A Region-Specific Ground-Motion Model for Inelastic Spectral Displacement in Northern Italy Considering Spatial Correlation Properties

The peak inelastic displacement of single‐degree‐of‐freedom bilinear systems (⁠Sdi Sdi⁠) is an effective intensity measure linking ground‐motion features to the inelastic response and subsequent structural and nonstructural damage of engineered systems. This study develops a region‐specific ground‐motion 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 two‐component horizontal ground‐motion records from 85 events in northern Italy with magnitudes ranging from 4.0 to 6.4 and source‐to‐site 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 region‐specific ground‐motion 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 (‘Cybershake NZ’). 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 ‘availability and application of science and technology to decision making’ in disaster risk reduction (DRR). Science and technology can play a crucial role in the world’s 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 ‘Innovations in Earthquake Risk Reduction for Resilience’, a group of experts from academia and industry met in London, UK, in July 2019. The workshop focused on both cutting-edge ‘soft’ (e.g., novel modelling methods/frameworks, early warning systems, disaster financing and parametric insurance) and ‘hard’ (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 June–December 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 “what 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 “what 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 “what 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 ‘wide’ 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 ‘narrow’ 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 ‘default’ that is expected to be sufficient in the majority of problems encountered in seismic hazard and demand analyses