Geological Survey Research Articles

Mapping Lithology with Hybrid Attention Mechanism–Long Short-Term Memory: A Hybrid Neural Network Approach Using Remote Sensing and Geophysical Data

Remote sensing provides an efficient roadmap in geological analysis and interpretation. However, some challenges arise when remote sensing techniques are integrated with machine learning in geological surveys. Factors including irregular spatial distribution, sample imbalance, interclass resemblances, regolith, and geochemical similarities impede geological feature diagnosis, interpretation, and identification across varied remote sensing datasets. To address these limitations, a hybrid-attention-integrated long short-term memory (LSTM) network is employed to diagnose, interpret, and identify lithological feature representations in a remote sensing-based geological analysis using multisource data fusion. The experimental design integrates varied datasets including Sentinel-2A, Landsat-9, ASTER, ALOS PALSAR DEM, and Bouguer anomaly gravity data. The proposed model incorporates a hybrid attention mechanism (HAM) comprising channel and spatial attention submodules. HAM utilizes an adaptive technique that merges global-average-pooled features with max-pooled features, enhancing the model’s accuracy in identifying lithological units. Additionally, a channel separation operation is employed to allot refined channel features into clusters based on channel attention maps along the channel dimension. The comprehensive analysis of results from comparative extensive experiments demonstrates HAM-LSTM’s state-of-the-art performance, outperforming existing attention modules and attention-based models (ViT, SE-LSTM, and CBAM-LSTM). Comparing HAM-LSTM to baseline LSTM, the HAM module’s integrated configurations equip the proposed model to better diagnose and identify lithological units, thereby increasing the accuracy by 3.69%.

A Rapid Evaluation Method of Permafrost Bearing Capacity in the Tibetan Plateau Region Based on the Correlation Between CPT-CBR

Permafrost, as a soil type under unique environmental conditions, has bearing characteristics that are highly susceptible to thermo-hydraulic environments. Rapid evaluation of the bearing characteristics of in situ permafrost at various depths in perennially frozen regions is a critical scientific issue urgently needing resolution in the road design and construction sectors in China. To address this, this study investigates the correlation between CPT parameters and laboratory mechanical indices under the combined effects of multiple factors in frozen sandy soils. By conducting both CPT and CBR tests on frozen sandy soils, the study analyzes the trends in changes in cone tip resistance (qc) and CBR values under the influence of temperature (T), moisture content (ω), and compaction degree (K) and establishes a functional relationship between them. Based on the standard requirements for indoor CBR, an evaluation criterion using qc for assessing the bearing capacity of frozen sandy soil is proposed. The results indicate that both CBR values and qc increase initially and then stabilize as K increases. With decreasing temperature, both indices stabilize after an initial increase, with turning points at −3.1 °C for CBR values and −2.5 °C for qc. As ω increases, both indices first increase and then stabilize, with a turning point at 40%ω. There is a robust linear relationship between the CBR values and qc, with the ratio of predicted CBR values to actual values showing a histogram and log-normal distribution accounting for 81% and 51.3%, respectively, within a 20% accuracy level, indicating good predictive performance. Referring to the highway subgrade specifications for indoor CBR, a standard for evaluating the bearing capacity of frozen sandy soils using CPT technology is proposed. This study provides new insights for geological surveys in perennially frozen regions and a theoretical basis for the application of CPT technology in evaluating the bearing capacity of permafrost.

The integrate geomorphological, morphotectonics investigations using remote sensing data from space as the basis for the efficiency increasing of geological works

The underestimation of the integrated application of geomorphological, morphotectonic information and materials of space remote data during a geological research, the geological survey and predictive-prospecting work significantly reduces their effectiveness. The imperfection of the geomorphological researches methodology focused on the study of territories relief as a collection of surfaces of geological bodies is one of the possible reasons for this. Perspectives opens the transition to the research of landforms and geological structures, bodies in their unity, as three-dimensional, volumetric objects. Fundamentally new opportunities for studying the geology of the seas and oceans bottom are associated, in particular, with the visualization of digital 3D relief models created on the basis of the global bathymetric database GEBCO 2014 (http ://Ocean3dproects...), regional echo-depth-sounder metering’s maps, altimetry materials and remote sensing of the Earth from space. The topicality of such investigations is also due to the fact determined that plate tectonics cannot explain many features of the structure of the Earth and individual regions relief. A number of examples show that modern geomorphology combined with methods of remote sensing from space and computerization should be considered as one of the necessary disciplines for geological mapping and work aimed at solving various geological problems. The further common development of the planet relief sciences (geomorphology + morphotectonics) determines the need to train geomorphologists at both geographical and geological faculties of universities.

Methods for the Construction and Editing of an Efficient Control Network for the Photogrammetric Processing of Massive Planetary Remote Sensing Images

Planetary photogrammetry remains an important technical means of producing high-precision planetary maps. High-quality control networks are fundamental to successful bundle adjustment. However, current software tools used by the planetary mapping community to construct and edit control networks exhibit very low efficiency. Moreover, redundant and invalid control points in the control network can further increase the time required for the bundle adjustment process. Due to a lack of targeted algorithm optimization, existing software tools and methods are unable to meet the photogrammetric processing requirements of massive planetary remote sensing images. To address these issues, we first proposed an efficient control network construction framework based on approximate orthoimage matching and hash quick search. Next, to effectively reduce the redundant control points in the control network and decrease the computation time required for bundle adjustment, we then proposed a control network-thinning algorithm based on a K-D tree fast search. Finally, we developed an automatic detection method based on ray tracing for identifying invalid control points in the control network. To validate the proposed methods, we conducted photogrammetric processing experiments using both the Lunar Reconnaissance Orbiter (LRO) narrow-angle camera (NAC) images and the Origins Spectral Interpretation Resource Identification Security Regolith Explorer (OSIRIS-REx) PolyCam images; we then compared the results with those derived from the famous open-source planetary photogrammetric software, the United States Geological Survey (USGS) Integrated Software for Imagers and Spectrometers (ISIS) version 8.0.0. The experimental results demonstrate that the proposed methods significantly improve the efficiency and quality of constructing control networks for large-scale planetary images. For thousands of planetary images, we were able to speed up the generation and editing of the control network by more than two orders of magnitude.

Seismic Site Characterization and Region-Specific Seismic Site Parameter Relationships of Essex County, Ontario, Canada

Abstract We perform a multimethod in situ seismic field campaign to assess variability in local site conditions throughout Essex County, Ontario, Canada. Fundamental peak frequencies (f0HV) determined at 86 sites from microtremor horizontal-to-vertical spectral ratios (MHVSRs) increase southward from Windsor (∼1.7 Hz) to Amherstburg (>4 Hz) and eastward within Amherstburg (up to 17 Hz). We determine similar VS for individual subsurface layers at the 11 array sites from constrained shear wave velocity (VS) depth (z) profiles obtained by joint inversion of the site’s fundamental-mode Rayleigh-wave dispersion curve and f0HV. This indicates that the spatial variation in f0HV is driven primarily by the resonator depth, which shallows southward. We compile our 11 noninvasive VS depth profiles with an additional 86 VS profiles from previous invasive field testing, to develop a VS–depth relationship for Essex County’s postglacial sediments. Use of most other VS–z relationships available in eastern Canada underpredict the fundamental site frequency in Essex County because the average VS typical of those regions is lower. We find that the velocities for Montreal and Charlevoix (Canada) are closest to the velocities of our study area and consistent with Holocene alluvium deposits in the U.S. Geological Survey national crustal model. Compilation of in situ measurements at 172 sites throughout Essex County enables determination of three region-specific predictive relationships of important seismic site characterization metrics that are applied to generate regional seismic microzonation maps.

Geological Survey of Brazil Spectral Library v. 1.0: Rock reflectance signatures in the visible to shortwave infrared range

Reflectance spectral libraries are essential reference databases for the mineralogical characterization of geological samples analyzed using visible and infrared spectroscopy. Since 2011, the Geological Survey of Brazil has been actively developing a comprehensive database of reflectance spectral signatures, based on samples collected from systematic geological mapping and mineral resource projects across the Brazilian territory. This spectral library is now available on a digital platform hosted by the Geological Survey of Brazil's geoscientific database, providing quantitative data for the numerical characterization of lithological types and their alteration products, whether due to weathering or hydrothermal processes.

Geological remote sensing interpretation via a local-to-global sensitive feature fusion network

Interpreting surface geological elements (such as rocks, minerals, soils, and water bodies) is the main task of geological survey, which plays a crucial role in geological environment remote sensing (GERS). However, the characteristics of geological elements, including high variabilities, various morphology, complicated boundaries and imbalanced class distribution, make it still a challenge for deep learning methods to interpret GERS images. Considering the correlations of geological elements as the regionalized variables in geostatistics, the sensitive features of GERS interpretation mainly include three aspects: tonal, textural and structural characteristics within a singular-class elements, spatial and spectral correlations of adjacent elements, and their global tectonic or spatial distribution. Thus, to simulate the manual interpretation process of geologists from local to global and promote GERS interpretation performance, we propose a local-to-global multi-scale feature fusion network (LGMSFNet). A geological object context represents the intra-class semantic dependencies of pixel sets with the same class. And a local feature aggregation module models the channel and spatial association. Then discriminative features are integrated by a global feature fusion module. For the model optimization, we focus on hard examples during the training process to achieve the balanced optimization of various categories. Two research areas that include large-scale rocks, soils and water exposed on the surface are selected. Massive experiments demonstrate the superiority of the LGMSFNet in GERS interpretation.

Data Visualisation To Understand How Data Is Structured Using K-Means And Hierarchical Cluster Analyses With Interactive Graphics

This study examines the structure of geothermal geochemisty data in India using k-means and hierarchical cluster analyses. The first attempt to list hot springs in India was made by Schlagintweit in 1852. The Geological Survey of India published a special publication titled 'Geothermal Atlas of India', and the government of India constituted a 'Hot Spring Committee' to examine the possibility of developing geothermal plants for power generation and other uses. In the Puga valley and Parvati projects, it is estimated that it is possible to harness 5000 MWh of geothermal energy from Puga valley, sufficient to sustain a 20 MWe power plant. The GSI, the repository of most information concerning geological and related data in the country, included an R&D item No. 7/WB-5 for the development of a computerised system of geothermal database system referred to as GTHERMIS in its field season 1993-94 program. The computational strategy involves assigning each data point to the cluster with the nearest center (or "centroid"), recalculating the centroids after each assignment, and repeating the procedure until the clusters are no longer statistically different. The k-means method, developed by MacQueen (1967), is one of the most widely used non-hierarchical methods, particularly suitable for large amounts of data. The data is scaled before cluster analysis, and the results are visualized using interactive graphics.

Rock coast geo model: process-response dynamics, resilience and vulnerability

Geology and geomorphology link starkly in coastal environments, exemplifying the importance of Fookes' geo model approach to understanding site dynamics. Cliffs, and the shore platforms that front them, are subject to both marine and subaerial processes. Throughout his work, Fookes emphasises the role of climate as a weathering agent, influencing material properties and requiring consideration in engineering projects. Comparatively, more is known about the operation of rock weathering processes on shore platforms than on cliffs. Yet, with changing climate, it is becoming apparent that winter salt and frost weathering, and summer salt and wetting-drying weathering contribute to more frequent occurrences of coastal rockfalls. Increasing storm activity and rising sea levels are enhancing marine and subaerial processes. Rock coasts are amongst the most rapidly eroding coastlines in Europe. New applications of technologies, including seismometers, Lidar and InSAR, provide a fuller understanding of rock coast process-response geo model behaviour and the resilience of rock coasts on engineering timescales. Communicating scientific understanding of rock coast dynamics to policy-makers, planners and the public remains a challenge. Assessments of hazard, risk, resilience and vulnerability of rock coasts associated with climate change provide useful communication tools. Databases such as the British Geological Survey GeoCoast geohazard data product, and EMODnet Geology (European Marine Observation and Data Network) coastal behaviour data products integrate and visualise available data and information to communicate situational awareness to a broad audience.

Analysis of Limestone Characteristics on the South Coast of Gorontalo Based on Specific Gravity and Water Absorption Tests

The southern coast of Gorontalo has complex geological conditions. This is indicated by the strong tectonic influence with the uplift of the Quaternary limestone at high elevations. The distribution of this limestone is very unique because it is located between the dominance of volcanic and plutonic rocks that form the northern arm of Sulawesi. The purpose of this study was to focus on the characteristics of limestone on the south coast of Gorontalo based on specific gravity and water absorption tests. The research methods used to achieve these objectives consist of field geological surveys and laboratory analysis of the specific gravity and water absorption tests of coarse aggregate. The field geological survey consisted of taking limestone samples for laboratory analysis and petrological analysis. The results showed that the limestone on the southern coast of Gorontalo is dominated by the coralline floatstone facies. Characteristics of the coralline floatstone facies based on laboratory analysis showed an average specific gravity of 1.74 and an apparent specific gravity of 2.04. While the average percentage of limestone water absorption is 8.41%.

Comparison of Line-Focused and Point-Focused Raman Mineral Analysis in Planetary Exploration

Raman spectroscopy plays a critical role in planetary exploration by providing detailed analysis of mineralogical and chemical compositions. However, the conventional point-focused Raman systems, while precise, are limited by their time-consuming nature, which hampers efficiency in space missions. This study compares a line-focused Raman spectroscopy system equipped with a cylindrical mirror array to a traditional point-focused system by testing various lunar-analogue minerals. The results demonstrate that the line-focused mode significantly reduces mineral detection time while covering larger sample surface areas, albeit with a slightly higher detection limit compared to the point-focused mode. Both modes exhibit similar capabilities in mineral identification and compositional analysis, with the line-focused system offering a more practical solution for rapid, high-throughput analysis in large-scale planetary geological surveys. These findings suggest that the line-focused Raman system could be a valuable tool in accelerating geochemical data collection during future deep space exploration missions.

In Search of the Lost Link: The Fascinating Platinum Host Rock of Chocó, Colombia

In Colombia, after nearly 500 years of the quest for the platinum source rock, a remarkable discovery of a fossiliferous limestone with gold and platinum now resides under the watch of the Geological Survey’s Museum in Medellín, registered as RS 2.2.1.1.3. Platinum group minerals, long sought after in Colombia’s placer deposits since the 19th century, typically found in the form of nuggets, have received special attention due to the missing link that exists between authigenesis in mafic/ultramafic rocks to detrital alluvium associations. Consequently, this finding unveils an entirely new environment hosting platinum. In this article, we delve into the historical context and the heritage value of a sample boasting ∼\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\sim $$\\end{document} 200-300 g/ton of platinum and ∼\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\sim $$\\end{document}30 g/ton of gold found by atomic absorption spectroscopy, embedded in a dolomitized biosparite. Various analyses, encompassing X-ray diffraction, micropetrographic characterization, and scanning electron microscopy coupled with energy-dispersive spectroscopy, were performed on the sample. The sample baffled experts due to its unassuming sedimentary rock appearance and the unusual circumstances of its arrival at the museum. Hence, it stands as one of those uncommon scientific curiosities with an unforeseen origin, accessible only through a stroke of chance and an unbiased perspective regarding its origin. Beyond its historical and geological significance, this specimen, safeguarded within the museum’s collection, encourages education and awareness regarding geosites, advocating for the preservation of one of the planet’s most biologically diverse regions, where platinum was first discovered.

Gradual Failure of a Rainfall-Induced Creep-Type Landslide and an Application of Improved Integrated Monitoring System: A Case Study.

Landslides cause severe damage to life and property with a wide-ranging impact. Infiltration of rainfall is one of the significant factors leading to landslides. This paper reports on a phase creep landslide caused by long-term rainfall infiltration. A detailed geological survey of the landslide was conducted, and the deformation development pattern and mechanism of the landslide were analyzed in conjunction with climatic characteristics. Furthermore, reinforcement measures specific to the landslide area were proposed. To monitor the stability of the reinforced slope, a Beidou intelligent monitoring and warning system suitable for remote mountainous areas was developed. The system utilizes LoRa Internet of Things (IoT) technology to connect various monitoring components, integrating surface displacement, deep deformation, structural internal forces, and rainfall monitoring devices into a local IoT network. A data processing unit was established on site to achieve preliminary processing and automatic handling of monitoring data. The monitoring results indicate that the reinforced slope has generally stabilized, and the improved intelligent monitoring system has been able to continuously and accurately reflect the real-time working conditions of the slope. Over the two-year monitoring period, 13 early warnings were issued, with more than 90% of the warnings accurately corresponding to actual conditions, significantly improving the accuracy of early warnings. The research findings provide valuable experience and reference for the monitoring and warning of high slopes in mountainous areas.

The geological maps of Italy at the Natural History Museum of Milan

The Library of the Museum of Natural History and Aquarium of Milan possesses approximately 3,200 geographical, topographical, and geological maps. In the present catalog, 630 geological maps related to the Italian territory, with particular regard to Lombardy, published since the late 18th century, are listed. Most of these belong to the series published by the Geological Survey of Italy; a considerable number also comes from monographic works or periodicals. [...]

Source-Scaling Comparison and Validation for Ridgecrest, California: Radiated Energy, Apparent Stress, and Mw Using the Coda Calibration Tool (2.6<Mw<7.1)

ABSTRACT The determination of accurate apparent stress, radiated energy, corner frequency, and their scaling with magnitude remains one of the most difficult seismological endeavors because of complicated 3D Earth structure, complex rupture, and limited broadband recordings. This study focuses on a comparison of four separate state-of-the-art methods that aim to compare and contrast common events using the well-recorded 2019 Ridgecrest, California, sequence, which was motivated in large part by the U.S. Geological Survey (USGS)/Southern California Earthquake Center (SCEC) Community Stress-Drop Validation Study group (Baltay et al., 2024). For this study, we calibrated the Ridgecrest and surrounding region using the Coda Calibration Tool (CCT) and compared them against recent generalized inversion technique (GIT) results of Bindi et al. (2021) (2.6<Mw<7.1) and two other state-of-the-art methods for moderate-sized events in the sequence (3.5<Mw<5.5). We find excellent agreement between the GIT and coda-derived results over a broad range of magnitudes, and for moderate-size events, we find equally good agreement with source estimates from finite-fault inversion method based on Dreger (1997) and a direct S-wave spectral method by Ji et al. (2024). As found in a recent comparative study in central Italy by Morasca et al. (2022) (3.5<Mw<6.3), we find that CCT and GIT results are in excellent agreement for events ranging between 2.6<Mw<7.1, and relative, weak-motion site terms are also in agreement. Although both approaches observe a modest increase in apparent stress with depth, the overall trend in apparent stress increasing with magnitude is supported by our findings. Finally, upon comparison with other regions, we find that the absolute apparent stress values from Ridgecrest are comparable to central Italy but significantly lower than both eastern Canada and the United Kingdom.

Chapter 1. Introduction to the Albertine Rift

Continental rifting is a fundamental geological process that has been responsible for breaking supercontinents apart and opening new ocean basins throughout Earth's history and the East African Rift System (EARS) is the best active example of this happening in the world today. The Albertine Rift lies at the northern end of the Western Arm of the EARS, consisting primarily of the Lake Albert and Lake Edward basins as they pass along the border between Uganda and the Democratic Republic of Congo. This Memoir describes the key geomorphological features found in the Albertine Rift Valley at the present day, identifying the sedimentary dynamic elements that dovetail together to characterise the dominant depositional environments in these early continental rift basins. These are then used to interpret the Pliocene - Holocene sedimentary sequences, documented during geological field surveys over an eight year period, exposed around the onshore parts of the Lake Albert and Lake Edward rift valleys. Ultimately, the sedimentary dynamics of the Albertine Rift and the stacking of its three-dimensional stratigraphic architecture, is shown to beat to the rhythm of oscillating global glacial - interglacial climatic cyclicity and how this affects the Equatorial Tropics of Africa.

A 30 Arcsec Resolution VS30 Map for Mainland China Using Refined Topographic Slope-Based Cokriging (SCK) Model

ABSTRACT In 2022, we proposed a VS30 proxy model based on the Cokriging method, integrating local VS30 measurements with topographic slope data (SCK model, Zhou et al., 2022). Utilizing this model, a VS30 map for mainland China was developed based on 7797 local boreholes. However, the initial VS30 map was produced with a coarse grid resolution of 360 arcsec and did not comprehensively cover mainland China due to sparse distribution of boreholes in certain areas. In this study, we refined the SCK model by explicitly accounting for the influence of surrounding topographic slopes, incorporating more distant VS30 measurements, and improving the spatial distribution of VS30 measurements used in the model calculation. Tests based on virtual cases were conducted to evaluate the characteristics of the refined SCK model. In addition, 142 VS30 measurements from strong-motion stations in western China were added to enhance spatial coverage and model accuracy in these regions. Employing the refined SCK model and the expanded VS30 data set, a new VS30 map for mainland China was generated. This updated map features a higher grid resolution of 30 arcsec and covers the entirety of mainland China, showing reduced estimation errors and improved continuity. Comparisons with the U.S. Geological Survey Global VS30 Mosaic indicate that the results from the refined SCK model are more reasonable, as evidenced by local topography, VS profiles, lithologic profiles, and geology map, which better capture the impact of local geomorphological differences and climatic conditions on VS30 values.

D-InSAR-Based Analysis of Slip Distribution and Coulomb Stress Implications from the 2024 Mw 7.01 Wushi Earthquake

On 23 January 2024, an Mw 7.01 earthquake struck the Wushi County, Xinjiang Uygur Autonomous Region, China. The occurrence of this earthquake provides an opportunity to gain a deeper understanding of the rupture behavior and tectonic activity of the fault system in the Tianshan seismic belt. The coseismic deformation field of the Wushi earthquake was derived from Sentinel-1A ascending and descending track data using Differential Interferometric Synthetic Aperture Radar (D-InSAR) technology. The findings reveal a maximum line-of-sight (LOS) displacement of 81.1 cm in the uplift direction and 16 cm in subsidence. Source parameters were determined using an elastic half-space dislocation model. The slip distribution on the fault plane for the Mw 7.01 Wushi earthquake was further refined through a coseismic slip model, and Coulomb stress changes on nearby faults were calculated to evaluate seismic hazards in surrounding areas. Results indicate that the coseismic rupture in the Mw 7.01 Wushi earthquake sequence was mainly characterized by left-lateral strike-slip motion. The peak fault slip was 3.2 m, with a strike of 228.34° and a dip of 61.80°, concentrated primarily at depths between 5 and 25 km. The focal depth is 13 km. This is consistent with findings reported by organizations like the United States Geological Survey (USGS). The fault rupture extended to the surface, consistent with field investigations by the Xinjiang Uygur Autonomous Region Earthquake Bureau. Coulomb stress results suggest that several fault zones, including the Kuokesale, Dashixia, Piqiang North, Karaitike, southeastern sections of the Wensu, northwestern sections of the Tuoergan, and the Maidan-Sayram Fault Zone, are within regions of stress loading. These areas show an increased risk of future seismic activity and warrant close monitoring.

On Algorithmically Determined Versus Traditional Macroseismic Intensity Assignments

Abstract The utility of macroseismic data, defined as the effects of earthquakes on humans and the built environment, has been increasingly recognized following the advent of online systems that now produce unprecedented volumes of macroseismic intensity information. Contributed reports from the U.S. Geological Survey “Did You Feel It?” (DYFI) system (Wald et al., 1999) are used to generate intensity values with an algorithm based on seminal work by Dengler and Dewey (1998). The algorithm was developed initially to reproduce intensity values assigned by expert opinion using questionnaire results collected by telephone survey. In this article, I discuss reasons why intensity values from (self-selected) DYFI responses can differ from values that would be assigned by expert opinion given more complete data from randomly selected participants. For example, with the data used by Dengler and Dewey (1998), intensities near 4 could be determined from the percentage of people who felt shaking in each town. With less spatially rich data from self-selected participants, this percentage often cannot be determined reliably. Audible noises are key additional diagnostic criteria for modified Mercalli intensity (MMI) 4, but, although the DYFI system includes a question about noise, following Dengler and Dewey (1998), the DYFI algorithm does not include a noise indicator. At the upper end of the scale, as defined the DYFI algorithm yields a maximum intensity value of 9.05, nominally corresponding to peak ground acceleration of 75%g. These and other factors can result in DYFI values that are low compared to traditional MMI values assigned using expert opinion, even absent factors that can bias traditional MMI assignments. Modern ground-motion intensity conversion equations determined using DYFI intensities are expected to be appropriate for DYFI intensities, but the results of this study suggest that biases may be introduced if DYFI and traditional intensities are assumed to be interchangeable.

The effect of earthquake fault rupture kinematics on tsunami generation: a numerical study of real events

Summary The study is devoted to the effect of the fault rupture kinematics in the earthquake source on tsunami generation. Sixteen events of 1992–2021 years are investigated. For each event, the kinematic tsunami source (bottom motion during the earthquake) and the static tsunami source (permanent bottom deformation) were calculated using the Finite Fault Models provided by the U.S. Geological Survey. For both sources, numerical tsunami simulations were carried out within the framework of linear long-wave theory. Comparison of the simulation results showed that in ten out of sixteen events, the energy of tsunami excited by the kinematic source is greater than that excited by the static source. The maximum energy amplification (9.1 per cent) is observed at the minimum ratio of average rupture velocity to long-wave velocity. The Illapel 2015 event has been investigated more thoroughly using dispersive tsunami models jagurs and cptm. This investigation showed that the kinematic source causes a spatial redistribution of tsunami amplitudes and a noticeable amplification of the high-frequency component in the time series of tsunami height. At some points along the Chilean coast, the difference between the kinematic and static calculations is more than 2 m.