Journal of Seismology最新文献

{"title":"H/V spectral ratio estimation using ensemble machine learning models: a case study from Türkiye","authors":"Ahmet Özdil,&nbsp;Hasan Erbay,&nbsp;Mohammadreza Najaftomaraei","doi":"10.1007/s10950-026-10433-0","DOIUrl":"10.1007/s10950-026-10433-0","url":null,"abstract":"<div><p>Local site effects represent a major source of ground-motion variability; however, the direct prediction of horizontal-to-vertical (H/V) spectral ratios remains relatively underexplored in seismic hazard modeling. This study introduces a data-driven framework for estimating period-dependent PSA-based H/V ratios using a multivariate ensemble of machine learning models. A comprehensive dataset comprising 38,504 strong-motion records from the Türkiye Strong-Motion Database (1976–2023) was utilized to capture the influence of seismic source (moment magnitude, Mw), propagation path (hypocentral distance, Rₕᵧₚ, and focal depth), and site conditions (Vs₃₀ and station elevation) across 946 stations. Three regression algorithms Gaussian Process Regression (GPR), Gradient Boosted Regression Trees (GBRT), and Random Forest (RF) were combined within an ensemble framework, with optimal period-dependent weights determined using a Genetic Algorithm (GA). The optimized ensemble achieved a mean root mean square error (RMSE) of 0.68 over the spectral period range of 0.01–4 s, corresponding to a 5.6% reduction in prediction error relative to the best-performing standalone model (RF) and an improvement of approximately 20% compared to the GPR baseline. In addition to its quantitative performance, the model demonstrates consistency with established seismological principles, effectively capturing low-frequency resonance behavior in soft-soil conditions and flatter spectral responses in stiff-rock environments. These findings highlight the potential of optimized machine learning ensembles as a reliable and scalable alternative for site-effect characterization, particularly in regions where detailed subsurface information is limited.</p></div>","PeriodicalId":16994,"journal":{"name":"Journal of Seismology","volume":"30 4","pages":""},"PeriodicalIF":1.3,"publicationDate":"2026-08-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148750659","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Seismograms and instrument-response functions for stations of the Lamont-IGY long-period seismograph network, 1957–1962","authors":"Göran Ekström,&nbsp;Jocely Lopez Luna","doi":"10.1007/s10950-026-10429-w","DOIUrl":"10.1007/s10950-026-10429-w","url":null,"abstract":"<div><p>Starting in the early 1950s, Lamont Geological Observatory of Columbia University operated long-period seismographs at multiple locations around the world. At the time of the 1957–1958 International Geophysical Year (IGY), seventeen stations were operating. The seismographs were of a similar design to that later adopted for the World Wide Standardized Seismograph Network (WWSSN), and the Lamont-IGY network can be considered an experimental prelude to that network. Most of the original seismograms from the Lamont-IGY network have been located in storage. Here we describe the network, the instrumentation, and seismogram availability. The heterogeneous instrument responses that are characteristic of the early years of the Lamont-IGY network pose a challenge for modern quantitative waveform analysis. We use detailed calibration data collected in 1962 to estimate instrument parameters at thirteen of the stations. The new instrument transfer functions are converted to a modern poles-zeros description of the seismograph response.</p></div>","PeriodicalId":16994,"journal":{"name":"Journal of Seismology","volume":"30 4","pages":""},"PeriodicalIF":1.3,"publicationDate":"2026-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148750900","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"FW-ANSI2D: A Python package for seismic ambient noise cross-correlation modelling and source inversion","authors":"Arjun Datta,&nbsp;Aileni Mahesh,&nbsp;Pankaj Lahon","doi":"10.1007/s10950-026-10421-4","DOIUrl":"10.1007/s10950-026-10421-4","url":null,"abstract":"<div><p>We present FW-ANSI2D, an open-source package for full waveform forward and inverse modelling of seismic ambient noise cross-correlations in two dimensions. It belongs to the so-called ‘interferometry without Green’s function retrieval’ class of methods, wherein noise cross-correlations are modelled numerically, for arbitrary spatio-spectral distributions of noise source power spectral density (PSD). A multifrequency inversion for the source PSD is achieved via a nonlinear finite-frequency waveform inversion technique, implemented under the assumption of a fixed Earth structure model. FW-ANSI2D seamlessly integrates with other open-source Python packages for seismic wave propagation modelling, most notably a C-based numerical solver for acoustic modelling in 2-D media. Whilst the package is currently limited to the acoustic modelling regime and flat geometries (Earth’s sphericity is unaccounted for), it is a powerful tool for ambient noise analysis at local scales. It exhibits certain advantages over other waveform inversion techniques for ambient noise sources, such as an enhanced ability to resolve sources outside the receiver network, and a relatively high tolerance for velocity model inaccuracies. Moreover, it is amenable to Hessian-based optimization, which ensures speedy convergence (<span>(approx 10)</span> iterations) of the nonlinear inverse problem, compared to purely gradient-based methods. We introduce the package in detail, describing both the serial and parallel versions of the code, and present synthetic tests designed to assess the efficacy of the inversion technique in realistic field scenarios. These tests show that reasonably good inversions are achievable even with relatively sparse receiver networks, and with sources lying outside the modelling domain.</p></div>","PeriodicalId":16994,"journal":{"name":"Journal of Seismology","volume":"30 4","pages":""},"PeriodicalIF":1.3,"publicationDate":"2026-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148613931","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Non-double-couple components of intraplate earthquakes","authors":"Boris Rösler","doi":"10.1007/s10950-026-10425-0","DOIUrl":"10.1007/s10950-026-10425-0","url":null,"abstract":"<div><p>Many earthquakes in global moment tensor catalogs contain non-double-couple (NDC) components, but it is often unclear whether they reflect source complexity or artifacts of the inversion. Global moment tensor catalogs constrain the isotropic component during the inversion and thus report deviatoric solutions. Therefore, this study analyzes the reported compensated linear vector dipole (CLVD) components in global catalogs. I test whether intraplate earthquakes with centroid depths of 60 km or less have larger NDC components than other earthquakes using the Global Centroid Moment Tensor (GCMT) catalog and the CMT3D catalog. In the GCMT catalog, 663 intraplate earthquakes have a mean <span>(|2varepsilon |)</span> of 26.35%, higher than the mean of the entire GCMT catalog, 23.51%, and higher than the mean of 54658 non-intraplate earthquakes, 23.49%. The difference between intraplate and non-intraplate earthquakes is 2.86 percentage points and is statistically significant (<span>(p=2.0times 10^{-4})</span>). The difference remains when continental and oceanic domains are analyzed separately, when different depth and distance thresholds are used, after excluding earthquakes near active volcanoes, and after accounting for differences in magnitude, centroid depth, mechanism, and geologic environment. Comparing the distributions of NDC components, I find that the difference in mean NDC components is not caused by a few events with very large NDC components, but reflects a broader shift toward larger <span>(|2varepsilon |)</span>. Earthquakes that appear in both the GCMT and CMT3D catalogs also show larger NDC components for intraplate events than for non-intraplate events, indicating that the difference is not specific to one catalog. The effect is small in absolute magnitude, but it is detected repeatedly when intraplate earthquakes are compared with non-intraplate earthquakes in global moment tensor catalogs. It is therefore consistent with greater source complexity of intraplate earthquakes, possibly due to rupture on immature or unfavorably oriented faults and to heterogeneous stress fields. However, the difference may also include artifacts of the moment tensor inversion caused by Earth-model uncertainty in intraplate regions. These results show that moment tensor inversions of intraplate earthquakes are expected to yield larger NDC components, which may reflect greater source complexity, inversion-related artifacts, or both.</p></div>","PeriodicalId":16994,"journal":{"name":"Journal of Seismology","volume":"30 4","pages":""},"PeriodicalIF":1.3,"publicationDate":"2026-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148613932","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Engineering characteristics of the strong ground motions from the 2023 Kahramanmaraş earthquake sequence in Türkiye","authors":"Yinfeng Dong,&nbsp;Fuchao Cao,&nbsp;Yiping Wang,&nbsp;Yiming Xie","doi":"10.1007/s10950-026-10424-1","DOIUrl":"10.1007/s10950-026-10424-1","url":null,"abstract":"<div><p>On February 6, 2023, consecutive M7.8 and M7.5 earthquakes struck southeastern Türkiye, which caused extensive damage to the local buildings and huge casualties. Some unique engineering characteristics of strong motion were observed during the processing of strong ground motion records. These characteristics provide suggestions for the seismic design of structures in the future. The paper analyzes the engineering characteristics of strong ground motion obtained in these earthquakes. This study systematically reveals the spectral acceleration amplification effect of damaged faults in the earthquake sequence, elucidates the impact characteristics of supershear ground motions, explicitly identifies the significant amplification feature of response spectrum values caused by acceleration pulses associated with the forward directivity of subshear ruptures, and simultaneously uncovers the nonlinear characteristics and liquefaction evolution of typical sites. Systematic comparisons reveal that supershear ruptures exhibit characteristics such as broad spectral width, slow attenuation, and significant low-frequency components in the far field.</p></div>","PeriodicalId":16994,"journal":{"name":"Journal of Seismology","volume":"30 4","pages":""},"PeriodicalIF":1.3,"publicationDate":"2026-07-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148613713","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Stochastic modelling of earthquake recurrence interval for North-East, India (Eastern-Himalayas) and its vicinity using Weibull, Gamma and Lognormal distribution","authors":"Timangshu Chetia,&nbsp;Santanu Baruah,&nbsp;Bijit Kumar Choudhury,&nbsp;Subhra Jyoti Baruah","doi":"10.1007/s10950-026-10419-y","DOIUrl":"10.1007/s10950-026-10419-y","url":null,"abstract":"<div><p>Northeastern India is a tectonically complex and seismically active region that has experienced several damaging earthquakes. Statistical analysis of earthquake recurrence can provide supporting insights into regional seismic behaviour.Despite its seismic significance, time-dependent statistical characterization of earthquake recurrence in this region remains limited, particularly using established renewal models applied in a comparative framework. In this study, cumulative probabilities and conditional probabilities (hazard rates) were estimated for earthquakes with magnitudes Mw &gt; 3.6, 4, 5, and 6 to examine which renewal model best describes earthquake recurrence in Northeastern India. Weibull, Gamma, and Lognormal distributions were applied to earthquake recurrence intervals. All three models provide a reasonable first-order description of recurrence behavior, with the Weibull distribution yielding a comparatively better statistical fit, followed by the Gamma distribution, while the Lognormal distribution shows weaker performance. Based on the Weibull model, characteristic recurrence intervals are estimated to be approximately 46, 58, 180, and 540 years for Mw &gt; 3.6, 4, 5, and 6 earthquakes, respectively. Over a 70-year period, the estimated conditional probabilities increase within lower and upper time bounds for each magnitude class, indicating higher likelihoods with increasing elapsed time since the last event. In conclusion, the results suggest that renewal-based statistical models, particularly the Weibull distribution, can provide a preliminary characterization of earthquake recurrence behavior in Northeastern India, though the estimates are subject to the assumptions and limitations inherent in such models. The present study is intended as a preliminary investigation. Future work incorporating physically based models (e.g., Brownian Passage Time), higher magnitude thresholds, and more rigorous treatment of dependent seismicity is required to improve the robustness and hazard relevance of time-dependent seismic assessments in the region. </p></div>","PeriodicalId":16994,"journal":{"name":"Journal of Seismology","volume":"30 4","pages":""},"PeriodicalIF":1.3,"publicationDate":"2026-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148465895","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A hazard-consistent hybrid framework for seismic site response analysis in deep alluvial soils: Application to the İzmir Basin","authors":"Şahin Çağlar Tuna,&nbsp;Selim Altun","doi":"10.1007/s10950-026-10418-z","DOIUrl":"10.1007/s10950-026-10418-z","url":null,"abstract":"<div><p>This study presents a hazard-consistent probabilistic–deterministic hybrid workflow for site-specific seismic response analysis in deep alluvial basins. The present implementation combines probabilistic hazard and input-motion characterization with deterministic site-response modeling based on reference soil shear-wave velocity (Vs) profiles and associated site parameters. The methodology integrates probabilistic seismic hazard analysis (PSHA), stochastic point-source (SMSIM) random-phase time-domain ground-motion simulation, and one-dimensional (1D) equivalent-linear and nonlinear site response modeling. Through Monte Carlo-based UHRS development, the workflow provides hazard-consistent input motions for evaluating local amplification effects under performance-based design principles. The proposed methodology is demonstrated through an application to the İzmir Basin, a seismically active region characterized by deep Quaternary alluvium. Validation against strong-motion records from the 2020 Samos Earthquake confirmed that the model reproduces observed amplification in the 0.5–1.5 s range. Subsequently, eleven spectrally matched ground motions representing the DD-2 hazard level (475-year return period) were propagated through representative soil profiles (Bayraklı, Bornova, Karşıyaka). Results indicated amplification factors up to 2.5–3.0 relative to the Turkish Building Earthquake Code (TBDY-2018), particularly at intermediate and long periods (T &gt; 1.0 s). These findings highlight the limitations of generic code spectra and demonstrate the value of a hazard-consistent hybrid workflow for site response analysis. The methodology, as demonstrated for the İzmir Basin, provides a validated and hazard-consistent basis for performance-based evaluation in deep alluvial basin conditions.</p></div>","PeriodicalId":16994,"journal":{"name":"Journal of Seismology","volume":"30 4","pages":""},"PeriodicalIF":1.3,"publicationDate":"2026-07-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148465800","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Deterministic seismic hazard assessment of Bihar, India: integrating a logic-tree framework with validation of ground motion prediction equations against regional seismicity","authors":"Rohit Singh Patel,&nbsp;Ajay Kumar Sinha","doi":"10.1007/s10950-026-10416-1","DOIUrl":"10.1007/s10950-026-10416-1","url":null,"abstract":"<div><p>This study presents a deterministic seismic hazard analysis for Bihar, a state in eastern India with rapidly growing urban infrastructure and high seismic vulnerability due to its proximity to the Himalayas. The region has already experienced catastrophic earthquakes, including the 1934 Bihar–Nepal (Mw 8.1) and the 2015 Nepal (Mw 7.8) events. To evaluate seismic risk, a seismotectonic map was prepared considering regional tectonics and rupture characteristics, defining 73 faults, 57 lineaments, and 7 shear zones within the control region. Maximum possible magnitudes were estimated and assigned to each linear source based on rupture parameters and deterministic scaling relations. Six region-specific ground motion prediction equations, applicable to Himalayan and Indo-Gangetic settings, were carefully selected, and their weights in the logic tree framework were assigned using the log-likelihood method to account for epistemic uncertainty. Seismic hazard maps for Bihar were generated at bedrock level under three scenarios with varying focal depths. The results indicate significant geographic variation in peak ground acceleration, ranging from 0.47 to 0.67 g in northern Bihar and 0.05 to 0.15 g in southern Bihar. Districts such as Sitamarhi, Madhubani, and Supaul, located near the Himalayan thrust faults, face higher seismic risk, while Purnia and Kishanganj are vulnerable due to their proximity to the Purnia–Everest lineament. These findings provide important inputs for earthquake-resistant structural design, urban planning, and seismic microzonation in Bihar.</p></div>","PeriodicalId":16994,"journal":{"name":"Journal of Seismology","volume":"30 4","pages":""},"PeriodicalIF":1.3,"publicationDate":"2026-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148465380","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Site-specific amplifications in Northwestern Türkiye: A generic approach","authors":"Gamze Muratoglu,&nbsp;Aysegul Askan,&nbsp;Alan Yong","doi":"10.1007/s10950-026-10420-5","DOIUrl":"10.1007/s10950-026-10420-5","url":null,"abstract":"<p>In this study, we derive generic site amplification functions applicable to Northwestern Türkiye and follow guidance on site classifications established by the United States National Earthquake Hazards Reduction Program (NEHRP). We employ the one-dimensional (1-D) equivalent linear ground response analysis method and focus on recordings from a select suite of free-field strong motion (SM) stations. These particular SM stations are associated with a comprehensive geotechnical site conditions dataset comprising 76 shear-wave velocity profiles. Despite their varying resolutions and depths, this diversity allows for a more representative analysis across different site conditions, enhancing the robustness of our findings. For analyses, we utilize a robust set of global ground motion records, selected from both within and outside of Türkiye, to serve as strong and weak input bedrock motions. Site amplification is determined by propagating these bedrock records through 76 site-specific <i>Afet ve Acil Durum Yönetimi Başkanlığı</i> (AFAD) station profiles and calculating the spectral acceleration ratio between the ground surface and the input motion. Our analyses reveal substantial disparities between the amplification functions derived from 1-D site response analyses using strong and weak input motions. These disparities are central to our analysis and inform the subsequent comparison with site amplification functions reported in the literature.</p><p>We compare the generic site amplification functions derived in this study with those reported in the literature for regions with similar geological and seismic conditions to Northwestern Türkiye. For example, site amplification functions for NEHRP Site Classes C and D have been documented for Greece and the United States utilizing frequency-dependent methods such as the quarter-wavelength approximation. Our findings reveal that the generic site amplification functions derived in this study exhibit differences in peak amplitudes and predominant frequencies compared to those in the literature, reflecting regional variations in geotechnical and seismic properties.</p><p>This study represents an initial effort to formulate generic site amplification functions for Türkiye, with a particular emphasis on the Northwestern region. A thorough literature review indicated no prior studies have proposed such functions specifically for this area.</p>","PeriodicalId":16994,"journal":{"name":"Journal of Seismology","volume":"30 4","pages":""},"PeriodicalIF":1.3,"publicationDate":"2026-07-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148465552","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Source depth effects on surface wave generation in 3D deep sedimentary basins","authors":"Valeria Soto-Moncada,&nbsp;Fernando Lopez-Caballero","doi":"10.1007/s10950-026-10411-6","DOIUrl":"10.1007/s10950-026-10411-6","url":null,"abstract":"<div><p>Surface wave amplification in sedimentary basins arises from a combination of geometric effects and source characteristics. However, the relative contributions of source depth, radiation pattern, and basin configuration to surface wave development remain incompletely understood. In this study, the influence of source depth and focal mechanism on surface wave development is examined through high-resolution three-dimensional numerical simulations. Surface waves are extracted from the computed ground motions using the Normalized Inner Product (NIP) method, which enables single-station identification and characterization in terms of polarization amplitude, central frequency, and azimuth. A range of basin geometries and sediment shear-wave velocities is considered. The results indicate that shallow sources with low incidence angles tend to generate stronger, lower-frequency surface waves concentrated near basin edges, while deeper sources lead to more symmetric amplification patterns. The radiation characteristics of the source influence the spatial distribution of wave energy and the orientation of motion, particularly in relation to basin boundaries. Surface responses across the basin are analyzed using a directional zoning framework, allowing for systematic comparison across models. The findings demonstrate that both the depth and orientation of the seismic source, together with the mechanical properties and geometry of the basin, significantly affect the nature and spatial variability of surface wave amplification.</p></div>","PeriodicalId":16994,"journal":{"name":"Journal of Seismology","volume":"30 4","pages":""},"PeriodicalIF":1.3,"publicationDate":"2026-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148380692","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}