Elena Florinela Manea

Evaluating the performance of probabilistic seismic hazard models against recorded data and their potential to forecast future earthquake ground shaking is an emerging research topic. In this study, we evaluate and test the results of the recently released 2020 European Seismic Hazard Model (ESHM20; Danciu et al., 2021a, 2024) against observations for several cities in Romania. The dataset consists of ground-shaking recordings and macroseismic observations that extend the observational time period to a few hundred years. The full distribution of the hazard curves, depicting the epistemic uncertainties in the hazard at the given location was considered, and the testing was performed for peak ground acceleration (PGA) values of 0.1 and 0.2 g. The results show consistency between ESHM20 and the ground motion observations for the cities located near the Vrancea intermediate-depth source (VRI) for both selected PGA levels. ESHM20's estimated values appear to be over the recorded VRI ground motions along the Carpathian Mountains and below those at the far-field locations outside the Carpathians yet inside the expected model variability. Some of these differences might be attributed to the uncertainties in data conversion, local site effects, or differences in the attenuation patterns of the ground motion models. Our analysis suggests that the observed exceedance rates for the selected PGA levels are consistent with ESHM20 estimates, but these results must be interpreted with caution given the limited time and spatial coverage of the observations.

In the present study, an effort to propose and adopt appropriate Ground Motion Prediction Equations (GMPEs) for the Rapid Earthquake Damage Assessment System (REDAS) in the Black Sea basin is attempted. Emphasis of GMPE harmonization in the cross-border areas (CBA) is given. For this reason, two distinct sub-areas are investigated, taking into consideration their seismotectonic regime. One sub-area refers to active shallow crustal earthquakes (Greece-Turkey, CBA) and the other to intermediate-depth and shallow crustal earthquakes (Romania-Moldova, Western Black Sea CBA). Testing and ranking of pre-selected GMPEs has been performed using strong motion data of the broader CBA regions of both sub-areas. The final proposed GMPEs to feed the REDA System may assure the effective estimation of ShakeMaps and—in combination with the appropriate vulnerability curves—reliable near-real-time damage assessment in the cross-border earthquake affected areas.

Evaluating the performance of probabilistic seismic hazard models against recorded data and their potential to forecast future earthquake’s ground shaking is an emerging research topic. In this study, we evaluate and test the results of the recently released European Seismic Hazard Model (ESHM20; Danciu et al., 2021) against observations for several cities in Romania. The dataset consists of ground shaking recordings and macroseismic observations, which extend the observational time-period to few hundred years. The full distribution of the hazard curves, depicting the epistemic uncertainties of the hazard at the given location was considered and the testing was done for peak ground acceleration (PGA) values i.e., 0.1 g and 0.2 g. The results show close agreement between the ESHM20 and the observations for the cities located near the Vrancea intermediate-depth source (VRI) for both selected PGA levels. ESHM20 appears to overestimate the VRI recorded ground motions along the Carpathian Mountain Range and underestimate those at the far-field locations outside the Carpathians. Some of these differences might be attributed to the uncertainties in data conversion, local site effects, or differences in the attenuation patterns of the ground motion models. Our analysis suggests that the observed exceedance rates for the selected PGA levels are consistent with ESHM20 estimates, but these results must be interpreted with caution given the limited time and spatial coverage of the observations.

This article summarizes the development of the 2023 New Zealand ground-motion database (NZGMDB). A preceding version was formally used as the central ground-motion database in the ground-motion characterization modeling for the 2022 New Zealand (NZ) National Seismic Hazard Model (NSHM) revision. The database contains ground motions for events with a moment magnitude greater than ∼3.0 from the years 2000 to the end of 2022. Several challenges associated with NZ earthquake source metadata are explained, including determination of earthquake location, magnitude, tectonic classification, and finite-fault geometry, among others. The site table leverages the site database developed as a part of the 2022 NZ NSHM revision, and several definitions of source-to-site distance are computed for the propagation path table. The ground-motion quality classification was initially assessed using a neural network. Subsequent waveform quality verification was conducted and additional quality criteria were enforced to ensure a sufficiently high-quality database. Standard processing techniques were applied to the ground motions before intensity measure (IM) calculation. IMs in the database include peak ground acceleration, 5%-damped pseudoacceleration response spectra, smoothed Fourier amplitude spectra, and other cumulative and duration-related metrics. The NZGMDB is publicly available and routinely updated as new and higher quality data become available.

This article summarizes the ground-motion characterization (GMC) model component of the 2022 New Zealand National Seismic Hazard Model (2022 NZ NSHM). The model development process included establishing a NZ-specific context through the creation of a new ground-motion database, and consideration of alternative ground-motion models (GMMs) that have been historically used in NZ or have been recently developed for global application with or without NZ-specific regionalizations. Explicit attention was given to models employing state-of-the-art approaches in terms of their ability to provide robust predictions when extrapolated beyond the predictor variable scenarios that are well constrained by empirical data alone. We adopted a “hybrid” logic tree that combined both a “weights-on-models” approach along with backbone models (i.e., metamodels), the former being the conventional approach to GMC logic tree modeling for NSHM applications using published models, and the latter being increasingly used in research literature and site-specific studies. In this vein, two NZ-specific GMMs were developed employing the backbone model construct. All of the adopted subduction GMMs in the logic tree were further modified from their published versions to include the effects of increased attenuation in the back-arc region; and, all but one model was modified to account for the reduction in ground-motion standard deviations as a result of nonlinear surficial site response. As well as being based on theoretical arguments, these adjustments were implemented as a result of hazard sensitivity analyses using models without these effects, which we consider gave unrealistically high hazard estimates.

The 2022 revision of Aotearoa New Zealand National Seismic Hazard Model (NZ NSHM 2022) has involved significant revision of all datasets and model components. In this article, we present a subset of many results from the model as well as an overview of the governance, scientific, and review processes followed by the NZ NSHM team. The calculated hazard from the NZ NSHM 2022 has increased for most of New Zealand when compared with the previous models. The NZ NSHM 2022 models and results are available online.

This article summarizes hazard sensitivities associated with the updated ground-motion characterization modeling (GMCM) scheme adopted in the recent revision of New Zealand National Seismic Hazard Model (NZ NSHM 2022). In terms of impact on ground-motion hazard, the current GMCM scheme (GMCM 2022) results in an overall, at times significant, increase in calculated mean hazard with respect to NZ NSHM 2010. With regard to relative impact, the update in GMCM accounts for the dominant change in high-hazard regions, whereas in low-hazard regions update in source characterization model dominate. Within GMCM 2022, the change in shallow crustal ground-motion models (GMMs) dominates the effect on calculated hazard, whereas change in subduction interface GMMs has a compounding effect for east coast of North Island and southwest of South Island. Impact of the two NZ-specific adjustments to some of the published GMMs is also discussed. The back-arc attenuation adjustment accounts for a 20%–30% reduction in calculated hazard for peak ground acceleration in northwest of North Island, whereas aleatory uncertainty adjustment accounts for 10%–20% reduction in high-hazard regions such as along the east coast of North Island and in the lower west of South Island.