27 research outputs found
A Region-Specific Ground-Motion Model for Inelastic Spectral Displacement in Northern Italy Considering Spatial Correlation Properties
The peak inelastic displacement of singleâdegreeâofâfreedom bilinear systems (â Sdi Sdiâ ) is an effective intensity measure linking groundâmotion features to the inelastic response and subsequent structural and nonstructural damage of engineered systems. This study develops a regionâspecific groundâmotion model for Sdi Sdi considering source, path, and site effects and explicitly accounting for the spatial correlation between intraevent residuals when the model parameters are estimated. The model is developed based on 2427 twoâcomponent horizontal groundâmotion records from 85 events in northern Italy with magnitudes ranging from 4.0 to 6.4 and sourceâtoâsite distances less than 200 km. An exponential stationary and isotropic model is considered to represent the spatial correlation properties of Sdi Sdi (after scrutinizing the appropriateness of the underlying assumptions for such a model). Comparisons are performed with existing models in the literature in terms of Sdi Sdi estimates, as well as the (spatial correlation) effective range parameter. Two practical applications of the developed model are presented: one on estimating the spatial distribution of Sdi Sdi (as an essential ingredient for seismic loss assessments) and one on the engineering validation of regionâspecific groundâmotion simulations. Challenges regarding such validations are also discussed
Cybershake NZ v17.9: New Zealand simulation-based probabilistic seismic hazard analysis
This paper presents the computational workflow and preliminary results of probabilistic seismic
hazard analysis (PSHA) in New Zealand based on physics-based ground motion simulations
(âCybershake NZâ). In the current work completed to date, the Graves and Pitarka (2010, 2015) hybrid
broadband ground motion simulation approach is utilized considering a transition frequency of 0.25
Hz, a detailed crustal model with a grid spacing of 0.4 km, and an empirically-calibrated local site
response model. Variation in hypocentre location and slip distribution are considered to partially
account for the variability in ground motion characteristics. Ruptures from the distributed seismicity
model are considered in the total hazard via empirical ground motion models. Intensity measures for
sample scenario ruptures and subsequently generated hazard curves are presented here. Treatment of
uncertainty in the context of simulation-based PSHA is discussed. Lastly, improvements for future
versions of the ongoing effort are outlined
Innovations in earthquake risk reduction for resilience: Recent advances and challenges
The Sendai Framework for Disaster Risk Reduction 2015-2030 (SFDRR) highlights the importance of scientific research, supporting the âavailability and application of science and technology to decision makingâ in disaster risk reduction (DRR). Science and technology can play a crucial role in the worldâs ability to reduce casualties, physical damage, and interruption to critical infrastructure due to natural hazards and their complex interactions. The SFDRR encourages better access to technological innovations combined with increased DRR investments in developing cost-effective approaches and tackling global challenges. To this aim, it is essential to link multi- and interdisciplinary research and technological innovations with policy and engineering/DRR practice. To share knowledge and promote discussion on recent advances, challenges, and future directions on âInnovations in Earthquake Risk Reduction for Resilienceâ, a group of experts from academia and industry met in London, UK, in July 2019. The workshop focused on both cutting-edge âsoftâ (e.g., novel modelling methods/frameworks, early warning systems, disaster financing and parametric insurance) and âhardâ (e.g., novel structural systems/devices for new structures and retrofitting of existing structures, sensors) risk-reduction strategies for the enhancement of structural and infrastructural earthquake safety and resilience. The workshop highlighted emerging trends and lessons from recent earthquake events and pinpointed critical issues for future research and policy interventions. This paper summarises some of the key aspects identified and discussed during the workshop to inform other researchers worldwide and extend the conversation to a broader audience, with the ultimate aim of driving change in how seismic risk is quantified and mitigated
Interdisciplinarity in practice: reflections from early-career researchers developing a risk-informed decision support environment for Tomorrow's cities
The concept of disaster risk is cross-disciplinary by nature and reducing disaster risk has become of interest for various disciplines. Yet, moving from a collection of multiple disciplinary perspectives to integrated interdisciplinary disaster risk approaches remains a fundamental challenge. This paper reflects on the experience of a group of early-career researchers spanning physical scientists, engineers and social scientists from different organisations across the global North and global South who came together to lead the refinement, operationalisation and testing of a risk-informed decision support environment for Tomorrow's Cities (TCDSE). Drawing on the notions of subjects and boundary objects, members of the group reflect on their individual and collective journey of transgressing disciplinary boundaries across three case studies between JuneâDecember 2021: operationalisation process of the TCDSE; development of a virtual urban testbed as a demonstration case for the implementation of the TCDSE; and consolidation of frequently asked questions about the TCDSE for communication purposes. The paper argues that (1) the production of boundary objects in interdisciplinary research nurtures relations of reciprocal recognition and the emergence of interdisciplinary subjects; (2) the intrinsic characteristics of boundary objects define the norms of engagement between disciplinary subjects and constrain the expression of interdisciplinary contradictions; and (3) affects and operations of power explain the contingent settlement of interdisciplinary disagreements and the emergence of new knowledge. Activating the interdisciplinary capacities of early-career researchers across disciplines and geographies is a fundamental step towards transforming siloed research practices to reduce disaster risk
Ground-motion selection for scenario ruptures using the generalized conditional intensity measure (GCIM) approach and its application for several major scenario earthquakes in New Zealand
Generalized conditional intensity measure (GCIM) method is extended to ground motion
selection for scenario ruptures. Using different rupture scenarios and site conditions, various
aspects of the GCIM methodology are scrutinized, including: (i) implementation of different
weight vectors and the composition of the IM vector; (ii) quantifying the importance of
replicate selections for different number of desired ground motions; and (iii) the effect of
considering bounds on the implicit causal parameters of the prospective ground motions.
Using the extended methodology, representative ground motion ensembles for several major
earthquake scenarios in New Zealand are developed. Cases considered include representative
ground motions for the occurrence of Alpine, Hope, and Porters Pass earthquakes in
Christchurch city, and the occurrence of Wellington, Wairarapa, and Ohariu fault ruptures in
Wellington city. Challenges in the development of ground motion ensembles for subduction
zone earthquakes are also highlighted. The selected scenario-based ground motion sets can
be used to complement ground motions which are often selected in conjunction with
probabilistic seismic hazard analysis, in order to understand the performance of structures for
the question âwhat if this fault ruptures?
The effect of bounds on magnitude, source-to-site distance and site condition in PSHA-based ground motion selection
In this paper, the effect of using bounds on magnitude, source-to-site
distance, and site condition of prospective records for the purpose of ground motion
selection based on probabilistic seismic hazard analysis (PSHA) is investigated. Although
it is common in ground motion selection to consider bounds on these causal parameters,
there is no consistent approach for setting the bounds as a function of the seismic hazard
at the site, and no guidance exists on how the bounds should be set considering the
distribution of causal scenarios affecting PSHA results. 36 PSHA cases are considered in
this paper to empirically illustrate the effects of alternative bounds on the characteristics
of selected ground motions, which cover a wide range of deaggregation distributions and
site conditions. The obtained results indicate that the use of excessively narrow bounds
encompassing only the dominant causal scenario can lead to ground motion ensembles
with a biased representation for the target hazard. In contrast, the use of relatively wide
bounds results in ensembles with an appropriate representation for the target intensity
measure distributions. Quantitative criteria for determining such bounds for general
problems are provided, which are expected to be sufficient in the majority of problems
encountered in ground motion selection for seismic demand analyses
Representative ground motion ensembles for several major earthquake scenarios in New Zealand
This paper develops representative ground motion ensembles for several
major earthquake scenarios in New Zealand. Cases considered include representative
ground motions for the occurrence of Alpine, Hope, and Porters Pass earthquakes in
Christchurch, and the occurrence of Wellington, Wairarapa, and Ohariu, fault ruptures in
Wellington. Challenges in the development of ground motion ensembles for subduction
zone earthquakes are also highlighted. The ground motions are selected based on the
generalized conditional intensity measure (GCIM) approach, ensuring that the ground
motion ensembles represent both the mean, and distribution of ground motion intensity
which such scenarios could impose. These scenario-based ground motion sets can be
used to complement ground motions which are often selected in conjunction with
probabilistic seismic hazard analysis, in order to understand the performance of structures
for the question âwhat if this fault ruptures?
Ground-motion selection for scenario ruptures using the generalized conditional intensity measure (GCIM) approach and its application for several major earthquake scenarios in New Zealand
Generalized conditional intensity measure (GCIM) method is extended to ground motion
selection for scenario ruptures. Using different rupture scenarios and site conditions, various
aspects of the GCIM methodology are scrutinized, including: (i) implementation of different
weight vectors and the composition of the IM vector; (ii) quantifying the importance of
replicate selections for different number of desired ground motions; and (iii) the effect of
considering bounds on the implicit causal parameters of the prospective ground motions.
Using the extended methodology, representative ground motion ensembles for several major
earthquake scenarios in New Zealand are developed. Cases considered include representative
ground motions for the occurrence of Alpine, Hope, and Porters Pass earthquakes in
Christchurch city, and the occurrence of Wellington, Wairarapa, and Ohariu fault ruptures in
Wellington city. Challenges in the development of ground motion ensembles for subduction
zone earthquakes are also highlighted. The selected scenario-based ground motion sets can
be used to complement ground motions which are often selected in conjunction with
probabilistic seismic hazard analysis, in order to understand the performance of structures for
the question âwhat if this fault ruptures?
Bounds on causal parameters of prospective ground motions and their effect on characteristics of selected ground motions
In this study, the effect of considering bounds on causal parameters of prospective
ground motions (e.g., magnitude, source-to-site distance, and site condition) for the purpose
of ground-motion selection is investigated. Although using bounds on causal parameters is
common practice in conventional approaches for ground motion selection, there is presently
no consistent approach for setting these bounds as a function of the seismic hazard at the site.
A rigorous basis is developed and sensitivity analyses performed for the consideration of
bounds on magnitude, source-to-site distance, and site condition for use in ground motion
selection. In order to empirically illustrate the effects of various causal parameter bounds on
the characteristics of selected ground motions, 78 and 36 cases of scenario seismic hazard
analysis (scenario SHA) and probabilistic seismic hazard analysis (PSHA) are considered,
which cover a wide range of causal parameters and site conditions. Ground motions are
selected based on the generalized conditional intensity measure (GCIM) approach, which
considers multiple ground motion intensity measures (IMs) and their variability in order to
appropriately represent characteristics of the seismic hazard at the site. It is demonstrated that
the application of relatively âwideâ bounds on causal parameters effectively removes ground
motions with drastically different characteristics with respect to the target seismic hazard
(improving computational efficiency in the selection process by reducing the subset of
prospective records), and results in an improved representation of the target causal
parameters. In contrast, the use of excessively ânarrowâ bounds can lead to ground motion
ensembles with a poor representation of the target IM distributions, especially for ground
motions selected to represent PSHA results. As a result, the causal parameter bound criteria
advocated in this study provide a good âdefaultâ that is expected to be sufficient in the
majority of problems encountered in seismic hazard and demand analyses