About

Ashly Cabas is an Associate Professor based at Fitts-Woolard Hall 3175, with an active research group focusing on seismic hazard analysis and the effects of local soil conditions on ground motion. Her research encompasses rapid post-earthquake seismic hazard analysis, site effects on spatial correlation of ground motion, and the incorporation of site effects into ground motion modeling and physics-based simulation. She supervises a diverse group of graduate students working on topics sponsored by organizations such as the Alaska Department of Transportation and the National Science Foundation. Professor Cabas's work also addresses intersectional impacts of earthquakes and the effects of temporal changes in site conditions on ground motion. Her mentorship extends to undergraduate research supervision and collaboration with alumni who have pursued advanced studies and professional careers in seismic hazard characterization, civil infrastructure assessment, and geotechnical earthquake engineering. The research group under her guidance contributes to advancing understanding of seismic hazards and improving resilience in civil infrastructure through detailed analysis of soil and site effects on seismic activity.

Research topics

• Computer Science
• Geology
• Artificial Intelligence
• Physics
• Optics
• History
• Geometry
• Soil science
• Seismology
• Classical mechanics
• Geotechnical engineering
• Mathematics
• Library science

Selected publications

• 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

  Scientific investigations report · 2025-01-01

  articleOpen access

  Cover.Map of Seismic hazard in the Central and Eastern United States and delineation of the Gulf and Atlantic Coastal Plains (regions to the southeast of the red solid line).Modified November 21, 2024, from Petersen and others' (2023) map of 1-second spectral accelerations having a 2-percent probability of being exceeded in 50 years for sites with a time-averaged shear-wave velocity within 30 meters of the Earth's surface of 760 meters per second.

  PublisherOA PDFDOI

• Preface to the Focus Section on Earthquake-Induced Ground Deformation

  Seismological Research Letters · 2025-09-30

  article
  PublisherDOI

• Quantifying the Effects of Ground-Motion Duration on Seismic Slope Displacement Analyses for Subduction Zone Earthquakes

  Seismological Research Letters · 2025-09-26 · 2 citations

  article

  Abstract Seismic slope displacement analyses are crucial for assessing the performance of earth systems and natural slopes under earthquake loading. Input ground motions are important components of such analyses and represent one of the main sources of variability in estimated values of slope displacement. Most studies on seismic slope displacement analyses have been conducted using shallow crustal earthquake motions. However, ground motions from subduction zones are known to have comparatively longer durations. This study proposes a framework to quantify the effects of ground-motion duration on slope displacements using short- and long-duration ground-motion suites from subduction zone earthquakes. Challenges in isolating duration effects from those associated with the amplitude and frequency content of ground motions are overcome by creating sets of ground motions with the same amplitude and similar spectral shape, but with different significant durations. These equivalent short- and long-duration suites of motions are then utilized in nonlinear finite-element analyses to evaluate their impact on slope displacement. The finite-element model is developed to numerically simulate the strength and stiffness degradation of soils under cyclic loading from strong ground shaking. We find that the long-duration motions in our dataset can cause larger permanent displacements compared to their short-duration counterparts (with similar spectral shape but different duration), especially at higher ground shaking intensity levels that can trigger nonlinear soil behavior. Comparisons with simplified analyses show that the simplified methods can result in biased estimates of permanent displacements from the long-duration motions in our study. This study provides a framework to develop ground motion sets that can enable more in-depth investigations of the role of duration on seismic slope displacements and the damage potential of ground motions, particularly from subduction events.

  PublisherDOI

• Implications of input ground‐motion selection techniques on site response analyses for different tectonic settings

  Earthquake Spectra · 2024-03-27 · 1 citations

  articleCorresponding

  This study investigates how current practices of input ground‐motion selection influence site response analysis results and their variability, when considering different tectonic settings. Study sites in Seattle and Boston are chosen to represent tectonic settings with contributions to the seismic hazard from shallow crustal and subduction events, as well as stable continental regions, respectively. Selected input ground‐motion suites for one‐dimensional site response analysis represent variations in the target spectrum definition, spectral period of interest, seismic source, and ground‐motion database. When directly incorporating different types of seismic sources (e.g. shallow crustal versus subduction) into target spectrum definitions and selecting ground motions from the corresponding databases (i.e. consistent with such seismic sources), differences on the estimated site response and its variability are observed. These effects are captured by spectral amplification factors and nonspectral intensity measures (significant duration and Arias intensity) and become particularly apparent for subduction zones. The variability in spectral amplification factors stemming from ground‐motion selection techniques is found to be also a function of the characteristics of the site, becoming higher near the fundamental period of the site. Estimated responses at stiffer sites are more significantly influenced by ground‐motion selection techniques, whereas the onset of nonlinear soil behavior at softer sites can reduce such variability.

  PublisherDOI

• Regional seismic velocity model for the U.S. Atlantic and Gulf Coastal Plains based on measured shear wave velocity, sediment thickness, and surface geology

  Earthquake Spectra · 2024-02-17 · 5 citations

  articleCorresponding

  The Atlantic and Gulf Coastal Plains (CPs) are characterized by widespread accumulations of low‐velocity sediments and sedimentary rock that overlay high‐velocity bedrock. Geology and sediment thickness greatly influence seismic wave propagation, but current regional ground motion amplification and seismic hazard models include limited characterization of these site conditions. In this study, a new regional seismic velocity model for the CPs is created by integrating shear wave velocity (V S ) measurements, surface geology, and a sediment thickness model recently developed for the CPs. A reference rock V S of 3000 m/s has been assumed at the bottom of the sedimentary columns, which corresponds to the base of Cretaceous and Mesozoic sediments underlying the Atlantic CP and the Gulf CP, respectively. Measured V S profiles located throughout the CPs are sorted into five geologic groups of varying age, and median V S profiles are developed for each group by combining measured V S values within layer thicknesses defined by an assumed layering ratio. Statistical analyses are also conducted to test the appropriateness of the selected groups. A power law model with geology‐informed coefficients is used to extend the median velocity models beyond the depths where measured data were available. The median V S profiles provide reasonable agreement with other generic models applicable for the region, but they also incorporate new information that enables more advanced characterizations of site response at regional scales and their effective incorporation into seismic hazard models and building codes. The proposed median velocity profiles can be assigned within a grid‐based model of the CPs according to the spatial distribution of geologic units at the surface.

  PublisherDOI

• Spatial variability of site effects and its correlation with site response in Japan

  Japanese Geotechnical Society Special Publication · 2024-01-01

  articleOpen accessSenior author

  Local soil conditions play an important role in regional seismic hazard assessments due to their influence on earthquake-induced ground shaking and deformation. The different levels of damage and site response at nearby locations correlate to site and geologic conditions variability, as has been reported after past earthquakes. Evaluating spatially variable ground motions (GMs) is key for earthquake reconnaissance efforts and regional seismic hazard assessments. This study focuses on the evaluation of spatial correlations in site parameters (e.g. time-averaged shear-wave velocity to a depth of 30 meters) at Kiban-Kyoshin Network (KiK-net), and their comparison to the observed spatial correlation of the residuals from ground motion intensity measures (IMs) from the Mw9.1 Tohoku earthquake. Current spatial correlation models treat site effects either as a fixed amplification factor or as randomized amplifications, but site effects are neither fixed nor random. Hence, geostatistical methods are used here to estimate spatial correlations between parameters that control site response and integrate their effects on resulting spatially variable ground motions. In this work, we evaluate the significance of the spatial correlation for different site parameters with respect to the GM amplification IMs residuals.

  PublisherOA PDFDOI

• Current Limitations of Near-Surface Attenuation Modeling at High Frequencies

  Japanese Geotechnical Society Special Publication · 2024-01-01

  articleOpen access

  Four decades after the introduction of the high frequency spectral decay parameter kappa (κ) to the scientific community, there has been relevant progress on our understanding of how it captures seismic attenuation and its multiple applications in stochastic modeling of ground motions, seismic hazard assessment, and site response analysis. Particularly, κ’s site-specific component, κ0, has been used to characterize near-surface attenuation, which offers additional information to site response analysis and site-specific seismic hazard assessments beyond that provided by other site parameters such as the average shear wave velocity over the top 30 m of a site (Vs30). The Japanese database KiK-net is rich with a dense array of stations (at the ground surface and at depth) providing thousands of high-quality ground motions. However, the unclear underlying physics of κ and its associated variabilities pose challenges to its further application in site-specific seismic hazard assessments. Thus, the objective of this work is to identify the current limitations and challenges for near-surface attenuation characterizations with κ. The downhole array of KiK-net allows to study the response of soil mediums between surface and borehole sensors directly. The difference between surface and borehole individual κ estimates (what we referred to as Dκ0), could capture the seismic attenuations contributed from the soil column between those two sensors. Larger borehole κ values (i.e., leading to negative Dκ0) are the focus of this study because Dκ0 is expected to be positive. With the assumptions that κ could serve as an attenuation parameter to characterize the dissipations of seismic wave energy, the negative Dκ0 are lack of physical explanations. The observation of larger κ estimates at depth compared to their counterparts at the ground surface (i.e., negative Dκ0) could result from multiple reasons. In this work, we specifically study the influences of ground motion directionality and site amplifications on Dκ0 estimates. A single KiK-net station was selected for this case study to figure out the main challenges that remain in characterizing near-surface attenuation with κ.

  PublisherOA PDFDOI

• Influence of sediment thickness and reference condition on ground motion amplification in the U.S. Atlantic and Gulf Coastal Plains

  Japanese Geotechnical Society Special Publication · 2024-01-01

  articleOpen access

  The Atlantic and Gulf Coastal Plains (CPs) in the eastern and southern United States consist of thick and soft sediments that overlie a stiff bedrock that increase the amplification and duration of earthquake ground motions. Understanding both the depth and the dynamic properties of these sediments is critical yet challenging at a regional scale. Sediment thickness and geology have been shown to be good indicators for regional characterization of shear wave velocity (VS). However, existing site amplification models within the CPs have limited characterization and modeling of these parameters. Therefore, we have developed a new site response and hazard model that uses a geology-based VS model and geotechnical model to characterize the CP sediments so that amplification and hazard levels can be estimated. A sensitivity study using one-dimensional linear site response analyses is conducted to determine the influence of sediment thickness and reference condition assumptions within the model. Sediment thickness values of 100, 200, and 1000 m are tested. Additionally, reference condition velocities of 2500, 3000, and 3500 m/s at the base are tested. Response spectra- and Fourier amplitude spectra-based amplification ratios are calculated. The change in sediment thickness values is found to have the largest impact on longer-period (lower-frequency) amplification ratios as the fundamental period shifts. The change in reference condition also impacts longer-period (lower-frequency) amplification ratios more significantly. Overall, the amplification ratios estimated by the model are found to be more sensitive to the change in sediment thickness than to the change in reference condition. The results of the sensitivity study indicate that caution should be taken when using the model for shallow sediment thickness values (100 m or less), as this may lead to unrealistically large amplification ratios depending on the VS value assumed for the reference condition.

  PublisherOA PDFDOI

• Lessons Learned from a Game-Based Learning Intervention in Civil Engineering

  2024-02-07 · 2 citations

  articleOpen accessSenior author

  Abstract The aim of our project is to create a scalable and sustainable educational model of mixed reality gaming in civil engineering education that provides practical experiences, develops engineering judgment competency, and engages a diverse student audience. Specifically, we have been building a game-based learning module focused on experiencing the field testing technique cone-penetration testing (CPT). As part of the module, students start a virtual internship at a fictional engineering company. After being briefed through a lecture on CPT, they enter a 3D (game) environment where they conduct CPTs. Students analyze CPT data extracted from the environment and submit a report. To assess student experience of this module, we collected pre/post surveys, game data (including in-game assessments), and student/faculty interviews. In this paper, we report the findings of implementing this CPT module in the initial three years of the project (2016-2019) at five institutions. Overall, we find that students are engaged, especially women and students from historically marginalized communities, increase their knowledge and confidence in the subject matter, and find the module valuable to gain much-needed (field) experience. More recently, we find that the game-based learning intervention seems resilient and, in fact, a solid solution to the disturbances caused by the pandemic, with many students providing positive remarks about being able to experience hands-on learning, which is key to quality engineering education and difficult to achieve through online education. Opportunities for improvement exist regarding access to technology, as well as the instructional design. While we demonstrate the scalability of this approach across multiple institutions and classrooms, open questions remain on how to transform institutions to embed game-based learning not as an intervention but as a key part of the curriculum.

  PublisherOA PDFDOI

• Sharing data and code facilitates reproducible and impactful research

  Earthquake Spectra · 2024-06-16 · 6 citations

  articleOpen access

  Modern research often involves the collection or analysis of data and the use of specialized computer algorithms. Traditional text articles thus provide only partial documentation of a research study. Readers have limited ability to reproduce or utilize work if the source data are not available or if it relies on an algorithm that is described, but code is not provided. Fortunately, a wide variety of tools are now available to support the publication of research data and code. The effort required to publish data is now relatively small, and the benefits can be immense. This opinion article discusses trends toward increased sharing in academic publishing. It describes opportunities and resources to support data and code sharing and describes the benefits for both authors and readers. Finally, it discusses how Earthquake Spectra is providing resources and enhancing its policies to establish the sharing of data as the default procedure when publishing in the journal, and encourage the sharing of code and other resources.

  PublisherOA PDFDOI

Frequent coauthors

• James Kaklamanos

  Merrimack College

  20 shared

• Brina M. Montoya

  North Carolina State University

  15 shared

• Chunyang Ji

  North Carolina State University

  14 shared

• Cassie Gann-Phillips

  North Carolina State University

  12 shared

• Chris H. Cramer

  University of Memphis

  11 shared

• Adrián Rodríguez-Marek

  Virginia Tech

  10 shared

• Zachary M. Militello

  North Carolina State University

  10 shared

• Albert Kottke

  PG&E Corporation (United States)

  9 shared

Labs

• Ashly Cabas Research GroupPI

  Rapid Post-Earthquake Seismic Hazard Analysis incorporating the Effects of Local Soil Conditions

Education

• Ph.D., Civil Engineering

  University of California, Berkeley

  2005

• M.S., Civil Engineering

  University of California, Berkeley

  2002

• B.S., Civil Engineering

  University of California, Berkeley

  2000

Awards & honors

• NSF CAREER Award (2022)