scholarly journals Site-specific seismic-hazard maps and deaggregation in the western United States using the NGA models for ground-motion prediction

2011 ◽  
Author(s):  
Stephen Harmsen
Keyword(s):  
United States ◽  
Seismic Hazard ◽  
Ground Motion ◽  
Western United States ◽  
Motion Prediction ◽  
Hazard Maps ◽  
Ground Motion Prediction ◽  
Site Specific ◽  
Seismic Hazard Maps

Probabilistic seismic hazard maps for California do not perform better relative to historical shaking data when site-specific VS30 is considered

2021 ◽  
Author(s):  
Molly Gallahue ◽  
Leah Salditch ◽  
Madeleine Lucas ◽  
James Neely ◽  
Susan Hough ◽  
...  
Keyword(s):  
Seismic Hazard ◽  
Ground Motion ◽  
Tall Buildings ◽  
Historical Period ◽  
Probabilistic Seismic Hazard ◽  
Hazard Maps ◽  
Site Specific ◽  
Seismic Hazard Maps ◽  
Intensity Mapping ◽  
Aleatory Variability

<div> <p>Probabilistic seismic hazard assessments forecast levels of earthquake shaking that should be exceeded with only a certain probability over a given period of time are important for earthquake hazard mitigation. These rely on assumptions about when and where earthquakes will occur, their size, and the resulting shaking as a function of distance as described by ground-motion models (GMMs) that cover broad geologic regions. Seismic hazard maps are used to develop building codes.</p> </div><div> <p>To explore the robustness of maps’ shaking forecasts, we consider how maps hindcast past shaking. We have compiled the California Historical Intensity Mapping Project (CHIMP) dataset of the maximum observed seismic intensity of shaking from the largest Californian earthquakes over the past 162 years. Previous comparisons between the maps for a constant V<sub>S30</sub> (shear-wave velcoity in the top 30 m of soil) of 760 m/s and CHIMP based on several metrics suggested that current maps overpredict shaking.</p> <p>The differences between the V<sub>S30</sub> at the CHIMP sites and the reference value of 760 m/s could amplify or deamplify the ground motions relative to the mapped values. We evaluate whether the V<sub>S30 </sub>at the CHIMP sites could cause a possible bias in the models. By comparison with the intensity data in CHIMP, we find that using site-specific V<sub>S30</sub> does not improve map performance, because the site corrections cause only minor differences from the original 2018 USGS hazard maps at the short periods (high frequencies) relevant to peak ground acceleration and hence MMI. The minimal differences reflect the fact that the nonlinear deamplification due to increased soil damping largely offsets the linear amplification due to low V<sub>S30</sub>. The net effects will be larger for longer periods relevant to tall buildings, where net amplification occurs. </p> <div> <p>Possible reasons for this discrepancy include limitations of the dataset, a bias in the hazard models, an over-estimation of the aleatory variability of the ground motion or that seismicity throughout the historical period has been lower than the long-term average, perhaps by chance due to the variability of earthquake recurrence. Resolving this discrepancy, which is also observed in Italy and Japan, could improve the performance of seismic hazard maps and thus earthquake safety for California and, by extension, worldwide. We also explore whether new nonergodic GMMs, with reduced aleatory variability, perform better than presently used ergodic GMMs compared to historical data.</p> </div> </div>

scholarly journals Site-specific seismic hazard levels at the economic zone of Duqm, Oman

2021 ◽  
Vol 18 (5) ◽  
pp. 740-760
Author(s):  
Ahmed Deif ◽  
Adel M E Mohamed ◽  
Issa El-Hussain ◽  
Yousuf Al-Shijbi ◽  
Sherif El-Hady ◽  
...  
Keyword(s):  
Seismic Hazard ◽  
Ground Motion ◽  
Return Period ◽  
Hazard Evaluation ◽  
Motion Prediction ◽  
Soil Parameters ◽  
Maximum Magnitude ◽  
Ground Motion Prediction ◽  
Site Specific ◽  
Economic Zone

Abstract A site-specific probabilistic seismic hazard assessment (PSHA) was achieved in the area of special economic zone authority of Duqm, involving hazard evaluation at the bedrock conditions and assurance of potential site influence on seismic ground motion at the bedrock. Appropriate source and ground-motion prediction models were selected and seismic hazards were identified by means of 5% damped Uniform Hazard Spectra (UHS) for three return periods of 475, 975, and 2475 years. A logic-tree algorithm was used to study the influence of the epistemic uncertainties on the source models, earthquake recurrency and maximum magnitude, along with ground-motion prediction equations (GMPEs). The local geology effects were characterized by fundamental resonance frequency (Fo) using the horizontal-to-vertical spectral ratio technique and the soil amplification factors. The effects of soil were assessed using SHAKE91 for soil parameters defined by 55 geotechnical boreholes in conjunction with surveys of 2D multichannel analysis of surface waves (MASW) at 90 sites. Scaling was performed for selected strong-motion applying spectral matching technique to be used at the soil column bottom. Selection of such records is based on scenarios characterized by deaggregation of the PSHA results on the bedrock tops. The Duqm area mostly features low amplifications, below 1.3 for the considered spectrum. Surface ground-motion maps show low hazard values with Peak Ground Accelerations (PGA) vary between about 2 and 5% g for a 475-year return period. Although several sites are assessed to be susceptible to liquefy, liquefaction analyses indicate that surface ground motions for a 475-year return period are insufficient to produce liquefaction.

scholarly journals Geodesy- and geology-based slip-rate models for the Western United States (excluding California) national seismic hazard maps

2014 ◽  
Author(s):  
Mark D. Petersen ◽  
Yuehua Zeng ◽  
Kathleen M. Haller ◽  
Robert McCaffrey ◽  
William C. Hammond ◽  
...  
Keyword(s):  
United States ◽  
Seismic Hazard ◽  
Slip Rate ◽  
Western United States ◽  
Hazard Maps ◽  
Seismic Hazard Maps

Ground Motion Models Used in the 2014 U.S. National Seismic Hazard Maps

2015 ◽  
Vol 31 (1_suppl) ◽  
pp. S59-S84 ◽  
Author(s):  
Sanaz Rezaeian ◽  
Mark D. Petersen ◽  
Morgan P. Moschetti
Keyword(s):  
United States ◽  
Seismic Hazard ◽  
Ground Motion ◽  
The United States ◽  
Hazard Maps ◽  
Source Characterization ◽  
Ground Acceleration ◽  
Seismic Hazard Maps ◽  
Motion Models ◽  
Ground Motion Models

The National Seismic Hazard Maps (NSHMs) are an important component of seismic design regulations in the United States. This paper compares hazard using the new suite of ground motion models (GMMs) relative to hazard using the suite of GMMs applied in the previous version of the maps. The new source characterization models are used for both cases. A previous paper ( Rezaeian et al. 2014 ) discussed the five NGA-West2 GMMs used for shallow crustal earthquakes in the Western United States (WUS), which are also summarized here. Our focus in this paper is on GMMs for earthquakes in stable continental regions in the Central and Eastern United States (CEUS), as well as subduction interface and deep intraslab earthquakes. We consider building code hazard levels for peak ground acceleration (PGA), 0.2-s, and 1.0-s spectral accelerations (SAs) on uniform firm-rock site conditions. The GMM modifications in the updated version of the maps created changes in hazard within 5% to 20% in WUS; decreases within 5% to 20% in CEUS; changes within 5% to 15% for subduction interface earthquakes; and changes involving decreases of up to 50% and increases of up to 30% for deep intraslab earthquakes for most U.S. sites. These modifications were combined with changes resulting from modifications in the source characterization models to obtain the new hazard maps.

Implementation of NGA-West2 Ground Motion Models in the 2014 U.S. National Seismic Hazard Maps

2014 ◽  
Vol 30 (3) ◽  
pp. 1319-1333 ◽  
Author(s):  
Sanaz Rezaeian ◽  
Mark D. Petersen ◽  
Morgan P. Moschetti ◽  
Peter Powers ◽  
Stephen C. Harmsen ◽  
...  
Keyword(s):  
United States ◽  
Seismic Hazard ◽  
Ground Motion ◽  
The United States ◽  
Hazard Maps ◽  
Seismic Hazard Maps ◽  
Motion Models ◽  
Seismic Source Models ◽  
Ground Motion Models ◽  
The U.S

The U.S. National Seismic Hazard Maps (NSHMs) have been an important component of seismic design regulations in the United States for the past several decades. These maps present earthquake ground shaking intensities at specified probabilities of being exceeded over a 50-year time period. The previous version of the NSHMs was developed in 2008; during 2012 and 2013, scientists at the U.S. Geological Survey have been updating the maps based on their assessment of the “best available science,” resulting in the 2014 NSHMs. The update includes modifications to the seismic source models and the ground motion models (GMMs) for sites across the conterminous United States. This paper focuses on updates in the Western United States (WUS) due to the use of new GMMs for shallow crustal earthquakes in active tectonic regions developed by the Next Generation Attenuation (NGA-West2) project. Individual GMMs, their weighted combination, and their impact on the hazard maps relative to 2008 are discussed. In general, the combined effects of lower medians and increased standard deviations in the new GMMs have caused only small changes, within 5–20%, in the probabilistic ground motions for most sites across the WUS compared to the 2008 NSHMs.

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