A5040840852- earthquake and tectonic studies
- Rock Mechanics and Modeling
- Seismic Imaging and Inversion Techniques
- Drilling and Well Engineering
- Geotechnical and Geomechanical Engineering
- Seismic Waves and Analysis
- Earthquake Detection and Analysis
- Seismology and Earthquake Studies
- High-pressure geophysics and materials
- Geological and Geochemical Analysis
- Mining Techniques and Economics
- Mineral Processing and Grinding
- Geophysical Methods and Applications
- Tunneling and Rock Mechanics
- Fault Detection and Control Systems
- Geoscience and Mining Technology
- Geological and Geophysical Studies
- Hydrocarbon exploration and reservoir analysis
- Tailings Management and Properties
- Geophysical and Geoelectrical Methods
- Methane Hydrates and Related Phenomena
- Reservoir Engineering and Simulation Methods
- Risk and Safety Analysis
- Geological Modeling and Analysis
- Geomechanics and Mining Engineering
Tohoku University
2016-2025
Association for the Development of Earthquake Prediction
2014-2020
Japan Science and Technology Agency
2019
Continental (Germany)
2019
Graduate School USA
2014
Ritsumeikan University
2010
National Research Institute for Earth Science and Disaster Resilience
2004
Yamagata University
2004
This article aims to investigate the frequency-magnitude characteristics and lower magnitude limits of microseismic catalog recorded with a seismic network sensitive high frequencies at Mponeng mine, South Africa. The network, composed one three-component accelerometer eight acoustic emission sensors, is located depth 3.5 km below surface covers limited volume approximately 300×300×300 m. was used estimate moment for number 135 events ( M w ranged from -4.1 -0.3) well by network. We use...
On 5 August 2014, the Orkney M5.5 earthquake, largest in South African gold mining districts, occurred with an unusual strike-slip mechanism at great depth of 4.78 km below surface. In a rare case, ML 5.5 earthquake within area covered by legacy 2D and 3D reflection seismic data acquired 1990s 2000s for exploration mine development. addition, rupture plane was recorded accurately delineated underground in-mine network near source region. The integration seismicity allowed us to identify...
We have determined the locations of more than 20,000 aftershocks (as small as moment magnitude Mw 4:4 or even smaller) following an M 2 event in a South African gold mine, using manually picked arrival times. Spatial clustering into fivegroupswasclearlydiscerned.Amajorityoftheaftershocksformedaplanarcluster (∼4 m apparent thickness, ∼100 × 80 areal extent). This cluster is thought to delineate rupture area mainshock because its orientation and spatial extent wereconsistent with...
Abstract Using a network of sensitive high‐frequency acoustic emission sensors, we observed foreshock activity an Mw 2.2 earthquake (main shock) in deep gold mine South Africa. Foreshock activity, which selectively occurred on part the rupture plane forthcoming main shock, lasted for at least 6 months until shock. Rock samples recovered from shock source region showed evidence ancient hydrothermal alteration plane, suggesting that preexisting weakness. The foreshocks during 3 before were...
Abstract A destructive large earthquake (the 2004 mid Niigata prefecture earthquake) sequence occurred in the central part (Chuetsu district) of prefecture, Japan on October 23, 2004. We have deployed a temporary seismic network composed 54 stations for aftershock observation just above and around focal area about month. Using travel time data from surrounding routine stations, we obtained precise distribution 3D velocity structure fault planes four major (M ≥ 6) aftershocks by...
Abstract This is the first report from JAGUARS ( JA panese- G erman U nderground A coustic Emission R esearch in S outh Africa) project, overall aim of which to observe ultra-small fracturing a more or less natural environment. We installed local (∼40-m span) network eight acoustic emission (AE) sensors, have capability up 200 kHz at depth 3.3 km South African gold mine. Our specific objective was monitor 30-m thick dyke that remains as dip pillar against active mining ∼90 m above our...
We have evaluated an anomalous crustal strain in the Tohoku region, northeastern Japan associated with a step-like stress change induced by 2011 off Pacific coast of Earthquake (Mw 9.0). Because source area event was extremely large, gradient observed eastward coseismic displacements that accompanied uniform had relatively EW extension Japan. Accordingly, deformation anomaly, which is determined subtracting predicted displacement half-space elastic media from displacement, should reflect...
Abstract We observed very small repeating earthquakes with −5.1 ≤ M w −3.6 on a geological fault at 1 km depth in gold mine South Africa. Of the 851 acoustic emissions that occurred during 2 month analysis period, 45% were identified as repeaters basis of waveform similarity and relative locations. They steadily same location similar magnitudes, analogous to plate boundaries, suggesting they are repeat ruptures asperity loaded by surrounding aseismic slip (background creep). Application...
Abstract Three months of acoustic emission (AE) monitoring in a South African gold mine down to M w −5 revealed newly emergent planar cluster 7557 events −3.9 ≤ −1.8 (typical rupture radius 6–70 cm) that expanded with time reach size 20 m on preexisting geological fault near an active mining front 1 km beneath the ground. It had sharply defined, configuration, hypocenters aggregated within thickness only several decimeters. We infer zone defines aseismic slip patch fault, wherein individual...
Abstract The Nojima Fault in Awaji, Hyogo prefecture, Japan, was ruptured during the 1995 Hyogo‐ken Nanbu earthquake ( M JMA = 7.2). Toshima is located close to fault segment, which a large dislocation has been observed on Earth’s surface. Ikuha near southern end of buried that extends from surface rupture. Stresses are measured core samples taken at depths 310 m, 312 m and 415 depth 351 Ikuha. stresses show both sites field strike–slip regime, but compression dominates Toshima. Defining...
Abstract We have investigated the depth variation in stress state at northern part of Chelungpu fault, Taiwan, which slipped during 1999 Chi-Chi earthquake ( M w 7.6). In-situ around fault was estimated based on memory rocks recovered from five depths (739–1316 m) a 2-km-deep-hole. The borehole intersects zone 1111 m (FZ1111), is best candidate for fault. Our main results are: (1) S Hmax direction parallel to slip and agrees with those local, regional, or tectonic scales various indicators;...
The Nojima fault in Hyogo prefecture, Japan, ruptured during the 1995 Hyogo-ken Nanbu earthquake (MJMA = 7.3). stress measurements at sites close to this have revealed that direction of largest horizontal is almost perpendicular strike sub-vertical and that, zone within about 100 m from core axis, ratio shear normal significantly small compared with outside. It thus logical consequence principal outside tends direct perpendicularly plane. A model called fracture process introduced for...
A multi-disciplinary study of the response rock mass to mining and mining-induced earthquakes has been conducted in six gold mines South Africa at sites deeper than 3 km, or with equivalent stress.More 80 holes (with a total length more 2.8 km) were drilled earthquake-prone areas locate faults install instruments.Microfracturing activity associated an ML2.1 event 3.3 km depth Mponeng Mine highly stressed 1 Ezulwini finely delineated analysed.A hole through hypocentre allowed stress strength...
Mining-induced earthquakes pose a risk to workers in deep mines, while natural everywhere, but especially near plate boundaries.A five year Japanese-South African collaborative project entitled 'Observational studies mitigate seismic risks mines' commenced August 2010.Here we report on the achievements of first 18 months project.Faults at Ezulwini, Moab-Khotsong and Driefontein gold mines considered likely become seismically active during mining activity were modelled using pre-existing...
A velocity‐step test was performed to examine effects of the macroscopic sliding‐rate on AE activity during steady‐state frictional sliding a pre‐cut fault in granite sample. Both amplitude‐frequency relation and number events per unit displacement changed response change sliding‐rate. its rate‐dependence evolved with sliding. The rate dependence cumulative seismic energy calculated from shows positive correlation that friction coefficient, suggesting is one origins rate‐dependent friction,...