Sean Kamran Ahdi (Former Employee)
Science and Products
Data Release for the 2023 U.S. 50-State National Seismic Hazard Model - Overview
This data release contains data sets associated with the 2023 50-State National Seismic Hazard Model Update. The 2023 50-State National Seimsic Hazard Model (NSHM) Update includes an update to the NSHMs for the conterminous U.S (CONUS, last updated in 2018), Alaska (AK, last updated in 2007), and Hawaii (last updated in 2001). Data sets include inputs like seismicity catalogs used as...
Updated Compilation of VS30 Data for the United States
VS30, the time-averaged shear-wave velocity (VS) to a depth of 30 meters, is a key index adopted by the earthquake engineering community to account for seismic site conditions. VS30 is typically based on geophysical measurements of VS derived from invasive and noninvasive techniques at sites of interest. Owing to cost considerations, as well as logistical and environmental concerns, VS30...
Empirical ground-motion basin response in the California Great Valley, Reno, Nevada, and Portland, Oregon
We assess how well the Next-Generation Attenuation-West 2 (NGA-West2) ground-motion models (GMMs), which are used in the US Geological Survey’s (USGS) National Seismic Hazard Model (NSHM) for crustal faults in the western United States, predict the observed basin response in the Great Valley of California, the Reno basin in Nevada, and Portland and Tualatin basins in Oregon. These GMMs...
Authors
Sean Kamran Ahdi, Brad T. Aagaard, Morgan P. Moschetti, Grace Alexandra Parker, Oliver S. Boyd, William J. Stephenson
The influence of anthropogenic regulation and evaporite dissolution on earthquake-triggered ground failure
Remote sensing observations of Searles Lake following the 2019 moment magnitude 7.1 Ridgecrest, California, earthquake reveal an area where surface ejecta is arranged in a repeating hexagonal pattern that is collocated with a solution-mining operation. By analyzing geologic and geotechnical data, here we show that the hexagonal surface ejecta is likely not a result of liquefaction...
Authors
Paula Madeline Burgi, Eric M. Thompson, Kate E. Allstadt, Kyle Dennis Murray, Henry (Ben) Mason, Sean Kamran Ahdi, Devin Katzenstein
The 2023 US National Seismic Hazard Model: Ground-motion characterization for the conterminous United States
We update the ground-motion characterization for the 2023 National Seismic Hazard Model (NSHM) for the conterminous United States. The update includes the use of new ground-motion models (GMMs) in the Cascadia subduction zone; an adjustment to the central and eastern United States (CEUS) GMMs to reduce misfits with observed data; an updated boundary for the application of GMMs for...
Authors
Morgan P. Moschetti, Brad T. Aagaard, Sean Kamran Ahdi, Jason M. Altekruse, Oliver S. Boyd, Arthur Frankel, Julie Herrick, Mark D. Petersen, Peter M. Powers, Sanaz Rezaeian, Allison Shumway, James Andrew Smith, William J. Stephenson, Eric M. Thompson, Kyle Withers
Recent applications of the USGS National Crustal Model for Seismic Hazard Studies
The U.S. Geological Survey is developing the National Crustal Model (NCM) for seismic hazard studies to facilitate modeling site, path, and source components of seismic hazard across the conterminous United States. The NCM is composed of a 1km grid of geophysical profiles, extending from the Earth’s surface into the upper mantle. It is constructed from a threedimensional (3D) geologic...
Authors
Oliver S. Boyd, James Andrew Smith, Morgan P. Moschetti, Brad T. Aagaard, Robert Graves, Evan Tyler Hirakawa, Sean Kamran Ahdi
The 2023 US 50-State National Seismic Hazard Model: Overview and implications
The US National Seismic Hazard Model (NSHM) was updated in 2023 for all 50 states using new science on seismicity, fault ruptures, ground motions, and probabilistic techniques to produce a standard of practice for public policy and other engineering applications (defined for return periods greater than ∼475 or less than ∼10,000 years). Changes in 2023 time-independent seismic hazard...
Authors
Mark D. Petersen, Allison Shumway, Peter M. Powers, Ned Field, Morgan P. Moschetti, Kishor S. Jaiswal, Kevin R. Milner, Sanaz Rezaeian, Arthur Frankel, Andrea L. Llenos, Andrew J. Michael, Jason M. Altekruse, Sean Kamran Ahdi, Kyle Withers, Charles Mueller, Yuehua Zeng, Robert E. Chase, Leah M. Salditch, Nico Luco, Kenneth S. Rukstales, Julie Herrick, Demi Leafar Girot, Brad T. Aagaard, Adrian Bender, Michael L. Blanpied, Richard W. Briggs, Oliver S. Boyd, Brandon Clayton, Christopher DuRoss, Eileen L. Evans, Peter J. Haeussler, Alexandra Elise Hatem, Kirstie Lafon Haynie, Elizabeth H. Hearn, Kaj M. Johnson, Zachary Alan Kortum, N. Simon Kwong, Andrew James Makdisi, Henry (Ben) Mason, Daniel McNamara, Devin McPhillips, P. Okubo, Morgan T. Page, Frederick Pollitz, Justin Rubinstein, Bruce E. Shaw, Zheng-Kang Shen, Brian Shiro, James Andrew Smith, William J. Stephenson, Eric M. Thompson, Jessica Ann Thompson Jobe, Erin Wirth, Robert C. Witter
Sediment thickness map of United States Atlantic and Gulf Coastal Plain Strata, and their influence on earthquake ground motions
With the recent successful accounting of basin depth ground-motion adjustments in seismic hazard analyses for select areas of the western United States, we move toward implementing similar adjustments in the Atlantic and Gulf Coastal Plains by constructing a sediment thickness model and evaluating multiple relevant site amplification models for central and eastern United States seismic...
Authors
Oliver S. Boyd, David Churchwell, Morgan P. Moschetti, Eric M. Thompson, Martin C. Chapman, Okan Ilhan, Thomas L. Pratt, Sean Kamran Ahdi, Sanaz Rezaeian
COSMOS Ground-Motion Simulation Working Group workshops #1 and #2
These 2 workshops were held in response to interest generated from sessions on the use of simulated earthquake ground motions at the 2020 and 2021 Consortium of Organizations for Strong Motion Observation Systems (COSMOS) Technical Sessions. The discussions at the Technical Sessions highlighted desires to promote the use of simulated earthquake ground motions for engineering applications...
Authors
Brad T. Aagaard, Aysegul Askan, Sanaz Rezaeian, Sean Kamran Ahdi, Alan Yong
Implementation of basin models and sediment depth terms in the 2023 update of the U.S. National Seismic Hazard Model: Example from Reno, Nevada
We present a framework to evaluate the inclusion of candidate basin depth models in the U.S. Geological Survey National Seismic Hazard Model. We compute intensity measures (peak and spectral amplitudes) from uniformly processed earthquake ground motions in and around the basin of interest and compare these to ground-motion model (GMM) estimates over a range of oscillator periods. The...
Authors
Sean Kamran Ahdi, Morgan P. Moschetti, Brad T. Aagaard, Kaitlyn Abernathy, Oliver S. Boyd, William J. Stephenson
NGA-Subduction research program
This article summarizes the Next Generation Attenuation (NGA) Subduction (NGA-Sub) project, a major research program to develop a database and ground motion models (GMMs) for subduction regions. A comprehensive database of subduction earthquakes recorded worldwide was developed. The database includes a total of 214,020 individual records from 1,880 subduction events, which is by far the...
Authors
Yousef Bozorgnia, Norman A. Abrahamson, Sean Kamran Ahdi, Timothy D. Ancheta, Linda Al Atik, Ralph J. Archuleta, Gail M. Atkinson, David M Boore, Kenneth W. Campbell, Brian S-J Chiou, Victor Contreras, Robert B. Darragh, Sahar Derakhshan, Jennifer L Donahue, Nick Gregor, Zeynep Gulerce, Izzat M Idriss, Chengxin Jiang, Tadahiro Kishida, Albert R. Kottke, Nicolas Kuehn, Dongyoup Kwak, Annie O-L Kwok, Person Lin, Jorge Macedo, Silvia Mazzoni, Saburoh Midorikawa, Sifat Muin, Grace Alexandra Parker, Sanaz Rezaeian, Hongjun Si, Walter J Silva, Jonathan P. Stewart, Melanie Walling, Katie Wooddell, Robert R Youngs
Relational database for horizontal‐to‐vertical spectral ratios
Frequency‐dependent horizontal‐to‐vertical spectral ratios (HVSRs) of Fourier amplitudes from three‐component recordings can provide useful information for site response modeling. However, such information is not incorporated into most ground‐motion models, including those from Next‐Generation Attenuation projects, which instead use the time‐averaged shear‐wave velocity (VSVS) in the...
Authors
Pengfei Wang, Paolo Zimmaro, Tristan E Buckreis, Tatiana Gospe, Scott J Brandenberg, Sean Kamran Ahdi, Alan Yong, Jonathan P. Stewart
2021 U.S. National Seismic Hazard Model for the State of Hawaii
The 2021 U.S. National Seismic Hazard Model (NSHM) for the State of Hawaii updates the two-decades-old former model by incorporating new data and modeling techniques to improve the underlying ground shaking forecasts of tectonic-fault, tectonic-flexure, volcanic, and caldera collapse earthquakes. Two earthquake ground shaking hazard models (public policy and research) are produced that...
Authors
Mark D. Petersen, Allison Shumway, Peter M. Powers, Morgan P. Moschetti, Andrea L. Llenos, Andrew J. Michael, Charles Mueller, Arthur Frankel, Sanaz Rezaeian, Kenneth S. Rukstales, Daniel E. McNamara, P. Okubo, Yuehua Zeng, Kishor S. Jaiswal, Sean Kamran Ahdi, Jason M. Altekruse, Brian Shiro
Horizontal-to-vertical spectral ratios from California sites: Open-source database and data interpretation to establish site parameters
Frequency-dependent horizontal-to-vertical spectral ratios (HVSR) of Fourier amplitudes from three-component recordings can provide information on one or more site resonant frequencies and relative levels of amplification at those frequencies. Such information is potentially useful for predicting site amplification but is not present in site databases that have been developed over the...
Authors
Pengfei Wang, Paolo Zimmaro, Tatiana Gospe, Sean Kamran Ahdi, Alan Yong, Jonathan P. Stewart
Science and Products
Data Release for the 2023 U.S. 50-State National Seismic Hazard Model - Overview
This data release contains data sets associated with the 2023 50-State National Seismic Hazard Model Update. The 2023 50-State National Seimsic Hazard Model (NSHM) Update includes an update to the NSHMs for the conterminous U.S (CONUS, last updated in 2018), Alaska (AK, last updated in 2007), and Hawaii (last updated in 2001). Data sets include inputs like seismicity catalogs used as...
Updated Compilation of VS30 Data for the United States
VS30, the time-averaged shear-wave velocity (VS) to a depth of 30 meters, is a key index adopted by the earthquake engineering community to account for seismic site conditions. VS30 is typically based on geophysical measurements of VS derived from invasive and noninvasive techniques at sites of interest. Owing to cost considerations, as well as logistical and environmental concerns, VS30...
Empirical ground-motion basin response in the California Great Valley, Reno, Nevada, and Portland, Oregon
We assess how well the Next-Generation Attenuation-West 2 (NGA-West2) ground-motion models (GMMs), which are used in the US Geological Survey’s (USGS) National Seismic Hazard Model (NSHM) for crustal faults in the western United States, predict the observed basin response in the Great Valley of California, the Reno basin in Nevada, and Portland and Tualatin basins in Oregon. These GMMs...
Authors
Sean Kamran Ahdi, Brad T. Aagaard, Morgan P. Moschetti, Grace Alexandra Parker, Oliver S. Boyd, William J. Stephenson
The influence of anthropogenic regulation and evaporite dissolution on earthquake-triggered ground failure
Remote sensing observations of Searles Lake following the 2019 moment magnitude 7.1 Ridgecrest, California, earthquake reveal an area where surface ejecta is arranged in a repeating hexagonal pattern that is collocated with a solution-mining operation. By analyzing geologic and geotechnical data, here we show that the hexagonal surface ejecta is likely not a result of liquefaction...
Authors
Paula Madeline Burgi, Eric M. Thompson, Kate E. Allstadt, Kyle Dennis Murray, Henry (Ben) Mason, Sean Kamran Ahdi, Devin Katzenstein
The 2023 US National Seismic Hazard Model: Ground-motion characterization for the conterminous United States
We update the ground-motion characterization for the 2023 National Seismic Hazard Model (NSHM) for the conterminous United States. The update includes the use of new ground-motion models (GMMs) in the Cascadia subduction zone; an adjustment to the central and eastern United States (CEUS) GMMs to reduce misfits with observed data; an updated boundary for the application of GMMs for...
Authors
Morgan P. Moschetti, Brad T. Aagaard, Sean Kamran Ahdi, Jason M. Altekruse, Oliver S. Boyd, Arthur Frankel, Julie Herrick, Mark D. Petersen, Peter M. Powers, Sanaz Rezaeian, Allison Shumway, James Andrew Smith, William J. Stephenson, Eric M. Thompson, Kyle Withers
Recent applications of the USGS National Crustal Model for Seismic Hazard Studies
The U.S. Geological Survey is developing the National Crustal Model (NCM) for seismic hazard studies to facilitate modeling site, path, and source components of seismic hazard across the conterminous United States. The NCM is composed of a 1km grid of geophysical profiles, extending from the Earth’s surface into the upper mantle. It is constructed from a threedimensional (3D) geologic...
Authors
Oliver S. Boyd, James Andrew Smith, Morgan P. Moschetti, Brad T. Aagaard, Robert Graves, Evan Tyler Hirakawa, Sean Kamran Ahdi
The 2023 US 50-State National Seismic Hazard Model: Overview and implications
The US National Seismic Hazard Model (NSHM) was updated in 2023 for all 50 states using new science on seismicity, fault ruptures, ground motions, and probabilistic techniques to produce a standard of practice for public policy and other engineering applications (defined for return periods greater than ∼475 or less than ∼10,000 years). Changes in 2023 time-independent seismic hazard...
Authors
Mark D. Petersen, Allison Shumway, Peter M. Powers, Ned Field, Morgan P. Moschetti, Kishor S. Jaiswal, Kevin R. Milner, Sanaz Rezaeian, Arthur Frankel, Andrea L. Llenos, Andrew J. Michael, Jason M. Altekruse, Sean Kamran Ahdi, Kyle Withers, Charles Mueller, Yuehua Zeng, Robert E. Chase, Leah M. Salditch, Nico Luco, Kenneth S. Rukstales, Julie Herrick, Demi Leafar Girot, Brad T. Aagaard, Adrian Bender, Michael L. Blanpied, Richard W. Briggs, Oliver S. Boyd, Brandon Clayton, Christopher DuRoss, Eileen L. Evans, Peter J. Haeussler, Alexandra Elise Hatem, Kirstie Lafon Haynie, Elizabeth H. Hearn, Kaj M. Johnson, Zachary Alan Kortum, N. Simon Kwong, Andrew James Makdisi, Henry (Ben) Mason, Daniel McNamara, Devin McPhillips, P. Okubo, Morgan T. Page, Frederick Pollitz, Justin Rubinstein, Bruce E. Shaw, Zheng-Kang Shen, Brian Shiro, James Andrew Smith, William J. Stephenson, Eric M. Thompson, Jessica Ann Thompson Jobe, Erin Wirth, Robert C. Witter
Sediment thickness map of United States Atlantic and Gulf Coastal Plain Strata, and their influence on earthquake ground motions
With the recent successful accounting of basin depth ground-motion adjustments in seismic hazard analyses for select areas of the western United States, we move toward implementing similar adjustments in the Atlantic and Gulf Coastal Plains by constructing a sediment thickness model and evaluating multiple relevant site amplification models for central and eastern United States seismic...
Authors
Oliver S. Boyd, David Churchwell, Morgan P. Moschetti, Eric M. Thompson, Martin C. Chapman, Okan Ilhan, Thomas L. Pratt, Sean Kamran Ahdi, Sanaz Rezaeian
COSMOS Ground-Motion Simulation Working Group workshops #1 and #2
These 2 workshops were held in response to interest generated from sessions on the use of simulated earthquake ground motions at the 2020 and 2021 Consortium of Organizations for Strong Motion Observation Systems (COSMOS) Technical Sessions. The discussions at the Technical Sessions highlighted desires to promote the use of simulated earthquake ground motions for engineering applications...
Authors
Brad T. Aagaard, Aysegul Askan, Sanaz Rezaeian, Sean Kamran Ahdi, Alan Yong
Implementation of basin models and sediment depth terms in the 2023 update of the U.S. National Seismic Hazard Model: Example from Reno, Nevada
We present a framework to evaluate the inclusion of candidate basin depth models in the U.S. Geological Survey National Seismic Hazard Model. We compute intensity measures (peak and spectral amplitudes) from uniformly processed earthquake ground motions in and around the basin of interest and compare these to ground-motion model (GMM) estimates over a range of oscillator periods. The...
Authors
Sean Kamran Ahdi, Morgan P. Moschetti, Brad T. Aagaard, Kaitlyn Abernathy, Oliver S. Boyd, William J. Stephenson
NGA-Subduction research program
This article summarizes the Next Generation Attenuation (NGA) Subduction (NGA-Sub) project, a major research program to develop a database and ground motion models (GMMs) for subduction regions. A comprehensive database of subduction earthquakes recorded worldwide was developed. The database includes a total of 214,020 individual records from 1,880 subduction events, which is by far the...
Authors
Yousef Bozorgnia, Norman A. Abrahamson, Sean Kamran Ahdi, Timothy D. Ancheta, Linda Al Atik, Ralph J. Archuleta, Gail M. Atkinson, David M Boore, Kenneth W. Campbell, Brian S-J Chiou, Victor Contreras, Robert B. Darragh, Sahar Derakhshan, Jennifer L Donahue, Nick Gregor, Zeynep Gulerce, Izzat M Idriss, Chengxin Jiang, Tadahiro Kishida, Albert R. Kottke, Nicolas Kuehn, Dongyoup Kwak, Annie O-L Kwok, Person Lin, Jorge Macedo, Silvia Mazzoni, Saburoh Midorikawa, Sifat Muin, Grace Alexandra Parker, Sanaz Rezaeian, Hongjun Si, Walter J Silva, Jonathan P. Stewart, Melanie Walling, Katie Wooddell, Robert R Youngs
Relational database for horizontal‐to‐vertical spectral ratios
Frequency‐dependent horizontal‐to‐vertical spectral ratios (HVSRs) of Fourier amplitudes from three‐component recordings can provide useful information for site response modeling. However, such information is not incorporated into most ground‐motion models, including those from Next‐Generation Attenuation projects, which instead use the time‐averaged shear‐wave velocity (VSVS) in the...
Authors
Pengfei Wang, Paolo Zimmaro, Tristan E Buckreis, Tatiana Gospe, Scott J Brandenberg, Sean Kamran Ahdi, Alan Yong, Jonathan P. Stewart
2021 U.S. National Seismic Hazard Model for the State of Hawaii
The 2021 U.S. National Seismic Hazard Model (NSHM) for the State of Hawaii updates the two-decades-old former model by incorporating new data and modeling techniques to improve the underlying ground shaking forecasts of tectonic-fault, tectonic-flexure, volcanic, and caldera collapse earthquakes. Two earthquake ground shaking hazard models (public policy and research) are produced that...
Authors
Mark D. Petersen, Allison Shumway, Peter M. Powers, Morgan P. Moschetti, Andrea L. Llenos, Andrew J. Michael, Charles Mueller, Arthur Frankel, Sanaz Rezaeian, Kenneth S. Rukstales, Daniel E. McNamara, P. Okubo, Yuehua Zeng, Kishor S. Jaiswal, Sean Kamran Ahdi, Jason M. Altekruse, Brian Shiro
Horizontal-to-vertical spectral ratios from California sites: Open-source database and data interpretation to establish site parameters
Frequency-dependent horizontal-to-vertical spectral ratios (HVSR) of Fourier amplitudes from three-component recordings can provide information on one or more site resonant frequencies and relative levels of amplification at those frequencies. Such information is potentially useful for predicting site amplification but is not present in site databases that have been developed over the...
Authors
Pengfei Wang, Paolo Zimmaro, Tatiana Gospe, Sean Kamran Ahdi, Alan Yong, Jonathan P. Stewart