Yusuke Mukuhira

Abstract Induced seismicity with unexpectedly large magnitude often occurs after shut‐in or end of stimulation, generating concerns at the end of stimulation. We investigated the physical mechanism of large‐magnitude induced seismicity during shut‐in following the hydraulic stimulation at Basel, Switzerland. Larger postinjection events occurred at the periphery of the seismic cloud. We estimated the pore pressure required to cause shear slip using Coulomb failure criteria from stress information

Abstract Understanding the details of pressure migration during hydraulic stimulation is important for the design of an energy extraction system and reservoir management, as well as for the mitigation of hazardous‐induced seismicity. Based on microseismic and regional stress information, we estimated the pore pressure increase required to generate shear slip on an existing fracture during stimulation. Spatiotemporal analysis of pore pressure migration revealed that lower pore pressure migrates f

Abstract Slab-derived fluids control crustal dynamics in the subduction zone. However, the slab-derived fluid budget has never been quantified beyond a geophysical and geological spatiotemporal resolution. Here, we target an intense earthquake swarm associated with the M9 Tohoku earthquake, which represented the critical dynamic behavior of slab-derived fluid. The fluid volume involved has been quantified, with a plausible range of 10 6 −10 8 m 3 , by utilizing injection-induced seismicity insig

Abstract Like natural seismicity, induced seismicity caused by injection also shows a power law size distribution, and its gradient b ‐value is used for seismic hazard analysis. Despite the well‐known result that b ‐value is negatively correlated with differential stress for natural earthquakes, there is no similar correlation for b ‐value variations because the differential stress is nearly constant for injection‐induced seismicity, we thus investigate the b ‐value dependence on the relative sh

Variability in the b-value, which describes the frequency distribution of earthquake magnitudes, is usually attributed to variations in differential stress in the setting of natural and laboratory earthquakes. However, differential stress is unlikely to explain b-value variations on the reservoir scale of injection-induced seismicity cases where significant differential stress variability can hardly be expected. We investigate the responsible geomechanical parameters for the b-value reduction ob

Abstract Forecasting microseismic cloud shape as a proxy of stimulated rock volume may improve the design of an energy extraction system. The microseismic cloud created during hydraulic stimulation of geothermal reservoirs is known empirically to extend in the general direction of the maximum principal stress. However, this empirical relationship is often inconsistent with reported results, and the cloud growth process remains poorly understood. This study investigates microseismic cloud growth

ABSTRACT The forecasting and risk assessment of induced seismicity associated with fluid injection have considerable importance for subsurface energy development. We have developed a seismic evaluation method called the possible seismic moment (PoSeMo) model to assess the potential seismic moment that could be released in the future based on current seismic activity. The PoSeMo model assumes the existence of a representative parameter that can describe the seismic characteristics of a given fiel

ABSTRACT Detection and analysis of small magnitude events is valuable for better characterization and understanding of reservoirs in addition to developing strategies for mitigating induced seismicity. Three-component (3C) receivers, which are now widely used, are commonly deployed in boreholes to provide continuous seismic data amenable to novel and powerful analysis. Using multicomponent continuous records of ground motion, we utilize two principal features of the direct P-wave arrival: (1) li

Determining the focal mechanisms of injection induced microseismicity provides beneficial information not only for understanding the features of induced seismicity but also for characterizing the fracture system in the reservoir. However, focal mechanisms of microseismicity are often not well determined with first motion information alone due to limited station coverage. We propose a new method to better constrain first motion focal mechanisms of fluid-induced seismicity by introducing in situ s

Hydraulic fracturing initiates the fractures along the direction of maximum-stress in a plane normal to a borehole by injecting high-pressure fluid. Nucleated fractures enhance permeability around boreholes, facilitating the extraction of various subsurface resources and the injection of storage fluids such as CO 2 or H 2 . However, hydraulic fracturing cannot technically generate fractures in directions other than that of the maximum-stress orientation; therefore, permeability enhancement is al

Occurrence of microseismic events with large magnitude, which are felt on the surface, has been recently receiving much attention as one of the practical problems in stimulation/production of HDR/HFR/EGS geothermal reservoirs. The microseismic activities with large magnitude have been also reported from some of the hydrothermal geothermal fields. Microseismic events with moment magnitude Mw exceeded 2.0 occurred in deeper and middle part of the microseismic cloud during and just after a hydrauli