Large earthquakes and tsunamis are major hazards at subduction zones, where segmentation governs rupture extent and magnitude. However, the mechanisms that define segment boundaries remain unclear. In the eastern Nankai Trough, which is anticipated to host future megathrust earthquakes, the forearc is divided into the Tonankai and Tokai segments. Here we use newly acquired 3D seismic reflection data (2021-2022), to image structures across the segment boundary. High-resolution profiles reveal three seafloor topographic highs associated with active folding and thrusting in forearc sediments, the accretionary wedge, and along the plate interface. These features trend NNE-NE in Tonankai but ENE in Tokai, across an arcuate syntaxis. Collision of the Paleo-Zenisu Ridge, a remnant of the Izu-Bonin arc on the Philippine Sea Plate, appears to impose the syntaxis structure of the upper plate. Our results demonstrate that the forearc structural complexity exerts a primary control on margin segmentation and associated hazards.

Slow earthquakes are crucial for understanding the nature of subducting plate boundaries and their seismic coupling. Although many very low-frequency earthquakes (VLFEs) have been recently recorded in the central part of the Nankai Trough, there have been only rare cases reported between the Kii Channel and Cape Shionomisaki. To investigate the structural features and their potential relationship with the slow events, in November 2018, JAMSTEC deployed a dense array of 96 ocean-bottom seismometers (OBS) to acquire an active-source seismic refraction dataset from the seaward side of the subduction trough to the accretionary prism off Cape Shionomisaki. We applied travel time and waveform tomography to the OBS data and reconstructed the seismic P-wave velocity model down to the upper mantle. The subsurface velocity model reveals some new discovered features, and describes the accretionary prism as consisting of a weak outer wedge and a strong inner wedge. The velocity anomaly bodies inside the wedge possibly link to specific deformation processes and the evolution of the accretionary prism. As compared to a transect across the adjacent Kumano Basin, where there are densely distributed VLFEs, the distinct results from these two locations reveal potential structural and physical differences that cause variability in seismic activities.

Large earthquakes and tsunamis are major hazards associated with subduction zones, whose segmentation controls rupture extent and event magnitude. However, the mechanisms governing segment size and shape remain poorly understood. Proposed controlling factors include variations in the geophysical-geological properties of the upper plate, lower plate, and megathrust interface. The Nankai Trough, Japan’s well-studied subduction zone, is anticipated to host future megathrust earthquakes within decades. Its eastern forearc is subdivided into the Tonankai and Tokai segments, both underthrust by the Philippine Sea (PHS) Plate. This study presents a new structural interpretation of 3D seismic reflection data acquired in 2021-22 focusing on the boundary between these segments. We investigate geological and geophysical features potentially influencing segmentation. High-resolution seabed and subsurface data identify three prominent topographic highs with active fold-and-thrusting in the inner forearc sediments and accretionary wedge, and plate interface. These features trend NNE–NE in the Tonankai segment and ENE in the Tokai segment, across a major arcuate structure (syntaxis). Paleo-Zenisu Ridge on the PHS plate—a backarc remnant of the Izu-Bonin arc—collides with the southern end of this NW-trending syntaxis and appears to impose geometric control on the segment boundary.

The clustered distribution of shallow slow earthquakes in the Nankai Trough has been attributed to different factors such as seamount subduction, pore fluid pressure, fluid migration, and sediment input. However, there is still a lack of comprehensive understanding of how these factors interact to generate slow earthquakes. We examined the seismic reflection profiles crossing four subducted seamounts off Muroto to understand how they deform the accretionary wedge. Along‐trough seismic reflection profiles within the accretionary wedge were also used to infer the lithology of the underthrusted sediments. The seamounts are at different stages of subduction and their associated underplated sediments were identified. Comparison with published sandbox models indicates that the underplated sediments comprise fluid‐rich trench fill sediments. Negative polarity decollement and transparent underthrust are observed off Muroto. The transparent underthrust is interpreted as mudstone, while stratified underthrust sediments in other regions are interpreted as turbidites. Comparing with previous numerical simulations, we propose the following deformational history: (a) subduction of the first seamount resulted in underplating of a large volume of fluid‐rich trench fill sediments, (b) the underplated sediments are undergoing horizontal compression from subsequent subduction of the three seamounts resulting in high pore pressure consistent with previously reported low velocity zones, and (c) the horizontal compression may also result in fluid expulsion and these fluids migrate updip and get trapped because the mudstones serve as an impermeable cap. This mechanism accounts the aforementioned factors associated with slow earthquakes and likely controls the clustered distribution off Muroto.

Abstract Recently, integrated geophysical‐geological surveys in the Nankai subduction zone in Japan have revealed that slow earthquakes repeatedly occur beneath the outer wedge of the forearc. During December 2020 to February 2021, clustered slow earthquakes propagated around the frontal thrust of the accretionary wedge. The frontal thrust ramps up from the basal décollement and slips over trench‐filling sediment along the landward edge of the Nankai trough floor. Here, the Paleo‐Zenisu ridge has been subducted beneath the inner‐outer slope border. In addition, ocean floor topography and geologic structure revealed by seismic reflection surveys completed before 2022 document that the basement of the Philippine Sea Plate beneath the frontal thrust has a seamount and a horst‐like basement high. The northern edge of the basement high is located at the ramp‐up position of the frontal thrust. The 2020–2021 clustered slow earthquakes started at the Paleo‐Zenisu ridge and propagated to the topographic highs beneath the deformation front. Considering that the relative plate convergence between the upper Amurian Plate of the Nankai forearc and the subducting Philippine Sea Plate is ∼6.0 cm/year, the basement high at the deformation front has uplifted the frontal crest of the wedge at an average rate of 2.7–5.7 mm/year for several tens to hundred thousand years. These rates are among some of the highest rock uplift rates measured in the world. The slow earthquakes in the off‐Kumano Nankai Trough in 2020–2021 are a snapshot of a “living” Nankai frontal thrust during the megathrust interseismic period.

Active and widespread CH 4 accumulations and emissions in the Nankai Trough subduction zone are attested by numerous mud volcanoes, gas plumes, and gas hydrates containing biogenic and thermogenic CH 4 . However, the source rocks of the thermogenic CH 4 and the geological source of H 2 for microbial CH 4 production by methanogens remain uncertain. Here, we reveal the timing and rate of thermogenic CH 4 and H 2 generation from shales and metapelites associated with oceanic plate subduction in the Nankai Trough by gas and geochemical analyses. The results show that the thermogenic CH 4 and H 2 are generated mainly in the underthrust sediments below the décollement. The sustainable H 2 supply from the underthrust sediments can potentially contribute to microbial CH 4 production. The findings enhance our understanding of the active CH 4 emission, large-scale gas hydrate formation, and subseafloor biosphere in the oceanic plate subduction zone.

Background Index tumors are the most aggressive tumors of the prostate. However, their clinical significance remains unclear. This study aimed to assess the incidence of index tumor location according to the zonal origin and whether these locations affect the prognosis after radical prostatectomy in patients with negative surgical margins.Methods This single-centered, retrospective study evaluated 1,109 consecutive patients who underwent radical prostatectomies. An index tumor was defined as the largest tumor in the prostate gland. We detected these locations based on McNeal's zonal origin using whole-mount sections. Biochemical recurrence (BCR) free survival curves were generated using the Kaplan-Meier method. Univariate and multivariate analyses using the Cox proportional hazards model were performed to determine the predictive factors for early BCR (within 1-year).Results A total of 621 patients with negative surgical margins who did not receive adjuvant therapy were included in this study. The index tumor were located in the transitional zone in 191 patients (30.8%), the peripheral zone in 399 patients (64.3%), and the central zone in 31 patients (5.0%). In total, 22 of 621 patients (3.5%) experienced early BCR and 70 patients (11.2%) experienced overall BCR at a median follow-up of 61.7 months. According to the index tumor location, the early BCR-free rates were 99.5%, 95.7 %, and 83.3% in the transitional, peripheral, and central zones, respectively. On multivariate analysis, the index tumor in the central zone was an independent predictor of early BCR with negative surgical margins following radical prostatectomy, followed by prostatectomy pathological grade, index tumor in the peripheral zone, and high prostate-specific antigen level.Conclusions We assessed the significance of index tumor location in patients with negative surgical margins following radical prostatectomy. Index tumors located in the central zone, although infrequent, were the strongest predictive factors for early BCR. Our results may allow urologists and patients to reconsider the therapeutic strategies for prostate cancer.

Abstract We examined the possible factors affecting the spatial distribution of very low frequency earthquakes and tremors in the shallow megathrust of Nankai Trough (<30 km) using a dense network of prestack depth migrated profiles at the frontal wedge. Geometrical parameters examined were decollement roughness, taper angle, and underthrust thickness. Physical properties such as effective basal friction (μb) and pore pressure ratio (λ*) were calculated from the taper angle and p‐wave velocity. Regions of low λ* (0.39 ± 0.08) and smooth decollement showed no slow earthquake activity. In contrast, high activity of slow earthquakes was observed in areas with a rough decollement due to the presence of subducted seamounts or bathymetric highs. The low taper angle (3.8°) off Muroto where slow earthquakes also occur translates to a wide zone of low μb (0.21 ± 0.06) and high λ* (0.66 ± 0.06). However, our results also show that slow earthquakes don't always occur in areas with high λ*.

The EV-301 trial showed the efficacy of Enfortumab-Vedotin (EV) in the 3rd-line therapy for metastatic Urothelial Carcinoma (mUC) previously treated with platinum-combined chemotherapy and immune-checkpoint inhibitor. Here we showed an initial report of EV in our institution. 25 patients (Pts) with mUC received EV from January 2021 to July 2023 at our institution. EV was administered 10mg/kg weekly until disease progression. Whole-body CT scan was performed every two months(Ms). We retrospectively evaluated progression free survival based on RECIST version 1.1 as efficacy and adverse events (AEs) rate based on the National Cancer Institute CTCAE, version 4.03 as safety. Of 25 patients (Pts), with median age of 73 (54-85), 16 (64%) Pts had bladder tumor, 9(36%) Pts had upper urinary tract, 1 Pt had both upper and lower urinary tract as primary. 18(72%) Pts had lymph node metastasis (Mets), 14(56%) Pts had lung Mets, 5 (20%) Pts had liver Mets 4 (16%) Pts had bone Mets. 5(20%) Pts had 4 regimens, 7(28%) Pts had 3 regimens and 13(52%) Pts had 2 regimens of pre-treated systemic therapy for mUC. During the median follow-up period of 7.0 (2.1-16.2) Months, 9 (36%) Pt had died. The best response during follow-up period was CR in2(8%), PR in 11(44%), SD in 11(44%) and PD in1(4%) Pts. Median PFS was 10.5 Ms and OS was 13.0. 8 Severe AEs (more than Grade3) was occurred in 8 (32%) Pts, derimatosis was the highest occurrence AE and 65% patients had ermatosis. OS of patiets with prior taxane therapy was significantly worse than that of patients without prior taxane therapy (11.4M vs 14.1M, p=0.027). Initial report of Enfortumab-Vedotin resulted in a median PFS of 10.5 Ms and 20% severe AE, which was as safe and effective as the report from clinical trial. OS of patients pre-treated with taxane therapy was significantly worse than that of patients without prior taxane therapy.

Abstract Mud volcanoes, gas plumes, and gas hydrates comprising thermogenic and biogenic CH4 are widely distributed in the Nankai Trough subduction zone, showing ongoing significant CH4 activity. However, the source rocks of the thermogenic CH4 and the geological source of H2 for microbial CH4 production remain uncertain. Here, we reveal the timing and amount of the thermogenic CH4 and H2 generation in shales and metapelites during diagenesis to metamorphism and estimate their current generation in the Nankai Trough from the movements of the oceanic plate and the accretionary prisms. The results show that the thermogenic CH4 and H2 are generated mainly in the underthrust sediments below the décollement. The sustainable H2 supply from the underthrust sediments can be another potential H2 contributing to microbial CH4 production. The findings enhance our understanding of the active CH4 emission, large-scale gas hydrate formation, and subseafloor biosphere in the oceanic plate subduction zone.

The causes for forearc basin and megathrust rupture zone segmentation are controversial. The Nankai forearc, Japan, is separated into five domains based on topography: Enshu, Kumano, Muroto, Tosa, and Hyuga. The boundaries of these domains correspond to the rupture limits of large earthquakes. We examined the geologic structure of the boundary region between the Kumano and Muroto domains off the Kii Peninsula using multichannel seismic reflection data to evaluate the role of upper plate composition in controlling segmentation. The results suggest that thick cover sediments and underlying accretionary prism are obliquely thrust landward over the igneous basement complex rock in the region of offshore of Cape Shionomisaki and separate the forearc basin. The igneous basement complex rocks directly overlying the plate interface in the hypocentral regions of 1944 Tonankai and 1946 Nankai earthquakes. The 1944 earthquake originated at the base of the complex, and the rupture extent slipped past its basement boundary, whereas the 1946 event nucleated at the updip boundary of the basement complex. The dense igneous rocks might have worked as a heavily loaded barrier on the seismogenic megathrust and separated the rupture area of both the earthquakes. Upper plate geology may be an important factor in controlling seismogenesis in the Nankai Trough and may serve as an example for understanding the controls on megathrust slip in other subduction zones.

To investigate structural characteristics associated with variations in slip behavior on the plate boundary in the Nankai subduction zone, we conducted seismic reflection surveys in the central‐western Nankai Trough. Data were processed by pre‐stack depth migration. The resulting depth map of the top of the subducting Philippine Sea plate shows detailed topographic features of the plate boundary, including subducting seamounts and large‐scale undulations of the plate surface. We report the presence of a structurally anomalous region, potentially with low velocity, in the overriding plate at the boundary between the zone of large coseismic slip during the 1946 Nankai earthquake and the area producing slow earthquakes. This anomaly appears to be related to depth‐dependent variations in plate boundary slip style and plate coupling in the central‐western Nankai Trough.

Recent studies have documented the occurrence of shallow very low frequency earthquakes (VLFE) in subduction zones. The heterogeneity of the materials or stresses that act on the plate interface results in the variable slip rate. Stress on the décollement can be controlled by the décollement geometry and the regional stress, which is also able to control the material properties. We determined the distribution of stress along the shallow portion of the décollement in the Nankai Trough using a three-dimensional (3D) seismic survey and regional stress analysis to construct maps of normalized slip tendency (Ts') and dilation tendency (Td). Alignments of VLFEs trend parallel to the trends of [Formula: see text] and [Formula: see text]. On the other hand, very low [Formula: see text] and [Formula: see text] areas probably act as barriers that limit the number of VLFEs that can migrate towards the trench. Because the [Formula: see text] and [Formula: see text] distributions are derived only from the décollement geometry and the regional stress without incorporating any data on sediment properties, the consistency between the trends suggests that the décollement geometry is the primary control on VLFE activity.

Abstract The frontal megathrust of the Nankai Trough subduction zone is recognized as a seismogenic fault based on a record of frictional heating, but the underlying micromechanical processes that act on the fault surface are poorly known. Here we present a layer of fault gouge ∼2 mm thick within a core drilled across the megathrust, in which smectite‐rich siltstone has been transformed into a preferentially oriented illite aggregate. The nearly complete breakdown of smectite is consistent with fast frictional heating on this fault; however, the microtextures of the gouge and its surroundings are asserted one produced experimentally by slow slip. We suggest that slow slip with small shear strain has overprinted the textures produced by the previous faster and larger slip. This interpretation based on microtectonic evidence suggests a slow slip around the frontal megathrust took place during slow down, afterslip, or interseismic as observed now going in subduction zone. We suggest that the illite‐dominated gouge is conditionally stable, likely to shift from rapid to slow slip at different times.

The variants of urothelial carcinoma such as micropapillary (MP), plasmacytoid (PC), and lipid cell (LC) carry a very poor prognosis. High progression speed and resistance to chemotherapy are considered to be part of the reasons for poor prognosis. Accordingly, early diagnosis and early treatment are important to improve prognosis. In this study, we elucidated the cytological diagnostic criteria of these variants, and also investigated whether preoperative urine cytology could diagnose these variants and the possible association between cytological predictability and pathological features. Between April 2015 and March 2020, 45 patients were histologically diagnosed as MP, PC, and LP by TURBT in our institution. The experienced cytologists (YW) in our hospital re-evaluated the preoperative urine cytology in these cases to determine whether or not the prediction of the variant histology is possible. The following findings were used as criteria, small papillary cell clumps with strong binding in MP, circular atypical cells similar to plasma cells in PC, and atypical cells similar to lipoblasts with empty cells in LC. Additionally, we analyzed whether histopathological findings such as muscle invasion, tumor size, tumor necrosis, lymphovascular invasion (LVI), CIS, affect the prediction of the variants. Of 45 cases, MP, PC and LC were 18 (40%), 13 (29%) and 14 (31%) patients, respectively. 3 cases of MP (17%), 5 of PC (38%) and 2 of LC (14%) could be predicted by re-evaluating preoperative urine cytology. In addition, positive preoperative urine cytology (class 4 or higher) was found in 14 cases in MP (78%), 8 cases in PC (62%), and 11 cases in LC (79%), with estimated probabilities of 21%, 62%, and 18%, respectively. Pathological features were not different between the predictable and unpredictable cases: muscle invasion, 90% vs 74% (P = 0.26); median tumor size, 31 mm vs 38 mm (P = 0.37); tumor necrosis, 20% vs 28% (P = 0.64); LVI, 60% vs 45% (P = 0.42); CIS, 40% vs 34% (P = 0.74), respectively. Although in some cases, atypical cells suggesting UC variants appeared in the urine cytology, this study suggested that the preoperative cytological diagnosis of bladder cancer variants seems to be difficult.

Logging data are measurements of physical properties of the formation surrounding a borehole, acquired in situ after completion of coring (wireline logging) or during drilling (Logging-While-Drilling, LWD). The range of data (resistivity, gamma radiation, velocity, density, borehole images,…) in any hole depends on the scientific objectives and operational constraints.

Logging data are measurements of physical properties of the formation surrounding a borehole, acquired in situ after completion of coring (wireline logging) or during drilling (Logging-While-Drilling, LWD). The range of data (resistivity, gamma radiation, velocity, density, borehole images,…) in any hole depends on the scientific objectives and operational constraints.

The Nankai Trough, Japan, is a subduction zone characterized by the recurrence of disastrous earthquakes and tsunamis. Slow earthquakes and associated tremor also occur intermittently and locally in the Nankai Trough and the causal relationship between slow earthquakes and large earthquakes is important to understanding subduction zone dynamics. The Nankai Trough off Muroto, Shikoku Island, near the southeast margin of the rupture segment of the 1946 Nankai earthquake, is one of three regions where slow earthquakes and tremor cluster in the Nankai Trough. On the Philippine Sea plate, the rifting of the central domain of the Shikoku Basin was aborted at similar to 15 Ma and underthrust the Nankai forearc off Muroto. Here, the Tosa-Bae seamount and other high-relief features, which are northern extension of the Kinan Seamount chain, have collided with and indented the forearc wedge. In this study, we analyzed seismic reflection profiles around the deformation front of accretionary wedge and stratigraphically correlated them to drilling sites off Muroto. Our results show that the previously aborted horst-and-graben structures, which were formed around the spreading center of the Shikoku Basin at similar to 15 Ma, were rejuvenated locally at similar to 6 Ma and more regionally at similar to 3.3 Ma and have remained active since. The reactivated normal faulting has enhanced seafloor roughness and appears to affect the locations of slow earthquakes and tremors. Rejuvenated normal faulting is not limited to areas near the Nankai Trough, and extends more than 200 km into the Shikoku Basin to the south. This extension might be due to extensional forces applied to the Philippine Sea plate, which appear to be driven by slab-pull in the Ryukyu and Philippine trenches along the western margin of the Philippine Sea plate.