Grace Parker
Grace Parker is a Research Geophysicist at the USGS Earthquake Science Center.
My primary research focus is earthquake ground motion characterization, with a special interest in seismic site response. I develop models to estimate where and how much shaking occurs during earthquakes. These models can be used in applications like seismic hazard analysis, earthquake early warning, and aid in understanding how ground shaking is connected to physical earthquake processes like fault rupture and seismic wave attenuation.
Professional Experience
2022- Research Geophysicist, U.S. Geological Survey
2019-2021 Mendenhall Postdoctoral Fellow, U.S. Geological Survey
2014-2018 Graduate Student Researcher and TA, UCLA Dept. of Civil and Environmental Engineering (CEE)
Education and Certifications
2018 PhD Civil and Environmental Engineering, UCLA
2014 B.S. Applied Geophysics, UCLA
Magna Cum Laude, Departmental Highest Honors
Science and Products
Data Release for Latency Testing of Wireless Emergency Alerts intended for the ShakeAlert earthquake early warning system for the West Coast of the United States of America
ShakeAlert, the earthquake early warning (EEW) system for the West Coast of the United States, attempts to provides crucial warnings before strong shaking occurs. However, because the alerts are triggered only when an earthquake is already in progress, and the alert latencies and delivery times are platform dependent, the time between these warnings and the arrival of shaking is variable. The Shak
Ground motions from the 2019 Ridgecrest, California, earthquake sequence
This project involves the compilation of ground motions, their derived parameters, and metadata for 133 earthquakes in the 2019 Ridgecrest, California, earthquake sequence. This dataset includes 22,991 records from 133 events from 4 July 2019 to 18 October 2019 with a magnitude range from 3.6 to 7.1.
Filter Total Items: 18
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 rely on sit
Authors
Sean Kamran Ahdi, Brad T. Aagaard, Morgan P. Moschetti, Grace Alexandra Parker, Oliver S. Boyd, William J. Stephenson
Performance-based earthquake early warning for tall buildings
The ShakeAlert Earthquake Early Warning (EEW) system aims to issue an advance warning to residents on the West Coast of the United States seconds before the ground shaking arrives, if the expected ground shaking exceeds a certain threshold. However, residents in tall buildings may experience much greater motion due to the dynamic response of the buildings. Therefore, there is an ongoing effort to
Authors
S. Farid Ghahari, Khachik Sargsyan, Grace Alexandra Parker, Dan Swensen, Mehmet Çelebi, Hamid Haddadi, Ertugrul Taciroglu
Data-driven adjustments for combined use of NGA-East hard-rock ground motion and site amplification models
Model development in the Next Generation Attenuation-East (NGA-East) project included two components developed concurrently and independently: (1) earthquake ground-motion models (GMMs) that predict the median and aleatory variability of various intensity measures conditioned on magnitude and distance, derived for a reference hard-rock site condition with an average shear-wave velocity in the uppe
Authors
Maria E. Ramos-Sepulveda, Jonathan P. Stewart, Grace Alexandra Parker, Morgan P. Moschetti, Eric M. Thompson, Scott J. Brandenberg, Youssef M A Hashash, Ellen Rathje
Panel review of Ground Motion Characterization Model in 2023 NSHM
The 2023 National Seismic Hazard Model (NSHM; Petersen et al., 2023) has two major components – a seismic source characterization (SSC) model and a ground motion characterization (GMC) model. The US Geological Survey (USGS) established separate panels to review and provide input on these two models. Both panels are advisory, meaning that they provide input on technical issues for consideration by
Authors
Jonathan P. Stewart, Norman A. Abrahamson, Gail M. Atkinson, John G. Anderson, Kenneth W. Campbell, Chris H. Cramer, Michael Kolaj, Grace Alexandra Parker
Ground‐motion variability from kinematic rupture models and the implications for nonergodic probabilistic seismic hazard analysis
The variability of earthquake ground motions has a strong control on probabilistic seismic hazard analysis (PSHA), particularly for the low frequencies of exceedance used for critical facilities. We use a crossed mixed‐effects model to partition the variance components from simulated ground motions of Mw 7 earthquakes on the Salt Lake City segment of the Wasatch fault zone. Total variability of si
Authors
Grace Alexandra Parker, Morgan P. Moschetti, Eric M. Thompson
High-pass corner frequency selection for implementation in the USGS automated ground motion processing tool
Earthquake ground motion processing for next-generation attenuation (NGA) projects required human inspection to select high-pass corner frequencies (fcHP), which is time-intensive and subjective. With growth in the number of recordings per event and interest in enhancing repeatability, we sought to develop automated procedures for fcHP selection. These procedures consider signal-to-noise ratio (SN
Authors
María E. Ramos-Sepulveda, Grace Alexandra Parker, Eric M. Thompson, Scott J. Brandenberg, Meibai Li, Okan Ilhan, Youssef M.A. Hashash, Ellen Rathje, Jonathan P. Stewart
Applications of nonergodic site response models to ShakeAlert case studies in the Los Angeles area
In this study, we explore whether the Parker and Baltay (2022) site response models for the Los Angeles (LA) basin region can improve ground‐motion forecasts in the U.S. Geological Survey ShakeAlert earthquake early warning system (hereafter ShakeAlert). We implement the peak ground acceleration and peak ground velocity site response models of Parker and Baltay (2022) in ShakeAlert via the earthqu
Authors
Rongrong Lin, Grace Alexandra Parker, Jeffrey J. McGuire, Annemarie S. Baltay Sundstrom
Spatially continuous models of aleatory variability in seismic site response for southern California
We develop an empirical, spatially continuous model for the single-station within-event (ϕSS) component of earthquake ground motion variability in the Los Angeles area. ϕSS represents event-to-event variability in site response or remaining variability due to path effects not captured by ground motion models. Site-specific values of ϕSS at permanent seismic network stations were estimated during o
Authors
Grace Alexandra Parker, Annemarie S. Baltay Sundstrom, Eric M. Thompson
Performance of NGA-East GMMs and site amplification models relative to CENA ground motions
We investigate bias in ground motions predicted for Central and Eastern North America (CENA) using ground motion models (GMMs) combined with site amplification models developed in the NGA-East project. Bias is anticipated because of de-coupled procedures used in the development of the GMMs and site amplification models. The NGA-East GMMs were mainly calibrated by adjusting CENA data to a reference
Authors
Maria E. Ramos-Sepulveda, Grace Alexandra Parker, Meibai Li, Okan Ilhan, Youssef M. A. Hashash, Ellen Rathje, Jonathan P. Stewart
Comparisons of the NGA-Subduction ground motion models
In this article, ground-motion models (GMMs) for subduction earthquakes recently developed as part of the Next Generation Attenuation-Subduction (NGA-Sub) project are compared. The four models presented in this comparison study are documented in their respective articles submitted along with this article. Each of these four models is based on the analysis of the large NGA-Sub database. Three of th
Authors
Nick Gregor, Kofi O. Addo, Norman A. Abrahamson, Linda Al Atik, Gail M. Atkinson, David Boore, Yousef Bozorgnia, Kenneth W. Campbell, Brian S.-J. Chiou, Zeynep Gulerce, Behzad Hassani, Tadahiro Kishida, Nicolas Kuehn, Silvia Mazzoni, Saburoh Midorikawa, Grace Alexandra Parker, Hongjun Si, Jonathan P. Stewart, Robert R. Youngs
The potential of using fiber optic distributed acoustic sensing (DAS) in earthquake early warning applications
As the seismological community embraces fiber optic distributed acoustic sensing (DAS), DAS arrays are becoming a logical, scalable option to obtain strain and ground‐motion data for which the installation of seismometers is not easy or cheap, such as in dense offshore arrays. The potential of strain data in earthquake early warning (EEW) applications has been recently demonstrated using records f
Authors
Noha Farghal, Jessie Kate Saunders, Grace Alexandra Parker
Empirical map-based nonergodic models of site response in the greater Los Angeles area
We develop empirical estimates of site response at seismic stations in the Los Angeles area using recorded ground motions from 414 M 3–7.3 earthquakes in southern California. The data are from a combination of the Next Generation Attenuation‐West2 project, the 2019 Ridgecrest earthquakes, and about 10,000 newly processed records. We estimate site response using an iterative mixed‐effects residuals
Authors
Grace Alexandra Parker, Annemarie S. Baltay Sundstrom
Science and Products
Data Release for Latency Testing of Wireless Emergency Alerts intended for the ShakeAlert earthquake early warning system for the West Coast of the United States of America
ShakeAlert, the earthquake early warning (EEW) system for the West Coast of the United States, attempts to provides crucial warnings before strong shaking occurs. However, because the alerts are triggered only when an earthquake is already in progress, and the alert latencies and delivery times are platform dependent, the time between these warnings and the arrival of shaking is variable. The Shak
Ground motions from the 2019 Ridgecrest, California, earthquake sequence
This project involves the compilation of ground motions, their derived parameters, and metadata for 133 earthquakes in the 2019 Ridgecrest, California, earthquake sequence. This dataset includes 22,991 records from 133 events from 4 July 2019 to 18 October 2019 with a magnitude range from 3.6 to 7.1.
Filter Total Items: 18
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 rely on sit
Authors
Sean Kamran Ahdi, Brad T. Aagaard, Morgan P. Moschetti, Grace Alexandra Parker, Oliver S. Boyd, William J. Stephenson
Performance-based earthquake early warning for tall buildings
The ShakeAlert Earthquake Early Warning (EEW) system aims to issue an advance warning to residents on the West Coast of the United States seconds before the ground shaking arrives, if the expected ground shaking exceeds a certain threshold. However, residents in tall buildings may experience much greater motion due to the dynamic response of the buildings. Therefore, there is an ongoing effort to
Authors
S. Farid Ghahari, Khachik Sargsyan, Grace Alexandra Parker, Dan Swensen, Mehmet Çelebi, Hamid Haddadi, Ertugrul Taciroglu
Data-driven adjustments for combined use of NGA-East hard-rock ground motion and site amplification models
Model development in the Next Generation Attenuation-East (NGA-East) project included two components developed concurrently and independently: (1) earthquake ground-motion models (GMMs) that predict the median and aleatory variability of various intensity measures conditioned on magnitude and distance, derived for a reference hard-rock site condition with an average shear-wave velocity in the uppe
Authors
Maria E. Ramos-Sepulveda, Jonathan P. Stewart, Grace Alexandra Parker, Morgan P. Moschetti, Eric M. Thompson, Scott J. Brandenberg, Youssef M A Hashash, Ellen Rathje
Panel review of Ground Motion Characterization Model in 2023 NSHM
The 2023 National Seismic Hazard Model (NSHM; Petersen et al., 2023) has two major components – a seismic source characterization (SSC) model and a ground motion characterization (GMC) model. The US Geological Survey (USGS) established separate panels to review and provide input on these two models. Both panels are advisory, meaning that they provide input on technical issues for consideration by
Authors
Jonathan P. Stewart, Norman A. Abrahamson, Gail M. Atkinson, John G. Anderson, Kenneth W. Campbell, Chris H. Cramer, Michael Kolaj, Grace Alexandra Parker
Ground‐motion variability from kinematic rupture models and the implications for nonergodic probabilistic seismic hazard analysis
The variability of earthquake ground motions has a strong control on probabilistic seismic hazard analysis (PSHA), particularly for the low frequencies of exceedance used for critical facilities. We use a crossed mixed‐effects model to partition the variance components from simulated ground motions of Mw 7 earthquakes on the Salt Lake City segment of the Wasatch fault zone. Total variability of si
Authors
Grace Alexandra Parker, Morgan P. Moschetti, Eric M. Thompson
High-pass corner frequency selection for implementation in the USGS automated ground motion processing tool
Earthquake ground motion processing for next-generation attenuation (NGA) projects required human inspection to select high-pass corner frequencies (fcHP), which is time-intensive and subjective. With growth in the number of recordings per event and interest in enhancing repeatability, we sought to develop automated procedures for fcHP selection. These procedures consider signal-to-noise ratio (SN
Authors
María E. Ramos-Sepulveda, Grace Alexandra Parker, Eric M. Thompson, Scott J. Brandenberg, Meibai Li, Okan Ilhan, Youssef M.A. Hashash, Ellen Rathje, Jonathan P. Stewart
Applications of nonergodic site response models to ShakeAlert case studies in the Los Angeles area
In this study, we explore whether the Parker and Baltay (2022) site response models for the Los Angeles (LA) basin region can improve ground‐motion forecasts in the U.S. Geological Survey ShakeAlert earthquake early warning system (hereafter ShakeAlert). We implement the peak ground acceleration and peak ground velocity site response models of Parker and Baltay (2022) in ShakeAlert via the earthqu
Authors
Rongrong Lin, Grace Alexandra Parker, Jeffrey J. McGuire, Annemarie S. Baltay Sundstrom
Spatially continuous models of aleatory variability in seismic site response for southern California
We develop an empirical, spatially continuous model for the single-station within-event (ϕSS) component of earthquake ground motion variability in the Los Angeles area. ϕSS represents event-to-event variability in site response or remaining variability due to path effects not captured by ground motion models. Site-specific values of ϕSS at permanent seismic network stations were estimated during o
Authors
Grace Alexandra Parker, Annemarie S. Baltay Sundstrom, Eric M. Thompson
Performance of NGA-East GMMs and site amplification models relative to CENA ground motions
We investigate bias in ground motions predicted for Central and Eastern North America (CENA) using ground motion models (GMMs) combined with site amplification models developed in the NGA-East project. Bias is anticipated because of de-coupled procedures used in the development of the GMMs and site amplification models. The NGA-East GMMs were mainly calibrated by adjusting CENA data to a reference
Authors
Maria E. Ramos-Sepulveda, Grace Alexandra Parker, Meibai Li, Okan Ilhan, Youssef M. A. Hashash, Ellen Rathje, Jonathan P. Stewart
Comparisons of the NGA-Subduction ground motion models
In this article, ground-motion models (GMMs) for subduction earthquakes recently developed as part of the Next Generation Attenuation-Subduction (NGA-Sub) project are compared. The four models presented in this comparison study are documented in their respective articles submitted along with this article. Each of these four models is based on the analysis of the large NGA-Sub database. Three of th
Authors
Nick Gregor, Kofi O. Addo, Norman A. Abrahamson, Linda Al Atik, Gail M. Atkinson, David Boore, Yousef Bozorgnia, Kenneth W. Campbell, Brian S.-J. Chiou, Zeynep Gulerce, Behzad Hassani, Tadahiro Kishida, Nicolas Kuehn, Silvia Mazzoni, Saburoh Midorikawa, Grace Alexandra Parker, Hongjun Si, Jonathan P. Stewart, Robert R. Youngs
The potential of using fiber optic distributed acoustic sensing (DAS) in earthquake early warning applications
As the seismological community embraces fiber optic distributed acoustic sensing (DAS), DAS arrays are becoming a logical, scalable option to obtain strain and ground‐motion data for which the installation of seismometers is not easy or cheap, such as in dense offshore arrays. The potential of strain data in earthquake early warning (EEW) applications has been recently demonstrated using records f
Authors
Noha Farghal, Jessie Kate Saunders, Grace Alexandra Parker
Empirical map-based nonergodic models of site response in the greater Los Angeles area
We develop empirical estimates of site response at seismic stations in the Los Angeles area using recorded ground motions from 414 M 3–7.3 earthquakes in southern California. The data are from a combination of the Next Generation Attenuation‐West2 project, the 2019 Ridgecrest earthquakes, and about 10,000 newly processed records. We estimate site response using an iterative mixed‐effects residuals
Authors
Grace Alexandra Parker, Annemarie S. Baltay Sundstrom