our first-order numerical simulations, which account for the diameter and number density of the generated NBs. Furthermore, our method is reversible, allowing DO levels to naturally re-equilibrate under atmospheric conditions. These findings highlight that NBs offer a promising, environmentally friendly, and cost-effective approach for dissolved gas replacement, opening new avenues for sustainable water treatment.

To image and characterize the lunar subsurface, we have developed an active seismic exploration system that combines a single ultra-compact seismic source with a single geophone. The seismic source employs a voice-coil actuator, a type of linear electromagnetic motor, which minimizes the source mass while maintaining a nearly constant force of 10 N over a wide frequency range. Despite its compact size of less than 800 g, the source can emit seismic signals repeatedly. Stacking the repeated signals enhances the signal-to-noise ratio, allowing both body-wave and surface-wave propagation over source-receiver distances exceeding 60 m, as demonstrated in field tests at Mount Fuji. When the seismic source is operated at multiple locations around a fixed geophone, astronauts or rovers can acquire multichannel-equivalent seismic datasets. This configuration enables retrieval of 2D or 3D S-wave velocity profiles to depths of 7 m through surface-wave analysis. In contrast, when both the seismic source and the geophone are mounted on separate rovers and moved independently, the system allows flexible multi-shot and multi-receiver acquisition geometries. This configuration enables body-wave-based seismic refraction and reflection surveys, allowing refraction tomography to derive 2D P-wave velocity models and reflection analysis to image subsurface structures to depths of 80 m. Finally, we optimized these systems and adapted them for space applications, enabling deployment by astronauts and integration with rovers in future space missions. (c) 2026 The Author(s). Published by Elsevier B.V. on behalf of COSPAR. This is an open access article under the CC BY license (http:// creativecommons.org/licenses/by/4.0/).

Nanobubble technology (NBT) enhances fluid flow in porous media by leveraging the unique properties of nanobubbles (NBs), such as nanoscale size, high stability, and low buoyancy, which are crucial for applications in enhanced oil recovery (EOR) and carbon sequestration. Bubble size in porous media affects rock chemistry and petrophysics, influencing resource sustainability. This review presents a multiscale perspective that bridges molecular, pore, and macroscopic levels, focusing on NBT and its effect on EOR and carbon sequestration. We summarize recent studies utilizing NBs' properties such as reduced interfacial tension, altered wettability, and enhanced dissolution, while integrating experimental and numerical insights into NBT's role for addressing global challenges. This review contributes to the evaluation of machine learning-integrated pore-scale modeling as a scalable methodology for overcoming limitations in traditional molecular dynamics (MD) simulations, offering promising pathways for real-time reservoir optimization in heterogeneous geologies. Recently, lab scale studies have shown promising results utilizing CO2, N2, and air NBs addressing the limitations of traditional methods in EOR and carbon sequestration. For instance, CO2 NBs have been reported to increase the oil recovery rates by 65% under oil-wet conditions. While the oil recovery rate is up to 80% under water-wet conditions, NBs also enhances contact between CO2 and water, promoting dissolution and mineralization reactions. Additionally, we have highlighted that despite advancements, key research gaps include limited field-scale validations of NBT and long-term stability assessments in reservoirs and carbon sequestration.

We developed a low-cost, environmentally friendly seismic source for monitoring nearshore CO2 storage sites where the operation of conventional large seismic vessels is impractical. The compact speaker-type source (<100 kg) is similar to 100 times lighter than conventional airgun seismic sources, while still providing sufficient energy to monitor deep CO2 reservoirs through stacking of highly repeatable signals. Field experiments demonstrate that stacking approximately 10 shots produces signal amplitudes exceeding those of a conventional small airgun source. Furthermore, at a planned CO2 storage site, the CO2 storage reservoir was successfully imaged to depths greater than 2 km in reflection seismic profiles, demonstrating the feasibility of monitoring injected CO2. The source can be deployed from small vessels, including autonomous surface vessels, and minimizes risk to marine life due to its low acoustic pressure. In addition, we confirm its compatibility with distributed acoustic sensing (DAS), enabling continuous, high spatiotemporal resolution monitoring. This seismic source has the potential to transform monitoring schemes for offshore CO2 storage sites and provides a realistic pathway toward automated, low-cost, and scalable monitoring.

The proliferation of space debris poses a significant challenge in modern space exploration, with potential repercussions for the future space environment and activities. Various research and technological developments have addressed these concerns, including estimating the number of space debris orbiting the Earth and its efficient removal. This paper proposes a novel resource-oriented perspective on space debris and focuses on the composition and resource potential of space debris. This study forecasts for the first time the annual mass changes in resource materials (Al, Al2O3, Ti, Fe, Cu, and Ag) by the year 2050 by employing a debris environment model simulation. Our simulation reveals that the masses of all the studied resource elements in an Earth orbital altitude of 400 km will increase by 2050. For example, Al and Ti at the 400 km altitude band will increase from 3.0 × 106 kg and 3.2 × 105 kg (in 2016) to 3.8 × 107 kg and 4.2 × 106 kg (in 2050), respectively, climbing at least ten times from 2016 to 2050, on the conservative estimates with a high post-mission disposal success rate. These comparative influxes of Al and Ti in 2050 due to space debris are at least 100 times higher than the natural influxes into the Earth's atmosphere due to meteoroids, further highlighting the significance of space debris. Our simulation results suggest that space debris may hold significant space resource potential in the next 25 years but can be a considerable environmental contaminant impeding space sustainability.

Direct Air Capture (DAC), a key component of Carbon Capture and Storage (CCS), has been widely studied. However, its large-scale deployment is hindered by the high energy cost of purifying captured CO2. Using impure CO2 can reduce energy consumption and overall costs, but it also lowers storage efficiency. This work employs molecular dynamics simulations to examine storage efficiency by analyzing the impurity systems' density across a wide temperature and pressure range. The results indicate a strong similarity between the density changes at the macroscopic level and the Van der Waals interaction changes at the molecular level. Additionally, the Normalized Storage Efficiency caused by Impurities (NSEI) is proposed, which can be used for storage potential and cost evaluation. A detailed NSEI analysis suggests that CO2 concentration should reach at least 70% to achieve economically viable storage. This finding provides practical guidance for DAC capture system design and impurity CCS project planning.

Deformation of trench-fill sediments at the central Japan Trench axis confirms that coseismic slip during the 2011 CE Mw 9.1 Tōhoku-oki earthquake extended to the shallowest part of the megathrust fault, contributing to the unexpectedly large tsunami that followed. Understanding the recurrence of “slip-to-the-trench” style earthquakes is therefore essential for diagnosing future hazard at the Japan Trench (and other subduction zones). Thermal biomarkers from the décollement indicate that similar shallow slip has occurred repeatedly, but the timing has not yet been linked to specific past earthquakes. We examine the sedimentary sequence of a trench-fill basin at 38.75°N (just north of the Tōhoku-oki slip zone) to investigate archives of past deformation caused by slip to the trench. Reprocessed seismic reflection and sub-bottom profiler data image several stratigraphic intervals of imbricate thrust wedge formation and paleo-seafloor uplift consistent with compression induced by locally enhanced coseismic slip along the décollement. The uplifted paleo-seafloor topography is onlapped by thick seismoturbidites that have been cored and dated by International Ocean Discovery Program Expedition 386, thus providing chronostratigraphic tie points. With this, we link the youngest coseismic deformation of trench-fill sediments to the 869 CE Jogan earthquake, indicating that rupture extended farther north and closer to the trench than previously estimated. Documenting slip to the trench for this historical megathrust event is proof of concept for our core-to-seismic correlation approach to constrain shallow slip in past earthquakes. Hence, we infer the several deeper intervals of imbricate thrust faulting and turbidites contain the means to unlock an extensive history of slip-to-the-trench style earthquakes and quantify the recurrence of shallow, tsunamigenic slip at the Japan Trench.

This paper investigated the impact of air ultrafine bubbles or air nanobubbles (ANBs) on the formation of calcium carbonate (CaCO3) scales in a water heater and their complete dissolution in the citric acid (CA) solution. We demonstrated a significant influence of ANBs on the physicochemical properties of the CaCO3 scales through a combination of analyses and dissolution tests in the CA solution. The scanning electron microscope images revealed a significant size reduction in CaCO3 crystals formed in ANBs-containing water, although the X-ray diffraction analysis confirmed that ANBs did not alter the CaCO3 crystalline phase. The mercury intrusion porosimeter measurements further provided the microstructural changes of CaCO3 scales due to ANBs. The specific surface area and total pore volume of CaCO3 scales were significantly higher in the presence of ANBs. Interestingly, the predominant pore diameter range of 100-1000 nm in the ANBs-containing water aligned with the size of ANBs, suggesting a potential influence of ANBs on pore formation during CaCO3 scale growth. The dissolution test in the CA solution revealed a significant enhancement in the dissolution rate of CaCO3 scales generated from the ANBs-containing water, accelerating for 123 % in dissolution processes. The higher surface area provided more contact areas available for the CA solution, whereas the increased pore volume facilitated penetration and mass transfer within the CaCO3 scale macroporous structure. Our study provides the coupled ANBs and CA method of CaCO3 dissolution, highlighting a novel environment-friendly method for the effective CaCO3 scale removal in a broad range of practical applications.

Abstract Mud volcanoes, common seafloor features in subduction zone forearcs, provide crucial insights into deep hydrogeological systems associated with plate subduction. Despite their widespread occurrence, the factors governing their uneven distribution remain unclear, and their internal physical properties are poorly understood. Using multiple seismic reflection profiles and high-resolution P-wave velocity (Vp) models, we examined the distribution and physical properties of mud diapirs in the Hyuga-nada subduction zone, southwest Japan, impacted by the Kyushu-Palau ridge seamount chain entering the junction of the Nankai Trough and the Ryukyu Trench. Our seismic reflection data revealed more than 60 diapiric structures, some breaching the seafloor, while others remain buried beneath shallow sediments. These diapirs predominantly occur where the subducting slab is 10–20 km deep, mainly on the leading edge of a large subducting seamount. Notably, there is a significant absence of diapirs directly above the seamount and within approximately 50 km of the trench axis. The findings suggest that once the slab reaches depths greater than 10 km, thermogenic hydrocarbon gas production, which gains significant buoyancy, drives upwelling fluid flows in the overriding plate. The ridge subduction also contributes to diapir distribution by enhancing dehydration of underthrust sediments on the downdip side and creating a porous fracture network in the upper plate. The Vp structure of an exposed mud volcano indicates that it contains methane levels similar to those in the Kumano-nada region of the central Nankai Trough. Buried mud diapirs, rooted in fluid- and gas-rich reservoirs at 1–5 km depths below the seafloor, exhibit significantly lower seismic velocities (Vp < 3.0 km/s), indicating higher fluid and hydrocarbon gas concentration at depth. These observations suggest the forearc wedge in the Hyuga-nada area contains more extensive fluid/gas reservoirs than previously recognized.

Impact responses of granular materials remain poorly understood, posing significant challenges to extraterrestrial exploration activities such as landing, sampling, drilling, and construction. We studied the crater morphology formed in the granular media and their granular behavior on low-velocity impact cratering by integrating three-dimensional surface scanning, machine learning-based classification, and x-ray computed tomography (X-CT) imaging. Our laboratory experiments focused on lunar (LHS-1 and LMS-1) and Martian regolith simulants (MGS-1) and terrestrial fine silica sand (T-8) as studied granular materials. The profiles of formed craters were analyzed under various experimental conditions, defined by different spherical projectile diameters and fall heights, accounting for the low kinetic energy at the granular surface contact of 0.1–0.5 mJ. In machine learning, we applied logistic regression models to classify target granular materials based on crater profile features, revealing primary morphological differences influenced by the given granular properties. The particle distribution from X-CT imaging revealed notable differences in the granular behavior of regolith simulants due to impact compared with T-8. These results underscored significant differences between the granular properties of terrestrial fine sand and regolith simulants. Additionally, our X-CT data emphasized that the high cohesion of LMS-1 significantly enhanced its resistance to impact, resulting in the porosity decline beneath the crater bottom of 0.20 and 0.03 on average in the LHS-1 and LMS-1 media, respectively, when the kinetic energy was 0.3 mJ. Our findings highlight the distinctive granular properties of regolith particles, advancing our understanding of their granular responses to impact.

In the context of Carbon Capture and Storage (CCS), the porosity of potential storage formations is a critical factor. Our study explores this aspect using computed tomography (CT) to assess how different scanning resolutions impact the accuracy of porosity measurements. We employed three CT systems - Geotek RXCT (resolution ~20-150 μm), Bruker 1272 (resolution ~5 μm), and DELab μCT-100 (resolution ~9 μm) - to scan sandstone cores of varying porosities. The aim was to identify an optimal scanning resolution that balances detail with practicality for CCS evaluations. This research addresses the challenges in high-resolution CT scanning, such as denoising effects that can alter accuracy, and the complexities of thresholding segmentation across various systems. Additionally, we examined the partial volume effect, crucial for interpreting pore sizes and distributions accurately. Our preliminary results suggest that scanning resolution significantly affects the perceived porosity. Different resolutions uncover diverse aspects of pore structure, highlighting the importance of choosing an appropriate resolution. Advanced image processing techniques, including effective denoising and accurate thresholding, are vital for reducing errors in porosity measurement. The study provides valuable insights into the use of CT scanning for CCS applications, emphasizing the need for a balanced approach in resolution selection and sophisticated image processing. These findings are instrumental in enhancing the reliability of geological evaluations for potential CCS sites, contributing to the broader efforts in carbon storage and climate change mitigation.

Numerous dark linear recurrent features called Recurring Slope Lineae (RSL) are observed on Martian surfaces, hypothesized as footprints of high-salinity liquid flow. This paper experimentally examined this “wet hypothesis” by analyzing the aspect ratios (length/width) of the flow traces on the granular material column to investigate how they vary with the granular material column, liquid and its flow rate, and inclination. While pure water produced low aspect ratios (<1.0) on the Martian regolith simulant column, high-salinity fluid (CaCl2(aq)) traces exhibited significantly higher aspect ratios (>4.0), suggesting that pure water alone is insufficient to explain RSL formulation. Furthermore, the aspect ratios of high-salinity fluid traces on Martian regolith simulants were among the highest observed across all studied granular materials with similar particle sizes, aligning closely with actual RSL observed on Martian slopes. The results further suggest that variable ARs of actual RSL at the given slope can partly be explained by variable flow rates of high-salinity flow as well as salinity (i.e., viscosity) of flow. The results can be attributed to the unique granular properties of Martian regolith, characterized by the lowest permeability and Beavers–Joseph slip coefficient among the studied granular materials. This distinctive microstructure surface promotes surface flow over Darcy flow within the regolith column, leading to a narrow and long-distance feature with high aspect ratios observed in Martian RSL. Thus, our findings support that high-salinity flows are the primary driver behind RSL formation on Mars. Our study suggests the presence of salts on the Martian surface and paves the way for further investigation into RSL formulation processes.

Direct Air Capture (DAC), a key component of Carbon Capture and Storage (CCS), has been widely studied. However, its large-scale deployment is hindered by the high energy cost of purifying captured CO2. Using impure CO2 can reduce energy consumption and overall costs, but it also lowers storage efficiency. This work employs molecular dynamics simulations to examine storage efficiency by analyzing the impurity systems’ density across a wide temperature and pressure range. The results indicate a strong similarity between the density changes at the macroscopic level and the Van der Waals interaction changes at the molecular level. Additionally, the Normalized Storage Efficiency caused by Impurities (NSEI) is proposed, which can be used for storage potential and cost evaluation. A detailed NSEI analysis suggests that CO2 concentration should reach at least 70

Pore structure is a critical factor in evaluating the quality of a reservoir or cap layer, influencing storage capacity, fluid flow efficiency, and reaction rates. Standard approaches, including Mercury Intrusion Porosimetry (MIP), Gas Pycnometry, and Brunauer-Emmett-Teller (BET) analysis, provide essential information; they are limited in their ability to capture pore connectivity and pathway complexity. X-ray Computed Tomography (CT) provides a distinct perspective, enabling three dimensional visualization of pore structures and insights into pore connectivity within 3D images. Accurate porosity analysis using CT, however, depends on careful evaluation of the segmentation process, especially the selection of thresholding methods, which can introduce biases and impact the reliability of the results. To address these challenges, this study introduces a new workflow leveraging grey-level terrain parameters from CT images as a reference index. Interbedded samples of muddy sandstone and siltstone are analyzed, with CT-derived porosity compared to experimental results obtained from an AccuPyc Helium Pycnometer. This comparison assesses the reliability and accuracy of the data-driven approach. By reducing uncertainties associated with porosity thresholding, the proposed workflow aims to establish a robust framework for CT-based pore structure analysis. It highlights the ability of CT imaging to deliver detailed 3D pore analysis, thereby supporting improved predictions of reservoir properties and resource management.

The granular mechanics of lunar and Martian regolith remain inadequately understood, impeding progress in successful exploration, landing, drilling, sampling, and construction activities on extraterrestrial surfaces. This study aims to bridge this knowledge gap by investigating the granular behavior of the lunar and Martian regolith under impact conditions. Impact cratering experiments were conducted for the lunar highlands, lunar mare, Martian regolith simulants (LHS-1, LMS-1, and MGS-1, respectively), and terrestrial silica sand with similar particle sizes as target granular materials, with a sphere projectile dropping at low velocities. A systematic analysis was undertaken to elucidate the influence of parameters, including the fall height of the projectile, impact velocity, kinetic energy of the projectile, porosity, cohesion, and internal friction angle, on the resulting crater depths. Our findings demonstrate that the crater depths of regolith layers of the lunar highlands and Martian surfaces are greater than those of the lunar mare regolith and terrestrial silica sand layers. For example, the crater depth of the lunar highland regolith layer is about two times greater than that of the terrestrial silica sand layer at an impact velocity of 40-70 cm/s. Additionally, our power-law scaling highlights less resistance to crater impact in the lunar and Martian regolith layers than in the terrestrial sand layer. Our study highlights a significant difference in granular behavior between the Earth's sand layer and the lunar and Martian regolith layers, providing valuable insights for future exploration, coring, drilling, and resource utilization endeavors on the lunar and Martian surfaces.

The International Ocean Discovery Program (IODP) Expedition 386, Japan Trench Paleoseismology, represents the first utilization of giant piston coring (GPC) within scientific ocean research drilling. This allowed for a Mission Specific Platform (MSP) multi-site, multi-hole, shallow subsurface coring in an ultra-deep water subduction zone trench. The primary objective of the expedition was to investigate the concept of submarine paleoseismology in the Japan Trench, which involves studying long-term records of deposits in the deep sea that can provide insights into past earthquake events. In this paper, we compile and interpret initial shipboard data and results to (1) establish first-order event stratigraphic correlation of thick event beds (> 50 cm in thickness) between sites, (2) test previously published event-stratigraphic predictions of earthquake-related event deposits as proposed based on high-resolution hydro-acoustic subbottom profiler (SBP) data, and (3) derive SBP-scale event deposits age estimates to (4) discuss the advantages and limitations of giant piston coring for scientific drilling operations and the potential of new event stratigraphy results for advancing submarine paleoseismology. The findings of the study identified a total of 77 SBP-scale event beds across 15 sites along a trench-parallel transect spanning over 600 km. These event beds exhibit clear expressions in SBP data, with approximately 49 % matching precisely with SBP units previously identified by Kioka et al. (2019a). For the remaining 51 % of SBPscale event beds, thin, acoustically-transparent bodies were observed between high-amplitude horizons, for which SBP-based seismic interpretation alone would not be definitive. Consequently, the study concluded that the SBP-scale event-stratigraphy observed in IODP 386 cores validates the event-bed mapping conducted by Kioka et al. (2019a) and improves SBP interpretation for event beds in the 0.5 to 1 m thickness range. The initial age constraints obtained from shipboard radiolarian biostratigraphy enable us to provide rough estimates of event ages by linearly interpolating between previously dated events occurring less than 2000 years ago and a datum around 11,000 years ago reported in four boreholes from trench basins in the Southern, Central, and Northern Japan Trench. Inter-site stratigraphic correlation reveals distinct SBP-scale event stratigraphies for the trench segments located to the north and south of the structurally complex "boundary area" at approximately 39.3-39.4(degrees)N, which is hypothesized to potentially act as a persistent rupture barrier for megathrust earthquakes. We observe more frequent but thinner event deposits in the Southern and Central Japan Trench, and fewer but thicker event beds in the Northern Japan Trench. This spatial variation may be related to the different seismogenic behavior of the various asperities along the Japan Trench megathrust and/or to differences in the response of slope sediments to earthquake shaking. However, here-presented investigations at the SBP-scale level are deemed too simplistic for robust application of the "submarine paleoseismology" approach. The extensive and high-quality dataset from IODP GPC, coupled with the encouraging initial correlation results presented here, leads us to hypothesize that further detailed studies can identify and characterize event deposition dynamics at the micro-facies level, refine sediment provenance, and constrain precise event ages necessary for evaluating synchronicity in paleoseismological interpretation. These studies will also enable robust exploration of along- strike correlations or variations, facilitating the extraction of paleo-earthquake signals from Japan Trench event stratigraphies.