Empirical ground motion models for the vertical component from shallow crustal earthquakes in active tectonic regions are derived using the PEER NGA-West2 database. The model is applicable to ...magnitudes 3.0-8.0, distances of 0-300 km, and spectral periods of 0-10 s. The model input parameters are the same as used by Abrahamson et al. (2014) except that the nonlinear site response and depth to bedrock effects are evaluated but found to be insignificant. Regional differences in large distance attenuation and site amplification scaling between California, Japan, China, Taiwan, Italy, and the Middle East are included. Scaling for the hanging-wall effect is incorporated using the constraints from numerical simulations by Donahue and Abrahamson (2014). The standard deviation is magnitude dependent with smaller magnitudes leading to larger standard deviations at short periods but smaller standard deviations at long periods. The vertical ground motion model developed in this study can be paired with the horizontal component model proposed by Abrahamson et al. (2014) to produce a V/H ratio. For applications where the horizontal spectrum is derived from the weighted average of several horizontal ground motion models, a V/H model derived directly from the V/H data (such as Gülerce and Abrahamson 2011) should be preferred.
Two approaches are used to develop the vertical design spectra in probabilistic seismic hazard assessment (PSHA): (i) performing PSHA for the vertical component using vertical ground motion models ...(GMMs), and (ii) utilizing the
V
/
H
ratio GMMs to scale the horizontal spectrum during or after the hazard calculations for the horizontal component. This study intends to develop a new framework for building a vertical ground motion logic tree that combines both vertical and
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/
H
ratio GMMs in the PSHA analysis. For this purpose, the Turkish strong motion database (TSMD) (Akkar et al. in Journal of Seismology 14(3): 457–479,
2010
) is updated with recordings from earthquakes that occurred between 2008 and 2015, including the
M
w
= 6.1 Elazığ and
M
w
= 7.2 Van earthquakes. The updated TSMD contains 2698 recordings, with the earthquake metadata, source-to-site distance metrics for the recordings, measured shear wave velocity profiles for the recording stations, and spectral accelerations for horizontal and vertical components. Four candidate
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/
H
ratio GMMs (proposed by Gülerce and Abrahamson in Earthquake Spectra 27(4): 1023–1047,
2011
; Gülerce and Akyuz in Seismological Research Letters 84(4): 678–687,
2013
; Akkar et al. in Bulletin of Earthquake Engineering 12(1): 517–547,
2014a
; Bozorgnia and Campbell in Earthquake Spectra, 32(2): 951–978,
2016
) are selected, and the model predictions are compared with the actual data in the updated TSMD using the analysis of the residuals and data-driven techniques. Analysis results showed that the median predictions of the
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/
H
ratio GMMs proposed by Gülerce and Akyuz (
2013
), Akkar et al. (
2014a
), and Bozorgnia and Campbell (
2016
) are compatible with the
V
/
H
ratios in the Turkish strong motion dataset. The findings of this study and the compatibility analysis of the vertical GMMs with the updated TSMD are combined in the accompanying manuscript (Gülerce et al. in Pure and Applied Geopyhsics, 2019, submitted) to provide the complete framework of ground motion characterization for vertical ground motion component.
The main objectives of this study are: (1) to choose the vertical ground motion models (GMMs) that are consistent with the magnitude, distance, depth, and site amplification scaling of the updated ...Turkish ground motion database, and (2) to combine the vertical GMMs with the
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/
H
ratio models selected in the accompanying paper (Alipour et al. in Pure Appl Geophys 1–22, 2019) to provide the ground motion characterization logic tree for the vertical ground motion component in Turkey. Four global vertical GMMs proposed by Bozorgnia and Campbell in Earthq Spectra 32(2):979–1004, 2016b; Stewart et al. in Earthq Spectra 32(2):1005–1031, 2016; Gülerce et al. in Earthq Spectra 33(2):499–528, 2017 using the NGA-West 2 database; and Çagnan et al. in Bull Earthq Eng 15(7):2617–2643, 2017 model based on the RESORCE database are selected, and the model predictions are compared with the actual data in the updated Turkish ground motion dataset using the analysis of the residuals. Analysis results showed that the magnitude scaling of Çagnan et al. (2017) model and the depth scaling of the Bozorgnia and Campbell (2016b) model are inconsistent with the Turkish strong motion database. Additionally, small-magnitude (SM) scaling of Stewart et al. (2016) and Gülerce et al. (2017) GMMs should be modified for a better fit with the Turkish dataset. Trellis plots of SM-modified Stewart et al. (2016) and SM-modified Gülerce et al. (2017) vertical GMMs and selected
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/
H
ratio models multiplied with NGA-West 2 and Turkey (TR)-adjusted horizontal NGA-West 1 models Gülerce et al. in Earthq Spectra 32(1):75–100, 2016 are used to determine the logic tree weights for the proposed vertical ground motion characterization logic tree for Turkey.
This paper contains ground-motion prediction equations (GMPEs) for the vertical-to-horizontal spectral acceleration (V/H) ratio, and the methods for constructing vertical design spectra that are ...consistent with the probabilistic seismic hazard assessment results for the horizontal ground motion component. The GMPEs for V/H ratio consistent with the horizontal GMPE of Abrahamson and Silva (2008) are derived using the Pacific Earthquake Engineering Research Center's Next Generation of Ground-Motion Attenuation Models (PEER-NGA) database (Chiou et. al. 2008). The proposed V/H ratio GMPE is dependent on the earthquake magnitude and distance, consistent with previous models, but it differs from previous studies in that it accounts for the differences in the nonlinear site-response effects on the horizontal and vertical components. This difference in nonlinear effects results in large V/H ratios at short spectral periods for soil sites located close to large earthquakes. A method to develop vertical design spectra dependent on the horizontal component uniform hazard spectrum that accounts for the correlation between the variability of the horizontal ground-motion model and the variability of the V/H ratio ground-motion model is proposed.
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•Horsetail splays link the Chaman transform fault to accretionary prism of the Makran subduction.•In the gently dipping Makran subduction, megathrust interface geometry varies PGA by ...up to 0.3 g.•Gentler and deeper extending subduction interface maximizes rupture width and PGA towards inland.•Alternative recurrence models for megathrust interface resulted in up to 10% change in PGA.•475 yrs PGA is between 0.5 and 0.7 g at accretionary prism down to trench and along transform in the south.
Seismic source characterization (SSC) for probabilistic seismic hazard assessment (PSHA) in regions characterized by subduction megathrust involves a considerable ambiguity. Lack of detailed geologic, seismic, and geodetic data increases the uncertainties. The enigma is enhanced in regions where thin-skinned accretionary prism faults are part of active deformation. In this study, a planar SSC model for seismically active eastern Makran subduction zone, its associated accretionary prism faults and Chaman transform fault zone is proposed based on a kinematic block model accounting strain partitioning. Sensitivity tests for various parameters of the SSC model are performed by computing peak ground acceleration (PGA) maps for 475-year return period. Among alternative magnitude distribution models, the truncated exponential model gives ~10% higher PGA values than the composite recurrence model, which is favored by the observed subduction seismicity. Especially in gently dipping subduction zones such as Makran, estimated PGA values and their spatial distribution are highly sensitive (changing up to 0.3 g) to the megathrust interface geometry near the surface, dip amount, and defined depth limits. Gentler and deeper extending subduction interface maximizes the rupture width and results in higher PGA values towards inland, while the inclusion of shallow aseismic portion produces larger PGA values near the trench. Through eastward transition from subduction to transform motion, thrust faults within the Makran accretionary prism bend northward, forming oblique fault systems with higher slip rates and accommodate part of the compression in accordance with the lateral slip rate variations identified on the Chaman transform fault zone. Using the selected SSC model, the PGA values for short return period (475-year) are estimated to be between 0.5 g and 0.7 g within the accretionary prism down to the trench across the Makran subduction and along southern section of Chaman transform fault zone where slip rates are higher relative to the north.
Earthquake-induced slope instability is one of the major sources of earthquake hazards in near fault regions. Simplified tools such as Newmark’s sliding block (NSB) analysis are widely used to ...estimate the sliding displacement of slopes during earthquake shaking. Additionally, empirical models for predicting NSB displacement using single or multiple ground motion intensity measures based on global (e.g. NGA-W1 database, Chiou et al.
2008
) or regional datasets are available. The objective of this study is to evaluate the compatibility of candidate NSB displacement prediction models for the probabilistic seismic hazard assessment (PSHA) applications in Turkey using a comprehensive dataset of ground motions recorded during the earthquakes occurred in Turkey. Then, application of the most suitable NSB displacement prediction model in the vector-valued PSHA framework is demonstrated using the seismic source characterization models developed for Bolu-Gerede Region (in northwest Turkey). The results are presented in terms of the NSB displacement hazard curves and the hazard curves are evaluated for the influence of parameter selection (site conditions, yield acceleration, distance to the fault plane, and other seismic source model parameters) on the final hazard output.
The objective of this study is to estimate and compare the site amplification factors (AFs) using two different one dimensional (1-D) equivalent-linear (EQL) site response analysis approaches: the ...time series (TS) approach and the random vibration theory (RVT) based method. For this purpose, random soil profiles combined with different soil types, EQL soil properties, and unit weights are tested at several input ground motion levels. Analysis results showed that the AFs estimated by the TS-approach are systematically higher than the AFs estimated by the RVT-based method in the short period range (T < 0.5 s), especially when the bedrock peak ground acceleration is higher than 0.2 g. The relative difference between the AFs estimated in both methods is most prominent in granular soils: differences reach up to 35–40% compared to 10–15% for clays. On the other hand, the AFs calculated in this study are in good agreement with the empirical AF models utilized in recent ground motion models, indicating that the RVT-based AF models may be preferred in the future to cover a larger range of scenarios than the empirical datasets.
•Evaluation of site amplification factors by equivalent-linear site response analysis.•Differences between amplification factors from TS and RVT approaches are evaluated.•Earthquake ground motion scenarios varies from very weak (0.02 g) to very strong (0.6 g).•Difference between the site AFs in both methods is most prominent in granular soils.•RVT-based AFs calculated are in good agreement with the empirical AF models.
The objective of this paper is to evaluate the differences between the Next Generation Attenuation: West-1 (NGA-W1) ground motion prediction models (GMPEs) and the Turkish strong ground motion data ...set and to modify the required pieces of the NGA-W1 models for applicability in Turkey. A comparison data set is compiled by including strong motions from earthquakes that occurred in Turkey and earthquake metadata of ground motions consistent with the NGA-W1 database. Random-effects regression is employed and plots of the residuals are used to evaluate the differences in magnitude, distance, and site amplification scaling. Incompatibilities between the NGA-W1 GMPEs and Turkish data set in small-to-moderate magnitude, large distance, and site effects scaling are encountered. The NGA-W1 GMPEs are modified for the misfit between the actual ground motions and the model predictions using adjustments functions. Turkey-adjusted NGA-W1 models are compatible with the regional strong ground motion characteristics and preserve the well-constrained features of the global models.
Due to the unique soil and morphological conditions prevailing in Izmir Bay basin, structural damage has been governed by site effects. Consistently, during October 30, 2020 M7.0 Samos Earthquake, ...which took place offshore of Samos Island, structural damage and life losses were observed to be concentrated in Bayrakli region of Izmir Bay, despite the fact that the fault rupture was at a distance of 65–75 km from the city of Izmir. Additionally, strong ground motions recorded in Izmir Bay showed unique site amplifications that were observed surprisingly at both rock and soil sites. Soil amplifications and duration elongations were mostly due to site effects governed by the response of very deep alluvial deposits of low plasticity. Similarly, due to very extensive faulting-induced fracturing and unusually stratified nature of rock sub-layers, unexpected long period amplifications were also observed at rock sites. These earthquake and site resonance effects were more pronounced in the period range of 0.5–1.5 s. When they were superposed with relatively coinciding natural period of 7–9 story residential buildings of Izmir City, it was concluded that the triple resonance effects among incoming rock ground motions, soil deposits, and the damaged buildings, amplified and prolonged the overall system response. Within the confines of this manuscript, the governing role of site effects leading to increased seismic demand was assessed, through a series of 1D equivalent linear, total stress-based site response assessments, the results of which clearly highlighted the variation of seismic demand in Izmir Bay.
•Samos Island earthquake produced rich long period rock spectral accelerations.•Deep soil sites in Izmir Bay, amplified these long period rich rock motions.•Due to resonance effects, 7-9 story buildings were subjected to larger shakings.•Site effects increased seismic demand and prolonged shaking duration.•These, along with poor design-construction practices caused structural damage.
We present a dataset of 77 strong ground motion records within 200 km epicentral distance from the 30 October 2020, M7.0 Samos Island (Aegean Sea) earthquake, which affected Greece and Turkey. ...Accelerograms from National Networks of both countries have been merged into a single dataset, including metadata that have been uniformly derived using a common preliminary source model. Initial findings from the analysis and comparative examination of acceleration time histories, Fourier amplitude spectra and 5%-damped response spectra are discussed along with significant source, propagation path and site effects. The long-period amplifications observed in most records in Izmir bay triggered failures and severe damages in weak structures. Yet, the spectral accelerations are observed to lie below the current and previous design spectra corresponding to the damaged regions. Peak ground motions are used to construct a purely instrumental-based macroseismic intensity map, which is capable of reflecting the actual earthquake damage caused by this considerably large event. Finally, peak ground motions are compared to various ground motion models (GMMs) and deviations are highlighted. Our overall preliminary analysis reveals a strong energy signature of the Samos earthquake in the period range 0.5–1.5 s at many sites, both on rock and soil, whereas records in the heavily hit Izmir city, at an epicentral distance circa 70 km, provide strong indication for additional amplification due to basin effects. At relatively large distance from the earthquake source (> 120 km), several recorded amplitudes are significantly lower than those predicted by many GMMs, implying that further studies are necessary toward the improvement of regional attenuation models.
