Sean K. Ahdi, Ph.D.
Associate
Civil Engineering
Los Angeles

Dr. Ahdi’s interdisciplinary expertise lies at the intersection of geotechnical and earthquake engineering with principles of geology, tectonics, seismology, and geophysics. Dr. Ahdi uses seismic and geological site characterization data to understand the behavior of earth materials during earthquake shaking. He has experience in collecting near-surface seismic geophysical data as well as leading an effort to assemble and manipulate these data into large national and international databases. He has overseen the development of a large public database of seismic and geotechnical site characterization data across the United States that is used in applications spanning international research studies on seismic site response to local engineering design practice. Dr. Ahdi has developed empirical models for predicting site conditions in the absence of in situ measurements from readily available geospatial information such as surficial and bedrock geology and geomorphic and topographic data, emphasizing the quantification of uncertainty in statistical modeling procedures.

Prior to joining Exponent, Dr. Ahdi was a doctoral researcher in Civil Engineering at UCLA, focusing on the development of new frameworks for the analysis and dissemination of seismic site characterization data used for studies developing earthquake ground motion models at subduction zones around the world. He works closely with leading experts in academia, industry, state and federal governments, and a variety of sponsoring agencies to link interrelated skills and vet data sets with variability in geospatial resolution. Dr. Ahdi currently serves as a Lecturer at UCLA for Engineering and Environmental Geology and has served as a teaching assistant in the past for courses soil mechanics principles and laboratory testing, and engineering ethics and technical writing. He is the Secretary of the Joint International Strong Motion Committee between the International Association of Earthquake Engineering (IAEE) and Consortium of Strong Motion Observation Stations (COSMOS) and has served as the Chair of the Student Leadership Council of the Geo-Institute of ASCE at the national level. Dr. Ahdi has presented the results of his research work at over 20 national and international conferences, technical workshops, and universities.

CREDENTIALS & PROFESSIONAL HONORS

  • Ph.D., Civil Engineering, University of California, Los Angeles (UCLA), 2018
  • M.S., Civil Engineering, University of California, Los Angeles (UCLA), 2014
  • B.S., Civil Engineering, University of California, Los Angeles (UCLA), 2013
  • B.S., Geology / Engineering Geology, University of California, Los Angeles (UCLA), 2013
  • United States Embassy in Malta: Sponsorship of Registration Grant, 36th General Assembly of the European Seismological Commission, 2018

    UCLA Henry Samueli School of Engineering and Applied Science Award for Student Welfare, 2013 & 2017

    Teaching Assistant of the Year, American Society of Civil Engineers (ASCE), UCLA Chapter, 2016

    Los Angeles Geo-Institute Chapter of ASCE, Outstanding Student Scholarship, 2015

    UCLA Outstanding Geotechnical Graduate Student of the Year, 2014

    National Science Foundation Research Experience for Undergraduates Award, 2012

LANGUAGES

  • Persian
  • Spanish

Publications

Ahdi SK. An Improved Framework for the Analysis and Dissemination of Seismic Site Characterization Data at Varying Resolutions. Ph.D. Dissertation, University of California, Los Angeles, 2018.

Bozorgnia Y, Kishida T, Abrahamson NA, Ahdi SK, Ancheta TD, Archuleta RJ, Atkinson GM, Boore DM, Campbell KW, Chiou B, Contreras V, Darragh RB, Gregor N, Idriss IM, Ji C, Kamai R, Kuehn N, Kwak DY, Kwok AO, Lin P-S, Magistrale H, Mazzoni S, Muin S, Midorikawa S, Si H, Silva WJ, Stewart JP, Wooddell KE, Youngs RR. NGA-Subduction Research Program. Eleventh U.S. National Conference on Earthquake Engineering (11NCEE), Los Angeles, California, Paper No. 1705, June 25–29, 2018.

Contreras V, Ruz F, Ahdi SK, Stewart JP. VS Profile Database and Proxy-Based Models for VS30 Prediction in Chile for NGA-Subduction. Eleventh U.S. National Conference on Earthquake Engineering (11NCEE), Los Angeles, California, Paper No. 1473, June 25–29, 2018.

Kishida, T, Bozorgnia Y, Abrahamson NA, Ahdi SK, Ancheta TD, Archuleta RJ, Boore DM, Campbell KW, Chiou B, Contreras V, Darragh RB, Gregor N, Ji C, Kamai R, Kuehn N, Kwak DY, Kwok AO, Lin P-S, Magistrale H, Mazzoni S, Muin S, Midorikawa S, Si H, Silva WJ, Stewart JP, Wooddell KE, Youngs RR. NGA-Sub Ground Motion Database. Eleventh U.S. National Conference on Earthquake Engineering (11NCEE), Los Angeles, California, Paper No. 1402, June 25–29, 2018.

Sadiq S, Ilhan O, Ahdi SK, Bozorgnia Y, Hashash YMA, Park D, Yong A, Stewart JP. A Proposed Seismic Velocity Profile Database Model. Eleventh U.S. National Conference on Earthquake Engineering (11NCEE), Los Angeles, California, Paper No. 1342, June 25–29, 2018.

Ahdi SK, Sadiq S, Ilhan O, Bozorgnia Y, Hashash YMA, Park D, Yong A, Stewart JP. Development of a United States Community Shear Wave Velocity Profile Database, 5th Conference on Geotechnical Earthquake Engineering and Soil Dynamics (GEESD-V), Austin, Texas, June 10–13, 2018.

Ahdi SK, Stewart JP, Ancheta TD, Kwak DY, Mitra D. Development of VS profile database and proxy-based models for VS30 prediction in the Pacific Northwest Region of North America. Bulletin of the Seismological Society of America 2017, 107:1781–1801.

Ahdi SK, Stewart JP, Ancheta TD, Kwak DY, Mitra D. Proxy-based VS30 prediction in Alaska accounting for limited regional data, Proc. 3rd International Conference on Performance-Based Design in Earthquake Geotechnical Engineering (PBD-III), Paper No. 482, Vancouver, Canada, July 16–19, 2017.

Kwak DY, Ancheta TD, Mitra D, Ahdi SK, Zimmaro P, Parker GA, Brandenberg SJ, Stewart JP. Performance evaluation of VSZ-to-VS30 correlation methods using global VS profile database, Proc. 3rd International Conference on Performance-Based Design in Earthquake Geotechnical Engineering (PBD-III), Vancouver, Canada, Paper No. 399, July 16–19, 2017.

Ahdi SK, Ancheta TD, Contreras V, Kishida T, Kwak DY, Kwok AO, Parker GA, Bozorgnia Y, Stewart JP. NGA-Subduction Site Database. Proc. 16th World Conference on Earthquake Engineering (16WCEE), Santiago, Chile, Paper No. 4926, January 9–12, 2017.

Kishida T, Bozorgnia Y, Abrahamson NA, Ahdi SK, Ancheta TD, Boore DM, Campbell KW, Chiou B, Darragh RB, Gregor N, Kamai R, Kwak DY, Kwok AO, Lin P-S, Magistrale H, Midorikawa S, Parker GA, Si H, Silva WJ, Stewart JP, Tsai C, Wooddell KE, Youngs RR (2017). Development of the NGA-Subduction Database. Proc. 16th World Conference on Earthquake Engineering (16WCEE), Santiago, Chile, Paper No. 3452, January 9–12, 2017.

Coe JT, Brandenberg SJ, Ahdi SK, Kordjazi A (2017). Geophysical Methods for Determining the Geotechnical Engineering Properties of Earth Materials. Report prepared for California Department of Transportation, Contract No. 65A0482, 304 p.

Presentations

Ahdi SK, Sadiq S, Ilhan O, Bozorgnia Y, Hashash YMA, Park D, Yong A, Stewart JP. Development of a United States Community Shear Wave Velocity Profile Database. Presentation, 2018 Le Val Lund Lifeline Infrastructure and Community Resilience Symposium, University of Southern California, Los Angeles, California, November 2, 2018.

Sadiq S, Ilhan O, Ahdi SK, Bozorgnia Y, Hashash YMA, Park D, Yong A, Stewart JP. A Proposed Seismic Velocity Profile Database Model. Poster, Annual Meeting of the Southern California Earthquake Center (SCEC), Palm Springs, California, September 9-12, 2018.

Ahdi SK, Sadiq S, Ilhan O, Bozorgnia Y, Hashash YMA, Park D, Yong A, Stewart JP. Development of a United States Community Shear Wave Velocity Profile Database. Presentation (invited), 36th General Assembly of the European Seismological Commission (ESC-GA) and COSMOS Workshop on Guidelines for Applying Noninvasive Geophysical Methods When Characterizing Seismic Site Conditions, Valletta, Malta, September 6 & 7, 2018.

Sadiq S, Ilhan O, Ahdi SK, Bozorgnia Y, Hashash YMA, Park D, Yong A, Stewart JP. A Proposed Seismic Velocity Profile Database Model. Oral and poster presentation, 11th National Conference on Earthquake Engineering (11NCEE), Los Angeles, California, June 25-29, 2018.

Ahdi SK, Sadiq S, Ilhan O, Bozorgnia Y, Hashash YMA, Park D, Yong A, Stewart JP. Development of a United States Community Shear Wave Velocity Profile Database. Presentation, 5th Geotechnical Earthquake Engineering and Soil Dynamics Conference (GEESD-V), Austin, Texas, June 12, 2018.

Ahdi SK, Sadiq S, Ilhan O, Bozorgnia Y, Hashash YMA, Park D, Yong A, Stewart JP. Development of a United States Community Shear Wave Velocity Profile Database. Presentation, Seismology of the Americas – Seismological Society of America Annual Meeting, Miami, Florida, May 15, 2018.

Ahdi SK. Seismic Site Characterization and Its Implementation in Ground Motion Modeling, Departmental Seminar (invited), Department of Mining and Geological Engineering, University of Alaska Fairbanks, April 27, 2018.

Ahdi SK, Sadiq S, Ilhan O, Bozorgnia Y, Hashash YMA, Park D, Yong A, Stewart JP. Development of a Community Shear-Wave Velocity Database in the United States: Focus on Nevada and the Intermountain West. Presentation, 2018 Working Group on Nevada Seismic Hazards Workshop, Reno, Nevada, February 6, 2018.

Ahdi SK, Sadiq S, Ilhan O, Bozorgnia Y, Hashash YMA, Park D, Yong A, Stewart JP. Development of a Community Shear-Wave Velocity Database in California: Focus on Northern California. Presentation (invited), Workshop on Northern California Site Response Efforts Since 2014 South Napa Earthquake, U.S. Geological Survey, Menlo Park, California, November 15, 2017.

Ahdi SK. Seismic Site Characterization and its Implementation in Ground Motion Modeling. Departmental Seminar (invited), Department of Civil and Environmental Engineering, University of California, Irvine, November 2, 2017 (invited).

Ahdi SK, Sadiq S, Ilhan O, Bozorgnia Y, Hashash YMA, Park D, Yong A, Stewart JP. Development of a Community Shear-Wave Velocity Database in California. Presentation (invited), Workshop on Nonlinear Shallow Crust Effects, Annual Meeting of the Southern California Earthquake Center (SCEC), Palm Springs, California, July 6, 2017.

Ahdi SK, Stewart JP, Ancheta TD, Kwak DY, Mitra D. VS30 Estimation in the Pacific Northwest and Alaska for the NGA-Subduction Project. Presentation, 3rd International Conference on Performance-Based Design in Earthquake Geotechnical Engineering (PBD-III), Vancouver, Canada, July 17, 2017.

Ahdi SK. The NGA-Subduction Project. Presentation, 9th Annual UCLA Geo-Expo, Los Angeles, California, May 18, 2017.

Ahdi SK, Ancheta TD, Contreras V, Kishida T, Kwak DY, Kwok AO, Parker GA, Bozorgnia Y, Stewart JP. NGA-Subduction Site Database, Presentation, 16th World Conference on Earthquake Engineering (16WCEE), Santiago, Chile, January 7, 2017.

Ahdi SK, Kishida T, Bozorgnia Y, Stewart JP, Farzanegan E. Site Characterization of Strong Motion Instrument Sites in Iran. Online Presentation (invited), Workshop at the Building Housing Research Council of Ministry of Road & Urban Development of Iran, Tehran, Iran, December 21, 2016.

Ahdi SK, Sadiq S, Ilhan O, Bozorgnia Y, Hashash YMA, Park D, Yong A, Stewart JP. Development of a Community VS Profile Database. Presentation (invited), COSMOS Workshop on Guidelines for Applying Noninvasive Geophysical Methods When Characterizing Seismic Site Conditions. Seismological Society of America (SSA) Annual Meeting, Reno, Nevada, April 23, 2016.

Ahdi SK, Stewart JP, Ancheta TD, Kwak DY, Mitra D. Estimation of VS30 from Geology-Based Proxy Developed for the Pacific Northwest. Poster, Seismological Society of America (SSA) Annual Meeting, Reno, Nevada, April 20-22, 2016.

Ahdi SK, Brandenberg SJ, Turner BJ. Constraining Rayleigh-Wave Dispersion Curve Inversion with Penetration Resistance Measurements. Presentation, Symposium on the Application of Geophysics to Engineering and Environmental Problems (SAGEEP), Denver, Colorado, March 23, 2016.

Ahdi SK, Brandenberg SJ, Turner BJ. Constraining Rayleigh-Wave Dispersion Curve Inversion with Penetration Resistance Measurements. Presentation, ASCE Geo-Structures Conference, Phoenix, Arizona, February 15, 2016.

Ahdi SK, Brandenberg SJ, Reinert ET. Comparison of Surface Wave Dispersion Curves Derived from Two Methods for a Very Soft Site. Poster, 2013 ASCE Geo-Congress, San Diego, California, March 4, 2013.

Prior Experience

UCLA Dept. of Civil & Environmental Engineering, Graduate Research Assistant, 2014-2018

GEOVision, Inc., Geophysical Intern, 2011

Pasco, Laret, Suiter, & Associates, Civil Engineering Intern, 2010

Academic Appointments

Lecturer, Department of Earth, Planetary, and Space Sciences, UCLA, 2019

Teaching Associate/Assistant, Henry Samueli School of Engineering & Applied Science, UCLA, 2014–2018

Professional Affiliations

Jan 2017 – present: Joint International Strong Motion Committee: International Association of Earthquake Engineering (IAEE) and Consortium of Strong Motion Observation Stations (COSMOS) (Secretary)

ASCE Geo-Institute (National) Student Leadership Council (Past Chair)

American Society of Civil Engineers (ASCE, Member since 2010)

Earthquake Engineering Research Institute (EERI, Member since 2014)

Engineering & Environmental Geophysics Society (EEGS, Member since 2015)

Seismological Society of America (SSA, Member since 2016)

Geotechnical Extreme Events Reconnaissance (GEER) Association (Member since 2017)

Project Experience

Led the development of the United States Community Shear-Wave Velocity Profile Database (VS PDB), including collecting data from research, government, and industry sources; integrating data into uniform formats; and leading data vetting process with expert opinion. Oversaw development of relational database management system and implementation on web-based interface. Organized two public workshops for community input into database development.

Developed and managed the site database for the NGA-Subduction ground motion modeling effort, including assigning site characteristics to earthquake recording stations at over 6000 locations in subduction zone regions around the world. Developed a new framework of methods for estimating site characteristics at locations which lack in situ measurements by relying on regional geophysical, geological, and geospatial data of variable quality and resolution.

Performed geophysical seismic field testing methods to characterize the shear-wave velocity structure at earthquake ground motion recording stations at over 60 sites throughout California as part of a U.S. Geological Survey (USGS)-funded project. Worked directly with USGS researchers to integrate data into VS PDB.

Participated in the development and writing of major guidelines documents, including guidelines outlining best practices for use of geophysical methods in geotechnical engineering projects for the California Department of Transportation, and describing the state-of-art and best practices for deploying non-invasive geophysical methods for seismic site characterization as part of a leading international research organization, COSMOS.

Additional Information

Peer Reviewer

Earthquake Spectra

Bulletin of the Seismological Society of America

Seismological Research Letters

Earth Sciences Research Journal

CREDENTIALS & PROFESSIONAL HONORS

  • Ph.D., Civil Engineering, University of California, Los Angeles (UCLA), 2018
  • M.S., Civil Engineering, University of California, Los Angeles (UCLA), 2014
  • B.S., Civil Engineering, University of California, Los Angeles (UCLA), 2013
  • B.S., Geology / Engineering Geology, University of California, Los Angeles (UCLA), 2013
  • United States Embassy in Malta: Sponsorship of Registration Grant, 36th General Assembly of the European Seismological Commission, 2018

    UCLA Henry Samueli School of Engineering and Applied Science Award for Student Welfare, 2013 & 2017

    Teaching Assistant of the Year, American Society of Civil Engineers (ASCE), UCLA Chapter, 2016

    Los Angeles Geo-Institute Chapter of ASCE, Outstanding Student Scholarship, 2015

    UCLA Outstanding Geotechnical Graduate Student of the Year, 2014

    National Science Foundation Research Experience for Undergraduates Award, 2012

LANGUAGES

  • Persian
  • Spanish