Continuous monitoring system for safe managements of CO2 storage and geothermal reservoirs.

We have developed a new continuous monitoring system based on small seismic sources and distributed acoustic sensing (DAS). The source system generates continuous waveforms with a wide frequency range. Because the signal timing is accurately controlled, stacking the continuous waveforms enhances the signal-to-noise ratio, allowing the use of a small seismic source to monitor extensive areas (multi-reservoir). Our field experiments demonstrated that the monitoring signal was detected at a distance of ~ 80 km, and temporal variations of the monitoring signal (i.e., seismic velocity) were identified with an error of < 0.01%. Through the monitoring, we identified pore pressure variations due to geothermal operations and rains. When we used seafloor cable for DAS measurements, we identified the monitoring signals at > 10 km far from the source in high-spatial resolution. This study demonstrates that multi-reservoir in an extensive area can be continuously monitored at a relatively low cost by combining our seismic source and DAS.

[CLINICAL STUDY OF OPEN RADICAL CYSTECTOMY AND ILEAL CONDUIT CONSTRUCTION FOR BLADDER CANCER: RESULTS OF 15-YEAR SINGLE CENTER EXPERIENCE].

(Objective) We retrospectively analyzed clinical outcome, prognostic factors and adjuvant chemotherapy for bladder cancer patients with open radical cystectomy (ORC) combined with ileal conduit construction (ICC). (Patients and methods) From February 2005 to February 2019, 179 patients underwent ORC and ICC for invasive bladder cancer or BCG unresponsive non-muscle invasive bladder cancer. We investigated intraoperative and early postoperative complications, overall survival (OS), cancer-specific survival (CSS), and poor prognostic factors affecting OS. Furthermore, we evaluated the prognosis of patients with pT3,4 or pN1-3 depending on adjuvant chemotherapy. (Results) Clavien-Dindo Grade 4 or 5 complications were not occurred. The 5-year and 10-year OS probability were 71.1% and 57.4%, respectively, while the 5-year and 10-year CSS probability were 76.5% and 71.5%, respectively. Multivariate analysis revealed that male (HR = 2.70, 95%CI [0.97-7.51]), pT3,4 (HR = 1.83, 95%CI [1.05-3.21]), and pN1-3 (HR = 2.85, 95%CI [1.62-5.03]) were independent poor prognostic factors. Adjuvant chemotherapy significantly improved OS (p = 0.03) and CSS (p = 0.017) in pN1-3 patients. (Conclusion) ORC combined with ICC was an effective operative method, and good results were obtained. Adjuvant chemotherapy may be effective for patients with positive regional lymph nodes.

Seismic evidence for sharp lithosphere-asthenosphere boundaries of oceanic plates.

The mobility of the lithosphere over a weaker asthenosphere constitutes the essential element of plate tectonics, and thus the understanding of the processes at the lithosphere-asthenosphere boundary (LAB) is fundamental to understand how our planet works. It is especially so for oceanic plates because their relatively simple creation and evolution should enable easy elucidation of the LAB. Data from borehole broadband ocean bottom seismometers show that the LAB beneath the Pacific and Philippine Sea plates is sharp and age-dependent. The observed large shear wave velocity reduction at the LAB requires a partially molten asthenosphere consisting of horizontal melt-rich layers embedded in meltless mantle, which accounts for the large viscosity contrast at the LAB that facilitates horizontal plate motions.

Weak interplate coupling by seamounts and repeating M approximately 7 earthquakes.

Subducting seamounts are thought to increase the normal stress between subducting and overriding plates. However, recent seismic surveys and laboratory experiments suggest that interplate coupling is weak. A seismic survey in the Japan Trench shows that a large seamount is being subducted near a region of repeating earthquakes of magnitude M approximately 7. Both observed seismicity and the pattern of rupture propagation during the 1982 M 7.0 event imply that interplate coupling was weak over the seamount. A large rupture area with small slip occurred in front of the seamount. Its northern bound could be determined by a trace of multiple subducted seamounts. Whereas a subducted seamount itself may not define the rupture area, its width may be influenced by that of the seamount.