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Accurate earthquake prediction is one of the ways to effectively reduce earthquake disasters. Until now, empirical earthquake prediction methods have remained in use, but the accuracy falls far short of what is needed to effectively mitigate earthquake disasters. The trend in earthquake prediction lies in the transition from empirical prediction to physical prediction, and the key to this transition is to achieve a deeper understanding, depiction, and tracking of the seismogenic process. According to the experimental results of rock mechanics, it can be found that before failure, the rock mainly experienced a stress-increase stage and a subsequent stage of sub-instability. We have analyzed the seismogenic process of some natural earthquakes. In the analysis, apparent stress and b-value are used together to obtain information on the stress variability of the crustal medium. The correlation between seismicity and Earth rotation (described by p-value) is used to obtain information about the critical state or sub-instability phase of the crustal medium. Thus, the seismogenic process can be depicted. In this paper, based on a case study of the seismigenic process for some natural strong earthquakes, we propose an idea and method for earthquake prediction based on the tracking of the seismogenic process, and provide a basis for the identification of short- to mid-term seismic risk regions. It is expected to be beneficial for practical earthquake prediction.

Fiber-reinforced polymer (FRP) wrapping is a potential technique for coal pillar reinforcement. In this study, an acoustic emission (AE) technique was employed to monitor coal specimens with carbon FRP (CFRP) jackets during uniaxial compression, which addressed the inability to observe the cracks inside the FRP-reinforced coal pillars by conventional field inspection techniques. The spatiotemporal fractal evolution of the cumulated AE events during loading was investigated based on fractal theory. The results indicated that the AE response and fractal features of the coal specimens were closely related to their damage evolution, with CFRP exerting a significant influence. In particular, during the unstable crack development stage, the evolutionary patterns of the AE count and energy curves of the CFRP-confined specimens underwent a transformation from the slight shock–major shock type to the slight shock–sub-major shock–slight shock–major shock type, in contrast to the unconfined coal specimens. The AE b-values decreased to a minimum and then increased marginally. The AE spatial fractal dimension increased rapidly, whereas the AE temporal fractal dimension fluctuated significantly during the accumulation and release of strain energy. Ultimately, based on the AE count and AE energy evolution, a damage factor was proposed for the coal samples with CFRP jackets. Furthermore, a damage constitutive model was established, considering the CFRP jacket and the compaction characteristics of the coal. This model provides an effective description of the stress–strain relationship of coal specimens with CFRP jackets.

The indication of b-value change and earthquake preparation has always been an important reference index for earthquake situation research and judgment. Based on the advantage that deep learning technology can mine the implicit characteristics of data, taking into account the natural phenomenon of frequent earthquakes in Sichuan and Yunnan in recent years and the high attention paid to the seismic activity of the Tanlu fault, this study uses the self-made data set of seismic events in Sichuan and Yunnan region from the earthquake catalogue of the China Earthquake Networks Center, and medium and strong earthquakes above \begin{document}$ {M}_{\mathrm{L}} $\end{document}4.5 are labeled as 1, weak earthquakes below \begin{document}$ {M}_{\mathrm{L}} $\end{document}3.0 are labeled as 0. The grid b-value in Sichuan-Yunnan region is calculated using the time sliding window method, and the b-value changes of each earthquake event in the five years before the earthquake are mapped to the labels. By using convolutional neural network models for training and classification, the optimized model is applied to the retrospective testing of medium and strong earthquakes in the central and southern section of the Tanlu fault zone. The verification accuracy can reach about 90%. Although the Sichuan-Yunnan region and the central and southern section of the Tanlu fault zone and their neighboring areas have different geographical and structural backgrounds, data-driven methods, reasonable generalization ideas, training datasets production, and deep learning model construction still have reference significance for mining strong earthquake laws.

Yogyakarta is one of the areas in Indonesia with a high risk of earthquakes due to its proximity to the subduction zone of the Indo-Australian Plate and Eurasian Plate and the presence of active fault activity, namely the Opak fault, which generates shallow earthquakes. A total of 13 destructive earthquakes were recorded in Yogyakarta and surrounding areas from 1840 to 2023, with the most destructive earthquake occurring in 2006 in Bantul. A total of 417 earthquakes were felt in the Yogyakarta area between May 2006 and March 2016. The high earthquake activity after the 26 May 2006 earthquake indicates a stress field on the active fault segment that has not been fully released. This study aims to analyze the seismotectonic parameter b-value spatially and temporally to determine the accumulation of tectonic stress in Yogyakarta. The method used is a frequency-magnitude distribution with Gutenberg-Richter relation and Maximum Likelihood approach. Earthquake data were obtained from ISC and BMKG catalogs, with a total of 205 events. The results show that spatially, the b-value of the Yogyakarta region is generally low with a range of values of 0.35 - 0.75 using a grid of 1.5 x 1.5 km and a radius of 15 km with low values around the Opak fault and Ngalang Fault, meaning that the area still holds a high accumulation of stress energy and has the potential for large earthquakes to occur again in the future. Temporal analysis of the b-value shows a tendency for the b-value to decrease before a large earthquake and increase afterwards, reflecting the accumulation and release of stress in the rock.

For earthquakes (M ≥ 4.0) occurring along and around the East Anatolian fault zone and the Dead Sea fault zone within ten years immediately before the MW7.8 Gaziantep earthquake, Türkiye, of February 6, 2023, we explored the correlation between seismicity and the earth's rotation. We statistically evaluated the correlation using the Schuster's test. The results are quantitatively assessed by a p-value. We found a clear downward trend in the p-values from early 2020 to late 2022 in the studied region. We also obtained a spatial distribution of the p-values showing a low p-value area near the northeastern end of the aftershock zone. Although the stress induced by the rotation of the earth is very weak, it could control the earthquake occurrence when the focal medium is loaded to the critical state to release a large earthquake. The decrease in the b-value in the Gutenberg–Richter (G-R) relation is considered in the form of the tectonic stress increase in the crust. We investigated the b-value as a function of time in the study region. We found that the b-value had decreased for about eleven years before the p-value started to decrease, with a relative reduction of 57%. Therefore, the result of the lower p-values obtained in the present study infers that the earthquakes were dominated by the earth's rotation prior to the MW7.8 Türkiye earthquake due to a critical state of the focal region.

Using the earthquake catalog provided by the Sichuan Earthquake Network Center, spatial and temporal b-value variations were calculated for in regional and local scales based on assessing the completeness of the earthquake catalog and declustering. The results show that (1) b-value temporal variations in regional scale ranged from 0.689 to 1.169, with a mean value of 0.928; while, the local-scale temporal variations ranged from 0.694 to 1.223, with a mean value of 0.925. The b-values in the study area were below the mean value before the moderate and large earthquakes occurrence, and all b-values exhibited the anomalous feature of a sudden decrease before the earthquake low peak rise after the earthquake. (2) The seismotectonic characteristic of the area is the higher value of slip rate of the NW section of Xianshui River Fault Zone; therefore, a large amount of stress was accumulated in the Moxi section of the SE section, leading to a M = 6.8 earthquake in Luding. Before the earthquake, the study area has a low b-value area. The b-value decreased within a short period after the earthquake, dividing the area into asperity. This area still has a future risk of moderate to strong earthquakes. (3) The error in the b-values for most of the earthquakes in the regional and local scales regions is between 0.05 and 0.15, and only individual grid points have larger b-value errors (> 0.2), indicating high confidence in the information. In addition, when conducting a b-value study, choosing a suitable study area is important to avoid missing the b-value anomaly area. [ABSTRACT FROM AUTHOR]

b-value analysis obtained using earthquake catalogues has been associated with stress accumulation for a very long time. In this study, the spatial and temporal distribution of the b-value, also known as the frequency magnitude distribution factor, was calculated and examined before and after the February 6, 2023, Kahramanmaraş earthquakes (Mw 7.7 and Mw 7.6). For this, all earthquakes that occurred between 1900 and the earthquakes of February 6, 2023, and all aftershocks that occurred until September 1, 2023, were used. A circular area with a radius of 300 km, including nearby active faults from the center of the first earthquake to the center of the second earthquake, was divided into grids of equal size. The b-value was calculated for each grid using the maximum likelihood method. Very low b values were detected in the area where the first earthquake occurred, and it was observed that the b-value decreased relatively in the area where the second earthquake occurred. From the change in b-value over time, it was determined that the b-value has decreased significantly in recent years. This situation is associated with stress accumulation in the area where both earthquakes occurred, especially the low b values of the region where the first earthquake occurred. The fact that b values obtained using aftershocks are still low suggests that stress in the region is not completely released, has not been completely relieved and aftershocks will continue for a long time. [ABSTRACT FROM AUTHOR]

Understanding the mechanical properties of rocks under high temperature thermal cycles is critically important for deep geotechnical engineering construction. In this study, the mechanical properties and fracture evolution characteristics of Beishan granite after different temperatures of 25–800 °C and thermal cycles were investigated through multiple experiments. The results show that the tensile strength (σt) decreased from 7.49 MPa to 0.47 MPa as the temperature increased from 25 ℃ to 800 ℃, and further decreased to 0.43 MPa after thermal cycling. Incremental temperatures led to more active AE events, with AE cumulative events increasing from 25,250 at 25 °C to 99,389 at 800 °C, but AE cumulative events decreased in thermal cycles. The b-value presented higher level fluctuations at T ≤ 400 °C. When T ≥ 600 °C, the b-value before failure decreased and maintained small dramatic fluctuations, but fluctuated upward in the post-peak failure stage, indicating that rock failure changed from brittle failure to plastic failure. The proportion of shear cracks increased substantially with temperature and thermal cycles, from 14.22% at 25 °C to 23.11% at 800 °C. It can be also found that the damage variable (DAE) increased with temperature under the same condition of stress. The physical and chemical reactions within granite at high temperature led to the initiation, development, and connectivity of numerous microcracks, especially when T ≥ 600 °C. The alternating thermal stress generated by cyclic heating will further promote the increase and propagation of microcracks, thereby exacerbating the damage to granite. [ABSTRACT FROM AUTHOR]

In the present study, an evaluation of the region-time-magnitude behaviours of the earthquake occurrences in the West Anatolian Region (WAR), Türkiye, is carried out using the statistical and seismotectonic parameters such as the b-value of Gutenberg-Richter relation, occurrence probabilities, and return periods of earthquakes. We also have mapped the Coulomb stress changes to observe the current and future earthquake hazard. In recent years, several large earthquakes such as the 1919 Soma (Mw = 6.7) and the 2022 and 2024 Aegean Sea (Mw = 5.3 and Mw = 5.1) revealed earthquake potential in the WAR. Coulomb stress analyses of 41 local events with mostly normal fault mechanisms have shown that positive lobes (> 0.0 in bars) are mainly confined in the crust and uppermost mantle depths around Samos, Kos, and south of Lesvos. The smaller b-values (< 1.0) are observed in the same regions. On the contrary, we have observed a higher b-value from the offshore to onshore, south to north-trending direction, and negative scattered stress lobes (< 0.0 in bars) in slightly NW--SE oriented. The relationship between an increased b-value and negative stress change may indicate a similar seismicity for the region. In addition, we have analyzed the occurrence probabilities and return periods of the earthquakes, which showed us that Mw = 6.0 may occur at 75% in the intermediate term with an estimation of ~7 years. Our results reflect that these types of multiple-parameter assessments are important to define regional seismicity, seismic, tectonic, and statistical behaviours. Consequently, the areas with reductions in b-values and increments in stress imply the possible seismic hazard in the intermediate/long term. [ABSTRACT FROM AUTHOR]

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Java Island is an island with a high earthquake vulnerability. Therefore, earthquake mitigation measures are needed to reduce the impact of earthquakes. Earthquake mitigation is done by knowing the zones with a high risk of earthquakes and high levels of rock stress. The methods used to map earthquake-prone zones are K-means clustering and B-value. The Kmeans clustering method can provide earthquake clusters based on their characteristics and the B-value can produce rock stress conditions in the area. The results of this study are that the K-means clustering method produces 7 earthquake clusters with 5 classifications of very low, low, medium, high, and very high. In contrast, the B-value process has a high Bvalue with a value of 1.2-1.5 in West Java and a low B-value with a value of 0.9-1.2 in the central to the eastern part of Java. [ABSTRACT FROM AUTHOR]

Gas extraction from the Groningen gas field resulted in significant induced seismicity. We analyze the magnitude‐frequency distribution of these earthquakes in space, time and in view of stress changes calculated based on gas production and reservoir properties. Previous studies suggested variations related to reservoir geometry and stress. While we confirm the spatial variations, we do not detect a clear sensitivity of b‐value to Coulomb stress changes. However, we find that b‐value correlates positively with the rate of Coulomb stress changes. This correlation is statistically significant and robust to uncertainties related to stress change calculation. This study thus points to a possible influence of stress change rate on the probability of the magnitude of induced earthquakes. Plain Language Summary: Gas extraction from an underground reservoir in the Netherlands has induced significant seismicity. We analyze how stress changes and the rate of stress changes influence the magnitude of these earthquakes. We find that more smaller earthquakes tend to occur at higher stress change rates. Earthquakes triggered at a lower stress change rate may thus grow to larger magnitudes than those triggered at high stress change rate. This observation is statistically significant and independent of the method used to calculate stress change. Key Points: We report a positive correlation between the b‐value and the rate of Coulomb stress change of induced earthquakes in GroningenThis trend is statistically significant and robust to changes in the mechanical model used to calculate the stress changesWe interpret earthquake growth inhibition through a decrease of nucleation lengths at high stress change rates [ABSTRACT FROM AUTHOR]

Seismic activity in Aswan is influenced by the complex interactions of tectonic plates, the accumulation of stress, and the presence of geological fault systems. It revealed that epicenters are well distributed along four fault segments in a conjugate pattern, indicating a prominent E-W compressional stress. This research aims to explore the characteristics of seismicity and seismotectonics, with a focus on assessing their implications for risk reduction and disaster management in this densely populated region. A data review from the Egyptian National Seismological Network (ENSN) identified 464 earthquakes occurred between 2000 and 2021, with local magnitudes ranging from 0.3 to 4.4, and depths up to 25 km. The calculated Gutenberg-Richter b-value is approximately 0.87 ± 0.05, indicating a gradual stress accumulation. The current analysis shows a more consistent level of moderate seismic activity, unlike previous studies in Aswan region that reported a wide range of b-values from 0.554 to 1.07. This suggests that while earlier research captured a wider range of seismic behaviors, recent data indicates a stabilization in earthquake frequency and intensity. Additionally, the fractal dimension (Dc) calculated at 1.57 ± 0.04 shows an intermediate level of complexity and reflecting a clustering pattern of earthquakes. The variations in the b-value with different magnitudes and depths signify the involvement of active smaller faults, responsible for earthquakes up to magnitude 2.2, which then transition to fractured zones inducing earthquakes up to magnitude 2.5. This transition is followed by a decline in seismic activity, indicating regions that are potentially more likely to experience larger earthquakes. Moreover, stress disparities at various depths contribute to smaller earthquakes within the 5-10 km depth range. Return period analysis suggests that the earthquakes of magnitude 3.7 or higher are expected to occur approximately once every decade in Aswan. These findings are of utmost importance for earthquake risk reduction, hazard assessment, and the sustainable development of Aswan area. [ABSTRACT FROM AUTHOR]

In order to research the acoustic emission characteristics of polypropylene fiber-reinforced recycled aggregate concrete under uniaxial load, 20 groups of test specimens with a coarse aggregate substitution rate of 25 % and 50 % are designed and fabricated to conduct the acoustic emission test under uniaxial compression, and the evolution laws of the acoustic emission b-value, the cracking modes and the acoustic emission RA-AF moving averages with time are studied. The laws of influence of the coarse aggregate substitution rate and coarse-fine polypropylene fiber on the acoustic emission b-value of RAC are discussed. The K-means clustering method is adopted for two-dimensional clustering analysis of the shear cracking and tensile cracking, and then the SVM is used to obtain the boundary between the two types of clusters. The time distribution laws of shear cracking and tensile cracking of the polypropylene fiber-reinforced recycled aggregate concrete are analyzed. The changes in the moving averages of RA and AF of RAC test specimens with time are studied, and the research indicates that as the RA value decreases, the shear cracking gradually reduces and the tensile cracking gradually increases and dominates. [ABSTRACT FROM AUTHOR]

Rock-burst prediction is an important issue faced by deep coal mining operations and holds significant significance for ensuring the safety of workers and the sustainable development of mines. This study investigates the crack-propagation behavior of coal and magnetite under uniaxial compression, introduces the characteristic parameter γ within the framework of the flicker noise spectrum (FNS), analyzes the trends in the variation of acoustic emission (AE) b-value and γ-value, and explores the relationship between these two parameters. Experimental results reveal that the proportion of tensile cracks is significantly higher than shear cracks during the loading process, shear failure becomes the main factor as the specimen approaches failure. Both the b-value and γ-value are proven to effectively reflect the damage evolution process of coal and magnetite and exhibit noticeable changes prior to collapse. Specifically, the peak γ-value serves as a precursor indicator for coal and magnetite collapse. Furthermore, this study uncovers a negative linear relationship between the b-value and γ-value. By delving into the feature parameter γ of AE signals, this research offers a new perspective and approach for predicting the instability of coal and magnetite formations and monitoring dynamic hazards. It contributes to a better understanding of the damage evolution process of coal and magnetite formations and provides valuable guidance and reference for preventing and mitigating dynamic hazards associated with coal and magnetite. Highlights: A novel monitoring indicator for coal and magnetite dynamic hazards, known as the γ-value, was introduced within the framework of the Flicker Noise Spectroscopy method. The study revealed a notable negative linear correlation between the b-value and the γ-value derived from acoustic emission signals. Experimental and on-site data have demonstrated that b-value and γ-value can effectively prevent rock burst. [ABSTRACT FROM AUTHOR]

The Red Sea region, situated between the Arabian and African Plates, experiences significant seismic activity due to its tectonic dynamics, with earthquakes ranging from minor to potentially destructive events. This study aims to develop smoothed seismicity models for the region by using an enhanced seismic catalog specific to the Red Sea. This facilitates a detailed spatial and temporal analysis of seismic events, focusing on seismic source characterization essential for probabilistic seismic hazard assessments. A rigorous declustering method excludes foreshocks and aftershocks, focusing on independent seismic events. The analysis uses a spatial grid (0.1 ∘ cells in latitude and longitude) to determine seismic event rates, which are then refined using various smoothing techniques. Special attention is given to seismic activity within 0–35 kms of depth, leading to distinct rate models that inform urban development and seismic hazard mitigation strategies in the Red Sea area. These models are crucial for improving resilience, safety, and informed decision-making for urban planning and disaster preparedness, addressing the challenges posed by the region's tectonic and seismic complexities. [ABSTRACT FROM AUTHOR]

Abstract The earthquake Magnitude‐Frequency‐Distribution is usually modeled with the Gutenberg‐Richter law, where the b‐value controls the relative rate of small and large earthquakes. b‐value shows an inverse dependence on differential stress, it increases with fault roughness and in areas with fluid involvement in faulting. b‐value analyses have been also applied to infer temporal evolution of the stress state along active faults or to discriminate between foreshocks and aftershocks. For the Mw 6.5 2016–2017 Central Italy seismic sequence, we show that: (a) away from the major earthquake faults, b‐values are controlled by lithology and style of deformation; (b) the absolute number of the b‐values depends on the adopted magnitude scale and catalog, but differences induced by lithology are preserved; (c) the selection of the fault source volume can strongly influence b‐value changes in time, highlighting some complexities on the applicability of the b‐value as fault stress meter.

Abstract This study explores the b-value variations prior to M ≥ 6.0 earthquakes in Taiwan, examining their potential as earthquake precursors. Focusing on the 2018 Hualien earthquake and others between 1999 and 2021, we found that many large earthquakes occurred in areas with low b-values a year prior, although there were no significant temporal changes near the epicenters. However, for more accurate earthquake precursors, incorporating additional factors is recommended to minimize uncertainty. Graphical Abstract

Abstract This work presents particle-based numerical simulations on coal pillars in a coal mine based underground water reservoir (CMUWR). We aim to replicate the stress–strain characteristics and present the acoustic emission behavior of the coal under complex dynamic stress paths. The study reveals failure characteristics of coal exposed to monotonic/cyclic shear load under constant/cyclic normal loads. Based on the evolution of stress-time-dependent bond diameter implemented in particle model, different damage paths are established for dry and water-immersed samples under two loading frequencies. Furthermore, the numerical Gutenberg–Richter’s b-value was calculated from the released energy emanating from bond failure, and this work presents the evolution of numerical Gutenberg–Richter’s b-value. The numerical simulation contributes to a micromechanical understanding of the failure mechanisms of coal under water-immersion and cyclic stress, providing valuable insights for strength prediction of CMUWR.

Dengan menggunakan data gempa bumi dari katalog USGS dan BMKG dari tahun 2009 hingga 2021, penelitian dilakukan untuk mengestimasi nilai Mc, nilai-b, dan nilai-a. Gempa bumi terjadi pada 6° LS - 2° LU dan 100° BT - 103° BT, dengan magnitudo 3 SR hingga 7 SR, dan kedalaman tertinggi adalah 300 km, yang mencakup wilayah provinsi Bengkulu. Penelitian ini dilakukan dengan menggunakan metode EMR dan software ZMAP 6.0 di Matlab digunakan. Menurut analisis di atas, USGS memperoleh Mc sekitar 4,7 SR hingga 5, nilai-b berkisar 0,9 hingga 1,5, dan variasi nilai-a sekitar 6 hingga 9,5. Sebaliknya, BMKG memperoleh Mc sekitar 3,8 hingga 5,2, nilai-b berkisar 0,55 hingga 0,85, dan variasi nilai-a sekitar 5,2 hingga 5,8. Pemetaan nilai Mc menunjukkan bahwa semua kabupaten di Provinsi Bengkulu memiliki nilai Mc yang rendah, yang menunjukkan bahwa data gempa untuk daerah-daerah ini cukup lengkap dibandingkan dengan daerah lain. Menurut pemetaan nilai-b dan nilai-a, wilayah yang memiliki tingkat kegempaan yang relatif tinggi dan memiliki potensi gempa besar berada di sekitar wilayah timur laut dan tenggara Provinsi Bengkulu.

This study explores the b-value variations prior to M ≥ 6.0 earthquakes in Taiwan, examining their potential as earthquake precursors. Focusing on the 2018 Hualien earthquake and others between 1999 and 2021, we found that many large earthquakes occurred in areas with low b-values a year prior, although there were no significant temporal changes near the epicenters. However, for more accurate earthquake precursors, incorporating additional factors is recommended to minimize uncertainty. [ABSTRACT FROM AUTHOR]

Purpose: Demonstrate the feasibility and evaluate the performance of single‐shot diffusion trace‐weighted radial echo planar spectroscopic imaging (Trace DW‐REPSI) for quantifying the trace ADC in phantom and in vivo using a 3T clinical scanner. Theory and Methods: Trace DW‐REPSI datasets were acquired in 10 phantom and 10 healthy volunteers, with a maximum b‐value of 1601 s/mm2 and diffusion time of 10.75 ms. The self‐navigation properties of radial acquisitions were used for corrections of shot‐to‐shot phase and frequency shift fluctuations of the raw data. In vivo trace ADCs of total NAA (tNAA), total creatine (tCr), and total choline (tCho) extrapolated to pure gray and white matter fractions were compared, as well as trace ADCs estimated in voxels within white or gray matter‐dominant regions. Results: Trace ADCs in phantom show excellent agreement with reported values, and in vivo ADCs agree well with the expected differences between gray and white matter. For tNAA, tCr, and tCho, the trace ADCs extrapolated to pure gray and white matter ranged from 0.18–0.27 and 0.26–0.38 μm2/ms, respectively. In sets of gray and white matter‐dominant voxels, the values ranged from 0.21 to 0.27 and 0.24 to 0.31 μm2/ms, respectively. The overestimated trace ADCs from this sequence can be attributed to the short diffusion time. Conclusion: This study presents the first demonstration of the single‐shot diffusion trace‐weighted spectroscopic imaging sequence using radial echo planar trajectories. The Trace DW‐REPSI sequence could provide an estimate of the trace ADC in a much shorter scan time compared to conventional approaches that require three separate measurements. [ABSTRACT FROM AUTHOR]

The Gutenberg-Richter (GR) and Gumbel methodologies were applied to analyze seismic activity parameters (specifically, b-values) in the central Himalaya region, covering latitudes between 26° and 31° E and longitudes between 80° and 88° N during the time frame from 1964 to 2021. Additionally, Gumbel's techniques were utilized to gauge the frequency of occurrence for moderate-tolargemagnitude earthquakes. Within a circular area with a diameter of 250 kilometers, we determined the b-values for the primary source regions of the ten past major earthquakes. The estimated b-value based on GR relation varies from 0.82±0.06 to 1.02±0.10, whereas the b-value based on Gumbel's method ranges from 0.86±0.30 to 1.88±0.32. The results indicate that Gumbel's distribution approach is effective for regions where large earthquake data is available, and the b-values, estimated from the GR method, are found to be more appropriate for the tectonics of the source regions. The Lo-Mustang earthquake region and Bajhang earthquake regions are identified as probable regions for the occurrence of a large earthquake in less than 100 years, which also supports the existence of a western Nepal seismic gap between Uttarakhand, India, and central Nepal. The findings describe the seismic risk in the epicenters of previous earthquakes in terms of b-value, recurrence intervals, and earthquake probability for each magnitude. [ABSTRACT FROM AUTHOR]

In the present study, the spatio-temporal variation of the seismic b-value in the vicinity of the Kopili fault and its surrounding area has been analysed using the unified and homogenous earthquake catalog of historical and instrumental (1950–2021) earthquake events. The study region is subdivided into 16 equisized square grids of 1° × 1° dimension, and the b-value is computed for each grid using the maximum likelihood method. The spatial distribution of the b-value varies from 0.58 to 1.14. The Kolmogorov–Smirnov (K-S) test has been conducted to check the significance of the spatial-temporal and depth-wise distributions of the b-value. The epicentral location of April 28th, 2021, lies in the low-b-value square grid. Likewise, the temporal b-value curve shows a decreasing trend before the occurrence of the April 28th, 2021 earthquake. The mean return period of the April 28th, 2021earthquake and the most probable maximum annual magnitude earthquake are also computed for this region. Meanwhile, the spatial associations and anomalous patterns between the b-value and factors like seismic moment or energy release and focal depth are assessed, as they contribute to a more comprehensive understanding of the seismicity in this area. The antithetical relationship between the b-value and seismic moment or energy release is established. While variation in b-value with depth provides new insights, low b-values are linked to the top of the crust, which could mean that the crust is uniform and that a lot of stress is building up. [ABSTRACT FROM AUTHOR]

The Tonga-Kermadec subduction zone lies between the Pacific and Australian plates. The location shows the highest rate of subduction for the Pacific plate and a dominant tension. Two great earthquakes occurred in the region in 2006 and 2009 whose magnitudes were Mw = 8.0 and 8.1. There are about 170 islands around the Tonga subduction zone; these islands are volcanic centers that have been regularly in eruption during the last several decades. The present study presents the results from the determination of time-dependent variations in the slope of the recurrence curve (the b-value) at the Tonga subduction zone during 2005–2022, and depth-dependent variations in b. The time-dependent variations in b reflect the general tendency of great earthquakes occurring upon the background of lower b-values in the surface layer only, at depths of 0–100 km. The comparison between the depth-dependent variations in b and the tectonic model for the Toga subduction zone implies the hypothesis that lower b-values may reflect greater stresses in the upper part of the plunging plate due to its bending. Higher b-values seem to be connected to tensional mechanisms. A region of higher b-values at depths of 90–100 km has been identified for the Tonga subduction zone, as well as for other subduction zones, which can be related to the presence of a magmatic front at these depths, which is related to active volcanism. [ABSTRACT FROM AUTHOR]

This study explores the feasibility of using fluctuations in the recurrence magnitude dispersion factor (b-value) as a seismic precursor for the Mizoram earthquake that occurred on November 26, 2021, in the Indo-Burma region of northeast India. Employing a comprehensive and homogeneous earthquake catalog spanning from 1900 to 2020, the seismic analysis involved delustering and completeness testing. The research implements a sub-sectional b-value calculation method, dividing the study area into uniformly sized grid cells (2° × 2°) and performing temporal b-value mapping for each grid. The epicenter of the Mizoram earthquake was located within a grid cell characterized by an intermediate b-value. Time-series analysis of the b-value indicated a notable decline preceding the main event, suggesting its potential as a seismic precursor. The study also examines depth-dependent variations in the b-value, revealing an inverse relationship between the b-value and crustal stress. To evaluate the significance of b-value anomalies, the Kolmogorov–Smirnov (K-S) statistic was employed instead of visual inspection. Additionally, the research provides probabilistic estimates of seismic hazard parameters, including the most probable maximum yearly earthquake, mean return period, and probabilities of earthquakes of varying magnitudes. These findings contribute to a deeper understanding of the complex seismotectonic framework and high lithospheric variability in the investigated region. [ABSTRACT FROM AUTHOR]

Anisotropic behaviors of layered rocks, characterized by the distinct mechanical responses to varying loading directions, have been widely studied in laboratory tests. However, understanding the microscale failure mechanisms of beddings and rock matrices is still challenging in laboratory scale. In this study, we present a numerical modeling based on PFC3D to investigate the mechanical responses of slates with five bedding angles (0°, 30°, 45°, 60°, 90°) under differential cyclic loading (DCL). The beddings and matrices are modeled using the same contact model to ensure the comparability of parameters, with the weakened parameters of beddings reasonably determined through X-ray diffraction (XRD). The damage evolution paths are characterized by the degradation of the bond diameter. The simulation results replicate realistic stress–strain curves documented in laboratory tests. We develop an acoustic emission (AE) algorithm for respectively monitoring the AE events occurring in beddings and matrices. Additionally, the release of the bond energy is captured to determine the b-values in simulation, and experimental data are used to validate its rationality. Finally, the macroscopic failure patterns obtained from numerical simulations are compared to the failed samples in laboratory test and the nuclear magnetic resonance (NMR) results, demonstrating a consistent correlation and verifying the validity of the proposed model. Highlights: The force chain evolution for different bedding angles was analyzed under differential cyclic loading. A dual system for monitoring AE events in beddings and rock matrices was created based on the 3D particle model. The method of calculating numerical b-value was given based on the released energy at bond failure. [ABSTRACT FROM AUTHOR]

The distinction between the shear behavior of tensile- and shear-induced fractures is critical to understanding the deformation and failure of geologic discontinuities at different scales. To investigate these differences, a series of direct shear tests were performed on sandstone specimens with a continuous fracture created by either splitting or shearing. The acoustic emission (AE) technique was used to examine variations in grain-size cracking behavior between specimens with tensile- and shear-induced fractures. An increase in normal stress for both fracture types correlates with increased microcrack density and energy release. However, there are notable differences: during the shear process, tensile-induced fractures produce AE sequences similar to the seismic patterns observed along natural tectonic faults, with foreshocks, mainshocks, and aftershocks. In contrast, the AE sequence for shear-induced fractures during the shear process lacks prominent mainshocks and deviates progressively from the power-law function with time as normal stress increases. In addition, the AE b-value for tension-induced fractures initially shows a gradual decrease as the mainshock approaches and then slowly increases during the aftershock period. In contrast, the b-value remains nearly constant for shear-induced fractures due to the low roughness and heterogeneity of the fracture surface. These differences highlight the strong correlation between AE responses and fault heterogeneity, paving the way for fault characterization and risk assessment in subsurface energy extraction. Highlights: The cracking behavior of both tensile- and shear-induced fractures in direct shear tests is investigated using the AE technique. In direct shear tests, the AE sequences of tensile fractures follow a power law, while a significant deviation from the power law is observed in the AE sequence of shear fractures. The power-law evolution of the AE sequence before and after the mainshock, together with anomalous b-values, can be used as indicators to distinguish young faults from mature faults. [ABSTRACT FROM AUTHOR]

This work presents particle-based numerical simulations on coal pillars in a coal mine based underground water reservoir (CMUWR). We aim to replicate the stress–strain characteristics and present the acoustic emission behavior of the coal under complex dynamic stress paths. The study reveals failure characteristics of coal exposed to monotonic/cyclic shear load under constant/cyclic normal loads. Based on the evolution of stress-time-dependent bond diameter implemented in particle model, different damage paths are established for dry and water-immersed samples under two loading frequencies. Furthermore, the numerical Gutenberg–Richter's b-value was calculated from the released energy emanating from bond failure, and this work presents the evolution of numerical Gutenberg–Richter's b-value. The numerical simulation contributes to a micromechanical understanding of the failure mechanisms of coal under water-immersion and cyclic stress, providing valuable insights for strength prediction of CMUWR. [ABSTRACT FROM AUTHOR]

Seismic activity in Aswan is influenced by the complex interactions of tectonic plates, the accumulation of stress, and the presence of geological fault systems. It revealed that epicenters are well distributed along four fault segments in a conjugate pattern, indicating a prominent E-W compressional stress. This research aims to explore the characteristics of seismicity and seismotectonics, with a focus on assessing their implications for risk reduction and disaster management in this densely populated region. A data review from the Egyptian National Seismological Network (ENSN) identified 464 earthquakes occurred between 2000 and 2021, with local magnitudes ranging from 0.3 to 4.4, and depths up to 25 km. The calculated Gutenberg-Richter b-value is approximately 0.87 ± 0.05, indicating a gradual stress accumulation. The current analysis shows a more consistent level of moderate seismic activity, unlike previous studies in Aswan region that reported a wide range of b-values from 0.554 to 1.07. This suggests that while earlier research captured a wider range of seismic behaviors, recent data indicates a stabilization in earthquake frequency and intensity. Additionally, the fractal dimension (Dc) calculated at 1.57 ± 0.04 shows an intermediate level of complexity and reflecting a clustering pattern of earthquakes. The variations in the b-value with different magnitudes and depths signify the involvement of active smaller faults, responsible for earthquakes up to magnitude 2.2, which then transition to fractured zones inducing earthquakes up to magnitude 2.5. This transition is followed by a decline in seismic activity, indicating regions that are potentially more likely to experience larger earthquakes. Moreover, stress disparities at various depths contribute to smaller earthquakes within the 5–10 km depth range. Return period analysis suggests that the earthquakes of magnitude 3.7 or higher are expected to occur approximately once every decade in Aswan. These findings are of utmost importance for earthquake risk reduction, hazard assessment, and the sustainable development of Aswan area.

The Alborz Mountains are among the areas exhibiting high tectonic and seismic activity in northern Iran. Studying key parameters of tectonic structures, including quantitative analysis and observational studies, in such active regions is essential to identify potential active faults and assess the consequent seismic hazards. This study focuses on seismicity and seismotectonics by analyzing seismic parameters, including b-value, mean seismic activity rate, earthquake recurrence time, seismic moment, and fractal dimension derived from micro and teleseismic data. The b-values vary between 0.6 and 1.1 in the tectonically active parts of the study area, corresponding with the reverse/thrust and strike-slip active faults. Large earthquakes might be prone to occur at 10–25 km depth because both catalogues show low b-values (b < 1.0) concentrations at this depth range. The high fractal dimension (> 1.5), high seismic activity rate, large seismic moment parameters, and its continuously increasing trend. Short recurrence periods (20–50 years) of M 6.5 events also emphasize the high seismic activity and high seismic hazard. On the other hand, the prevalence of low b-values is notably observed in areas encompassing densely populated cities such as Rasht, Lahijan, Amol, Babol, Sari, Behshahr, Gorgan, and the megacity of Tehran. Furthermore, we have identified asperities where the Gorgan Plain, the Khazar, and the Alamutrud Fault Zones are located. These findings emphasize the seismic hazard potential in the identified areas and urban centers within the study area. Therefore, particular attention should be directed towards areas exhibiting low b-values when assessing and mitigating seismic hazards. It underscores the necessity for additional focus on seismic hazard assessment and implementation of mitigation strategies in the Alborz region. [ABSTRACT FROM AUTHOR]

This paper introduces a software tool developed within the MATLAB environment, called Tremors, aimed at streamlining the pre-processing and analysis of seismic catalogues, with a particular emphasis on determining the Magnitude of Completeness. It will outline the criteria for event selection, as well as various techniques to derive the Magnitude of Completeness values, including the recent and widely used Lilliefors statistical method. The study also addresses the important issue of short-term aftershock incompleteness and proposes solutions for managing it. Moreover, the software generates high-quality, customizable figures, and georeferenced raster images in.tif format as output. A standalone version of the App is also available (i.e., the users do not need a MATLAB license on their PC/laptop). [ABSTRACT FROM AUTHOR]

We use the Godano et al. (2022, https://doi.org/10.1029/2021ea002205) method for evaluating the b maps of the faults associated with the largest earthquakes M ≥ 7.0 that occurred in California. The method allows an independent evaluation of the b parameter, avoiding the overlap of the cells and the omission of some earthquakes, while keeping all the available information in the catalog. We analyzed four large earthquakes: Landers, Hector Mine, Baja California, and Searles Valley. The maps obtained confirm that the b value can be considered as a strain meter and allow us to elucidate the presence of barriers, such as obstacles to the propagation of the fracture, on the fault of the analyzed earthquakes. A further estimated parameter is the time window during which aftershocks occur in the cell, Δt. This quantity is very useful for a better definition of the aftershock generation mechanism. It reveals where the stress is released in a short time interval and how the complexity of the faulting process controls the occurrence of aftershocks on the fault, and also the duration of the entire sequence. Plain Language Summary: The use of the Godano et al. (2022, https://doi.org/10.1029/2021ea002205) method for evaluating the b maps for the on‐fault seismicity during the occurrence of aftershocks allows us to put some constraints on the faulting process during the aftershock sequences. Key Points: Independent cells b value spatial maps evaluationNew operator‐independent griding method for spatial discretization [ABSTRACT FROM AUTHOR]

Objective: To compare image quality and diagnostic performance using different b-values for the zooming technique with diffusion-weighted imaging (ZOOMit-DWI) in thyroid nodules Materials and Methods: A total of 51 benign thyroid nodules and 50 thyroid papillary carcinomas were included. ZOOMit-DWI was performed with b-values of 0, 500, 1000, 1500 and 2000 s/mm². The sharpness was evaluated as subjective index. The signal intensity ratio (SIR), signal-to-noise ratio (SNR) and apparent diffusion coefficient (ADC) were measured as objective indices. Pairwise comparisons were performed among the different b-value groups using the Friedman test. A receiver operating characteristic curve of the ADC value was used to evaluate diagnostic performance. The DeLong test was used to compare diagnostic effectiveness among the different b-value groups Results: In both the papillary carcinoma group (P = 0.670) and the benign nodule group (P = 0.185), the sharpness of nodules was similar between b-values of 1000 s/mm2and 1500 s/mm². In the papillary carcinoma group, the SIRnodule was statistically higher in DWI images with a b-value of 1500 s/mm²than in DWI images with b-values of 500 s/mm²(P = 0.004), 1000 s/mm²(P = 0.002), and 2000 s/mm²(P = 0.003). When the b-values were 1500 s/mm²(P = 0.008) and 2000 s/mm²(P = 0.009), the SIRnodule significantly differed between the papillary carcinoma group and the benign nodule group. When b = 500 s/mm², the ADC had an AUC of 0.888. When b = 1000 s/mm², the ADC had an AUC of 0.881. When b = 1500 s/mm², the ADC had an AUC of 0.896. When b = 2000 s/mm², the ADC had an AUC of 0.871. The DeLong test showed comparable diagnostic effectiveness among the different b-value groups except for between b-values of 2000 s/mm2and 1500 s/mm², with a b-value of 2000 s/mm²showing lower effectiveness Conclusion: This study suggests that 1500 s/mm²may be a suitable b-value to differentiate benign and malignant thyroid nodules in ZOOMit-DWI images, which yielded better image quality. [ABSTRACT FROM AUTHOR]

On 6 February 2023, Türkiye experienced a pair of consecutive earthquakes with magnitudes of Mw 7.8 and 7.5, and accompanied by an intense aftershock sequence. These seismic events were particularly impactful on the segments of the East Anatolian Fault Zone (EAFZ), causing extensive damage to both human life and urban centers in Türkiye and Syria. This study explores the analysis of a dataset spanning almost one year following the Turkiye mainshocks, including 471 events with a magnitude of completeness (Mc) ≥ 4.4. We employed the maximum likelihood approach to estimate the b-value and Omori-Utsu parameters (K, c, and p-values). The estimated b-value is 1.21 ± 0.1, indicating that the mainshocks occurred in a region characterized by elevated stress levels, leading to a sequence of aftershocks of larger magnitudes due to notable irregularities in the rupture zone. The aftershock decay rate (p-value = 1.1 ± 0.04) indicates a rapid decrease in stress levels following the main shocks. However, the c-value of 0.204 ± 0.058 would indicate a relatively moderate or low initial productivity of aftershocks. Furthermore, the k-value of 76.75 ± 8.84 suggests that the decay of aftershock activity commenced within a range of approximately 68 to 86 days following the mainshocks. The fractal dimension (Dc) was assessed using the correlation integral method, yielding a value of 0.99 ± 0.03. This implies a tendency toward clustering in the aftershock seismicity and a linear configuration of the epicenters. The slip ratio during the aftershock activity was determined to be 0.75, signifying that 75% of the total slip occurred in the primary rupture, with the remaining fraction distributed among secondary faults. The methodologies and insights acquired in this research can be extended to assist in forecasting aftershock occurrences for future earthquakes, thus offering crucial data for future risk assessment. [ABSTRACT FROM AUTHOR]

Earthquake sources in Aceh have distinct characteristics. Understanding the seismic characteristics of each earthquake source is crucial for comprehending earthquake cycles and assessing seismic hazards. A key parameter in characterizing an earthquake source is the b-value, which indicates the relationship between the number of earthquakes and their magnitudes, influenced by the magnitude of completeness (Mc). The present study analyzed the seismic characteristics of two subduction zone segments and sixteen fault segments using the least squares method on selected earthquake data specific to each segment. The analysis revealed that the b-value ranged from 0.5 to 0.6 in the subduction zone segments and from 0.3 to 1.0 in the fault segments. These variances in b-value reflect the different seismic characteristics of the earthquake sources that shape the tectonic settings in Aceh. A lower b-value signifies an elastic zone capable of holding higher stress levels, whereas a higher b-value indicates a brittle zone that can only withstand lower stress levels. [ABSTRACT FROM AUTHOR]