Journal of Seismology最新文献

Muş region in eastern Türkiye is located within a geodynamically complex region shaped by the interaction of the Anatolian, Arabian, and Eurasian plates. Despite the presence of multiple active fault systems, integrated local-scale studies that jointly address seismicity characteristics, fault kinematics, and the crustal stress field remain limited. This study presents a regional-scale seismotectonic assessment of the Muş region using an earthquake catalog compiled from data from the Kandilli Observatory and Earthquake Research Institute (KOERI), covering the period 1903–2025. Reported magnitudes were homogenized to moment magnitude (M_w) using General Orthogonal Regression (GOR), and dependent events were removed to isolate background seismicity. The Gutenberg–Richter relationship, recurrence parameters, and annual probabilities were derived from the completeness-controlled 2000–2025 dataset, yielding a b-value of 1.08 ± 0.04. Focal mechanism solutions obtained from national and international sources were analyzed to identify dominant faulting styles, and the regional stress tensor was determined through inversion. The results indicate that seismicity in the Muş region is dominated by shallow earthquakes, predominantly strike-slip faulting, and a transpressional stress regime characterized by N–S principal compression. By integrating completeness-controlled seismicity statistics with focal-mechanism classification and stress inversion, this study provides a locally constrained seismotectonic framework for the Muş region. The proposed approach refines the understanding of active deformation processes in this tectonically complex transition zone and offers a transferable methodological basis for future seismic hazard assessments in eastern Türkiye.

The present study brings forth the first comprehensive broadband ground motion simulations for the 2025 M_w 7.7 Myanmar earthquake, addressing the critical data scarcity in a highly seismic region with sparse strong motion instrumentation. As one of the most devastating events in the region’s history, the earthquake inflicted widespread destruction across Myanmar and neighboring countries. In the absence of a comprehensive strong motion instrumentation specifically along the Sagaing fault (seismic zone V), physics-based simulations offer an essential window into understanding the spatial variability of ground motions and their implications for seismic hazard assessment. In the present study, broadband ground motions are simulated over a near-field domain spanning approximately a 3° × 5° region around the multi-segmented fault plane of the event. To generate these ground motion time histories, the deterministic low-frequency waveforms are combined with stochastic high-frequency components, informed by regional crustal velocity models, topography and detailed source rupture parameters. The reliability of the simulated ground motions is assessed through comparisons with the limited available recordings in the near-field region, with residual analysis quantifying the level of agreement. Furthermore, the ground motions are synthesized on a dense grid of 0.1° × 0.1° and visualized through contour maps of peak ground acceleration (PGA). The highest PGA values are found to be 0.71 g, 0.86 g, and 0.40 g in the EW, NS, and vertical components, respectively. Additionally, the spatial distribution of the peak ground residual displacements is illustrated along with the stations proximal to the fault plane. Finally, the simulated PGAs are compared against global empirical ground motion models developed for subduction zones to evaluate their consistency and regional applicability. Thus, the study demonstrates the importance of simulation-based approaches for seismic hazard evaluation in data-scarce regions, thus offering valuable input for guiding future seismic instrumentation strategies and improving hazard awareness along the Sagaing Fault.

The seismic attenuation parameter, kappa (κ), is a critical factor in characterizing high-frequency ground motion and plays a vital role in seismic hazard assessment, ground motion prediction equation (GMPE) calibration, and site response modeling. This study investigates the spatial variability of κ in Northeast India, a tectonically active region at the convergence of the Himalayan orogeny and the Indo-Burmese arc, and examines the influence of geological and site conditions using 199 three-component seismic records from 115 earthquakes (M_w 2.5–6.8) at epicentral distances up to 400 km. κ was estimated using strong motion data from PESMOS and local broadband recordings from Mizoram, applying a modified Anderson and Hough (Bull Seismol Soc Am 74(5):1969-1993, 1984) approach with exponential decay fitting to the raw amplitude spectra. The analysis shows κ values ranging from 0.019—0.156 s for the EW component, 0.013—0.134 s for the NS component, and 0.005—0.120 s for the vertical component, with higher attenuation at sites underlain by unconsolidated sediments and alluvium with average κ values between 0.020 and 0.176 s, while hard rock sites show lower averages of 0.030–0.080 s. Vertical components generally yield smaller κ than horizontal components, consistent with global observations. The systematic partitioning analysis further confirms the strong correlation between κ values and lithological heterogeneity. By integrating site-specific κ estimations with regional geological assessments, this study provides critical insights for seismic hazard evaluation, GMPE development, and site-specific seismic design in Northeast India.

In 2021 and 2022, two offshore small-magnitude earthquakes (3.5 and 3.7) occurred in the northeastern Brazilian continental margin. Both occurrences produced hydroacoustic T-waves, which were recorded by H10N and H10S hydrophone arrays located near Ascension Island and owned by the Comprehensive Nuclear-Test-Ban Treaty Organization. We analyzed hydroacoustic T-waves recorded by the two arrays using cross-correlation of three-hydrophone pairs with a 2D plane-wave fitting approach. Back-azimuth and apparent velocity were derived from slowness vector inversion to locate T-wave excitation points along the northeastern Brazilian continental margin. Despite the powerful acoustic signals, no seismic T-waves were recorded at neighboring coastal land seismic stations. This pattern shows that seismic energy is efficiently coupled into the SOFAR channel from the continental slope. The high acoustic levels for such small magnitudes suggest favorable source conditions, most likely involving thick sediment cover, shallow hypocenters, and fault geometries dominated by normal or reverse motion, which are consistent with regional stress regimes and known offshore faulting systems in other continental margin areas of Brazil. Comparisons with empirical relationships provide support for the theory of greater coupling at the margin-water contact. These results suggest that active faulting likely occurs along the northeastern Brazilian margin and highlight the critical role of margin morphology and sedimentary structures in T-wave generation and coupling efficiency.

Iran is located in the collision and compression zone between the Arabian Plate and the Eurasian Plate, where earthquakes occur frequently. The tectonic earthquake in north-central Iran on October 5, 2024, was once questioned as a nuclear explosion, drawing widespread attention. P/S spectral ratio was demonstrated to be an effective method for event discrimination. To distinguish whether an event is abnormal, this study established a basic screening baseline via the P/S spectral ratios from earthquakes in Iran with stations both inside and outside Iran. We firstly investigated the amplitude characteristics of regional seismic phases Pn, Pg, Sn, and Lg in Iran. For Iranian seismic events recorded by stations inside Iran, the Pn, Pg, Sn, and Lg phases are well-developed at most stations. For Iranian seismic events recorded by stations outside Iran, the Pn, Pg, Sn, and Lg phases are well-developed for earthquakes in northwestern Iran at many stations. For earthquakes in southern and east-central Iran, the Pn and Sn phases are developed at some stations, while the Pg and Lg phases are not. Based on the phase attenuation characteristics, we calculated the magnitude and distance amplitude corrected P/S ratios for each stations. According to the corrected Pg/Lg, Pn/Lg and Pn/Sn spectral ratios of earthquakes in Iran, we selected stations with relatively smaller P/S ratios as advantageous stations for screening abnormal seismic events. The distributions of Pg/Lg, Pn/Lg, and Pn/Sn spectral ratios for historical tectonic earthquakes in Iran are presented, providing a baseline for rapidly screening of abnormal earthquakes. We calculated the P/S spectral ratio residuals of the earthquake occurred on October 5, 2024 in north-central Iran. The results show that the P/S ratios of the earthquake are similar to the historical tectonic earthquakes in a common region.

The Northeastern Region of India is one of the most seismically active and tectonically complex regions globally, situated at the convergent boundary of the Indian Plate, the Eurasian Plate, and the Burmese microplate. Reliable characterisation of seismic wave attenuation in this region is critical for seismic hazard assessment and regional ground-motion prediction. In this study, we estimate the frequency-dependent crustal quality factor of Lg waves for Northeast India using spectral amplitude decay of broadband waveforms from regional earthquakes. A total of 1,313 high-quality station–event records were analysed following rigorous quality-control criteria based on signal-to-noise ratio, epicentral distance, and waveform characteristics. A regional-average, frequency-dependent (Q_{textrm{Lg}}) model was derived over the 0.5–8 Hz frequency range and fitted using a power-law relationship, yielding (Q_0 = 502 pm 27) and (eta = 0.80 pm 0.05), indicative of moderate attenuation and strong frequency dependence. Residual and site-term behaviour indicate the presence of unresolved lateral heterogeneity and highlight the limitations of a single uniform attenuation model in a tectonically heterogeneous region. The resulting (Q_{textrm{Lg}}) model provides a robust regional-average baseline for seismic hazard assessment, regional ground-motion modelling, and future attenuation studies in Northeast India.

The increased success of earthquake early warning systems (EEWS) worldwide has warranted the need to explore the same for earthquake prone regions such as the active Himalayas of India. While network-based EEWS has been successfully implemented, the scope for on-site EEWS in the region has yet to be investigated. The current study presents a deep learning model, which is aimed at enabling the on-site EEWS in India. The model is developed for predicting broadband spectral acceleration of the expected ground motion using the initial P-wave portion of the seismic recording. By utilizing ground motion parameters derived from the first 3 s of the P-wave, the model can provide rapid and accurate predictions of the associated spectral acceleration between periods 0.01 s and 4.0 s. The research leverages data from multiple seismic networks in the Western Himalayas, encompassing 689 ground motion records from 124 earthquakes with magnitudes ranging from M_w 3.0 to 7.8. The model's performance is evaluated through rigorous sensitivity analyses and validation procedures, demonstrating its potential for real-time application in EEWS.

The absence of a standardized magnitude determination framework in China’s coal mine microseismic (MS) monitoring networks has led to substantial discrepancies in magnitude estimates across different mines, as well as systematic deviations from the magnitudes reported by the China Earthquake Networks. These inconsistencies arise primarily from inconsistent methodologies, the complex high-frequency wave propagation characteristics and inappropriate application of regional attenuation models to near-field MS data. Together, these issues undermine the comparability, reliability, and practical utility of MS monitoring results. To address this challenge, we propose a unified magnitude calibration framework specifically designed for coal mine MS monitoring in China, with the goal of aligning MS magnitude estimates with national seismic standards. Based on data from 29 controlled underground blasting experiments conducted at four geologically distinct coal mines using hybrid monitoring networks (surface and underground sensors), we derived site-specific high-resolution calibration functions and calculated the corresponding event magnitudes. Our results revealed that while surface stations exhibit stable attenuation characteristics, underground propagation paths vary significantly between sites. Importantly, vertical component amplitudes showed equivalent reliability to horizontal components, enabling simplified processing approaches. For mines where blasting experiments were unfeasible, empirical average attenuation models were developed based on observational data from four coal mines. Finally, application of the model to a mining-induced high-energy event demonstrated improved magnitude consistency and largely eliminated systematic distance-dependent bias. These findings support the integration of the newly developed magnitude scales into existing mining-induced seismic monitoring systems, which can be calibrated through localized data accumulation. This integration systematically enhances monitoring effectiveness across two critical dimensions—disaster assessment accuracy and early warning timeliness—specifically tailored to address the prevention and control demands of rockbursts and other mining-induced seismic events.

We present an updated empirical relationship between moment magnitude (M_w), epicentral intensity (I₀, EMS), and macroseismic focal depth (h_m, km) for earthquakes in Croatia and its surroundings. The analysis is based on the updated, revised and uniformly processed Croatian Macroseismic Database and the corresponding Croatian Macroseismic Catalogue, which together provide a homogeneous macroseismic dataset spanning the period 1520–2022. From these, 139 triplets (M_w, ℎ_m, I₀) were selected corresponding to events with independently determined moment magnitudes and reliably derived macroseismic parameters. A three-axes weighted orthogonal regression was performed to obtain a symmetric relationship linking the three variables. The resulting triaxial regression plane is expressed as (-0.390 ,{M}_{w}+0.960 logleft({h}_{m}+1right)+0.285,{I}_{0}=1) from which closed-form expressions allow consistent estimation of any one parameter given the other two. The new relations exhibit stable predictive performance under out-of-sample conditions, and provide improved consistency across the full range of observed magnitudes, intensities, and focal depths. They also agree well with the most commonly used Croatian macroseismic relation that relates magnitude to epicentral intensity and focal depth. These results enable coherent reassessment of magnitudes for historical earthquakes and rapid post-event estimation of maximum intensity. Adoption of the new relationships would also support the homogenization of macroseismic magnitudes in the Croatian Earthquake Catalogue and provide a solid foundation for future intensity-based seismic hazard assessments in the region.

Single station ambient noise analysis provides a practical approach for monitoring seismic velocity changes (dv/v) but its sensitivity to shallow structure makes it susceptible to environmental influences at higher frequencies. We investigate dv/v variations at seismic station UU.NOQ, the nearest three component seismic station to the 2020 M5.7 Magna, Utah earthquake epicenter. We observe a 0.1% coseismic dv/v drop at 1-2 Hz. However at higher frequencies we observe an annual cyclical variations dominating the dv/v signal which obscured the earthquake related dv/v drop. Through cross correlation and coherence analyses comparing dv/v with temperature, precipitation, and GPS derived groundwater proxies, we give evidence that shows temperature as the primary driver of seasonal dv/v variations. Notably the dv/v signal lags surface temperature by approximately 55 days. We apply thermoelastic strain modeling to explain this lag which can be explained due to the presence of an unconsolidated sediment layer that acts as a thermal delay filter. The estimated layer thickness of approximately 1.5 m is independently verified using Horizontal to Vertical Spectral Ratio analysis, which shows a fundamental site frequency above 5 Hz consistent with thin sedimentary cover. Our results demonstrate that thermoelastic strain can significantly influence shallow dv/v measurements in certain scenarios and provide a methodological framework for characterizing temperature induced effects in similar kind of ambient noise monitoring studies.