Probabilistic seismic hazard analysis (PSHA) is generally recognized as the rational method to quantify the seismic threat. Classical formulation of PSHA goes back to the second half of the twentieth ...century, but its implementation can still be demanding for engineers dealing with practical applications. Moreover, in the last years, a number of developments of PSHA have been introduced; e.g., vector-valued and advanced ground motion intensity measure (IM) hazard, the inclusion of the effect of aftershocks in single-site hazard assessment, and multi-site analysis requiring the characterization of random fields of cross-correlated IMs. Although software to carry out PSHA has been available since quite some time, generally, it does not feature a user-friendly interface and does not embed most of the recent methodologies relevant from the earthquake engineering perspective. These are the main motivations behind the development of the practice-oriented software presented herein, namely REgionAl, Single-SitE and Scenario-based Seismic hazard analysis (REASSESS V2.0). In the paper, the seismic hazard assessments REASSESS enables are discussed, along with the implemented algorithms and the models/databases embedded in this version of the software. Illustrative applications exploit the potential of the tool, which is available at
http://wpage.unina.it/iuniervo/doc_en/REASSESS.htm
.
Purpose
This Study aims to present the seismic hazard assessment of the earthquake-prone eastern of Iran that has become more important due to its growing economic importance. Many cities in this ...region have experienced life and financial losses due to major earthquakes in recent years. Thus, in this study the seismic hazard maps and curves, and site-specific spectrums were obtained by using probabilistic approaches for the region.
Design/methodology/approach
The seismotectonic information, seismicity data and earthquake catalogues were gathered, main active seismic sources were identified and seismic zones were considered to cover the potential active seismic regions. The seismic model based on logic tree method used two seismic source models, two declustered catalogues, three choices for earthquake recurrence parameters and maximum considered earthquakes and four ground motion predicting (attenuation) models (GMPE).
Findings
The results showed a wide range of seismic hazards levels in the study region. The peak ground acceleration (PGAs) for 475 years returns period ranges between 0.1 g in the north-west part of the region with low seismic activity, to 0.52 g in the south-west part with high levels of seismicity. The PGAs for a 2,475-year period, also ranged from 0.12 to 0.80 g for the same regions. The computed hazard results were compared to the acceptable level of seismic hazard in the region based on Iran seismic code.
Originality/value
A new probabilistic approach has been developed for obtaining seismic hazard maps and curves; these results would help engineers in design of earthquake-resistant structures.
Based on field investigations, interpretations of high‐resolution UAV images, and analyses of available InSAR data, we mapped the fault geometry and surface ruptures of the 2021 Mw 7.4 Maduo ...earthquake that occurred on a low‐activity strike‐slip fault within the Tibetan Plateau. The results indicate that (a) the earthquake activated a fault that is ∼161 km long and has complicated structural geometry; (b) the surface rupture occurs over a distance of 148 km, but is separated into three distinct segments by two large gaps (38 and 20 km, respectively); (c) within the surface‐rupture segments, the horizontal and vertical displacements are typically 0.2–2.6 m (much lower than the InSAR‐based slip maximum of 2–6 m at depth) and ≤0.4 m, respectively. The two large gaps of the Maduo surface rupture represent the two largest surface‐rupture discontinuities of strike‐slip earthquakes ever documented, and coincide with structurally complicated fault portions and near‐surface soft sediments.
Plain Language Summary
Evaluating the seismic potential of low‐activity strike‐slip faults is commonly challenging because of (a) the difficulty in mapping of causative fault geometry that has subtle topographic expression, and (b) limited fault slip at the surface (relative to that at depth) produced by each earthquake. Our investigation of the 2021 Maduo earthquake demonstrates that, along the low‐activity strike‐slip fault, laterally significant gaps (up to 40 km wide) may separate extensive co‐seismically ruptured regions on either end of such gaps, which can thereby compromise typical methodologies used to assess paleoseismic ruptures and may lead to underestimates of seismic hazard. This observation increases the challenge of assessing the seismic potential of low‐activity strike‐slip faults.
Key Points
The Maduo earthquake activated a 161‐km‐long strike‐slip fault with subtle topographic expression and complicated structural geometry
The surface rupture occurs over a distance of 148 km, but includes two large gaps that are 38 and 20 km, respectively
Within the surface‐rupture segments, the horizontal slip is 0.2–2.6 m, much lower than the InSAR‐based slip maximum of 2–6 m
Editor’s summaryThe Kahramanmaraş earthquake sequence in Turkey on 6 February 2023 caused a tremendous amount of damage and loss of life. The sequence occurred across several faults, including and ...associated with the East Anatolian Fault, a strike-slip fault that has had many major earthquakes in the past. Jia et al. used an array of geophysical observations to produce models of how the ruptures occurred. The earthquake sequence ruptured at least six faults, including a large portion of the East Anatolian Fault. The rupture sequence was complex and contained surprises in the details of how the rupture occurred. These observations and models are important for understanding strike-slip faults and forecasting seismic hazards. —Brent Grocholski
The seismic scenario of the peninsular India has been changed due to many devastating earthquakes in the past few decades. The present paper discusses the hazard analysis with deterministic and ...probabilistic approaches for Vadodara region. Homogeneous seismic catalogue has been prepared covering the longitude 68° E to 77° E and latitude 18° N to 26° N for the study region and seismotectonic model has been developed for the different moment magnitude range of the earthquake events. Four ground motion prediction relationships have been used to evaluate the peak ground acceleration value at rock level for the Vadodara region.
We describe the main structure and outcomes of the new probabilistic seismic hazard model for Italy, MPS19 Modello di Pericolosità Sismica, 2019. Besides to outline the probabilistic framework ...adopted, the multitude of new data that have been made available after the preparation of the previous MPS04, and the set of earthquake rate and ground motion models used, we give particular emphasis to the main novelties of the modeling and the MPS19 outcomes. Specifically, we (i) introduce a novel approach to estimate and to visualize the epistemic uncertainty over the whole country; (ii) assign weights to each model components (earthquake rate and ground motion models) according to a quantitative testing phase and structured experts’ elicitation sessions; (iii) test (retrospectively) the MPS19 outcomes with the horizontal peak ground acceleration observed in the last decades, and the macroseismic intensities of the last centuries; (iv) introduce a pioneering approach to build MPS19_cluster, which accounts for the effect of earthquakes that have been removed by declustering. Finally, to make the interpretation of MPS19 outcomes easier for a wide range of possible stakeholders, we represent the final result also in terms of probability to exceed 0.15 g in 50 years.
Synchronous rupture involving two or more antithetic or synthetic faults results in higher levels of ground shaking hazard compared to that computed separately for each fault. We describe ...methodologies to estimate the ground motions both deterministically and probabilistically using a square-root-sum-of-the-squares approach and provide a case study for the Salt Lake City segment of the Wasatch fault zone and the antithetic West Valley fault zone in the Salt Lake Valley, Utah. The amount of increased hazard between the fault pairs will depend on their fault dips and horizontal separation which will dictate their potential rupture areas and hence their maximum magnitudes. For the case study, the increased hazard between the Salt Lake City segment and the West Valley fault zone can range up to 30% primarily at short to moderate periods (<1 s).
A consistent seismic hazard and fragility framework considering combined capacity-demand uncertainties is proposed, in light of the probability density evolution method (PDEM). The PDEM has solid ...theoretical basis in the reliability field, and it is integrated within the performance-based earthquake engineering (PBEE) for hazard-fragility assessment in this paper. During the analysis, the sample sets with different assigned probability are required to determine in advance, and the equivalent extreme events with virtual stochastic process are required to establish for solution. Both the uncertainties of capacity and demand are considered, and a combined performance index (CPI) is defined as concerned physical variable in PDEM, through pushover static and timehistory dynamic analyses. A non-stationary stochastic earthquake model is introduced using spectral representation of random functions, and the real characteristics of ground motions are reflected by one or two variables for each probability space. The peak ground acceleration (PGA) and spectral acceleration of the first period Sa(T1) of non-stationary stochastic ground motions are then obtained for each earthquake level, and the equivalent extreme events are also performed to discuss the statistical information of PGA or Sa(T1) through PDEM. The exceeding probability of PGA or Sa(T1) for each earthquake level is acquired, and a connection between the fragility value and hazard extent is built. The final 3D consistent hazard-fragility curves are then given, and the exceeding probability for different limit states, earthquake levels as well as intensity exceeding conditions can be predicted. Moreover, a comparison with the four classic approaches in the state-of-the-art is performed to verify the accuracy of PDEM procedure. In general, the framework avoids the pre-defined lognormal fragility shape and proves the combined efficiency and accuracy with the Monte Carlo simulation (MCS). The consistency from probabilistic hazard to fragility is realized without re-selecting earthquake waves, which is mainly attributed to the application of PDEM and non-stationary ground motions. The proposed framework provides new ideas for the consistent non-parametric hazard and fragility assessment scheme in the PBEE.
•Propose a consistent seismic hazard-fragility framework based on the PDEM and non-stationary stochastic earthquake.•Consider the combined capacity-demand uncertainties and a combined performance index with different assigned probability.•Give the 3D hazard-fragility curves incorporating different limit states, earthquake levels and intensity exceeding conditions.•Avoid the predefined lognormal curve shape and prove the combined efficiency and accuracy.
This work focuses on how the progress in earthquake science that follows a large, deeply studied earthquake might be promptly combined with updated approaches of seismic hazard analysis to guide ...applicative choices for seismic risk reduction, such as postevent seismic microzoning and building design. Both seismic microzoning and seismic design of structures require strong motion records to perform numerical site response analyses. These records have to be related to the seismotectonic context and historical seismicity of the investigation area. We first performed a fault‐based probabilistic seismic hazard analysis in the area struck by the 2016 central Italy seismic sequence to individuate reference uniform hazard spectra at rock conditions. We used two different seismic hazard models, one considering 27 individual seismogenic sources (ISSs), and the second one involving grid point seismicity, using a fixed‐radius smoothing approach. The geological and seismotectonic data of the 2016 seismic sequence were used to update the model of ISSs. We performed a deaggregation analysis to evaluate the contribution of the ISS in the hazard of four representative sites and to select the magnitude‐distance pairs useful in the selection of the real accelerograms. The deaggregation analysis has been performed to identify which source and magnitude most contribute to the hazard for each site, and for different periods of spectral accelerations. Finally, we select, for each site, a set of natural accelerograms, from both nonimpulsive and pulse‐like records, based on the magnitude‐distance pairs that are compatible on average with target uniform hazard spectra.
Key Points
A fault‐based and time‐dependent approaches give a complementary view of PSHA
We provide Input ground motion for site effects studies in central Italy
We consider this approach useful for reconstruction projects
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