Sean Kamran Ahdi (Former Employee)
Science and Products
Data Release for the 2023 U.S. 50-State National Seismic Hazard Model - Overview 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 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...
Filter Total Items: 19
2023 Earthquake Ground-Motion Workshop for the Central and Eastern United States, with a focus on the Gulf and Atlantic Coastal Plains—Agenda and abstracts 2023 Earthquake Ground-Motion Workshop for the Central and Eastern United States, with a focus on the Gulf and Atlantic Coastal Plains—Agenda and abstracts
The U.S. Geological Survey held a virtual workshop December 7–8, 2023, to share research and ideas about earthquake ground motions in the Central and Eastern United States, with a focus on the Atlantic and Gulf Coastal Plains. The workshop was organized to learn about potential regionalization of ground-motion characteristics (source, path, and site), consider new explanatory variables...
Authors
Oliver Boyd, Julie Herrick, Ashly Cabas, Sean Ahdi
The 2023 U.S. National Seismic Hazard Model: Subduction ground motion models The 2023 U.S. National Seismic Hazard Model: Subduction ground motion models
The US Geological Survey National Seismic Hazard Models (NSHMs) are used to calculate earthquake ground-shaking intensities for design and rehabilitation of structures in the United States. The most recent 2014 and 2018 versions of the NSHM for the conterminous United States included major updates to ground-motion models (GMMs) for active and stable crustal tectonic settings; however...
Authors
Sanaz Rezaeian, Peter Powers, Jason Altekruse, Sean Ahdi, Mark Petersen, Allison Shumway, Arthur Frankel, Erin Wirth, James Smith, Morgan Moschetti, Kyle Withers, Julie Herrick
Empirical ground-motion basin response in the California Great Valley, Reno, Nevada, and Portland, Oregon 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 Ahdi, Brad Aagaard, Morgan Moschetti, Grace Parker, Oliver Boyd, William Stephenson
The influence of anthropogenic regulation and evaporite dissolution on earthquake-triggered ground failure 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 Burgi, Eric Thompson, Kate Allstadt, Kyle Murray, Henry Mason, Sean Ahdi, Devin Katzenstein
The 2023 US National Seismic Hazard Model: Ground-motion characterization for the conterminous United States 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 Moschetti, Brad Aagaard, Sean Ahdi, Jason Altekruse, Oliver Boyd, Arthur Frankel, Julie Herrick, Mark Petersen, Peter Powers, Sanaz Rezaeian, Allison Shumway, James Smith, William Stephenson, Eric Thompson, Kyle Withers
Recent applications of the USGS National Crustal Model for Seismic Hazard Studies 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 Boyd, James Smith, Morgan Moschetti, Brad Aagaard, Robert Graves, Evan Hirakawa, Sean Ahdi
The 2023 US 50-State National Seismic Hazard Model: Overview and implications 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 Petersen, Allison Shumway, Peter Powers, Ned Field, Morgan Moschetti, Kishor Jaiswal, Kevin Milner, Sanaz Rezaeian, Arthur Frankel, Andrea Llenos, Andrew Michael, Jason Altekruse, Sean Ahdi, Kyle Withers, Charles Mueller, Yuehua Zeng, Robert Chase, Leah Salditch, Nico Luco, Kenneth S. Rukstales, Julie Herrick, Demi Girot, Brad Aagaard, Adrian Bender, Michael Blanpied, Richard Briggs, Oliver Boyd, Brandon Clayton, Christopher DuRoss, Eileen L. Evans, Peter J. Haeussler, Alexandra Hatem, Kirstie Haynie, Elizabeth Hearn, Kaj Johnson, Zachary Kortum, N. Kwong, Andrew Makdisi, Henry Mason, Daniel McNamara, Devin McPhillips, P. Okubo, Morgan Page, Frederick Pollitz, Justin Rubinstein, Bruce Shaw, Zheng-Kang Shen, Brian Shiro, James Smith, William Stephenson, Eric Thompson, Jessica 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 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 Boyd, David Churchwell, Morgan Moschetti, Eric Thompson, Martin Chapman, Okan Ilhan, Thomas Pratt, Sean Ahdi, Sanaz Rezaeian
COSMOS Ground-Motion Simulation Working Group workshops #1 and #2 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 Aagaard, Aysegul Askan, Sanaz Rezaeian, Sean 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 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 Ahdi, Morgan Moschetti, Brad Aagaard, Kaitlyn Abernathy, Oliver Boyd, William Stephenson
NGA-Subduction research program 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 Ahdi, Timothy D. Ancheta, Linda Al Atik, Ralph Archuleta, Gail Atkinson, David Boore, Kenneth Campbell, Brian Chiou, Victor Contreras, Robert Darragh, Sahar Derakhshan, Jennifer Donahue, Nick Gregor, Zeynep Gulerce, Izzat Idriss, Chengxin Jiang, Tadahiro Kishida, Albert Kottke, Nicolas Kuehn, Dongyoup Kwak, Annie Kwok, Person Lin, Jorge Macedo, Silvia Mazzoni, Saburoh Midorikawa, Sifat Muin, Grace Parker, Sanaz Rezaeian, Hongjun Si, Walter Silva, Jonathan Stewart, Melanie Walling, Katie Wooddell, Robert Youngs
Relational database for horizontal‐to‐vertical spectral ratios 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 Buckreis, Tatiana Gospe, Scott Brandenberg, Sean Ahdi, Alan Yong, Jonathan Stewart
Science and Products
Data Release for the 2023 U.S. 50-State National Seismic Hazard Model - Overview 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 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...
Filter Total Items: 19
2023 Earthquake Ground-Motion Workshop for the Central and Eastern United States, with a focus on the Gulf and Atlantic Coastal Plains—Agenda and abstracts 2023 Earthquake Ground-Motion Workshop for the Central and Eastern United States, with a focus on the Gulf and Atlantic Coastal Plains—Agenda and abstracts
The U.S. Geological Survey held a virtual workshop December 7–8, 2023, to share research and ideas about earthquake ground motions in the Central and Eastern United States, with a focus on the Atlantic and Gulf Coastal Plains. The workshop was organized to learn about potential regionalization of ground-motion characteristics (source, path, and site), consider new explanatory variables...
Authors
Oliver Boyd, Julie Herrick, Ashly Cabas, Sean Ahdi
The 2023 U.S. National Seismic Hazard Model: Subduction ground motion models The 2023 U.S. National Seismic Hazard Model: Subduction ground motion models
The US Geological Survey National Seismic Hazard Models (NSHMs) are used to calculate earthquake ground-shaking intensities for design and rehabilitation of structures in the United States. The most recent 2014 and 2018 versions of the NSHM for the conterminous United States included major updates to ground-motion models (GMMs) for active and stable crustal tectonic settings; however...
Authors
Sanaz Rezaeian, Peter Powers, Jason Altekruse, Sean Ahdi, Mark Petersen, Allison Shumway, Arthur Frankel, Erin Wirth, James Smith, Morgan Moschetti, Kyle Withers, Julie Herrick
Empirical ground-motion basin response in the California Great Valley, Reno, Nevada, and Portland, Oregon 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 Ahdi, Brad Aagaard, Morgan Moschetti, Grace Parker, Oliver Boyd, William Stephenson
The influence of anthropogenic regulation and evaporite dissolution on earthquake-triggered ground failure 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 Burgi, Eric Thompson, Kate Allstadt, Kyle Murray, Henry Mason, Sean Ahdi, Devin Katzenstein
The 2023 US National Seismic Hazard Model: Ground-motion characterization for the conterminous United States 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 Moschetti, Brad Aagaard, Sean Ahdi, Jason Altekruse, Oliver Boyd, Arthur Frankel, Julie Herrick, Mark Petersen, Peter Powers, Sanaz Rezaeian, Allison Shumway, James Smith, William Stephenson, Eric Thompson, Kyle Withers
Recent applications of the USGS National Crustal Model for Seismic Hazard Studies 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 Boyd, James Smith, Morgan Moschetti, Brad Aagaard, Robert Graves, Evan Hirakawa, Sean Ahdi
The 2023 US 50-State National Seismic Hazard Model: Overview and implications 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 Petersen, Allison Shumway, Peter Powers, Ned Field, Morgan Moschetti, Kishor Jaiswal, Kevin Milner, Sanaz Rezaeian, Arthur Frankel, Andrea Llenos, Andrew Michael, Jason Altekruse, Sean Ahdi, Kyle Withers, Charles Mueller, Yuehua Zeng, Robert Chase, Leah Salditch, Nico Luco, Kenneth S. Rukstales, Julie Herrick, Demi Girot, Brad Aagaard, Adrian Bender, Michael Blanpied, Richard Briggs, Oliver Boyd, Brandon Clayton, Christopher DuRoss, Eileen L. Evans, Peter J. Haeussler, Alexandra Hatem, Kirstie Haynie, Elizabeth Hearn, Kaj Johnson, Zachary Kortum, N. Kwong, Andrew Makdisi, Henry Mason, Daniel McNamara, Devin McPhillips, P. Okubo, Morgan Page, Frederick Pollitz, Justin Rubinstein, Bruce Shaw, Zheng-Kang Shen, Brian Shiro, James Smith, William Stephenson, Eric Thompson, Jessica 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 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 Boyd, David Churchwell, Morgan Moschetti, Eric Thompson, Martin Chapman, Okan Ilhan, Thomas Pratt, Sean Ahdi, Sanaz Rezaeian
COSMOS Ground-Motion Simulation Working Group workshops #1 and #2 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 Aagaard, Aysegul Askan, Sanaz Rezaeian, Sean 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 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 Ahdi, Morgan Moschetti, Brad Aagaard, Kaitlyn Abernathy, Oliver Boyd, William Stephenson
NGA-Subduction research program 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 Ahdi, Timothy D. Ancheta, Linda Al Atik, Ralph Archuleta, Gail Atkinson, David Boore, Kenneth Campbell, Brian Chiou, Victor Contreras, Robert Darragh, Sahar Derakhshan, Jennifer Donahue, Nick Gregor, Zeynep Gulerce, Izzat Idriss, Chengxin Jiang, Tadahiro Kishida, Albert Kottke, Nicolas Kuehn, Dongyoup Kwak, Annie Kwok, Person Lin, Jorge Macedo, Silvia Mazzoni, Saburoh Midorikawa, Sifat Muin, Grace Parker, Sanaz Rezaeian, Hongjun Si, Walter Silva, Jonathan Stewart, Melanie Walling, Katie Wooddell, Robert Youngs
Relational database for horizontal‐to‐vertical spectral ratios 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 Buckreis, Tatiana Gospe, Scott Brandenberg, Sean Ahdi, Alan Yong, Jonathan Stewart