title: How topography-dependent are topographic effects? Complementary numerical modeling of centrifuge experiments

authors: Jeong, Seokho

subjects: Science & Technology

abstract: Topographic effects, the modification of seismic shaking by irregular topographies compared to flat ground, have been extensively studied. Very few studies, however, have investigated the effects of the stratigraphy and nonlinear response of the underlying geology on topographic amplification. Furthermore, most experimental studies have been performed in the field, where it is often difficult to establish an ideal flat-ground reference station, as well as to characterize the soil properties and their spatial variability in sufficient detail. Dafni [1] recently tested the seismic response of step-like slopes in a series of centrifuge experiments, where the incident motion, reference station and material properties were characterized in detail. In this study, we investigated the influence of the container boundary on topographic effects observed in the centrifuge experiments by performing numerical simulations with and without the container boundary. Our analysis suggested that the rigid-body rocking motion of the centrifuge container likely increased the experimental topographic spectral ratios, contributing to the discrepancy between the simulated and observed spectral ratios. We also found that although the laminar box lateral boundaries caused spurious reflections, they didn’t qualitatively affect the ground surface amplification pattern compared to numerical predictions of the same configuration without boundaries. At the same time, and most importantly, however, we found that the baseplate –by trapping waves scattered and distracted by the slope– amplified the ground motion at the crest up to one order of magnitude compared to numerical predictions of the response in absence of the baseplate. Our results show that topographic effects can be significantly affected by the underlying soil stratigraphy; and allude to the potentially significant role of this phenomenon in elevating seismic risk in regions with strong topographic relief. The findings of this study also suggest that future studies will benefit from clear understanding and careful considerations of capabilities and limitations of different investigation methods and that the numerical modelling and the lab testing (or the field testing) methods should complement each other.

text: How topography-dependent are topographic effects? Complementary numerical modeling of centrifuge experiments Topographic effects, the modification of seismic shaking by irregular topographies compared to flat ground, have been extensively studied. Very few studies, however, have investigated the effects of the stratigraphy and nonlinear response of the underlying geology on topographic amplification. Furthermore, most experimental studies have been performed in the field, where it is often difficult to establish an ideal flat-ground reference station, as well as to characterize the soil properties and their spatial variability in sufficient detail. Dafni [1] recently tested the seismic response of step-like slopes in a series of centrifuge experiments, where the incident motion, reference station and material properties were characterized in detail. In this study, we investigated the influence of the container boundary on topographic effects observed in the centrifuge experiments by performing numerical simulations with and without the container boundary. Our analysis suggested that the rigid-body rocking motion of the centrifuge container likely increased the experimental topographic spectral ratios, contributing to the discrepancy between the simulated and observed spectral ratios. We also found that although the laminar box lateral boundaries caused spurious reflections, they didn’t qualitatively affect the ground surface amplification pattern compared to numerical predictions of the same configuration without boundaries. At the same time, and most importantly, however, we found that the baseplate –by trapping waves scattered and distracted by the slope– amplified the ground motion at the crest up to one order of magnitude compared to numerical predictions of the response in absence of the baseplate. Our results show that topographic effects can be significantly affected by the underlying soil stratigraphy; and allude to the potentially significant role of this phenomenon in elevating seismic risk in regions with strong topographic relief. The findings of this study also suggest that future studies will benefit from clear understanding and careful considerations of capabilities and limitations of different investigation methods and that the numerical modelling and the lab testing (or the field testing) methods should complement each other.

year: 2019

title: A virtual community of practice approach to teacher professional development and learning

authors: Keown, Paul Ashley

subjects: community of practice

abstract: Research over a long period has suggested that professional development and learning for teachers often produces disappointing results. Recent theory suggests that teacher professional learning presented within a situated learning and community of practice framework is likely to be more effective than the more traditional forms of in-service professional development and learning. Further, recent technological developments since the mid 1990s have created increasingly sophisticated means of bringing widely distributed learners together, within flexible timeframe, online (virtual) discussion communities. This study set out to develop a workable approach to teacher professional development and learning (TPDL), using situated learning and community of practice learning theory and the opportunities afforded by Web 2 virtual learning environments. The literatures of learning theory, teacher professional development and communities of practice were reviewed and best practice principles identified. These principles were then used to design a virtual community of practice (VCoP) approach to teacher professional development and learning.  The approach was then implemented as the underpinning framework for three virtual professional development modules for secondary school Geography and Social Studies teachers. 

     The study used a grounded theory and action learning action research methodology, which enabled the researcher and the research participants to evaluate and fine tune the approach throughout the study.  A mixed method research design resulted in the collection of rich quantitative and qualitative data during each module. Naturalistic data were drawn from the online module record and from semi-structured focus group discussions. More structured and reflective data were collected through a final post-module evaluative questionnaire. The data collected were analysed using a range of techniques, including narrative analysis, structural analysis, semantic analysis, and domain analysis. The results of these analyses are presented from three contrasting perspectives: a structural analysis narrative of each module (Chapter 5), a content and personal case study narrative of selected participants (Chapter 6), and a qualitative and quantitative analysis of a final post module reflective survey (Chapter 7).    

     The main findings of the study were that an ongoing virtual community of practice approach appears to be a viable and effective form of TPDL, under certain conditions.  Grounded action learning action research experiences indicated that a meso-scale VCoP experience of between 12 to 15 weeks was an optimal timeframe. Reading and discussion requirements also needed to be carefully judged in order to ensure VCoP modules did enough to be challenging, yet remain manageable for busy classroom teachers. Features of the approach found to be very effective included the mix of activities used including, reading key literature, discussing ideas, sharing activities and experiences, flexible use of time, quality facilitation, and the situated nature of the approach. Features of the approach identified as requiring further refinement included improvements to the module website and maintaining a satisfactory level of contribution across all participants. 

     The concluding discussion found that while 'classic' VCoPs have proven to be effective in business there are very few examples of similar success in the field of TPDL. This study found that VCoPs can be effective for teachers but only when the classic model of VCoP is adapted to ensure VCoPs are manageable for, and tailored to, the nature of teachers' working lives.  The study concludes by considering the research in a wider context and considering the implications of the findings for further research and development.

text: A virtual community of practice approach to teacher professional development and learning Research over a long period has suggested that professional development and learning for teachers often produces disappointing results. Recent theory suggests that teacher professional learning presented within a situated learning and community of practice framework is likely to be more effective than the more traditional forms of in-service professional development and learning. Further, recent technological developments since the mid 1990s have created increasingly sophisticated means of bringing widely distributed learners together, within flexible timeframe, online (virtual) discussion communities. This study set out to develop a workable approach to teacher professional development and learning (TPDL), using situated learning and community of practice learning theory and the opportunities afforded by Web 2 virtual learning environments. The literatures of learning theory, teacher professional development and communities of practice were reviewed and best practice principles identified. These principles were then used to design a virtual community of practice (VCoP) approach to teacher professional development and learning.  The approach was then implemented as the underpinning framework for three virtual professional development modules for secondary school Geography and Social Studies teachers. 

     The study used a grounded theory and action learning action research methodology, which enabled the researcher and the research participants to evaluate and fine tune the approach throughout the study.  A mixed method research design resulted in the collection of rich quantitative and qualitative data during each module. Naturalistic data were drawn from the online module record and from semi-structured focus group discussions. More structured and reflective data were collected through a final post-module evaluative questionnaire. The data collected were analysed using a range of techniques, including narrative analysis, structural analysis, semantic analysis, and domain analysis. The results of these analyses are presented from three contrasting perspectives: a structural analysis narrative of each module (Chapter 5), a content and personal case study narrative of selected participants (Chapter 6), and a qualitative and quantitative analysis of a final post module reflective survey (Chapter 7).    

     The main findings of the study were that an ongoing virtual community of practice approach appears to be a viable and effective form of TPDL, under certain conditions.  Grounded action learning action research experiences indicated that a meso-scale VCoP experience of between 12 to 15 weeks was an optimal timeframe. Reading and discussion requirements also needed to be carefully judged in order to ensure VCoP modules did enough to be challenging, yet remain manageable for busy classroom teachers. Features of the approach found to be very effective included the mix of activities used including, reading key literature, discussing ideas, sharing activities and experiences, flexible use of time, quality facilitation, and the situated nature of the approach. Features of the approach identified as requiring further refinement included improvements to the module website and maintaining a satisfactory level of contribution across all participants. 

     The concluding discussion found that while 'classic' VCoPs have proven to be effective in business there are very few examples of similar success in the field of TPDL. This study found that VCoPs can be effective for teachers but only when the classic model of VCoP is adapted to ensure VCoPs are manageable for, and tailored to, the nature of teachers' working lives.  The study concludes by considering the research in a wider context and considering the implications of the findings for further research and development.

year: 2009

title: Stemming the colonial environmental tide

authors: Joseph, Robert

subjects: human activities

abstract: Stemming the colonial environmental tide supports an Aotearoa New Zealand context that fundamentally acknowledges mātauranga and tikanga Māori law and shared co-governance and concurrent jurisdiction through 7 Aotearoa New Zealand EBM principles.

text: Stemming the colonial environmental tide Stemming the colonial environmental tide supports an Aotearoa New Zealand context that fundamentally acknowledges mātauranga and tikanga Māori law and shared co-governance and concurrent jurisdiction through 7 Aotearoa New Zealand EBM principles.

year: 2022-05