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INSTRUCTORS:
Rashid Shams
Fransisco Javier Ornelas
Chenying Liu, Ph.D
Tristan E. Buckreis
Purpose and Background
These presentations were recorded at the Geo-Extreme 2025 conference.
Spatial Variability of Ground Motions Using Sub-Basins in Los Angeles Basin (14 minutes)
This presentation examines how spatial variability in ground motions is influenced by sub-basin structures within the Los Angeles Basin. Rather than treating the basin as a single uniform entity, the study subdivides it into geologically meaningful regions to better capture localized amplification effects. Ground motion residuals are analyzed to identify systematic trends associated with basin geometry and sediment thickness. Results demonstrate that sub-basin-specific behavior contributes significantly to observed variability in recorded motions. The findings highlight limitations of ergodic assumptions when applied to complex sedimentary basins. Implications for seismic hazard analysis and performance-based design in urban basins are discussed.
Improving Iso-Surface Depth (Z1.0) Estimates for California Sites Using Measured Profiles and Geologic Information (17 minutes)
This presentation focuses on improving estimates of Z1.0, the depth to shear-wave velocity of 1.0 km/s, which is a key parameter in ground motion models. Traditional empirical correlations often produce large uncertainties, particularly in geologically complex regions. By integrating measured velocity profiles with detailed geologic and geomorphic information, the study develops refined regional Z1.0 estimation approaches for California. Comparisons with existing models demonstrate improved consistency and reduced bias. The results enhance the reliability of basin and site amplification predictions. Applications to seismic hazard and building code development are also discussed.
Identification of Site Response Features Using Microtremor HVSR (9 minutes)
This presentation explores the use of microtremor horizontal-to-vertical spectral ratio (HVSR) techniques to identify site response characteristics. HVSR analysis provides a cost-effective and non-invasive method for estimating fundamental site frequencies. The study demonstrates how spectral peaks relate to subsurface impedance contrasts and sediment thickness. Case examples illustrate both the strengths and limitations of HVSR in complex geological settings. Comparisons with borehole and geophysical data are used to validate interpretations. The presentation emphasizes best practices for applying HVSR in engineering site investigations.
Estimating Systematic Source, Site, and Path Effects in Non-Ergodic Ground Motion Models: Insights from the Turkish Ground Motion Database (12 minutes)
This presentation presents a non-ergodic ground motion modeling framework using data from the Turkish Ground Motion Database. The study separates systematic source, site, and path effects to capture repeatable regional behaviors that are obscured in ergodic models. Advanced statistical techniques are applied to quantify spatial correlations and reduce aleatory variability. Results show substantial reductions in model uncertainty when non-ergodic terms are included. The findings underscore the importance of regional datasets for next-generation seismic hazard assessments. Implications for site-specific hazard analysis and risk-informed design are discussed.
Regional Datasets Included in the NGA-West3 Ground Motion Database (12 minutes)
This presentation provides an overview of the regional datasets incorporated into the NGA-West3 Ground Motion Database. It highlights new data contributions from diverse tectonic environments and their importance for improving ground motion models. The presentation discusses criteria for data selection, metadata quality, and site characterization consistency. Special attention is given to how regional datasets support non-ergodic modeling and basin-specific analyses. Examples illustrate how NGA-West3 data enhance model robustness across magnitude and distance ranges. The presentation concludes with guidance on applying the database in research and engineering practice.
Benefits and Learning Outcomes
Upon completion of these sessions, you will be able to:
- Explain how sub-basin structures contribute to spatial variability in ground motions within the Los Angeles Basin.
- Describe how geologic information and measured velocity profiles can improve Z1.0 estimates for seismic site characterization.
- Identify key site response features that can be inferred from microtremor HVSR measurements.
- Discuss how non-ergodic modeling improves the representation of source, site, and path effects in ground motion prediction.
- List key characteristics and engineering benefits of the regional datasets included in the NGA-West3 Ground Motion Database.
Assessment of Learning Outcomes
Students' achievement of the learning outcomes will be assessed via a short post-test assessment (true-false, multiple choice, and/or fill in the blank questions).
Who Should Attend?
- Geotechnical Engineers
- Structural Engineers
- Civil Infrastructure Designers
- Researchers and Academics
- Risk and Resilience Analysts
- Construction and Project Managers
How to Earn your CEUs/PDHs and Receive Your Certificate of Completion
To receive your certificate of completion, you will need to complete a short post-test online and receive a passing score of 70% or higher within 1 year of purchasing the course.
How do I convert CEUs to PDHs?
1.0 CEU = 10 PDHs [Example: 0.1 CEU = 1 PDH]