Hirokazu Moriya

Hirokazu Moriya

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77
Publications
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860
Citations
Citations since 2017
13 Research Items
383 Citations
20172018201920202021202220230204060
20172018201920202021202220230204060
20172018201920202021202220230204060
20172018201920202021202220230204060

Publications

Publications (77)
Preprint
In geothermal development, microseismic monitoring is important technique to monitor the various phenomena in the reservoirs throughout location, activity, and magnitude of microseismicity. Picking P-and S-wave arrivals accurately from seismic data is inevitable process for subsequent seismic analyses. However, the manual phase picking is a time-an...
Article
The presence of fault gouge and the generation of wear material between two sliding rock surfaces plays a critical role in slip weakening and propagation of ruptures along underground brittle shear fractures forming ahead of tabular excavations in deep and high stress gold mining. We performed two types of friction experiments: one with a fault gou...
Article
Full-text available
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 powerf...
Article
A highly-stressed shaft pillar is prone to large seismic events, falls of ground and rockbursts, which may cause injuries and loss of production, especially in weak geotechnical zones. It is thus important to identify weak geotechnical zones in order to mitigate risks. In this study, we present integrated studies (underground mapping, petrology, ro...
Article
We investigated the activities of very small (−5.10 ≤ MW ≤ −2.35) repeating earthquakes that occurred during 14 months on a geological fault at a 1 km depth in the Cooke 4 gold mine in South Africa. Out of 4214 acoustic emissions occurring on the fault, 1785 (42.36% of the total) were identified as repeaters on the basis of the waveform similarity...
Article
Full-text available
Acoustic emission (AE)/seismicity activity increased near the city of Sendai, Japan, after the 11 March 2011 Tohoku earthquake in a newly seismically active region near the Nagamachi-Rifu fault, which caused a magnitude 5.0 earthquake in 1998. The source of this activity was around 12 km beneath an artificial lake. At the same time, activity on the...
Article
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 sli...
Article
Full-text available
Gold mines in South Africa have mining depths of up to ~4 km. Mining in such depths under high-stress conditions induces many earthquakes, which pose serious hazard to mine workers. To mitigate seismic risks and to understand the role ofmicroearthquakes in earthquake generation processes, we have conducted ultra-sensitive seismic observations, whic...
Article
We observed very small repeating earthquakes with -5.1≤Mw≤-3.6 on a geological fault at 1km depth in a gold mine in South Africa. Of the 851 acoustic emissions that occurred on the fault during the 2month analysis period, 45% were identified as repeaters on the basis of waveform similarity and relative locations. They occurred steadily at the same...
Article
Full-text available
We applied advanced mapping techniques to 291 230 acoustic emission (AE) events as small as around M -4 that were recorded over 50 days by an ultra-high resolution network close to the active front of a tabular mining stope being advanced northward at 1. km depth in the Cooke 4 Gold Mine in South Africa. We first applied joint hypocenter determinat...
Article
Acoustic Emissions (AE) down to MW ~ –4 were recorded at a site 1 km beneath the surface in the Cooke 4 Mine, South Africa. Several planar AE clusters with 10–100 m lateral extents were identified. Most of them were located several tens of meters away from the mining front, and exhibited steady activity during the analysis period of about two month...
Article
Three months of acoustic emission (AE) monitoring in a South African gold mine down to MW –5 revealed a newly emergent planar cluster of 7557 events –3.9 ≤ MW ≤ –1.8 (typical rupture radius of 6–70 cm) that expanded with time to reach a size of 20 m on a preexisting geological fault near an active mining front 1 km beneath the ground. It had a shar...
Conference Paper
Full-text available
A multi-disciplinary study of the response of the rock mass to mining and mining-induced earthquakes has been conducted in six gold mines in South Africa at sites deeper than 3 km, or with equivalent stress. More than 80 holes (with a total length of more than 2.8 km) were drilled in earthquake-prone areas to locate faults and install instruments....
Article
Full-text available
We investigated frequency-magnitude distribution (FMD) of acoustic emissions (AE) occurring near an active mining front in a South African gold mine, using a catalog developed from an AE network, which is capable of detecting AEs down to M W −5. When records of blasts were removed, FMDs of AEs obeyed a Gutenberg−Richter law with similar b values, n...
Article
We measured the thickness of the transverse structures associated with the bovine coccygeal transverse processes (bone specimen) by using ultrasonic waves and examined the reliability of this measurement for use in spinal surgery. We first measured the velocity of ultrasonic waves propagating in the spinous process. We then made a hole in the trans...
Article
We provide a status report on a 5-year project to monitor in-situ fault instability and strong motion in South African gold mines. The project has two main aims: (1) To learn more about earthquake preparation and generation mechanisms by deploying dense arrays of high-sensitivity sensors within rock volumes where mining is likely to induce signific...
Article
Identification of similar seismic events is important for precise estimation of source locations and for evaluation of subsurface structure. Phase-only correlation is well known as a real-time image-matching method for fingerprint identification. I applied the phase-only correlation in a geophysical context to identify similar waveforms among micro...
Conference Paper
Identification and clustering of similar seismic events are important for precise estimation of source locations and for evaluation of subsurface structure. Phase-only correlation is well known as a real-time image-matching method for fingerprint identification. In this paper, I propose a method of cluster analysis using phase-only correlation (POC...
Article
Full-text available
In this paper, the quantitative evaluation of performance and advantages of Geothermal Heat Pump (GeoHP) system in Yumoto District in Fukushima Prefecture, Japan, was studied comparing to other ordinary areas, where the geothermal gradient and the thermal conductivity these values are 3-4 and 1.7 times larger than those in other ordinary areas show...
Article
Full-text available
In this paper, we examine how the thermal conductivity estimated on line-source theory is affected by geothermal gradient, where we discuss it through a numerical simulation referring the real data obtained at Yumoto, Fukushima, Japan. The thermal conductivity of layer estimated though thermal response test is usually apparent thermal conductivity...
Conference Paper
In this paper, we discuss the relationship between the accurate hypocentral distribution and three-dimensional (3-D) geological structure in and around the Horonobe area in northern Hokkaido, Japan. The multiplet-clustering analysis was applied to the 421 micro-earthquakes which occurred from 1 September, 2003 to 30 September, 2007. The 3-D geologi...
Article
The relationship between induced microseismic multiplets and fluid injection during hydraulic stimulation of geothermal reservoirs is a possible technique for monitoring fluid flow in fractures and identifying major fluid flow paths in reservoirs. We have identified induced microseismic multiplets in a reservoir zone where preexisting fractures wer...
Article
Full-text available
Local earthquakes observed at Sendai, Japan, were analyzed to confirm the validity of a method of polarization analysis using the spectral matrix of seismic wave and its application to seismic reflection studies of the crust using local earthquake data. Reflectors (Bright spots) are known below the Nagamachi-Rifu fault, which caused an M 5.0 class...
Article
Full-text available
A simulator for the geothermal heat pump system considering the groundwater flow has been developed. It is known that the groundwater flow affects the ability of heat extraction such as transient response and recovery of temperature. Therefore, it is necessary to simulate the dynamic behavior of the underground heat extraction system in order to ev...
Conference Paper
A new method for detecting the arrivals of linearly or elliptically polarized waves by using a spectral matrix has been developed and the method has been applied to reflection imaging of the earth's crust. In this paper, the theory for the detection of polarized wave is described and the detectability of polarized waves has been discussed using the...
Article
A new method for detecting the arrivals of linearly or elliptically polarized waves by using a spectral matrix was developed and applied to reflection imaging of the earth"fs crust and upper mantle. In this method, parameter values representing the confidence levels of the detection of the arrivals of linearly or elliptically polarized waves are us...
Article
I present a statistical method for detecting the arrival times of polarized seismic waves on three-component seismic observations in the time and frequency domains. In this method, the polarization, which is a representation of the 3D particle motion of seismic waves, is evaluated on the basis of a spectral matrix in the time and frequency domains...
Article
Full-text available
We have developed a numerical model of Geothermal Heat Pump (Geo HP) Systems as an element in the simulator of Integrated Renewable Energy Systems (TRES). The numerical model of Geo HP systems consists of three parts;one is heat extraction fluid in U-tube, the other is layer around the U-tube, and the other is heat pump. The model, which represents...
Article
A series of injection-induced slip experiments using pre-fractured granitic rock specimens was conducted to investigate the dynamic hydraulic responses of existing fractures during hydraulic stimulation. The results show a characteristic stepwise slip and temporal increase in fluid flow in the fractures during slip. This increase is considered to r...
Article
Full-text available
Summary Microseismic multiplets, which are groups of events showing highly similar waveform despite different origin time and magnitude, can be effectively used to determine relative location of the hypocenters with high accuracy. The authors clustered multiplets from microseismic events collected during a hydraulic stimulation in the Deep Heat Min...
Article
In this paper, we discuss the pore-pressure propagation and fluid flow in the geothermal reservoir at Soultz geothermal field, France, by making use of the induced microearthquakes during hydraulic stimulation. The locations of possible seismic and hydraulically activated fractures can be estimated using the induced seismic events associated with t...
Article
We present results from laboratory experiments that simulate an injection-induced slip in a preexisting fracture using granite specimens that contain the simulated fracture. Our objective is to obtain fundamental understanding of mechanical and hydrological properties of injection-induced slip on fractures, which is often problematic in interpretin...
Article
The model experiments which simulated shear slip induced by injection of pore fluid have been conducted under triaxial compressive stress condition using a roughened bare fault. The objective is to understand characteristics of the induced slip behaviour, especially after the slip initiation obeying Coulomb failure criterion and pore fluid behaviou...
Article
A small change in traveltime and shear-wave splitting in elastic waves transmitted through a pressurized single fracture has been detected through downhole triaxial cross-hole seismic measurements. A field experiment was carried out at Higashi-Hachimantai Field of Tohoku University, Japan, where an artificial single fracture had been created at 369...
Article
Full-text available
Hydraulic fracturing experiments were carried out at the Bernburg salt mine in Germany. The induced acoustic emission (AE) events were detected by accelerometers surrounding the sources, and the observed AE events had a frequency component of over 40 kHz. Many similar waveforms were identified in the detected events, and their source locations were...
Article
Full-text available
In previous work (Kumano et al., 2003, Asanuma et al., 2004), we analyzed the AE data set obtained at Cooper Basin Hot Fractured Rock (HFR) geothermal field, Australia, during hydraulic stimulation conducted in the last quarter of 2003. Source locations of microseismic events were determined using a standard earthquake location procedure, SED. Loca...
Article
A high-rate injection of 20 000 m3 of water into granite between 2.8 and 3.4 km depth at the Soultz hot dry rock (HDR) test site in France in 1993 September led to a 200-fold increase in borehole transmissivity and produced a subvertical cloud of microseismicity of dimensions 0.5 km wide, 1.2 km long, 1.5 km high and oriented 25 deg NW. The resulti...
Article
ABSTRUCT Fractures were created as a Hot Dry Rock reservoir by hydraulic fracturing from a 1,000 m depth well at Ogachi, northern Japan. The fracture location and extension were evaluated by the microearthquake (AE) event observation and the electrical methods. Recently a three-dimensional underground structure model was constructed by compiling th...
Article
We have been developing a simulator for evaluating the dynamic behavior of integrated renewable energy systems (IRES), which consists of Wind Turbine, Photovoltaic, Lead-Acid Battery, etc.. Geothermal Heat Pumps (GeoHP), also known as Ground-Source Heat Pumps (GSHP) or GroundCoupled Heat Pumps (GCHP), is included in the simulator, because GeoHP can...
Article
Pore-pressure of seismically activated fractures during hydraulic stimulation of geothermal reservoir at Soultz HDR field, France is estimated based on the high-resolution mapping method of induced microseismic events. The microseismic events with similar waveforms are analyzed, and the seismically activated fracture planes are estimated using the...
Article
Multiplet-clustering analysis is a method for precise determination of microseismic event locations and is used to identify subsurface fractures and fracture networks. A multiplet is a group of microseismic events with very similar waveforms, despite different origin times, and it is likely the expression of stress release on the same structure. Th...
Article
Reservoir structure and stress field at the Ogachi Hot Dry Rock field, Japan, have been examined using hydraulically induced AE (Acoustic Emission / Microseismic) events. Two large scale hydraulic fracturing tests were conducted by CRIEPI (Central Research Institute of Electric Power Industry, Japan) in 199J and 1992. The fracturing tests were carr...
Article
The reservoir structure of the Soultz HDR ®eld has been investigated by examining induced microearthquake multiplets. Microseismic events with similar waveforms have been selected from microseismic data obtained during a 1993 hydraulic fracturing experiment. Precise relative arrival times and source locations have been determined by cross-spectrum...
Article
Full-text available
Acoustic emission events from a salt rock specimen have been analyzed based on the modified collapsing method, that is an advanced mapping method used for estimation of subsurface fractures, in order to delineate structures inside the rock specimen. A triaxial compression test of a core specimen from Asse salt mine, Germany, was performed, and AE e...
Article
Detailed fracture and stress field in deep reservoir at Soultz have been estimated based on the multiplet-clustering analysis of induced microseismic events. The multiplet-clustering analysis is one of several high-resolution mapping techniques and can estimate multiplet clusters, which consist of group of similar microseismic events. As the result...
Article
Seismic and borehole measurements provide significant information about HDR/HWR reservoirs that is useful for reservoir development, reservoir characterization, and performance evaluation. Both techniques have been widely used during all HDR/HWR development projects. Seismic measurements have advanced from making passive surface measurements during...
Article
We observed traveltime delays of transmitted waves during pressurization of a subsurface artificial fracture at Higashi Hachimantai geothermal field, Iwate Prefecture, Japan. The transmitted waves generated by a downhole air gun were observed by the downhole triaxial seismic detector during pressurization. Traveltime delay was detected by the cross...
Article
In the Ogachi Hot Dry Rock program, many microearthquake or acoustic emission (AE) events, were observed during hydraulic fracturing and water circulation experiments. The observed AE events were located to evaluate fracture location and dimension as HDR reservoirs. However, the geological condition is so complicated at Ogachi that the errors of th...
Article
We have developed a signal processing technique for three-component microseismic data that allows the precise determination of P-wave arrival times. The method is based on a time-frequency representation of the signal that allows the evaluation of the 3-D particle motion from seismic waves in both time and frequency domains. A spectral matrix is co...
Article
We propose a procedure to characterize the dynamic behavior of subsurface crack systems on the basis of triaxial doublet analysis, which estimates precise relative source location of microseismic doublets in the downhole 3-component measurement. A doublet is a pair or a group of microseismicity with very similar waveforms despite different originat...
Article
Full-text available
We describe a downhole AE measurement performed at Ogachi Hot Dry Rock field in Akita prefecture during a hydraulic fracturing. Two types of AE signals, i.e., high frequency events and low frequency events containing of both P-and S-waves, were measured. Kaiser effect was clearly observed when total flow exceeded that of a previous experiment. The...
Article
We have developed a precise relative source location technique using acoustic emission doublets (AE doublets) in the triaxial hodogram method to evaluate the direction and distance of subsurface extension cracks. An AE doublet is a pair of acoustic emissions with similar waveforms and adjacent locations on the same crack but which occur at differen...
Article
Microseismic multiplet has been used to estimate detailed structures of deep reservoir at Soultz HDR field, France. The multiplet is a group of microseismic events with similar waveforms in spite of different origin times. A hydraulic fracturing experiment was carried out at Soultz in 2000, and the artificial geothermal reservoir was created around...
Article
Full-text available
The model experiments that simulate shear slip of preexisting fracture have been conducted under a confining pressure condition in order to investigate the controlling parameters of "aseismic" fracture. In this paper, we discuss the normal stress and the slip velocity as the possible controlling parameters of AE (Acoustic Emission) occurrence and e...
Article
Full-text available
Microseismic multiplets, which are groups of events showing highly similar waveform despite different origin time and magnitude, can be effectively used to determine relative location of the hypocenters with high accuracy. The authors clustered multiplets from microseismic events collected during a hydraulic stimulation in the Deep Heat Mining Proj...
Article
Full-text available
Microseismic multiplets are introduced to estimate the critical pore-pressure of fractures required for shear slip during hydraulic fracturing of a geothermal reservoir. Because the multiplets can be used to estimate the precise source locations using cross-spectrum analysis, the orientations of hydraulically activated fractures are derived from th...
Article
Full-text available
Advantages and appropriate operation of Geothermal Heat Pump (GeoHP) system in Yumoto District have been quantitatively studied, where the geothermal gradient and the thermal conductivity are 3 -4 and 1.7 times larger than those in other ordinary areas. It has been revealed that the GeoHP system of Yumoto District cuts 7 % of power consumption of a...
Article
Full-text available
Hypocenter locations of shallow earthquakes in Horonobe area, northern Hokkaido, Japan, which is near the convergent boundary between Okhotsk and Amuria plates, were determined to reveal the subsurface structure and the mechanisms of earthquake occurrence. The absolute source locations of 211 earthquakes which occurred in the period from December 2...
Article
Evaluation of reservoir structure at Ogachi HDR field of CRIEPI (Central Research Institute of Electric Power Industry) has been carried out using multiplets observed during the hydraulic fracturing experiment in 1991. The source distribution of relative location of multiplets suggests that the fracture orientations are NNE-SSW and nearly vertical,...
Article
Full-text available
Multiplet is a group that consists of seismic events with similar waveforms, and observed in a variety fields, e.g. oil or geothermal reservoir or natural seismicity. In this paper we deal with induced microseismic (AE) multiplets observed during hydraulic fracturing at Soultz-sous-Forêts HDR field, France in 1993. The multiplet analysis has been o...
Article
Full-text available
In this study we investigated the waveform similarity, by analyzing the microseismic data-set obtained at Cooper Basin HFR field. Waveform of P-wave onset portion was highly similar among the most events, consisting with identical focal mechanism and parallel seismic clusters. But their coda wave were slightly different and its similarity was accor...
Article
Full-text available
We have developed a simulator for evaluating dynamic behavior of Integrated Renewable Energy System (IRES), based on concept of EIMY. The simulator has been developed using the multipurpose software and is consists of the modules representing each device and RE system. Through the simulations using the real data at a rural village located near the...
Article
Full-text available
11th South African Geophysical Association Biennial Technical Meeting and Exhibition, Swaziland, 16-18 September 2009 Mining-induced earthquakes pose a hazard to workers in deep South African mines, while natural earthquakes pose a hazard to people living close to plate boundaries. Researchers introduce a 5-year Japanese-South African collaborative...
Article
Full-text available
Southern African Institute of Mining and Metallurgy, Hard Rock Safe Safety Conference 2009. Sun City, South Africa, 28-30 September, 2009. pp 1-20 Mining-induced seismicity poses a hazard to workers in deep South African mines, while natural earthquakes pose a hazard to people living in Japan and other regions of the world that are close to plate b...

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