Artur Cichowicz | Council for Geoscience (original) (raw)
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Papers by Artur Cichowicz
Bulletin of the Seismological Society of America, Feb 1, 1993
An algorithm has been developed for the automatic picking of the S phase from three-component sei... more An algorithm has been developed for the automatic picking of the S phase from three-component seismic data. Three parameters of the signal are calculated in the program: deflection angle, degree of polarization, and the ratio between transverse energy and total energy. The S phase is declared when the product of the three parameters increases above the reference level. Most parameters are computed automatically and modified if necessary. The S-phase picker is used to analyze data from a local underground mine seismic network.
The frequency-dependent properties of Rayleigh-type surface waves can be utilized for imaging and... more The frequency-dependent properties of Rayleigh-type surface waves can be utilized for imaging and characterizing the shallow subsurface. Most surface-wave analysis relies on the accurate calculation of phase velocities for the horizontally traveling fundamental-mode Rayleigh wave acquired by stepping out a pair of receivers at intervals based on calculated ground roll wavelengths. Interference by coherent source-generated noise inhibits the reliability of shear-wave velocities determined through inversion of the whole wave field. Among these nonplanar, nonfundamental-mode Rayleigh waves (noise) are body waves, scattered and nonsource-generated surface waves, and higher-mode surface waves. The degree to which each of these types of noise contaminates the dispersion curve and, ultimately, the inverted shear-wave velocity profile is dependent on frequency as well as distance from the source. Multichannel recording permits effective identification and isolation of noise according to distinctive traceto-trace coherency in arrival time and amplitude. An added advantage is the speed and redundancy of the measurement process. Decomposition of a multichannel record into a time variable-frequency format, similar to an uncorrelated Vibroseis record, permits analysis and display of each frequency component in a unique and continuous format. Coherent noise contamination can then be examined and its effects appraised in both frequency and offset space. Separation of frequency components permits real-time maximization of the S/N ratio during acquisition and subsequent processing steps. Linear separation of each ground roll frequency component allows calculation of phase velocities by simply measuring the linear slope of each frequency component. Breaks in coherent surface-wave arrivals, observable on the decomposed record, can be compensated for during acquisition and processing. Multichannel recording permits single-measurement surveying of a broad depth range, high levels of redundancy with a single field configuration, and the ability to adjust the offset, effectively reducing random or nonlinear noise introduced during recording. A multichannel shot gather decomposed into a sweptfrequency record allows the fast generation of an accurate dispersion curve. The accuracy of dispersion curves determined using this method is proven through field comparisons of the inverted shear-wave velocity (v s) profile with a downhole v s profile.
Japan Geoscience Union, Mar 10, 2016
Japan Geoscience Union, 2015
Earthquakes pose a significant risk to workers in deep and overstressed mines, such as South Afri... more Earthquakes pose a significant risk to workers in deep and overstressed mines, such as South African gold mines. A 5-year collaborative project entitled OBSERVATIONAL STUDIES IN SOUTH AFRICAN MINES TO MITIGATE SEISMIC RISKS was launched in August 2010 to gain knowledge, develop and transfer technology, and build capacity. It was funded by the JST-JICA Science and Technology Research Partnership for Sustainable Development (SATREPS). Research sites were established at three deep gold mines: Cooke #4 Shaft, Hlanganani and Moab Khotsong. Boreholes were drilled to locate faults accurately that were considered capable of producing mining-induced seismic events. A variety of sensors were installed to monitor the quasi-static deformation of the rock mass, the accumulation of strain, tilt changes during the seismic event and post seismic creep phase and damage during the earthquake preparation phase, and changes in dynamic stress produced by the propagation of the rupture front. The Council...
Examining the occurrence of seismic activity in South Africa, the authors point out that the seis... more Examining the occurrence of seismic activity in South Africa, the authors point out that the seismic event on 9 March 2005 could be ascribed to past mining, and that seismic events will continue to occur in the gold mining districts as long as deep-level mining takes place and are likely to persist for some time even after mine closure. Seismic monitoring should continue after mine closure, and the seismic hazard should be taken into account when the future use of mining land is considered. The national and local monitoring networks, operated by the Council for Geoscience and mining companies, respectively, are on a par with those installed in seismically active mining districts elsewhere in the world. However, steps should be taken to improve the quality of seismic monitoring and to ensure continuity, especially as mines change hands. The Klerksdorp and Free State gold mining districts are incorporating the risks of seismicity in their disaster management plans, and Johannesburg is urged to do likewise. Some buildings are considered vulnerable to damage by large seismic events, posing safety and financial risks. It is recommended that an earthquake engineer inspect the building stock and review the content and enforcement of building codes. Appropriate training should be provided to all members of emergency services, and drills should be practiced regularly at public buildings to avoid panic should a large seismic event occur.
We will report on coseismic strain step ranging 10-5 to 10-4 recorded with 24bit 25Hz continuous ... more We will report on coseismic strain step ranging 10-5 to 10-4 recorded with 24bit 25Hz continuous monitoring, associated with seismic events with M~2 at a distance about 100m at Bambanani mine, Welkom, South Africa. We have been observing mine tremors of -1.2<M<3 at a hypocentral distance of near dozens of meters since September 2000 at the mine. We installed an
The aim of this project is optimization of rockburst support systems by the systematic evaluation... more The aim of this project is optimization of rockburst support systems by the systematic evaluation and quantification of the peak particle velocity recorded underground.
AGU Fall Meeting Abstracts, Dec 1, 2008
The objective of this evaluation is to determine the crustal amplification function of the seismi... more The objective of this evaluation is to determine the crustal amplification function of the seismic signal for different regions in South Africa. In order to model crustal amplification, models of the S-wave velocity and the shear quality factor Q are determined. All currently run seismic hazard assessment projects in South Africa are utilizing the attenuation equations mostly from central and
Japan Geoscience Union, 2015
Japan Geoscience Union, 2015
In this study, we analyzed the main shock waveforms and aftershock distribution of then 2014 Orkn... more In this study, we analyzed the main shock waveforms and aftershock distribution of then 2014 Orkney earthquake, South Africa, to understand the rupture process of this earthquake. We picked P and S wave arrival times of the main shock and found two sets of phases in those seismograms. One pair is radiated by earlier and smaller event (ML<4), which is the initial rupture occurred at shallower depth and the other by main rupture occurred at northward of initial. Next, we applied double-difference relocation method to P and S wave arrival times of the aftershocks and the initial and main ruptures of the main shock. We found vacant space in the deep parts of the planarly aftershock distribution, which correspond to the mainshock hypocenter. Additionally, we applied Isochrone backprojection method to mainshock S-wave waveforms. Strong rupture distribution seems to fill the vacant space of the aftershocks distribution and main shock hypocenter.
Proceedings of the International Conference on Deep and High Stress Mining
A multidisciplinary study of the response of the rock mass to mining and mining-induced earthquak... more A multidisciplinary 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. Microfracturing activity associated with an ML2.1 event at 3.3 km depth in Mponeng Mine and a highly stressed rock mass at 1 km depth in Ezulwini Mine were finely delineated and analysed. A hole drilled through the hypocentre of the ML2.1 event at Mponeng Mine allowed the stress and strength in the seismogenic area to be constrained. Previously published in situ stress measurements had been limited to depths or stresses smaller than 2.7 km or 100 MPa, respectively. We successfully measured stress at depths and stresses up to 3.4 km and 146 MPa, respectively, at four mines. These in situ measured stresses were used to calibrate elastic stress modelling and yielded better estimates of stress and strength on the rupture planes of seven earthquakes (ML2.1 to 4). Comparison of the elastically modelled stress with the constrained stress in a hole drilled across the ML2.1 fault and the strain change monitored in situ at a close distance showed that the elastically modelled stress was smaller but correctable. The South African National Seismograph Network was enhanced by installing 10 surface strong-motion seismometer stations in the Far West Rand mining district. Two other such dense surface networks are https://papers.acg.uwa.edu.au/p/1410_06_Ogasawara/ Observational studies of the rock mass response to mining in highly stressed H Ogasawara et al. gold mines in South Africa 124 Deep Mining 2014, Sudbury, Canada currently operated in mining areas by the Council for Geoscience: 25 stations in the Klerksdorp region, supported by the Mine Health and Safety Council; and 17 stations in the Central Rand to monitor fluid-induced seismicity. Research on the routine processing of spectral parameters was carried out using seismicity recorded by these 52 new surface stations.
AIST, Sep 1, 2013
The Japanese-South African intergovernmental science and technology project "Observational studie... more The Japanese-South African intergovernmental science and technology project "Observational studies to mitigate seismic risks in mines" includes seismological studies aimed at a better understanding of how a seismic event is prepared and strong motion is generated and amplified. This paper highlights another important aspect of mitigating the seismic risk, the improvement of geotechnical models, constitutive models, and the knowledge of boundary conditions to enable better numerical assessment of seismic hazard in South African gold mines. Some preliminary results of the activities of in-situ monitoring of the rock mass are documented, which include an attempt to constrain stress and strength on a rupture plane accurately delineated by AE monitoring. Optimized to the condition in South African gold mines, a Japanese technique is introduced to measure in-situ stress in rock mass.
Strong pulse-type motions are observed in the near source region of large earthquakes; however, t... more Strong pulse-type motions are observed in the near source region of large earthquakes; however, there is a lack of waveforms collected from small earthquakes at very close distances recorded underground in mines. The results presented in this paper are relevant for structures of with the height of a few meters, placed in an underground excavation. The strong ground motion sensor was installed in a deep gold mine at the surface of a seismic active stope. The strongest monitored horizontal ground motion was caused by an event of magnitude 2 at a distance of 90 m with PGA 103 m/s 2 and PGV 0.365 m/s, and the final displacement was 6.2 mm. The drift response technique based on a continuous shear beam model is employed here to estimate the drift response subjected the near-field earthquakes. The main features of velocity response spectra and drift spectra are similar, which is an indication that the larger damage comes from the large velocity peaks. The strong ground motions with PGA larger than 10 g cause drifts of 50%, which are unobserved at the earth's surface. Drift larger than several percents could cause non elastic deformation. The damping constant of a structure has to be increased significantly to decrease a value of the drift. The weak underground motion has spectral characteristics similar to the strong ground motion observed on the earth's surface; the drift spectrum has a maximum value less than 1% in frequency range relevant to a high underground structure.
Bulletin of the Seismological Society of America, Feb 1, 1993
An algorithm has been developed for the automatic picking of the S phase from three-component sei... more An algorithm has been developed for the automatic picking of the S phase from three-component seismic data. Three parameters of the signal are calculated in the program: deflection angle, degree of polarization, and the ratio between transverse energy and total energy. The S phase is declared when the product of the three parameters increases above the reference level. Most parameters are computed automatically and modified if necessary. The S-phase picker is used to analyze data from a local underground mine seismic network.
The frequency-dependent properties of Rayleigh-type surface waves can be utilized for imaging and... more The frequency-dependent properties of Rayleigh-type surface waves can be utilized for imaging and characterizing the shallow subsurface. Most surface-wave analysis relies on the accurate calculation of phase velocities for the horizontally traveling fundamental-mode Rayleigh wave acquired by stepping out a pair of receivers at intervals based on calculated ground roll wavelengths. Interference by coherent source-generated noise inhibits the reliability of shear-wave velocities determined through inversion of the whole wave field. Among these nonplanar, nonfundamental-mode Rayleigh waves (noise) are body waves, scattered and nonsource-generated surface waves, and higher-mode surface waves. The degree to which each of these types of noise contaminates the dispersion curve and, ultimately, the inverted shear-wave velocity profile is dependent on frequency as well as distance from the source. Multichannel recording permits effective identification and isolation of noise according to distinctive traceto-trace coherency in arrival time and amplitude. An added advantage is the speed and redundancy of the measurement process. Decomposition of a multichannel record into a time variable-frequency format, similar to an uncorrelated Vibroseis record, permits analysis and display of each frequency component in a unique and continuous format. Coherent noise contamination can then be examined and its effects appraised in both frequency and offset space. Separation of frequency components permits real-time maximization of the S/N ratio during acquisition and subsequent processing steps. Linear separation of each ground roll frequency component allows calculation of phase velocities by simply measuring the linear slope of each frequency component. Breaks in coherent surface-wave arrivals, observable on the decomposed record, can be compensated for during acquisition and processing. Multichannel recording permits single-measurement surveying of a broad depth range, high levels of redundancy with a single field configuration, and the ability to adjust the offset, effectively reducing random or nonlinear noise introduced during recording. A multichannel shot gather decomposed into a sweptfrequency record allows the fast generation of an accurate dispersion curve. The accuracy of dispersion curves determined using this method is proven through field comparisons of the inverted shear-wave velocity (v s) profile with a downhole v s profile.
Japan Geoscience Union, Mar 10, 2016
Japan Geoscience Union, 2015
Earthquakes pose a significant risk to workers in deep and overstressed mines, such as South Afri... more Earthquakes pose a significant risk to workers in deep and overstressed mines, such as South African gold mines. A 5-year collaborative project entitled OBSERVATIONAL STUDIES IN SOUTH AFRICAN MINES TO MITIGATE SEISMIC RISKS was launched in August 2010 to gain knowledge, develop and transfer technology, and build capacity. It was funded by the JST-JICA Science and Technology Research Partnership for Sustainable Development (SATREPS). Research sites were established at three deep gold mines: Cooke #4 Shaft, Hlanganani and Moab Khotsong. Boreholes were drilled to locate faults accurately that were considered capable of producing mining-induced seismic events. A variety of sensors were installed to monitor the quasi-static deformation of the rock mass, the accumulation of strain, tilt changes during the seismic event and post seismic creep phase and damage during the earthquake preparation phase, and changes in dynamic stress produced by the propagation of the rupture front. The Council...
Examining the occurrence of seismic activity in South Africa, the authors point out that the seis... more Examining the occurrence of seismic activity in South Africa, the authors point out that the seismic event on 9 March 2005 could be ascribed to past mining, and that seismic events will continue to occur in the gold mining districts as long as deep-level mining takes place and are likely to persist for some time even after mine closure. Seismic monitoring should continue after mine closure, and the seismic hazard should be taken into account when the future use of mining land is considered. The national and local monitoring networks, operated by the Council for Geoscience and mining companies, respectively, are on a par with those installed in seismically active mining districts elsewhere in the world. However, steps should be taken to improve the quality of seismic monitoring and to ensure continuity, especially as mines change hands. The Klerksdorp and Free State gold mining districts are incorporating the risks of seismicity in their disaster management plans, and Johannesburg is urged to do likewise. Some buildings are considered vulnerable to damage by large seismic events, posing safety and financial risks. It is recommended that an earthquake engineer inspect the building stock and review the content and enforcement of building codes. Appropriate training should be provided to all members of emergency services, and drills should be practiced regularly at public buildings to avoid panic should a large seismic event occur.
We will report on coseismic strain step ranging 10-5 to 10-4 recorded with 24bit 25Hz continuous ... more We will report on coseismic strain step ranging 10-5 to 10-4 recorded with 24bit 25Hz continuous monitoring, associated with seismic events with M~2 at a distance about 100m at Bambanani mine, Welkom, South Africa. We have been observing mine tremors of -1.2&lt;M&lt;3 at a hypocentral distance of near dozens of meters since September 2000 at the mine. We installed an
The aim of this project is optimization of rockburst support systems by the systematic evaluation... more The aim of this project is optimization of rockburst support systems by the systematic evaluation and quantification of the peak particle velocity recorded underground.
AGU Fall Meeting Abstracts, Dec 1, 2008
The objective of this evaluation is to determine the crustal amplification function of the seismi... more The objective of this evaluation is to determine the crustal amplification function of the seismic signal for different regions in South Africa. In order to model crustal amplification, models of the S-wave velocity and the shear quality factor Q are determined. All currently run seismic hazard assessment projects in South Africa are utilizing the attenuation equations mostly from central and
Japan Geoscience Union, 2015
Japan Geoscience Union, 2015
In this study, we analyzed the main shock waveforms and aftershock distribution of then 2014 Orkn... more In this study, we analyzed the main shock waveforms and aftershock distribution of then 2014 Orkney earthquake, South Africa, to understand the rupture process of this earthquake. We picked P and S wave arrival times of the main shock and found two sets of phases in those seismograms. One pair is radiated by earlier and smaller event (ML<4), which is the initial rupture occurred at shallower depth and the other by main rupture occurred at northward of initial. Next, we applied double-difference relocation method to P and S wave arrival times of the aftershocks and the initial and main ruptures of the main shock. We found vacant space in the deep parts of the planarly aftershock distribution, which correspond to the mainshock hypocenter. Additionally, we applied Isochrone backprojection method to mainshock S-wave waveforms. Strong rupture distribution seems to fill the vacant space of the aftershocks distribution and main shock hypocenter.
Proceedings of the International Conference on Deep and High Stress Mining
A multidisciplinary study of the response of the rock mass to mining and mining-induced earthquak... more A multidisciplinary 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. Microfracturing activity associated with an ML2.1 event at 3.3 km depth in Mponeng Mine and a highly stressed rock mass at 1 km depth in Ezulwini Mine were finely delineated and analysed. A hole drilled through the hypocentre of the ML2.1 event at Mponeng Mine allowed the stress and strength in the seismogenic area to be constrained. Previously published in situ stress measurements had been limited to depths or stresses smaller than 2.7 km or 100 MPa, respectively. We successfully measured stress at depths and stresses up to 3.4 km and 146 MPa, respectively, at four mines. These in situ measured stresses were used to calibrate elastic stress modelling and yielded better estimates of stress and strength on the rupture planes of seven earthquakes (ML2.1 to 4). Comparison of the elastically modelled stress with the constrained stress in a hole drilled across the ML2.1 fault and the strain change monitored in situ at a close distance showed that the elastically modelled stress was smaller but correctable. The South African National Seismograph Network was enhanced by installing 10 surface strong-motion seismometer stations in the Far West Rand mining district. Two other such dense surface networks are https://papers.acg.uwa.edu.au/p/1410_06_Ogasawara/ Observational studies of the rock mass response to mining in highly stressed H Ogasawara et al. gold mines in South Africa 124 Deep Mining 2014, Sudbury, Canada currently operated in mining areas by the Council for Geoscience: 25 stations in the Klerksdorp region, supported by the Mine Health and Safety Council; and 17 stations in the Central Rand to monitor fluid-induced seismicity. Research on the routine processing of spectral parameters was carried out using seismicity recorded by these 52 new surface stations.
AIST, Sep 1, 2013
The Japanese-South African intergovernmental science and technology project "Observational studie... more The Japanese-South African intergovernmental science and technology project "Observational studies to mitigate seismic risks in mines" includes seismological studies aimed at a better understanding of how a seismic event is prepared and strong motion is generated and amplified. This paper highlights another important aspect of mitigating the seismic risk, the improvement of geotechnical models, constitutive models, and the knowledge of boundary conditions to enable better numerical assessment of seismic hazard in South African gold mines. Some preliminary results of the activities of in-situ monitoring of the rock mass are documented, which include an attempt to constrain stress and strength on a rupture plane accurately delineated by AE monitoring. Optimized to the condition in South African gold mines, a Japanese technique is introduced to measure in-situ stress in rock mass.
Strong pulse-type motions are observed in the near source region of large earthquakes; however, t... more Strong pulse-type motions are observed in the near source region of large earthquakes; however, there is a lack of waveforms collected from small earthquakes at very close distances recorded underground in mines. The results presented in this paper are relevant for structures of with the height of a few meters, placed in an underground excavation. The strong ground motion sensor was installed in a deep gold mine at the surface of a seismic active stope. The strongest monitored horizontal ground motion was caused by an event of magnitude 2 at a distance of 90 m with PGA 103 m/s 2 and PGV 0.365 m/s, and the final displacement was 6.2 mm. The drift response technique based on a continuous shear beam model is employed here to estimate the drift response subjected the near-field earthquakes. The main features of velocity response spectra and drift spectra are similar, which is an indication that the larger damage comes from the large velocity peaks. The strong ground motions with PGA larger than 10 g cause drifts of 50%, which are unobserved at the earth's surface. Drift larger than several percents could cause non elastic deformation. The damping constant of a structure has to be increased significantly to decrease a value of the drift. The weak underground motion has spectral characteristics similar to the strong ground motion observed on the earth's surface; the drift spectrum has a maximum value less than 1% in frequency range relevant to a high underground structure.