Jul 2026· Bulletin of The Seismological Society of America (BSSA)· 0 citations· 74 references
Abstract
Ground-motion model (GMM) site terms developed from continuously available geospatial data and enhanced with site-specific measured geotechnical data have been demonstrated to be an effective approach for site term development in California (Roberts et al., 2025; Roberts et al., 2026). This study extends this methodology to the Basin and Range physiographic province in the western United States. Ground-motion data from 16,852 recordings at 433 stations in the Next Generation Attenuation-West3 database (Buckreis and Stewart, 2025) are used for model development. A base site term model is developed using mapped geospatial variables (e.g., sediment thickness, elevation, and surficial geologic units) to capture trends in soil stiffness and basin effects. The target site amplifications of peak ground acceleration, peak ground velocity, and pseudospectral accelerations from 0.01 to 10 s are decomposed from the residuals of the Boore et al. (2014) (BSSA14) GMM. A linear mixed-effects regression model is then developed to predict each target site amplification using geospatial variables. The resulting model is a linear geospatial site term that provides a consistent site term for all locations in the region. The geospatial site term shows a substantial reduction in site-to-site variability; on average, an 8.5% reduction is achieved compared with BSSA14. This base geospatial model is then enhanced with local geotechnical information where available. The proposed geotechnical site term adjustment models are developed using microtremor horizontal-to-vertical spectral ratio data (Anbazhagan et al., 2025) and measured VS30 data (Buckreis and Stewart, 2025). Additional reductions in the site-to-site variability are achieved when the geotechnical adjustments are applied. This study illustrates that the approach of incorporating broadly available geospatial data before site-specific geotechnical data is effective in regions outside of California and demonstrates how geospatial site amplification models with explicit uncertainty characterization can be developed where ground-motion data are sparse.
The Wellington central business district (CBD) in New Zealand overlies a complex sedimentary basin that significantly amplifies surface ground motions, as observed during events like the 2016 Mw 7.8 Kaikōura earthquake. This article presents a study on site amplification in Wellington predicted through 3D physics-based ground-motion simulations. Eight alternative models of the Wellington basin geometry are used to quantify predicted site amplification and the between-model epistemic uncertainty associated with basin representation. Response spectral amplification factors (for periods 0.5–10 s) are shown at several locations across the Wellington CBD, along 2D transects, and in spatial maps. When compared with observed site amplification, the simulations capture broad spectral amplification peaks and provide comparable levels of site amplification at some deeper basin sites. At shallower basin sites, the simulations have discrepancies in the predicted level and period dependence of site amplification, partially due to model spatial resolution and minimum S-wave velocity (500 m/s for this study) limitations. Linear simulated spectral amplification factors are as high as 8 in some locations. These results illustrate future opportunities for improving the simulations, which include better constrained basin-depth geometry and velocity characterization of the sediments within the basin; higher spatial-resolution simulations; decreasing the minimum S-wave velocity in the simulations; and near-surface nonlinear site response modeling using physics-based approaches.
Robin L. Lee, Brendon A. Bradley, M. Hill et al.· Bulletin of The Seismologica...· 0 citations
Seulawah Agam, located in Aceh Province, is a Quaternary stratovolcano with notable geothermal manifestations, making it a promising target for renewable energy exploration. This study aims to evaluate the geothermal system and its structural controls through an integrated geological and geophysical approach. Geologically, Fault Fracture Density derived from remote sensing data is used to identify major fault zones, ridgelines, and structural trends that may act as conduits for geothermal fluid migration. Land Surface Temperature (LST) data from thermal infrared satellite imagery are employed to detect surface thermal anomalies indicative of subsurface geothermal activity. Geophysically, gravity data processed into Complete Bouguer Anomaly (CBA) and derivative maps are used to delineate subsurface structures, density contrasts, and potential heat sources. The study area covers approximately 17 × 16 km, with Bouguer anomaly values ranging from a minimum of 394.74 mGal to a maximum of 614.23 mGal. The integration of these datasets allows for the correlation between surface features and deeper geothermal reservoirs, highlighting structurally controlled zones with elevated geothermal potential. Preliminary findings indicate that NE-SW and NW-SE trending lineaments intersect with thermal anomalies and gravity lows, suggesting the presence of deep-seated fractures and fault zones associated with heat migration pathways. The study emphasizes the importance of structural mapping and geophysical validation in assessing geothermal viability. This integrated approach provides a robust foundation for future exploration efforts in Seulawah Agam and supports Indonesia’s broader goals for sustainable and renewable energy development in tectonically active regions.
Gibran Dewabrata, Mahatvavirya Shukma Ajie, B. Ginting et al.· IOP Conference Series: Earth...· 0 citations
The U.S. Atlantic and Gulf Coastal Plain (CP) sediments are kilometers‐thick, low‐velocity deposits underlain by high‐velocity bedrock that create regional patterns of amplification and attenuation of ground motions. Capturing these effects is challenging because of the limited subsurface information available, particularly the shear wave velocity (
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) structure down to bedrock (or assumed reference rock condition) and the associated uncertainties. This paper introduces a new suite of regional velocity models for the CPs, called CPVMv2.0, which builds upon previous efforts integrating geology,
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measurements, and sediment thickness in the region. CPVMv2.0 uses 750 measured
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profiles and identifies nine surficial‐geologic‐age‐based and geography‐based groups (with alternative physiographic‐province‐based subgroupings) to create surface‐based median
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profiles. This suite of new models also includes six subsurface‐based median profiles developed using geologic age boundaries from depth‐dependent stratigraphic sequences extracted from the U.S. Geological Survey National Crustal Model. In addition to quantifying aleatory variability in sediment velocity, weathered‐rock velocity, bedrock velocity, and the depth to the top of weathered rock and bedrock, CPVMv2.0 provides alternative profile models that allow for the characterization of the epistemic uncertainty. This is a unique and relevant feature of CPVMv2.0. Our suite of models was validated using measured and estimated fundamental resonant frequencies as well as other
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models in the region. CPVMv2.0 enables the incorporation of crustal velocities (and their associated variability and uncertainty) into physics‐based ground‐motion simulations in the eastern United States and into the development of new ground‐motion models aiming to characterize systematic site effects via
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, depths to
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isosurfaces, and/or sediment thickness in the region.
Cassie Gann‐Phillips, Ashly Cabas, Chunyang Ji et al.· Earthquake spectra· 0 citations
Abstract A geothermal potential assessment was conducted in the Suban Curup–Rejang Lebong Hot Spring Area, Bengkulu Province, Indonesia. This study aimed to identify subsurface geological structures—faults, volcanic features, and sedimentary layering—that may control the development of geothermal reservoirs and caprock units. Two complementary geophysical approaches were integrated: (1) Three-dimensional (3-D) inversion modeling of Bouguer gravity anomalies derived from Global Gravity Model plus (GGMplus) 2013 and corrected using SRTM2gravity at 1,937 measurement points, and (2) microtremor acquisition at 106 sites with 60-minute recording duration, processed using the Horizontal-to-Vertical Spectral Ratio (HVSR) method. The residual gravity inversion results reveal density contrasts of 2.40–3.40 g/cm3 and sediment thicknesses exceeding 80 m, interpreted as potential geothermal reservoir units. These findings are consistent with the HVSR results, which show moderate to high amplification (A0 = 3–9) and natural frequencies of 1–10 Hz, indicating porous and fractured formations favorable for fluid storage. Overall, the integration of satellite gravity and microtremor data highlights the presence of thick sedimentary deposits and structurally controlled pathways, suggestive of promising geothermal reservoir targets in the Suban Curup area.
P. K. Putri, Ahmad Fauzi Pohan, A. M. Lubis et al.· Civil and Environmental Engi...· 0 citations
Geospatial techniques have emerged as effective tools that contribute substantially to the assessment of terrain characteristics for the sustainable development and management of watershed resources. This study highlights the rapid and cost-effective application of RS-GIS to assess the terrain of the Upper North Koel Watershed, which encompasses the Latehar and Gumla districts of Jharkhand, with the aim of optimising resource management and supporting sustainable livelihoods within the basin. The river originates in the forested hill tracts of Latehar district, flows northwards through Betla National Park, and joins the Son River, thereby contributing to the region’s biodiversity. In this study, various terrain parameters were generated in QGIS v. 3.40.6 using Landsat 8 satellite imagery (date of acquisition: 25th November, 2025) and SRTM data at a spatial resolution of 30 m. Additional sources included Survey of India toposheets Nos. 73 A/2, 73 A/3, 73A/6 and 73 A/8 at a scale of 1:50,000, FAO data, and Bhukosh. The study area comprises 1,278 sq. km of highly dissected terrain within the Chotanagpur Plateau and is dominated by crystalline rocks. The pediment–pediplain complex (60%), Ferric Luvisols and Lithosols, dendritic to sub-dendritic and rectangular drainage patterns, and varied slopes suggest moderate structural control and susceptibility to surface runoff and erosion. Hydrological indices indicate moderate forest cover in the central portion, with patches of agricultural land in the south (NDVI: 0.09 to 0.41), moderate vegetation moisture (NDMI: -0.1450 to 0.2613), approximately 40% built-up development concentrated in the southern portion, and sparse water bodies (NDWI: -0.41 to 0.10). These results underline the watershed’s vulnerability to moisture loss, runoff, and erosion, emphasising the need for basin-level intervention. Agricultural development, which is largely confined to the southern region of the watershed, underscores the need to manage and prioritise groundwater resources. The study demonstrates that RS-GIS-based terrain characterisation can be applied to similar hard-rock regions.
Mable Martha Toppo, S. Ray, Neetu Kumari· International Journal of Env...· 0 citations
3D geological models provide digital representations of subsurface architecture and are increasingly applied in both academic research and industry. Their construction can follow implicit or explicit approaches, depending on data availability and final modelling applications. While 3D models based on subsurface data are traditionally employed in several fields of study, models derived from outcrop data are increasingly being developed. In this study, newly acquired geological mapping data from the Pasubio Massif (Southern Alps, northern Italy), covering an area of ~36 km² within the geographic extent of the CARG sheet 081 “Rovereto”, were used to develop and test an iterative explicit workflow for 3D geological modelling using Move software. The workflow is based on the construction of a structured grid of geological cross-sections, followed by the interpolation of stratigraphic horizons and fault surfaces through Ordinary Kriging. Field observations indicate that the lithostratigraphic units cropping out in the study area form a gently NW-dipping monoclinal structure, exhibit overall constant thicknesses and are affected by the Schio-Vicenza fault system. Model validation first involved a qualitative comparison between mapped geological boundaries and faults with those obtained from the intersection of the modelled surfaces with the topography (DEM), followed by thickness maps evaluation as an internal consistency check. Where inconsistencies emerged, cross-sections were refined and the model was iteratively updated until geological geometries and thickness trends became consistent with field-mapped evidence. A final quantitative assessment was then performed by analysing thickness deviations from mean unit thicknesses and by measuring the spatial overlap between mapped and model-interpolated geological boundaries and fault traces. Comparison between the preliminary and validated models, supported by thickness deviation statistics, indicates that most residual discrepancies are constrained within ±10–20% of expected thickness values. The results highlight the critical role of iterative validation in ensuring geologically robust 3D models, emphasising common sources of uncertainty in explicit geomodelling workflows. This study provides a methodological framework for producing reliable 3D geological models in data-poor regions, complementing the recently published ISPRA guidelines for the organisation and standardisation of model datasets and supporting future applications in academic research and regional or national geological surveys.
Niccolò Coccia, F. Carboni, M. Marini et al.· Italian Journal of Geoscienc...· 0 citations
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