Journal of Seismology最新文献

We utilise a long-term, declustered dataset of 9,230 earthquakes recorded between 1803 and 2023 from multiple catalogues, offering an unprecedented temporal and spatial coverage for Himalayan seismic belt (HSB) and its surroundings. The maximum likelihood method was deployed in computing b-values, while D_c-values were derived through the correlation integral technique. Further, we segregated the study area into three equal zones (A, B and C) and found that Zone B, covering the Garhwal and Kumaun regions, exhibited the lowest b-values and concentrated stress, indicating the highest seismically active zone. The shorter temporal quiescence periods in Zone B, compared to Zones A and C, suggest a higher probability of recurring seismic events in the future. We also accomplished the fine-resolution grid-based seismic risk assessment: we selected 0.5° × 0.5° grid areas based on earthquake density, where low b-values and D_c-values indicate increased seismic hazard potential. Additionally, we delineated the relative variation of a transition zone depth within the 10–15 km depth, characterised by low b-values, fluid presence and past seismic clustering, which highlights its significance in crustal deformation and seismic risk assessment. Topographic and geological analyses using swath profiles further revealed the tectonic influence of the Mid-Crustal Ramp along the HSB, relates the structural dynamics and associated seismic activity. This integrated multi-parametric assessment provides critical insights into seismic hazard assessment, helping to identify high-risk zones and offering valuable information for hazard zoning, seismic-resistant infrastructure and emergency preparedness strategies in the Himalayas and adjoining region.

This study employs the classical approach of Probabilistic Seismic Hazard Analysis (PSHA) to explore the potential regional seismic hazard in Bejaia City and its surrounding regions in Algeria. The analysis explicitly focuses on individual active faults by integrating the fundamental concepts of the characteristic earthquake model. The research unfolds in three key phases: First, a comprehensive and homogeneous earthquake catalog was compiled and updated, following the methodology of the Unified Moment Magnitude (M_W) parametric earthquake catalog for Algeria and adjacent regions (PECAAR). This updated catalog forms a consistent and a reliable basis for estimating the Gutenberg-Richter parameters. Second, active and potentially active fault networks were identified and characterized using seismotectonic data. Critical earthquake hazard parameters, such as the expected maximum magnitude (({m}_{max})), slip rate along the fault ((dot{s})), and rupture area (({A}_{f})), were estimated for each fault. These parameters provide a deeper insight into the region’s earthquake potential. Third, ground motion models (GMMs) were selected for the Bejaia region. The PSHA was conducted using these GMMs, and the results are presented as Peak Ground Acceleration (PGA) seismic hazard maps illustrating the spatial distribution of expected seismic hazard levels for two key return periods 475 years (10% probability of exceedance in 50 years) and 2475 years (2% probability of exceedance in 50 years. The findings highlight the Gulf of Bejaia as the most earthquake-prone area, with an estimated PGA value of 0.264 g for the 475-year return period and 0.400 g for the 2475-year return period. The Soummam basin follows with 0.236 g and 0.344 g, respectively, while the Western Offshore of Bejaia exhibits PGA values of 0.235 g and 0.380 g. The Djemila region records lower but still significant values of 0.229 g and 0.353 g for the respective return periods. These results emphasize the heightened seismic hazard in these areas, highlighting the importance of incorporating both standard maximum ground motions into seismic zoning updates and the design of earthquake-resistant structures to enhance regional safety and resilience.

The Acts of the Apostles report an earthquake that hit Philippi (NE Macedonia, Greece), a region of low seismicity, during the imprisonment of Apostles Paul and Silas after the first Christian community was established in European land circa AD 50. This earthquake, famous in the Christian religious tradition, is described as a miracle that led to the liberation of the Apostles. However, the seismological significance of this information is a matter of debate. This article presents new literary, historical, and archaeological evidence that the whole scene of the Philippi earthquake reported in the Acts, known as the scene of prison escape, resembles the prison scene of the ancient Greek tragedy Bacchae by Euripides. Furthermore, the prison in Philippi was described as similar to the prison of St Peter in Rome (“Tullianum”), while a cistern built about 100 years later is indicated by tradition as the prison of St Paul in Philippi. These results, in combination with the textual differences of the surviving Codices of the Acts and their inferred history, imply that the Philippi earthquake reflects a later editorial change in the original manuscript, not unusual for an ancient Codex, and of no seismological significance. This result has important implications for many other earthquakes described as a divine intervention (“providentialism”). The seismological evaluation of such cases requires: (i) the study of earthquake information within their context, and in combination with the available commentaries; (ii) the study of the ancient sources as a function of time; and (iii) the examination of editorial selections to produce a compound text using the various surviving Codes which differ from each other because of scribe errors and addition or removal of small or large parts of texts, and because of poor preservation of ancient manuscripts.

This study presents a comparative analysis of multidirectional site response modeling conducted for a well-instrumented downhole array in Alaska, examining seven long-duration earthquake events. While traditional one-dimensional (1D) analyses provide valuable insight into vertical wave propagation, they often simplify real conditions by neglecting the full range of seismic input components that may influence ground motion characteristics. By incorporating all three earthquake directions as East–West, North–South, and Vertical in a multidirectional site response approach, we aim to achieve a more accurate evaluation of site amplification. The results reveal distinct differences in modelled ground motions between three-dimensional and one-dimensional models across various soil depths, demonstrating the improved reliability provided by a multidirectional framework. These findings emphasize the necessity of employing more comprehensive modeling strategies, particularly in high-seismicity regions like Alaska.

This study considers the problem of improving the accuracy of earthquake forecasting in Kazakhstan using deep learning methods. Special attention is paid to forecasting in zones with increased seismic activity, which is a unique feature of the regional plan. The main goal of the work is to develop a model based on the architecture of deep neural networks with direct propagation of signals to analyze historical data containing the time of occurrence, geographic coordinates and magnitude of earthquakes. This model is used as a basis for classification and regression, allowing to evaluate the level of agreement between the predicted values and those obtained. Evidence of earthquake prediction capability is demonstrated using this methodology, achieving 86% accuracy in magnitude classification, and a Mean Squared Error of 0.22 in forecasting the magnitude itself in regression utilizing computational power as well as advanced neural network techniques. The significance of this study is that it contributes to the development of processes and methods that promote the application of deep learning in seismology to improve the accuracy and efficiency of diagnosis and prevention of natural disasters, also opens new perspectives in this direction.

Tsunamis, one of the most devastating natural disasters on Earth, pose a substantial hazard and risk to coastal infrastructure, human life and the built environment. The Indo-Pacific region is highly vulnerable to tsunamis, with over 83% of global occurrences documented in this area, as determined from the National Oceanic and Atmospheric Administration (NOAA) historical tsunami database. Therefore, tsunami hazard analysis and forecasting are essential for safeguarding people and assets in this region. However, a study on the comprehensive tsunami potential requires further detailed investigation. For this purpose, the Indo-Pacific region (60⁰N to 60⁰S and 30⁰E to180⁰E) was divided into eight tsunamigenic zones based on tsunamicity, physiography, and seismotectonics. Tsunamigenic earthquake data from 1737 to 2022 were analyzed using stochastic tools and Artificial Neural Network (ANN) algorithms to precisely forecast the time, magnitude, and location of impending tsunamigenic earthquakes. This study indicates that Zones 5 (Tohoku Seismic Zone), 7 (Banda Arc), and 8 (Solomon Subduction Zone) are highly vulnerable to tsunami occurrence between periods 2030–2033 (M_W 8), 2030–2034 (M_W 7) and 2031–2034 (M_W 8.2), respectively. At the same time, Zones 1 (Sumatra Subduction Zone), 4 (Kamchatka Trench), and 6 (Visayas Fault Zone) might become vulnerable in the long run between periods 2051–2064 (M_W 8.9—M_W 9.3), 2062–2081 (M_W 7.3) and 2077–2120 (M_W 7.7), respectively. The study advocates that out of eight tsunamigenic zones considered, Zone 1 might experience the strongest tsunamigenic earthquake (8.9 MW – 9.3 MW) by the mid-century (2051–2064). The forecast was validated by back-testing the ANN model considering the last five events that had already occurred in each zone. The case study of the recent significant tsunamigenic earthquake events—the 2004 Indian Ocean tsunami, the 2011 Tohoku tsunami, and the recent Japan earthquake of January 01, 2024–have also been validated. Additionally, the Epidemic Type Aftershock Sequence (ETAS) model and Coulomb stress change studies have been applied to improve location accuracy.

A hybrid method that combines the finite element method in the field of explosive dynamics and the frequency wavenumber method in the field of seismology is proposed in this study to simulate the seismic displacement generated by a 3-D explosive source in a multilayered Earth medium appropriate for any source-receiver distances based on the representation theorem. The performance of the hybrid method is demonstrated by two numerical tests. The first numerical test compares the simulated results obtained by the hybrid method with the basic theory of seismic propagation. The simulated results obtained from the hybrid method imply that the amplitudes of the P waves and Rayleigh waves produced by a 3-D cuboid explosive source lack directivity and that the particle of Rayleigh waves moves counterclockwise along an ellipse, which conforms to the basic theory of seismic propagation. The second numerical test compares the hybrid method with the traditional moment tensor-based method across synthetic scenarios. The results shows that although the amplitude and phase of the synthetic seismograms calculated by the hybrid method using the 3-D cuboid explosive model were consistent with those calculated by the traditional moment tensor-based method using an isotropic source, there were slight numerical differences indicated that the 3-D cuboid explosion source was not entirely isotropic. To verify the practicability of the proposed hybrid method, we compared between the hybrid method and the traditional moment tensor-based method via waveform simulations of underground explosions conducted by the Democratic People’s Republic of Korea (DPRK) in January 2016. For the period of 8–30 s, which is used in most seismic waveform inversions, a comparison of the observed and synthetic waveforms calculated by these two methods proves that the proposed hybrid method can better explain the real observations of the radial components (R components) and vertical components (Z components) than the moment tensor-based simulation. More importantly, this hybrid method can directly associate the far-field seismic effects with the yield of the explosion and can be coupled with a more complex explosive process. This function is not available in traditional moment tensor-based methods.

This study investigated frequency dependent attenuation of seismic waves from earthquakes in Izmir and its surroundings. Earthquakes with a magnitude of M ≥ 2.3, recorded by the local seismic network in the region between 2008–2023, were used. The network of 26 accelerometers is predominantly deployed near the gulf to monitor tectonic features characterized by high seismic activity. The attenuation properties related to seismic wave propagation were evaluated by applying Coda Q analysis. Attenuation in coda waves is due to wave propagation between the inelastic medium and discontinuities or scattering of heterogeneities. The frequency dependence of the seismic quality factor for the coda wave was determined using Q₀ multiplied by fⁿ. Various center frequencies (1,2,4,8,16) were selected to calculate the coda wave quality factor, and bandpass filtering was applied. The CODAQ algorithm in the SEISAN software (Havskov et al. 2020) was used in the study. It was observed that elevated Q values in the study area are associated with geologically stable zones, whereas lower Q₀ values reflect areas of heightened seismic activity. The complex tectonic regime of Izmir and its surrounding areas aligns with the low Q₀ values, suggesting significant heterogeneity in the crust. We found the result Q_c = 61,9. f^0,9 with investigating the Q change examined using different lapse times (20 s,30 s and 40 s) and geometrical spreading (0.5 and 1) parameters.

Local amplification is an important factor when assessing local earthquake ground motion in an area covered by soft sedimentary deposit (lithological site effects), 2D basins and/or marked by the presence of hills or mountains (topographical site effects). In the present study, we propose to estimate the local ground motion linked to these site effects in Anse-à-Veau, a municipality in the Nippes Department of Haiti. This region was also affected by intense seismic shaking during the M 7.2 Nippes earthquake in August 2021, and the numerous aftershocks. The surveys have been carried out during the measurement campaigns in 2021, 2022 and 2023, and include ambient noise and earthquake recordings, seismic surveys as well as electrical resistivity measurements along profiles. The two first ones were processed, respectively, in terms of horizontal to vertical spectral ratios and standard spectral ratios, the seismic tests both as seismic refraction tomography and by multichannel surface wave analysis and the last measurements as electrical resistivity tomography. In total, more than 150 ambient noise recordings, 22 seismic profiles and 8 electric profiles have been completed. All related results were then compiled within one multi-data 3D geomodel and submitted to a spatial analysis by applying a conditional geostatistical simulation which is expected to take advantage of the relationships between the different type of seismic data in order to better estimate the potential site effects in the study area. The site amplification parameters are then used to compute local ground motion for the 2021 Nippes Earthquake at Anse-à-Veau using Next Generation Attenuation.

Geological evidence of extreme high-energy sea wave events can be preserved in coastal areas as depositional and/or erosional deposits. In this work we present field evidence for the existence of high energy sea wave depositional features, in the Mostaganem region, northwestern Algeria, which include: (i) unusual marine sedimentary features trapped in a waterway valley, in an old coastal notch, and in low-lying parts of the coastal zone, (ii) carried, imbricate and oriented large boulders of weight ranging between 1.2- 32.6 tons. Both the boulders and the sedimentary deposits fit the characteristics of high energy waves deposits while at least some of them fit the tsunamis waves ones. Hydrodynamic analysis of the joint bound and the submerged boulders, considered in this study, yield values ranging between 0.40m to 29.24m for storm waves height (Hs) and 0.10m to 7.31m for tsunamis waves height (Ht). The threshold minimum velocity ranges between 1.91m/s—17.14m/s. Therefore, the majority of the boulders may have both storm and/or tsunami origin while some of them (weight exceeding 25 tons) requires very high storm waves unlikely to occur in the study area; Consequently, the tsunami origin is the most possible for this case. On the other hand, tsunami modeling, considering near shore active faults, has shown that the maximum heights of 1.21m, 0.81m, 0.35m, 0.41m and 0.34m can be expected at Stidia (where the boulders are described), Les Andalouse, AinTurck (north-west Algeria), Almeria and Cartagena (Southern Spain), respectively. these heights are comparable to the ones described during the Oran October 9th, (I₀ = IX) historical earthquake in northwestern Algeria and Southern Spain. Nevertheless, the maximum wave height needed to move some of the very big boulders found in the study area exceeds 7 m, possible likely, not from near shore earthquakes, but from Iberian or Mediterranean offshore earthquakes considered in previous study as a possible source for northern Algerian tsunamis. This work should encourage further research in the prevention of tsunami hazards along the Algerian coast, densely populated and where important economic infrastructures are located, which is insufficiently studied compared to other Mediterranean regions.