Geology topics

Shaghayegh Karimzadeh

Publications and source records attributed to Shaghayegh Karimzadeh.

5 recordsLinked to original sources

USGS2026

Simulated ground motion dataset in the Azores Plateau, Portugal, on rock and soil sites

Building on a previously developed bedrock dataset, this study extends the Azores Plateau ground motion simulations to include soil-amplified records and introduces a comprehensive validation framework. Soil amplification is modeled using one-dimensional soil profiles. A stochastic source-based approach is employed to generate the dataset, incorporating randomization of input-model parameters to account for the aleatory uncertainty in seismic activity. The accuracy of the dataset is verified through a comprehensive validation framework, showing that the randomization effectively captures variance and inter-period correlation observed in records. This work provides a robust dataset for advancing seismic hazard and risk assessment in the Azores Plateau.

central and eastern Azores islands↗

USGS2025

Broadband stochastic simulation of earthquake ground motions with multiple strong phases with an application to the 2023 Kahramanmaraş, Turkey (Türkiye), earthquake

Stochastic ground motion simulation models are often less accurate at lower frequencies than at higher frequencies when fitting recorded data unless supplemented by a deterministic forward directivity velocity pulse model. Moreover, time-modulated stochastic models, which adjust ground motion amplitudes over time, typically use functions that fail to capture multiple strong-motion phases. The February 2023 Turkey (Türkiye) earthquake exhibited diverse recordings, including near-fault and far-field motions with pulse-like and non-pulse-like characteristics, along with single and multiple strong-motion phases. To better represent such a diverse set of recordings, this study enhances a fully non-stationary site-based stochastic model without combining it with a deterministic model. Improvements include a new band-pass filter with upper- and lower-frequency limits, which refines the representation of the low-frequency content. Moreover, a time-modulating function that can represent energy arrival in multiple strong phases is introduced. The reference model’s parameters are identified by fitting to the energy content, zero-level crossings, and cumulative counts of positive-minima and negative-maxima of a target accelerogram. This fitting procedure is modified to address the increased number of parameters. These improvements broaden the reference model’s applicability while preserving its simplicity, a key aspect appealing to engineering practitioners. The improved model’s applicability is demonstrated by simulating a dataset from the February 2023 Türkiye earthquake, and the accuracy is tested using a pulse-like Next Generation Attenuation Relationships for Western United States dataset. Validations are performed based on total energy, zero-level crossings, Fourier amplitude spectrum, elastic response spectra, and peak ground motion parameters. Validations are performed schematically in the time and frequency domains and quantitatively using goodness-of-fit scores, various validation-metrics errors, and inter-period correlations. Overall, the improved stochastic model can effectively simulate a set of diverse ground motion recordings, including near-fault pulse-like records, records with multiple strong phases, and far-field motions across a broad frequency range.

Kahramanmaraş↗

USGS2024

Seismic response comparison of a historical masonry church subject to real and simulated ground motions

In recent years, advanced numerical models and high-performance computing have facilitated the utilization of ground motion time series in the assessment of the non-linear dynamic behavior of historic masonry structures. Since recorded accelerograms can be sparse for specific analysis conditions, stochastic ground motion simulations have become a viable alternative to overcome this limitation. This study simulates the recorded acceleration time series of the Central Italy 2016 earthquake event at the closest station to the town of Macerata using a site-based stochastic approach. The simulated motions are seismologically evaluated using a goodness-of-fit method in terms of various intensity measures. The simulated records, in conjunction with real records, are used to study the non-linear dynamic behavior of San Filippo Neri church located in Macerata. The church of San Filippo represents an important example of Baroque religious architecture in central Italy, which was damaged and closed off to the public after the 2016 earthquake events. The construction was investigated with a vast diagnostic campaign which included on-site testing and dynamic identification tests. The collected data is used to calibrate the dynamic response of a three-dimensional finite element model of the church. The model is finally used to compare the non-linear seismic responses under real and simulated ground motions with the site recorded damage. The results of structural responses demonstrate a strong agreement between the real and simulated records, providing evidence to support the validation of the site-based stochastic simulation.

Macerata↗

USGS2024

Simulated ground-motion records for the seismic assessment of monumental masonry structures

Earthquakes are natural disasters that can cause widespread devastation and loss of life. Simulated ground-motion records can be useful in regions with limited seismic stations or a history of damaging but infrequent earthquakes. This is especially true in areas with a high concentration of heritage masonry structures, which are especially susceptible to damage, as simulated records can be crucial in predicting their seismic response and protecting these buildings from seismic damage. Despite the importance of simulated earthquakes, few studies have investigated how effective they are compared to real earthquakes when assessing the structural response of heritage buildings. To address this knowledge gap, we employ two different simulation methods of the Mw 6.2 Faial earthquake, which occurred on July 9th, 1998, in the Azores, to replicate the recorded time-series at four available stations within an epicentral distance of 150 km. The study has two objectives: first, to validate the simulated records of the 1998 Faial earthquake using alternative stochastic ground-motion simulation approaches, and second, to determine how these approaches impact the seismic assessment of historic masonry structures. To accomplish these objectives, this study uses real and simulated ground-motion datasets to conduct non-linear response history analyses of the São Francisco Church, a monumental structure in Horta that sustained damage during the Faial earthquake. The results show that both simulation approaches yield structural responses similar to the observed records.

Conference Paper↗

USGS2023

Stochastic simulation of earthquake ground motions for the seismic assessment of monumental masonry structures: Source-based vs site-based approaches

Earthquakes are among the most destructive natural disasters and have resulted in a massive number of fatalities and economic losses all over the world. Simulated ground motion records are valuable, particularly for regions lacking seismic stations or with a limited history of large-magnitude earthquakes. Notably, a significant percentage of monumental masonry buildings are located in regions with limited access to real records; hence, simulated records play a paramount role in their seismic protection. However, few studies have investigated the structural response of heritage buildings via response history analyses to assess the performance of simulated earthquakes against real ones. To accomplish this, this study simulates the recorded time-series of the 9th of July 1998 Faial earthquake in the Azores (M w = 6.2) at four available stations, using two different simulation approaches, that is, a source-based stochastic finite-fault method and a site-based broadband stochastic method. First, two masonry facades with sidewalls characterized by different slenderness levels are adopted to conduct this research. Moreover, the proposed approach is also applied to an existing monumental structure, that is, São Francisco Church, located at Horta, which was affected by damage during the Faial earthquake. Results demonstrate that both simulation approaches provide similar results in terms of structural response prediction. The proposed framework also demonstrates that a small mismatch in terms of predicted damage patterns can result in a significant relative error in terms of displacement predictions.

Earthquake Engineering and Structural Dynamics↗