Geospatial Information Authority of Japan

ABSTRACT The South Kitakami Belt of Japan yields a number of mesothermal auriferous vein deposits, hosted in Paleozoic‐Mesozoic sedimentary rocks in the vicinity of Cretaceous intrusive rocks. We investigated lithology, mineralogy, and chemistry of the host sedimentary rocks (Late Triassic Isatomae Formation) in the Ishinomaki district to evaluate gold mineralizing potential in the belt. The formation consists of shallow‐marine continental shelf sedimentary rocks that underwent prehnite‐pumpellyite facies of contact metamorphism. The analyzed three representative slate samples of the formation contain diagenetic‐metamorphic minerals such as calcite, K‐feldspar, albite, pumpellyite, titanite, and apatite, in addition to micro‐nodules and seams consisting of carbonaceous matter (CM) and/or sulfides. The carbonaceous matter in the nodules and seams was partly or mostly substituted by sulfides; pyrite with minor cobaltite and pyrrhotite, which occur as framboids, compact spheres, and compact anhedral grains. Cobaltite contains rarely electrum grains. These samples are characterized by high Ca contents, and are depleted in Mg, Fe, Na, and K, compared to the underlying Paleozoic and Mesozoic shale and overlying Jurassic sedimentary rocks of the belt. A sulfide nodule‐bearing sample is enriched in metals such as As, Cr, Co, Ni, Cu, and Sb. Depletion of sulfur mole ratio of the pyrites, in particular, framboidal/spherical pyrite, compared to the stoichiometric ratio, suggests that the pyrites formed from monosulfides. Most of the trace elements such as As, Bi, Pb, Tl, Sb, and Mo are more enriched in pyrite than pyrrhotite. These analytical results of the Isatomae Formation indicate that this slate was accumulated in an anoxic seawater environment and enriched in metallic elements, which may have been adsorbed to Fe‐oxyhydroxide particles originally. The successive diagenetic reaction with pore water sulfurized the Fe‐oxyhydroxides to monosulfides, which finally transformed into pyrite. The narrow and enriched range (+0.3‰ to +0.5‰) δ 34 S values of sulfides in the Isatomae slate suggest that this diagenetic reaction occurred in a closed system, where seawater sulfate hardly diffused into the sediments. Subsequent prehnite‐pumpellyite metamorphism transformed pyrite to pyrrhotite, during which metamorphism, the trace elements including Au may have exsolved into metamorphic fluids. These results show a gold mineralizing potential for the Isatomae Formation.

To improve the explainability of a YOLOv5-based model for anterior segment disease diagnosis by combining gradient-weighted class activation mapping ++ (Grad-CAM++) and cut-and-paste validation and evaluate the influence of extracorneal information on diagnostic accuracy. In total, 1039 slit-lamp photographs across nine diagnostic categories were analyzed using a previously developed YOLOv5 model. Grad-CAM++ was implemented to visualize the attention patterns across key network layers. To quantitatively assess clinical relevance, attention maps were compared against expert-delineated lesion boundaries using Intersection over Union (IoU). Furthermore, cut-and-paste validation was performed by systematically swapping the corneal regions with different backgrounds to probe the reliance of the model on contextual information. Grad-CAM++ analysis revealed hierarchical attention focus, progressing from broad in the early layers to highly localized in the final layers, with layer 23 showing distinct disease-specific patterns. Cut-and-paste validation demonstrated that model accuracy was highly dependent on the background context for certain diseases; for instance, the accuracy for infectious keratitis and acute primary angle closure dropped significantly upon background alteration. Critically, the clinical relevance of the attention maps measured by the IoU against expert annotations was significantly higher for correct predictions than for incorrect predictions, linking the model's visual explanation to its diagnostic reliability. Combining Grad-CAM++ with cut-and-paste validation provided a robust framework for evaluating the explainability of the YOLOv5 model. This dual approach reveals layer-specific attention dynamics and quantifies the model's reliance on clinically relevant extracorneal features, thereby enhancing the transparency and trustworthiness of artificial intelligence-based diagnostic systems in ophthalmology.

Geographic Information Systems (GIS) are an important tool in the environmental management of protected areas, offering advanced technological methods for biodiversity protection and spatial planning.In the Divjakë-Karavasta National Park, the integration of GIS technology has significantly improved the monitoring and management of its rich ecosystems. The use of GIS in this park has enabled a detailed inventory of the health of vegetation, enabling the creation of accurate maps of the distribution of biodiversity.These maps are essential for identifying areas of special ecological importance and for determining appropriate conservation measures. GIS and RS technology provides a solid methodology used to evaluate and analyse different factors that influence a decision with regards to forest health. It helps assess risk to forest health by considering various ecological, climatic and environmental factors(temperatures, humidity, the spread of fires, air pollution etc.) affecting forest health, thus enabling improved management of the forest environment. A set of satellite images from SN32-Satellite Nusat 32 (Albania 1)/SN33-Satellite Nusat 33 (Albania 2), year 2024 are used as main data source to analyze risk factors in forest health of the park. Important indices namely Normalized Difference Vegetation Index (NDVI), Green Normalized Difference Vegetation Index (GNDVI), Land Cover (LC) and Road infrastructure have been calculated in a GIS environment using ArcGIS Desktop 10.8.2/Pro 3.2. The spatial patterns that study reveal indicate that the majority of forest areas in Divjake-Karavasta National Park resides in an adequate environment under supportive health factors.Moreover, GIS enables real-time monitoring of environmental changes, such as the appearance of invasive species or habitat degradation, providing valuable data for quick and effective interventions. The integration of GIS in the management of the Divjakë-Karavasta. National Park has brought many benefits, but it has also encountered various challenges. One of the main challenges is the need for staff training in the use of advanced GIS technology and the provision of the necessary equipment. However, the benefits of this integration are obvious, including improved efficiency in natural resource management and increased capacity to respond to environmental threats.

Using Global Navigation Satellite System data, we investigated the interplate slip before, during, and after the 2024 Hyuga-nada earthquake in Japan. Before the earthquake, a moment magnitude (Mw) 6.0 slow-slip event (SSE) was observed from late 2023 in a downdip extension of the mainshock. The coseismic slip was adjacent to the 1996 Hyuga-nada earthquake source. The afterslip resolved near the hypocenter area and in the downdip extension of the mainshock, reaching Mw 6.7 on 16 September 2024. Leading up to the earthquake, the recurrence interval for SSEs in the preslip area shortened from an average of 2 years, estimated from observations over the past 30 years, to 1 year, consistent with simulations in which the weakening of the Nankai megathrust was attributed to the cause.

Three Global Navigation Satellite System observation networks realize the detection of an evident transient crustal deformation induced by volcanic inflation activity at the Kussharo caldera, eastern Hokkaido, Japan, from 2021 to 2023. To explain this deformation field, we model three types of volcanic deformation sources, the Mogi, spheroid, and sill, using the Markov Chain Monte Carlo method. Although the spheroid and sill models also show no large differences and can generally explain the observations, the Mogi model best represents the observations, with the source of deformation estimated to be in the center of the caldera at a depth of approximately 5 km. The location of the deformation source is roughly the same regardless of which model was assumed. The inflation source is located west of the Atosanupuri fumaroles, which is the most active area in this caldera, and consistent with the center of the volcanic inflation source in the 1990s detected by the Interferometric Synthetic Aperture Rater analysis. The estimated depth of the deformation source is roughly consistent with the upper limit of the low electrical resistivity region, suggesting the presence of some fluid-like media. The volume change is distributed around 1.1 × 107 m3, about half that of the 1990s event. This study suggests a possibility that the center of the Kussharo caldera usually contracts slowly and quietly but sometimes induces inflations repeatedly. It is still unclear what triggers the inflation event and how it relates to the long-term activity of the volcano, but future monitoring will provide further insight.Graphical

We developed an AI system capable of automatically classifying anterior eye images as either normal or indicative of corneal diseases. This study aims to investigate the influence of AI’s misleading guidance on ophthalmologists’ responses. This cross-sectional study included 30 cases each of infectious and immunological keratitis. Responses regarding the presence of infection were collected from 7 corneal specialists and 16 non-corneal-specialist ophthalmologists, first based on the images alone and then after presenting the AI’s classification results. The AI’s diagnoses were deliberately altered to present a correct classification in 70% of the cases and incorrect in 30%. The overall accuracy of the ophthalmologists did not significantly change after AI assistance was introduced [75.2 ± 8.1%, 75.9 ± 7.2%, respectively (P = 0.59)]. In cases where the AI presented incorrect diagnoses, the accuracy of corneal specialists before and after AI assistance was showing no significant change [60.3 ± 35.2% and 53.2 ± 30.9%, respectively (P = 0.11)]. In contrast, the accuracy for non-corneal specialists dropped significantly from 54.5 ± 27.8% to 31.6 ± 29.3% (P < 0.001), especially in cases where the AI presented incorrect options. Less experienced ophthalmologists were misled due to incorrect AI guidance, but corneal specialists were not. Even with the introduction of AI diagnostic support systems, the importance of ophthalmologist’s experience remains crucial.

SUMMARY Earthquake-volcano interactions have been discussed to understand the underlying mechanisms of seismic ruptures or eruptions, yet the involvement of volcanic activity and the environment with fault slip termination remains unclear. Here, we present an unprecedented high-resolution image of fault motions and crustal structure at the rupture terminus in volcanic area from the 2016 Kumamoto earthquake by conducting synthetic aperture radar (SAR) data analysis and gravity inversion. We obtained a 3-D displacement field by applying multiple SAR analysis methods: standard SAR interferometry, split-bandwidth interferometry and pixel offset. We successfully mapped the ground displacements with a high-spatial resolution in the Aso caldera which was located on the eastern extension of the Futagawa fault that was the main source fault of this seismic event. We found that the rupture propagating on the Futagawa fault eastward penetrated into the Aso caldera and was divided into two major fault systems: a right-lateral fault system on the northern side and a left-lateral fault system on the southern side. However, they progressively converged immediately after penetrating into the caldera. A gravity-inferred 3-D density contrast structure revealed that a locally distributed low-density body existed in the shallow part (from the subsurface to a depth of ∼3 km) of the western edge of the caldera. The slip distribution model showed that the slips on the bifurcated faults penetrated into the low-density region and subsequently dissipated. A numerical simulation on 3-D dynamic rupture demonstrated that the low-stress state in the caldera played a role in suppressing the rupture evolution. A thermally activated hydrothermal field has developed in the area where the fault slips were attenuated. We interpret that the hydrothermal system may create conditions favourable for low-stress field, and plastic properties in the hydrothermal environment may facilitate a further decrease in rock brittleness owing to the high temperature, resulting in the terminus of fault rupture.

ABSTRACT Drone-based synthetic aperture radar (SAR) analysis offers a simple and efficient technique for acquiring observational data from various research areas. However, fundamental research on observation techniques, including the investigation of drone flight parameters, remains insufficient. This study focuses on improving the resolution of intensity images of a single-look complex (SLC) via drone-based SAR observations. By conducting experiments at different flight speeds and analysing the obtained SLC images, we demonstrated that higher drone speeds resulted in enhanced image resolution under the conditions investigated at flight speeds of ≤ 5 m s−1. A comparison with satellite SAR images highlighted the superior performance of drone-based SAR in capturing topographic features. The analysis also suggested that factors including trajectory deviation and Doppler rate affected the resolution and azimuth position. The simulation results supported the experimental findings on the relationship between drone speed and resolution. Our results emphasize the potential of drone-based SAR observations for monitoring slope failures and suggest the importance of the drone flight parameter selection. In the future, drone-based SAR is expected to produce intensity images of slopes and locate slope deformations associated with blasting for mining and earthquakes.

According to a 2013 report by the Earthquake Research Committee of Japan, it was estimated that the probability of the occurrence of the next Nankai earthquake within the next three decades is 70–80%. Therefore, to realize hazard estimation, it is crucial to estimate the state of the plate interface in the Nankai Trough subduction zone. In this study, we focused on a transient from 2018 in the subduction zone of the Nankai Trough, southwest Japan, detected by the Global Navigation Satellite System (GNSS) network. Thereafter, we estimated the spatiotemporal evolution of the slip at the plate interface by subjecting the GNSS position time series to time-dependent inversion. The results obtained showed that a long-term slow-slip event (l-SSE) possibly occurred on the Kii Peninsula in 2020. The Kii-Channel l-SSE (Mw 6.3), with an irregular recurrence interval, was observed from 2019 to 2022. Additionally, the Central Shikoku l-SSE (Mw 6.5) was observed from 2019 to 2023, and there appeared to be a correlation between the Central Shikoku l-SSE and the northwestern Shikoku short-term slow-slip event (s-SSE). l-SSE occurred from July 2018 to August 2019 in the northern Hyuga-nada and Bungo channel, and in late 2018, another l-SSE occurred in southern Hyuga-nada before the May 2019 Hyuga-nada earthquake. Further, after the 2018–2019 events, the southern Hyuga-nada l-SSE occurred from mid-2020 to early 2021 and in January 2023 and is still ongoing, consistent with the expected recurrence interval. The seemingly transient slip off the Ohsumi Peninsula, detected after the Mw 5.7 earthquake of October 2022, continued until July 2023 with Mw 6.1. Furthermore, after the 2019 Tanegashima earthquake, an l-SSE occurred for approximately 4 years. The moment magnitude (Mw) of the afterslip of the Tanegashima earthquake was estimated to be 6.7, larger than that of the main shock (Mw 6.4). We also noted that the transient slip off Tanegashima included four possible s-SSEs that occurred in 2020, 2021, 2022, and 2023. Therefore, the sporadic aseismic slips along the Nankai Trough changed the stress state of the areas neighboring the aseismic slip zones in favor of the interplate slip.Graphical