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Jailolo, the capital of West Halmahera Regency, faces earthquake risks due to its proximity to a Jailolo volcano and a double subduction zone in Eastern Indonesia. This study is aimed at investigating the seismic hazard characteristics in Jailolo through the analysis of statistic and signal parameters. Analyzing seismic hazard characteristics in this region is crucial for assessing earthquake risks and understanding how local soil conditions influence ground shaking. Earthquake catalogs from several databases spanning from 1970 to 2018 were utilized. Additionally, 40 locations around Jailolo were surveyed using a short‐period seismometer to gather microtremor data. The earthquake catalogs underwent b value analysis using the maximum likelihood method, while microtremor data were examined for f0 and A0 using the horizontal‐to‐vertical spectrum ratio (HVSR) method. VS30 profiles were derived using the H/V curve inversion method. The b value characterizes earthquake size distribution, HVSR evaluates ground properties, especially the shallow subsurface, and VS30 represents the time‐averaged shear wave velocity in the upper 30 m of the Earth's surface. The findings revealed the average b value around Jailolo is 1.36 with a 15% deviation, categorizing the area as earthquake prone and volcanic. The values of f0 and A0 ranged from 0.536 to 2.44 Hz and 8.97 to 21.2, respectively. The results of f0 and A0 suggested that the Jailolo area is predominantly characterized by thick sediment. The H/V curve analysis provided a VS30 profile ranging from 109 to 460 m/s, indicating that the area is dominated by sediment consisting of stiff soil, very dense soil, and soft rock. In conclusion, Jailolo is highly prone to earthquakes due to its seismic and volcanic activity, supported by soil characteristics that can amplify seismic waves and increase ground shaking intensity during earthquakes. These findings stress the need for long‐term seismic monitoring and community involvement to mitigate seismic risks. [ABSTRACT FROM AUTHOR]

Using continuous waveform data from 27 fixed seismic stations in Ningxia spanning nearly a decade from 2013 to September 2022, the automatic detection matching method (PALM) was employed to capture 34,373 seismic events across the region, which is twelve times more than manual cataloging during the same period. The events were used as a template to search for smaller seismic events in the Haiyuan-Liupanshan region. After location, a total of 14,741 microseismic events were detected. Based on this expanded dataset, we calculated b value and analysis the depth profiles of seismic. The findings indicate that the distribution of microseismicity has characteristics of zonation, clustering and interruption. Seismic activity aligns with active faults and closely correlates with tectonic zones. The areas with seismic gaps and low b-value zones indicate a higher stress level on the north side of the middle section of the Haiyuan Fault, which was also the epicenter of the magnitude 4.9 Pingchuan earthquake on December 31, 2023. The seismic profiles show that the regional earthquakes mainly occur at a depth of more than 30 km. The depth distribution of these earthquakes reflects the inclination of the fault and thus corresponds exactly to the actual conditions.

A M8.5 earthquake struck the Haiyuan area in 1920 and resulted in a 240-km long surface rupture zone along the Haiyuan fault (HYF). In this study, to determine the spatial relationship between soil gases and fault activity on a regional scale, radon (Rn) and carbon dioxide (CO2) concentrations in soil gas were measured in situ with a grid spacing of 5 ∼ 10 km along the Haiyuan surface rupture zone (HYSRZ). Ordinary Kriging (OK) and Inverse Distance Weight (IDW) interpolation were used to investigate spatial variations in Rn and CO2 concentrations. Synchronous soil gas anomalies were identified in southern Haiyuan County and at the southern end of the HYSRZ, and were correlated with higher slip rate, larger deformation, and larger degree rupture size than other segments. Moreover, soil gas anomalies were spatially highly coupled with seismically active zones and low b value areas, suggesting that the permeability and porosity of gas emissions are enhanced by higher stress. Two seismic velocity profiles across the gas anomaly area confirmed that low-velocity bodies exist at 0 ∼ 10 km below the surface, as revealed by magnetotelluric (MT) sounding results, indicating that gas emissions are associated with the migration of deep fluids. Our results provide new insight into the source of fluids in the HYSRZ and offer support for the design of a continuous geochemical measurement network in this area.

The epidemic-type aftershock sequence (ETAS) model is the state-of-the-art approach for modelling short-term earthquake clustering and is preferable for short-term aftershock forecasting. However, due to the large variability of different earthquake sequences, the model parameters must be adjusted to the local seismicity for accurate forecasting. Such an adjustment based on the first aftershocks is hampered by the incompleteness of earthquake catalogues after a mainshock, which can be explained by a blind period of the seismic networks after each earthquake, during which smaller events with lower magnitudes cannot be detected. Assuming a constant blind time, direct relationships based only on this additional parameter can be established between the actual seismicity rate and magnitude distributions and those that can be detected. The ETAS-incomplete (ETASI) model uses these relationships to estimate the true ETAS parameters and the catalogue incompleteness jointly. In this study, we apply the ETASI model to the SE Türkiye earthquake sequence, consisting of a doublet of M 7.7 and M 7.6 earthquakes that occurred within less than half a day of each other on 6 February 2023. We show that the ETASI model can explain the catalogue incompleteness and fits the observed earthquake numbers and magnitudes well. A pseudo-prospective forecasting experiment shows that the daily number of detectable m ≥ 2 can be well predicted based on minimal and incomplete information from early aftershocks. However, the maximum magnitude (M max ) of the next day's aftershocks would have been overestimated due to the highly variable b value within the sequence. Instead, using the regional b value estimated for 2000–2022 would have well predicted the observed M max  values. [ABSTRACT FROM AUTHOR]

The northeastern margin of the Tibetan Plateau (NE Tibetan Plateau) exhibits active geological structures and has experienced multiple strong earthquakes, with M ≥ 7, throughout history. Particularly noteworthy is the 1920 M81/2 earthquake in the Haiyuan region that occurred a century ago and is documented as one of the deadliest earthquakes. Consequently, analyzing seismic risks in the northeastern margin of the Tibetan Plateau holds significant importance. The b value, a crucial parameter for seismic activity, plays a pivotal role in seismic hazard analyses. This study calculates the spatial b values in this region based on earthquake catalogs since 1970. The study area encompasses several major active faults, and due to variations in b values across different fault types, traditional grid-search methods may introduce significant errors in calculating the spatial b value within complex fault systems. To address this, we employed the hierarchical space–time point–process (HIST-PPM) method proposed by Ogata. This method avoids partitioning earthquake samples, optimizes parameters using Akaike's Bayesian Information Criterion (ABIC) with entropy maximization, and theoretically allows for a higher spatial resolution and more accurate b value calculations. The results indicate a high spatial heterogeneity in b values within the study area. The northwestern and southeastern regions exhibit higher b values. Along the Haiyuan fault zone, the central rupture zone of the Haiyuan earthquake has relatively higher b values than other regions of this fault zone, which is possibly related to the sufficient release of stress during the main rupture of the Haiyuan earthquake. The b values vary from high in the west to low in the east along the Zhongwei fault. On the West Qinling fault zone, the epicenter of the recent Minxian–Zhangxian earthquake is associated with a low b value. In general, regions with low b values correspond well to areas with moderate–strong seismic events in the past 50 years. The spatial differences in b values may reflect variances in seismic hazards among fault zones and regions within the same fault zone. [ABSTRACT FROM AUTHOR]

This research aimed to determine the effect of modified kepok banana starch substitution on the texture (hardness, adhesiveness, cohesiveness, and gumminess) and caramel sponge color with four different modified starch substitution percentages. This research is experimental research with RAL (Completely Randomized Design). The research results show that the values of hardness for caramel sponge cake were 27.48 N, 26.89 N, 26.86 N, and 16.66 N. The values of adhesiveness were 0.38 Nmm, 0.14 Nmm, 0.63 Nmm, and 1.21 Nmm. The cohesiveness values for the caramel cake were 0.34, 0.43, 0.40, 0.31. The values of gumminess were 9.85 N, 11.90 N, 11.02 N, 5.20 N. The L values for caramel cake were 26.61, 25.92, 32.00, and 32.31. The a values for caramel cake were 7.22, 8.83, 8.34, and 6.73, whereas the b values were 15.17, 13.64, 14.84, and 11.56. This research demonstrates that there is an effect of modified kepok banana starch substitution on the texture profile of hardness and on the L value of caramel cake color. [ABSTRACT FROM AUTHOR]

Dynamic failure of surrounding rock often causes many casualties and financial losses. Predicting the precursory characteristics of rock failure is of great significance in preventing and controlling the dynamic failure of surrounding rock. In this paper, a triaxial test of granite is carried out, and the acoustic emission events are monitored during the test. The fractal characteristics of acoustic emission events' energy distribution and time sequence are analyzed. The correlation dimension and the b value are used to study the size distribution and sequential characteristics. Furthermore, a rock failure prediction method is proposed. The correlation dimension is chosen as the main index and the b value is chosen as a secondary index for the precursor of granite failure. The study shows that: (1) The failure process can be divided into an initial stage, active stage, quiet stage, and failure stage. (2) The b value and correlation dimension both can describe the process of rock failure. There is a continuous decline before failure. Because of the complexity of the field, it is difficult to accurately estimate the stability of surrounding rock using a single index. (3) The combination of the b value and correlation dimension to establish a new method, which can accurately represent the stability of the surrounding rock. When the correlation dimension is increasing, the surrounding rock is stable with stress adjusting. When the correlation dimension is decreasing and the b value remains unchanged after briefly rising, the surrounding rock is stable, and stress is finished adjusting. When the correlation dimension and b value are both decreasing, the surrounding rock will be destroyed. [ABSTRACT FROM AUTHOR]

Rock burst is one of serious disasters that inhibit safe and high efficient coal mining. The realization of intelligent pre-warning of rock burst is the critical path to ensure coal mine intelligent and safe mining. As the b value is an effective monitoring indicator of rock burst, it is of great significance for a timely pre-warning of rock burst to grasp the evolution trend of b value in the process of mining. Therefore, based on the phase space reconstruction (PSR) and deep learning, a short-term forecast method for the b value of time sequence in mine exploitation is proposed. The b value of time sequence identified by CNN and denoised is extended to a high-dimensional space through phase space reconstruction technique, and then the long short-term memory (LSTM) network optimized by the genetic algorithm (GA) learns the high-dimensional data feature, which constructs the b value prediction Model (PSR−GA−LSTM). Combined with the W1123 fully mechanized mining face of the Kuangou coal mine identified rock burst mine, the b value of time sequence denoised is reconstructed using the optimized parameters of PSR. The prediction performance of different models is evaluated and the case research of the optimal prediction model is carried out. The research results show that after the b value of time sequence is processed by noise reduction technology, the learning ability of the model for the b value trend feature can be enhanced and the interference of noise to the precursory information of rock burst can be reduced. After the b value of time sequence is reconstructed in phase space and the hyperparameters of the LSTM are optimized, the prediction accuracy of the model can be significantly improved. Compared with other models, the residual fluctuation range of the PSR−GA−LSTM model is the smallest and stable within 0.005, and its root mean square error (RMSE), mean absolute error (MAE) and the mean absolute percentage error (MAPE) is 0.001 51, 0.001 33, 0.29%, which are lower than other models. After the PSR−GA−LSTM model is trained on the b value of time sequence, the predicted b value trend contains the precursory information of rock burst, which can provide b value pre-warning indicators for the occurrence of rock burst events in advance. The model has a better ability to predict the trend development of the b value of rock burst mine with uniform advance, and the method used in this paper can provide a reference for the prediction and pre-warning research on the evolution of rock burst in time.

Magnesium oxychloride cement recycled concrete (MOCRC) has the advantages of low carbon emissions and energy savings. To better understand the rebar corrosion problem in MOCRC under a salt lake environment, this paper presents the investigation of rebar corrosion behavior in MOCRC, as well as the difference of protective influence between single and double protective methods. During the investigation, the concrete surface strengthening materials and rebar type selection were selected as protective methods, and an electrochemical test based on linear polarization method and Tafel method was introduced. According to the time-varying characteristics of corrosion current density and mass loss of rebar in different specimens, a time-varying model of corrosion current density of rebar was established. The results show that the B values of corroded hot-rolled plain steel (HS), corroded HS with self-developed coating (CS), uncorroded CS, and uncorroded stainless steel (SS) were 28, 34, 41, and 45 mV, respectively. Also, the rebar type selection has far better protective influence than the concrete surface strengthening materials, and the double protective method was better than the single protective method. Besides, it was noticed that the time-varying characteristic of rebar corrosion in MOCRC conformed to the logarithmic-type time-varying model, which has an upward trend in the earlier stage and exponential-type time-varying model with a downward trend in the later stage. Finally, this study presents a profound investigation for the reinforcement corrosion in low-carbon and energy-saving building MOCRC structures. [ABSTRACT FROM AUTHOR]

In order to obtain the acoustic emission parameters of different bedding coal and provide reference for the analysis and determination of its fracture mechanism and fracture precursors, the uniaxial compression acoustic emission experimental study of coal samples with bedding angles of 45°, 90° and 0° was carried out, the corresponding relationship between b values of coal samples with different loading angles and stress and energy was analyzed, the variation laws of acoustic emission parameters RA and AF values were studied, and the b value and r value under loading angle of 0 ° were analyzed. The results show that: after the peak stress, a large amount of energy is released, resulting in the penetration of micro cracks into large cracks. The b values of coal samples with loading angles of 45 ° and 90 ° are close to and significantly greater than that of 0 ° coal sample, and the b value of each specimen decreases after reaching the peak stress; when the loading angle is 45 °, the failure form of coal sample is tension shear composite failure. The loading angles of 90 ° and 0 ° are mainly tensile failure; the period of sharp decrease of b value is the same as that of sharp increase of r value, and r value can be used as an index to describe the degree of coal damage.

For earthquakes (M ≥ 4.9) that occurred in the region limited by latitudes 2°S–16°N and longitudes 90°E–101°E from 1 January 1973 to 25 December 2004, we investigated temporal variations of the b value in the aftershock zone to determine its abnormal characteristics prior to the 2004 Mw9.0 Sumatra earthquake. The b value was estimated via the maximum likelihood method. We found that the b value significantly decreased by ∼36% in the aftershock zone from January 1990 to December 1999. From 2000 onwards until the Sumatra earthquake, the b value was persistently low (between 1.0 and 1.2). Furthermore, we calculated the spatial distribution of the relative changes in b value from 1990 to 1999. Only one area of larger relative declines in b value (>25%) was located very near to the epicentre of the Sumatra event. We also calculated the b values as a function of time for earthquakes in this area and its immediate vicinity. The result shows that the changes of b value with time around the epicentre is similar to that in the aftershock zone, but the relative decline amount is ∼40% around the epicentre, greater than that in the aftershock zone. Therefore, if our finding is confirmed, it will help to better constrain the location of future great earthquakes in seismic hazard analysis.

The weight–length relationship (WLR) of fish is a crucial tool in fish biology research and has received extensive attention. However, fish growth is influenced by many factors, and the WLR also changes accordingly. Our aim was to investigate how fish body shape is affected by various factors by analyzing the existing parameters of the relationship between fish body length and weight. We analyzed 198,354 fish specimens belonging to 402 species of 82 families in China and investigated the change of fish body shape in the function of their ecology. Herbivorous fish tended to be shorter and fatter than carnivorous fish, and omnivorous fish fall somewhere in between. This difference could be due to variations in feeding habits and the availability of food sources. Additionally, fish living in lentic waters tended to have a shorter and fatter body shape compared to those living in lotic waters. This could be attributed to differences in swimming behavior in these environments. Furthermore, our results showed that the b value decreased as altitude increased, and fish tended to be thinner and longer due to lower oxygen and temperature levels in high-altitude waters. Overall, our study provides valuable insights into the WLR of fish and the impact of multiple factors on fish body shape. [ABSTRACT FROM AUTHOR]

This research aimed to determine the effect of modified kepok banana starch substitution on the texture (hardness, adhesiveness, cohesiveness, and gumminess) and caramel sponge color with four different modified starch substitution percentages. This research is experimental research with RAL (Completely Randomized Design). The research results show that the values of hardness for caramel sponge cake were 27.48 N, 26.89 N, 26.86 N, and 16.66 N. The values of adhesiveness were 0.38 Nmm, 0.14 Nmm, 0.63 Nmm, and 1.21 Nmm. The cohesiveness values for the caramel cake were 0.34, 0.43, 0.40, 0.31. The values of gumminess were 9.85 N, 11.90 N, 11.02 N, 5.20 N. The L values for caramel cake were 26.61, 25.92, 32.00, and 32.31. The a values for caramel cake were 7.22, 8.83, 8.34, and 6.73, whereas the b values were 15.17, 13.64, 14.84, and 11.56. This research demonstrates that there is an effect of modified kepok banana starch substitution on the texture profile of hardness and on the L value of caramel cake color.

The northeastern margin of the Tibetan Plateau (NE Tibetan Plateau) exhibits active geological structures and has experienced multiple strong earthquakes, with M ≥ 7, throughout history. Particularly noteworthy is the 1920 M81/2 earthquake in the Haiyuan region that occurred a century ago and is documented as one of the deadliest earthquakes. Consequently, analyzing seismic risks in the northeastern margin of the Tibetan Plateau holds significant importance. The b value, a crucial parameter for seismic activity, plays a pivotal role in seismic hazard analyses. This study calculates the spatial b values in this region based on earthquake catalogs since 1970. The study area encompasses several major active faults, and due to variations in b values across different fault types, traditional grid-search methods may introduce significant errors in calculating the spatial b value within complex fault systems. To address this, we employed the hierarchical space–time point–process (HIST-PPM) method proposed by Ogata. This method avoids partitioning earthquake samples, optimizes parameters using Akaike’s Bayesian Information Criterion (ABIC) with entropy maximization, and theoretically allows for a higher spatial resolution and more accurate b value calculations. The results indicate a high spatial heterogeneity in b values within the study area. The northwestern and southeastern regions exhibit higher b values. Along the Haiyuan fault zone, the central rupture zone of the Haiyuan earthquake has relatively higher b values than other regions of this fault zone, which is possibly related to the sufficient release of stress during the main rupture of the Haiyuan earthquake. The b values vary from high in the west to low in the east along the Zhongwei fault. On the West Qinling fault zone, the epicenter of the recent Minxian–Zhangxian earthquake is associated with a low b value. In general, regions with low b values correspond well to areas with moderate–strong seismic events in the past 50 years. The spatial differences in b values may reflect variances in seismic hazards among fault zones and regions within the same fault zone.

On 21 May 2021, the MS 6.4 earthquake struck Yangbi County, Dali City, Yunnan Province. Minor seismic activities were common both before and after the earthquake; the foreshock sequence activity characteristics of this earthquake were studied to gain a better understanding and more perspective. First, between May 18 and 5 July 2021, we collected data of the seismic events from the Yangbi MS 6.4 earthquake sequence, determined the minimum magnitude of completeness of the sequence based on the magnitude-frequency relationship, filtered out the more complete earthquake sequences, and performed double-difference earthquake relocation using the HypoDD method. Then, we improved the nearest-neighbor distance algorithm and used it in conjunction with the Gaussian mixed model fitting method to conduct a comprehensive multiple factor analysis of the Yangbi MS 6.4 earthquake sequence. The main findings of our preliminary analysis are as follows: 1) We distinguished the foreshocks, mainshocks, and aftershocks of the Yangbi earthquake sequence as well as their higher-order aftershocks, using the method described in this paper, and we can obtain clear intergenerational relationships between them. We identified eight “foreshocks” with statistically greater physical significance than the others and found that majority of the shocks occurred shortly after the mainshock were direct aftershocks, with secondary or higher-order aftershocks gradually increasing in the later stage of the sequence. 2) Combining the double-difference earthquake relocation and the event distribution on the fault plane, we found that the b-value of the Yangbi foreshock sequence was clearly on the lower end of the spectrum, with an obvious nonlinear amplification process, and can be divided into three foreshock sub-sequences: sub-sequence I with the lowest b-value and a concentrated spatial distribution, which is an F-value foreshock sequence; subsequence II with an overall shallower source depth and an obvious rebound in b-value, which is an explosive aftershock sequence; subsequence III with a lower b-value and a rapid rupture spread, which is a typical U-F-ρ foreshock. 3) We constructed a topological tree of the Yangbi foreshock sequence in Yunnan Province using the nearest-neighbor distance algorithm, combining the correlation between earthquake sequence type and fault rupture intensity. We analyzed the distribution and topology of the three sub-sequences (combined) of the Yangbi MS 6.4 foreshock sequence and found the following: the topology of subsequence I was more linear than the sequence II, each was the parent event of the subsequent event, and its rupture mode was similar to the fluid intrusion rupture in a specific channel; sequence II had a relatively simple topology, exhibiting a spray topology, and independently formed a main-aftershock mini-sequence, probably triggered by its shallow brittle rupture, which caused the fluid intrusion rupture to spread faster and eventually triggered the Yangbi MS6.4 mainshock.

Dynamic failure of surrounding rock often causes many casualties and financial losses. Predicting the precursory characteristics of rock failure is of great significance in preventing and controlling the dynamic failure of surrounding rock. In this paper, a triaxial test of granite is carried out, and the acoustic emission events are monitored during the test. The fractal characteristics of acoustic emission events’ energy distribution and time sequence are analyzed. The correlation dimension and the b value are used to study the size distribution and sequential characteristics. Furthermore, a rock failure prediction method is proposed. The correlation dimension is chosen as the main index and the b value is chosen as a secondary index for the precursor of granite failure. The study shows that: (1) The failure process can be divided into an initial stage, active stage, quiet stage, and failure stage. (2) The b value and correlation dimension both can describe the process of rock failure. There is a continuous decline before failure. Because of the complexity of the field, it is difficult to accurately estimate the stability of surrounding rock using a single index. (3) The combination of the b value and correlation dimension to establish a new method, which can accurately represent the stability of the surrounding rock. When the correlation dimension is increasing, the surrounding rock is stable with stress adjusting. When the correlation dimension is decreasing and the b value remains unchanged after briefly rising, the surrounding rock is stable, and stress is finished adjusting. When the correlation dimension and b value are both decreasing, the surrounding rock will be destroyed.

A systematic decay of the aftershock rate over time is one of the most fundamental empirical laws in Earth science. However, the equally fundamental effect of a mainshock on the size distribution of subsequent earthquakes has still not been quantified today and is therefore not used in earthquake hazard assessment. We apply a stacking approach to well-recorded earthquake sequences to extract this effect. Immediately after a mainshock, the mean size distribution of events, or b value, increases by 20–30%, considerably decreasing the chance of subsequent larger events. This increase is strongest in the immediate vicinity of the mainshock, decreasing rapidly with distance but only gradually over time. We present a model that explains these observations as a consequence of the stress changes in the surrounding area caused by the mainshocks slip. Our results have substantial implications for how seismic risk during earthquake sequences is assessed.

The paper represents a test investigation of the mechanical properties and acoustic emission (AE) characteristics of low-strength coal specimens subjected to cyclic loading and unloading. From the lab tests, the following conclusions can be obtained: (1) The axial strain is very well linear with the loading–unloading cycle number, and the circumferential and volumetric strains are approximately quadratic functions with the loading–unloading cycle number; (2) Under the same loading stress interval, the elastic modulus firstly increases and then remains stable with the loading–unloading cycle number. In addition, the higher the maximum stress of a loading–unloading cycle, the more significant the plastic strengthening effect produced by this cycle; (3) The damage calculated by the cumulative AE hit count can better reflect the fact that the damage has been increasing in the loading phase and keeps basically unchanged in the unloading phase. So, the AE hit count, as a damage variable, can better describe the damage development of coal specimens. (4) The significant fluctuation of the AE b value can be used as the precursor of coal specimen failure. Additionally, the AE b value decreases rapidly at coal specimen failure. (5) The closer to the loading–unloading cycle of coal specimen failure, the more accurate the predicted "maximum magnitude" at coal specimen failure. [ABSTRACT FROM AUTHOR]

In order to reveal the fracture development and damage evolution law of marble under the influence of temperature, the deformation and failure characteristics and acoustic emission activity of marble under the conditions of 30, 60, 90, 120 ℃ and 150 ℃ were studied by using triaxial servo testing machine and acoustic emission testing system. The results show that the triaxial compression failure of marble under high temperature goes through four stages: compaction and elastic deformation stage, plastic deformation stage, ductile failure stage and instability failure stage. The higher the test temperature is, the longer the compaction deformation stage and ductile failure stage are, and the rock gradually transforms from elastic brittle failure to elastic-plastic failure. The peak strength, elastic modulus and internal friction angle of marble decrease with the increase of temperature. The acoustic emission activity of rock and the correspondence between AE location and macroscopic crack decrease with the increase of test temperature. By analyzing the characteristics of acoustic emission signal amplitude, impact, ring down count, acoustic emission energy, peak frequency and b value in the damage evolution process of marble, it is found that the amplitude fluctuation of acoustic emission is small and the temperature sensitivity is poor, but the peak frequency and b value parameters can better characterize the crack development inside the rock. The peak frequency has the highest temperature sensitivity, which is favorable as the prediction index of rock failure and instability. In the process of triaxial compression failure, tension-shear composite cracks appear in marble, of which shear cracks are dominant. High temperature inhibits the initiation of internal cracks in rock mass. The higher the test temperature is, the weaker the tensile failure and the stronger the shear failure are. The test results shed light on the study of rock thermal damage mechanism and engineering thermal damage monitoring and prediction.

The rock acoustic emission (AE) technique has often been used to study rock destruction properties and has also been considered an important measure for simulating earthquake foreshock sequences. Among them, the AE b value is an essential parameter for the size distribution characteristics and probabilistic hazard analysis of rock fractures. Variations in b values obtained in rock AE tests and earthquakes are often compared to establish analogies in the damage process and precursory analysis. Nevertheless, because the amplitudes measured on the sample boundary by an acoustic sensor (apparent amplitude) are often used to estimate the b value, which cannot descript the source size distribution, it is necessary to develop a method to obtain the size distribution characteristics of the real source from the apparent amplitude in doubly truncated distribution. In this study, we obtain AE apparent amplitudes by applying an attenuation operator to source amplitudes generated by a computer with an underlying exponential distribution and then use these simulated apparent amplitudes to perform a comparative analysis of various b value estimation methods that are used in earthquakes and propose an optimal b value estimation procedure for rock AE tests through apparent amplitudes. To further verify the reliability of the newly proposed procedure, a b value characteristics analysis was carried out on a non-explosive expansion agent rock AE test and transparent refractive index experiment with red sandstone, marble, granite, and limestone. The results indicate that mineral grains of different sizes and compositions and different types of discontinuities of rock specimens determine the rock fracture characteristics, as well as the b value. The dynamic b values decreased linearly during the loading process, which confirms that variations in the b value also depend on the stress. These results indicate that the newly proposed procedure for estimating the b value in rock AE tests based on apparent amplitudes has high reliability. [ABSTRACT FROM AUTHOR]

The b value deduced from the Gutenberg–Richter law is an important parameter for sequence and precursory analyses, both in laboratory acoustic emission tests and seismology. As the b value is a statistical value, the maximum likelihood estimation is mostly used to estimate the b value. However, traditional singly truncated maximum likelihood estimation in seismology only considers the minimum magnitude, while the acquisition device in rock acoustic emission tests will set the threshold value and maximum value of the amplitude; therefore, maximum likelihood estimation will estimate the b value in a doubly truncated size distribution, and its confidence limits need to be discussed. Here, in this study, we derive the calculation equations of the b value and the corresponding confidence limits for the maximum likelihood estimation with a narrow amplitude span in a doubly truncated frequency–amplitude distribution. The maximum likelihood b values estimated by the scheme of a singly and doubly truncated frequency–amplitude distribution are compared through acoustic emission data with the known underlying distribution. The results show that the maximum likelihood b value and confidence limits estimation scheme derived for rock acoustic emission tests with a narrow amplitude span is more reasonable. Then, the derived estimation scheme is applied to the rock dilation rupturing test; the results confirm its applicability. [ABSTRACT FROM AUTHOR]

Abstract The southern part of the Okinawa Trough forms a narrow back-arc rift basin where evidence for submarine volcanoes and active hydrothermal venting is observed. The region is also known to cause large crustal earthquakes frequently which often accompany a rapid increase in seismicity rate. Although such swarm-like activities are common in active volcanic regions and are considered to be primarily induced by crustal fluid flows, potential interactions between tectonic, magmatic and hydrologic processes have been poorly examined in the southern Okinawa Trough despite these processes happening in the proximity. Here, I report the spatial and statistical characteristics of seismic activity in the southern Okinawa Trough and discuss their relation to other rifting-related phenomena. Most of the earthquakes with magnitude greater than 5 are localized around the rift axes (the Yaeyama Rift and the Yonaguni Rift) where seismic reflection data indicated the presence of solidified magmatic intrusions into the shallow sedimentary layers. I found the areas around the rift axes show low b values of 1.2) are found around the Ishigaki Knoll and the Hatoma Knoll. These two areas are located between the rift axes and the Ryukyu Islands and correspond to potential submarine volcanoes proposed by seafloor bathymetry and seismic reflection images. This result may constrain the location of the volcanic front in the region.

The weight–length relationship (WLR) of fish is a crucial tool in fish biology research and has received extensive attention. However, fish growth is influenced by many factors, and the WLR also changes accordingly. Our aim was to investigate how fish body shape is affected by various factors by analyzing the existing parameters of the relationship between fish body length and weight. We analyzed 198,354 fish specimens belonging to 402 species of 82 families in China and investigated the change of fish body shape in the function of their ecology. Herbivorous fish tended to be shorter and fatter than carnivorous fish, and omnivorous fish fall somewhere in between. This difference could be due to variations in feeding habits and the availability of food sources. Additionally, fish living in lentic waters tended to have a shorter and fatter body shape compared to those living in lotic waters. This could be attributed to differences in swimming behavior in these environments. Furthermore, our results showed that the b value decreased as altitude increased, and fish tended to be thinner and longer due to lower oxygen and temperature levels in high-altitude waters. Overall, our study provides valuable insights into the WLR of fish and the impact of multiple factors on fish body shape.

The Gutenberg–Richter b value describes the ratio between large and small events. A number of studies have suggested that the b value decreases before large earthquakes. In this study, we investigate the temporal variation of the b value of an area along the main rupture zone of the 2008 Wenchuan earthquake (M8.0) prior to the great event. Before estimating b values, we tested the earthquake catalog to make sure that we use the reliable frequency–magnitude distribution by the calculation of MC (completeness of magnitude). We define parameter P (ΔAIC ≧ 2) values to examine the significance level of b-value changes in the temporal variation by combining a boostrap method with Akaike's Information Criterion (AIC). The b value in the main rupture zone shows a long-term decrease trend. We then focus on a smaller area where the initial rupture starts. The results show that b values significantly changed about 3 months before the 2008 Wenchuan earthquake in the initial rupture area, indicating that the b value has a potential capability to monitor and detect precursory phenomena of great earthquakes. [ABSTRACT FROM AUTHOR]

Both apparent stress and b value can reveal stress changes in the crust. As the stress increases，the apparent stress increases and the b value decreases. Therefore，the stress variation could result in a negative correlation between apparent stress and b value so that the variation of crustal tectonic stress can be investigated according to this negative correlation. In present study，on the basis of apparent stresses for earthquakes （3.0≤ML≤3.6）and earthquakes （2.0≤ML≤4.3）occurring in the aftershock region of the 2019 MS6.0 Changning earthquake from January 2000 to December 2019，we analyzed the temporal evolutions of the apparent stress and b value. It was found that from February 2013 to March 2017，the apparent stress showed a rising trend lasting for about 4 years. Within the two years before the earthquake，the apparent stress remained at a higher level. During the period when the apparent stress was increasing，b value was decreasing. When the apparent stress maintained at a higher level，b value maintained at a lower level with no distinct change. That is，before the Changning MS6.0 earthquake occurred，the apparent stress in the rupture zone increased，while the b value decreased. It indicates that there is an obvious increase of the tectonic stress in the fracture zone before the MS6.0 Changning earthquake，which has important implications for the understanding of earthquake gestation process and earthquake prediction.

The southernmost Ryukyu subduction zone may have a geodetically inferred Mw 7.5 to 8.7 megathrust earthquake in a shallow locked region, the Ryukyu fault. Paleoseismological evidence of historical earthquakes available from the last 417 years indicates that only a 1920 Mw 7.7 earthquake occurred within this magnitude range, near the downdip end of the Ryukyu fault. As slow slip events downdip the locked seismogenic zone may trigger a large subduction earthquake, we investigate how the first observed slow slip events in 2005, 2009, and 2015 initiated downdip in the Ryukyu fault interface affect the occurrence of a megathrust. We establish possible megathrust earthquake cycles from Mw 7.5 to 8.7 on the Ryukyu fault using constraints from the magnitude-frequency relation based on local historical earthquakes. This analysis shows a b value of 1.2 for magnitudes greater than Mw 7.0, which is higher than the empirical 1.0 value. This indicates that the recurrence of an event up to Mw 8.7 is longer than previously thought if the megathrust events follow the observed magnitude-frequency relation. Then, we quantify the influence of slow slip events on the triggering of a potential megathrust earthquake by calculating the static stress increase. We find that stress perturbations caused by the three slow slip events are generally consistent with the values that have triggered the large interplate earthquakes in several subduction zones. However, a large earthquake has not yet been triggered on the Ryukyu fault after a sequence of slow slip events. If the 1920 Mw 7.7 earthquake is the last rupture of the Ryukyu fault, the earthquake cycle on the Ryukyu fault is very likely in an early stage. However, this is not true if the slow slip events occur toward the end of the earthquake cycle and there has been no megathrust earthquake at the fault interface in the last 417 years, as the 2011 Mw 9.0 Tohoku earthquake. Thus, higher potential for a megathrust earthquake may occur in the southernmost Ryukyu subduction zone.

BackgroundTo evaluate the effect of b value or the magnetic field strength (B0) on the sensitivity and specificity of quantitative breast diffusion-weighted imaging (DWI).MethodsA total of 126 patients underwent clinical breast MRI that included pre-contrast DWI imaging using b values of both 1,000 and 1,500 s/mm2 at either 1.5 T (n=86) or 3.0 T (n=40). Quantitative apparent diffusion coefficients (ADC) were measured and compared for 18 benign, 33 malignant lesions, and 126 normal breast tissues. Optimal ADCmean threshold for differentiating benign and malignant lesions was estimated and the effect of b values and B0 were examined using a generalized estimating equations (GEE) model.ResultsThe optimal ADCmean threshold was 1.235×10-3 mm2/s for b value of 1,000 and 0.934×10-3 mm2/s for b value of 1,500. Using these thresholds, the sensitivities and specificities were 96% and 89% (b value =1,000, B0 =1.5 T), 89% and 98% (b value =1,000, B0 =3.0 T), 88% and 96% (b value =1,500, B0 =1.5 T), and 67% and 100% (b value =1,500, B0 =3.0 T). No significant difference was found between different B0 (P=0.26) or b values (P=0.28).ConclusionsBetter sensitivity is achieved with DWI of b value =1,000 than with b value =1,500. However, b value and B0 do not significantly impact diagnostic performance of DWI when using appropriate thresholds.

In order to analyze the spatial and temporal distribution laws of mine earthquake induced by thrust fault coal-bump under mining disturbance, according to the power distribution law of G-R seismic activity, combined with the in-situ monitoring micro-seismic data and numerical simulation method, the frequency and energy release levels of high-magnitude events in underground mine earthquake activities are analyzed by b value and seismic moment M0.The results show that:the distribution law of underground micro-seismic activity is similar to the seismic distribution law of the crust.The activity of micro-seismic events is related to the b value.The smaller the b-value is, the higher the frequency of high-magnitude mine shock event in the entire mine shock events, and the more serious the impact on the working face.The analysis finds that the b value is affected by the in-situ stress, mining disturbance, and fault properties.Specifically:increasing the maximum and minimum principal stress difference, mining rate, fault throw or decreasing fault dip angle will reduce b value, resulting in high activity of micro-seismic activity, inducing coal-bump, and threatening the safe mining.There is obvious difference in the spatial distribution of thrust fault seismic moment M0.Under the influence of mining disturbance, the seismic moment in the upper area of the fault is relatively large.As the working face is approached, the overall value of the seismic moment is continuously increasing, and the area of high peak seismic moment is continuously expanding from top to bottom.The increase of the seismic moment value on the fault means that the level of releasable energy continues to increase, and the corresponding disturbance to the working face will be more intense, further increasing the risk of coal bumps.

In order to study the mechanical characteristics of coal deformation and failure and the evolution of acoustic emission b value of coal in parallel bedding direction, the coal sample in Bijie Mining Area of Guizhou Province is taken as the research object. In this paper, the indoor multi-stage cyclic loading and unloading test is conducted with MTS815. The results show that the elastic modulus exhibits a three-stage change trend, namely, a sharp increase-a slow increase-a sharp decrease; Poisson’s ratio and irreversible strains also exhibit a three-stage change tendency, that is, a slow increase-a gradual increase-a sharp increase. As the stress level increases, the b value of acoustic emission fluctuates somewhat and then stabilizes. When the coal sample is close to rupture, the acoustic emission b value is further reduced.

To study the energy evolution and acoustic emission characteristics of layered sandstone under anchorage in the process of deformation and failure, the sandstone samples from Chuxiong Yi Autonomous Prefecture, Yunnan Province were selected for uniaxial compression testing. The energy evolution in the process of sandstone failure and the spatial fractal characteristics of acoustic emission events in the process of deformation and failure were investigated. Research results show that anchoring can make layered sandstone store more energy, the stored energy first increases, then decreases with the increase of bedding angle; the B value of sandstone under anchorage is generally higher than that of unanchored sandstone in the whole deformation and failure process, and the continuous decline in B value can be used to indicate a precursor to instability and failure; under the action of anchoring, the D value of sandstone (its fractal dimension) also increases, then decreases with the increase of bedding angle. The D value changes within [2, 3]. At a given bedding angle, the D value of anchored sandstone is greater than that of unanchored sandstone, the D value of 30° anchored sandstone increased the most (by 12.33%); the maximum D value occurred in 45° anchored sandstone (reaching 2.72) and the spatial distribution of acoustic emission events and damage of sandstone under anchorage is also more uniform; under increasing stress, the number of acoustic emission events is less widely distributed in the early stage and more densely distributed in the later stage. The growth rate of the D value varies across different peak stress ranges, which is more significant under the action of anchorage. The acoustic emission event counts grow evenly and slowly in the space, and the toughness of sandstone is improved to a certain extent under the action of anchorage.

Purpose To determine whether the unsupervised domain adaptation (UDA) method with generated images improves the performance of a supervised learning (SL) model for prostate cancer (PCa) detection using multisite biparametric (bp) MRI datasets. Materials and Methods This retrospective study included data from 5150 patients (14 191 samples) collected across nine different imaging centers. A novel UDA method using a unified generative model was developed for PCa detection using multisite bpMRI datasets. This method translates diffusion-weighted imaging (DWI) acquisitions, including apparent diffusion coefficient (ADC) and individual diffusion-weighted (DW) images acquired using various b values, to align with the style of images acquired using b values recommended by Prostate Imaging Reporting and Data System (PI-RADS) guidelines. The generated ADC and DW images replace the original images for PCa detection. An independent set of 1692 test cases (2393 samples) was used for evaluation. The area under the receiver operating characteristic curve (AUC) was used as the primary metric, and statistical analysis was performed via bootstrapping. Results For all test cases, the AUC values for baseline SL and UDA methods were 0.73 and 0.79 ( P < .001), respectively, for PCa lesions with PI-RADS score of 3 or greater and 0.77 and 0.80 ( P < .001) for lesions with PI-RADS scores of 4 or greater. In the 361 test cases under the most unfavorable image acquisition setting, the AUC values for baseline SL and UDA were 0.49 and 0.76 ( P < .001) for lesions with PI-RADS scores of 3 or greater and 0.50 and 0.77 ( P < .001) for lesions with PI-RADS scores of 4 or greater. Conclusion UDA with generated images improved the performance of SL methods in PCa lesion detection across multisite datasets with various b values, especially for images acquired with significant deviations from the PI-RADS-recommended DWI protocol (eg, with an extremely high b value). Keywords: Prostate Cancer Detection, Multisite, Unsupervised Domain Adaptation, Diffusion-weighted Imaging, b Value Supplemental material is available for this article. © RSNA, 2024.

The accurate identification and quantification of rock damage are important for the reliable safety assessment of rock engineering. In this paper, stress-strain behavior, passive acoustic emission (AE), and active ultrasonic transmission were measured simultaneously under uniaxial compression to characterize the fracture damage of granites. The deformation and acoustic behaviors with respect to crack initiation and crack damage thresholds were analyzed. Meanwhile, irreversible damage was quantified using different methods. The results show that the marked increase in the AE rate and the average hit energy coincide with the crack initiation stress, ranging from 0.41σc–0.45σc (uniaxial compressive strength), which occurs earlier than the decrease of the P -wave velocity and onset of the rock dilation. The moment in which the average hit energy and ratio of low-frequency AEs start to increase rapidly corresponds to the crack damage stress of 0.71σc–0.74σc. In addition, the fracture damage was quantified by the crack volumetric strain, dissipated energy, modulus loss, AE characteristics, b value (defined as the log-linear slope of the frequency-magnitude distribution of AEs), and ultrasonic properties. It is revealed that the majority of rock damage accumulates after the crack damage stress, corresponding to the appearance of most high-magnitude hypocenters. Rock damage quantified by dissipated energy and AE energy with clear physical meaning is more reasonable and less subjective. Moreover, the precipitous reduction of the b value, a sharp increase in AE energy, and the ratio of low-frequency AEs prior to peak failure is a perfect precursor of potentially brittle failure. [ABSTRACT FROM AUTHOR]

The paper represents a test investigation of the mechanical properties and acoustic emission (AE) characteristics of low-strength coal specimens subjected to cyclic loading and unloading. From the lab tests, the following conclusions can be obtained: (1) The axial strain is very well linear with the loading–unloading cycle number, and the circumferential and volumetric strains are approximately quadratic functions with the loading–unloading cycle number; (2) Under the same loading stress interval, the elastic modulus firstly increases and then remains stable with the loading–unloading cycle number. In addition, the higher the maximum stress of a loading–unloading cycle, the more significant the plastic strengthening effect produced by this cycle; (3) The damage calculated by the cumulative AE hit count can better reflect the fact that the damage has been increasing in the loading phase and keeps basically unchanged in the unloading phase. So, the AE hit count, as a damage variable, can better describe the damage development of coal specimens. (4) The significant fluctuation of the AE b value can be used as the precursor of coal specimen failure. Additionally, the AE b value decreases rapidly at coal specimen failure. (5) The closer to the loading–unloading cycle of coal specimen failure, the more accurate the predicted “maximum magnitude” at coal specimen failure.

Changes in the stress state of faults and their surroundings is a highly plausible mechanism explaining earthquake interaction. These stress changes can impact the seismicity rate and the size distribution of earthquakes. However, the effect of large earthquakes on the earthquake size distribution along the Longmenshan fault has not been quantified. We evaluated the levels of the b value for the stable state before and after the large earthquakes on 12 May 2008 (Wenchuan, MS 8.0) and 20 April 2013 (Lushan, MS 7.0) along the Longmenshan fault. We found that after the mainshocks, the size distribution of the subsequent earthquakes shifted toward relatively larger events in the Wenchuan aftershock zone (b value decreased from 1.21 to 0.84), and generally remained invariable in the Lushan aftershock zone (b value remained at 0.76). The time required for the b value to return to stable states after both mainshocks was entirely consistent with the time needed by the aftershock depth images to stop visibly changing. The result of the temporal variation of b values shows decreasing trends for the b value before both large earthquakes. Our results are available for assessing the potential seismic risk of the Longmenshan fault as a reference. [ABSTRACT FROM AUTHOR]

The southern part of the Okinawa Trough forms a narrow back-arc rift basin where evidence for submarine volcanoes and active hydrothermal venting is observed. The region is also known to cause large crustal earthquakes frequently which often accompany a rapid increase in seismicity rate. Although such swarm-like activities are common in active volcanic regions and are considered to be primarily induced by crustal fluid flows, potential interactions between tectonic, magmatic and hydrologic processes have been poorly examined in the southern Okinawa Trough despite these processes happening in the proximity. Here, I report the spatial and statistical characteristics of seismic activity in the southern Okinawa Trough and discuss their relation to other rifting-related phenomena. Most of the earthquakes with magnitude greater than 5 are localized around the rift axes (the Yaeyama Rift and the Yonaguni Rift) where seismic reflection data indicated the presence of solidified magmatic intrusions into the shallow sedimentary layers. I found the areas around the rift axes show low b values of < 0.8 and suggest that stress changes directly induced by dike intrusions beneath the rift axes control the occurrence of swarm activities. On the contrary, regions with high b values (> 1.2) are found around the Ishigaki Knoll and the Hatoma Knoll. These two areas are located between the rift axes and the Ryukyu Islands and correspond to potential submarine volcanoes proposed by seafloor bathymetry and seismic reflection images. This result may constrain the location of the volcanic front in the region. [ABSTRACT FROM AUTHOR]

Cervical cancer is the second most common type of cancer worldwide, it is reaching 15% of all kind of cancer in women. There are several ways to diagnose cervical cancer, one of them is an MRI. One of the MRI sequences which can perform the pathology of cervical cancer is Diffusion-Weighted Image. The aim of this research is to find out the anatomical differences between axial slice image of Pelvic MRI which is using DWI sequence with the variation of b value in the case of cervical cancer, and also to reveal the optimal b value to obtain the image of Pelvic MRI which is using DWI sequence in the case of cervical cancer. The method of this research is experimental with the comparison of static groups. Data is 30 images of axial DWI Pelvic MRI from 10 patients in the case of cervical cancer with 3 different variations of b value, which are 600 s/mm2, 800 s/mm2, and 1000 s/mm2. Assessment of information image data done by the radiologist. Data analysis by Friedman and Wilcoxon Test. The result showed that there are differences of image information between axial Pelvic MRI which is using the DWI sequence with the variation of b value in the case of cervical cancer with a significant p-value 0.001. Differences in image information occur in the tumor, expansion of tumor, parametrium until the pelvic wall and lymph. The optimal use of b value for axial Pelvic MRI with DWI sequence in the case of cervical cancer is 600 s/mm2.

Abstract Background Differentiation between malignant and benign masses is essential for treatment planning and helps in improving the prognosis of malignant tumors; the aim of this work is to determine the role of diffusion-weighted magnetic resonance imaging (DW-MRI) and the apparent diffusion coefficient (ADC) in the differentiation between benign and malignant solid head and neck masses by comparing diagnostic performance of low b values (0.50 and 400 s/mm2) versus high b values (800 and 1000 s/mm2) and comparing the result with histopathological finding. Results The study included 60 patients (34 male and 26 female) with solid head and neck masses > 1 cm who referred to radiodiagnosis department for MRI evaluation. Multiple b values were used 50, 400, 800, and 1000 s/mm2 (at least 2 b values). DWI and ADC value of all 60 patients were acquired. Mean ADC values of both malignant and benign masses were statistically measured and compared, and cut off value was determined. Solid head and neck masses in our study DWI with the use of high b value 800 and 1000 s/mm2 were of higher significance (P value 0.001*). There was a significant difference in the mean ADC value between benign and malignant masses (P

The rock acoustic emission (AE) technique has often been used to study rock destruction properties and has also been considered an important measure for simulating earthquake foreshock sequences. Among them, the AE b value is an essential parameter for the size distribution characteristics and probabilistic hazard analysis of rock fractures. Variations in b values obtained in rock AE tests and earthquakes are often compared to establish analogies in the damage process and precursory analysis. Nevertheless, because the amplitudes measured on the sample boundary by an acoustic sensor (apparent amplitude) are often used to estimate the b value, which cannot descript the source size distribution, it is necessary to develop a method to obtain the size distribution characteristics of the real source from the apparent amplitude in doubly truncated distribution. In this study, we obtain AE apparent amplitudes by applying an attenuation operator to source amplitudes generated by a computer with an underlying exponential distribution and then use these simulated apparent amplitudes to perform a comparative analysis of various b value estimation methods that are used in earthquakes and propose an optimal b value estimation procedure for rock AE tests through apparent amplitudes. To further verify the reliability of the newly proposed procedure, a b value characteristics analysis was carried out on a non-explosive expansion agent rock AE test and transparent refractive index experiment with red sandstone, marble, granite, and limestone. The results indicate that mineral grains of different sizes and compositions and different types of discontinuities of rock specimens determine the rock fracture characteristics, as well as the b value. The dynamic b values decreased linearly during the loading process, which confirms that variations in the b value also depend on the stress. These results indicate that the newly proposed procedure for estimating the b value in rock AE tests based on apparent amplitudes has high reliability.

The b value deduced from the Gutenberg–Richter law is an important parameter for sequence and precursory analyses, both in laboratory acoustic emission tests and seismology. As the b value is a statistical value, the maximum likelihood estimation is mostly used to estimate the b value. However, traditional singly truncated maximum likelihood estimation in seismology only considers the minimum magnitude, while the acquisition device in rock acoustic emission tests will set the threshold value and maximum value of the amplitude; therefore, maximum likelihood estimation will estimate the b value in a doubly truncated size distribution, and its confidence limits need to be discussed. Here, in this study, we derive the calculation equations of the b value and the corresponding confidence limits for the maximum likelihood estimation with a narrow amplitude span in a doubly truncated frequency–amplitude distribution. The maximum likelihood b values estimated by the scheme of a singly and doubly truncated frequency–amplitude distribution are compared through acoustic emission data with the known underlying distribution. The results show that the maximum likelihood b value and confidence limits estimation scheme derived for rock acoustic emission tests with a narrow amplitude span is more reasonable. Then, the derived estimation scheme is applied to the rock dilation rupturing test; the results confirm its applicability.

This paper collects and sorts out a large amount of fault data of a series of CNC lathes, and analyzes the fault data to classify fault levels. The values of a and b are obtained by Gutenberg--Richter (G-R) curve fitting, and then the relationship between a and b is used. The b value under each division criterion is obtained. By analyzing and comparing these b values, the rationality of classifying the fault levels according to these three methods is verified. The b-value is towards 1.0 when the reliability level of CNC lathes was promoted through ten years' reliability promotion. [ABSTRACT FROM AUTHOR]

In deep mining, granite is stored with high energy duing to its structural integrity and brittleness. Rock bursts usually occur because stress changes and mining disturbances during mining, which seriously threaten safe production. Focusing on the factor -water- which may reduce the brittleness and rockburst tendency of granite, this work discussed the brittleness index and AE characteristics of dry and saturated water granite samples under uniaxial loading. The results show that the peak strength and elastic modulus of the saturated water granite are reduced. The damage degree of the water sample is larger than that of the dry sample, and the brittle failure is significantly reduced. The cumulative number of acoustic emission (AE) events in saturated water granite is significantly reduced compared to the dry sample, which is a decrease of 31.5%. However, AE event rate is higher than that of dry granite in the late loading period; AE quiet period of saturated water granite lasts longer and is more obvious than that of dry granite. Dry granite stores and releases more energy during the whole loading process, and the proportion of high energy level AE events in the later stage of loading is higher. The b value of the two samples show a downward trend with fluctuation in the critical state of fracture and a jump increases at the moment of instability. The decrease of b values of dry granite is larger than that of saturated water granite. Results suggest that the decline of AE b value of granite can be taken as the precursor of rock burst, and water can significantly reduce the rockburst tendency of granite.

The Gutenberg–Richter b value describes the ratio between large and small events. A number of studies have suggested that the b value decreases before large earthquakes. In this study, we investigate the temporal variation of the b value of an area along the main rupture zone of the 2008 Wenchuan earthquake (M8.0) prior to the great event. Before estimating b values, we tested the earthquake catalog to make sure that we use the reliable frequency–magnitude distribution by the calculation of MC (completeness of magnitude). We define parameter P (ΔAIC ≧ 2) values to examine the significance level of b-value changes in the temporal variation by combining a boostrap method with Akaike’s Information Criterion (AIC). The b value in the main rupture zone shows a long-term decrease trend. We then focus on a smaller area where the initial rupture starts. The results show that b values significantly changed about 3 months before the 2008 Wenchuan earthquake in the initial rupture area, indicating that the b value has a potential capability to monitor and detect precursory phenomena of great earthquakes.

The acoustic emission b value is an important and widely used parameter for the early prediction of rock fractures. In this study, five groups of true triaxial compression tests were conducted on granite specimens to analyze changes in b value during the process of rock failure, and to investigate the b value characteristics of acoustic emission events. First, the acoustic emission events that simultaneously triggered at least four sensors were located using P-wave arrivals and sensor coordinates. Then, considering various intervals of acoustic emission event counts, stress magnitude, and stress proportion, b values were calculated using the values of the maximum amplitude, average amplitude, maximum absolute energy, and average absolute energy of the acoustic emission events. In addition, the goodness of the fitting curves was used to evaluate the fitting reliability of the b values. The results indicated higher accuracy of b value when calculated using the average amplitude setting for intervals of acoustic emission event counts of 200 or greater, stress magnitude of 20 MPa or greater, and stress proportion of 10% or greater. Moreover, the interval of event counts of 200 is suggested as a window parameter for b value calculations, and the b values are observed to exhibit a decreasing trend before fracture for more than 80% of the specimens. Furthermore, the b value tends to decrease with an increase in confining pressure. Thus, the b value can be used as an indicator for validating the stress concentration area, including magnitudes and accumulative probability density distribution of events, which is a beneficial complement to clarifying precursor information of rock mass instability.

The influence of variety and growing location on the carotenoid and vitamin E content of 184 different varieties of durum wheat of each of the German locations Hohenheim and Seligenstadt was analyzed by HPLC. In addition, the yellow pigment content was measured as b value using a chroma meter. The results showed that the measured parameters vary both between sites and varieties, with higher variance between varieties. Finally, we elaborated a high genetic variance and heritability for lutein and total carotenoids and no negative correlations to important agronomic and quality traits in durum wheat. Thus, future durum breeding could produce varieties with improved agronomy, quality, and increased contents of lutein and total carotenoids. Vitamin E has only a minor importance due to the low contents in durum wheat. Due to the high correlation between the b value and the total carotenoid content, the b value could be used as a cheap and rapid method to initially screen high numbers of breeding lines before testing individual promising breeding lines with HPLC, warranting efficient and accurate selection of durum lines with increased carotenoid content. [ABSTRACT FROM AUTHOR]

Access tunnel in the main powerhouse of Shuangjiangkou hydropower station was deep buried with high in situ stress and complex geological conditions. Microseismic monitoring technology was established to monitor microcrack evolution process inside the surrounding rock in early excavation stage. Serious falling blocks in the left spandrel of the tunnel were predicted in a timely manner by delimiting major damage areas in the tunnel. Based on comparative analysis on microseismic activity law and field failure characteristics of the access tunnel, a quantitative index was supposed between slight rockburst like falling blocks and microseismic events. Moreover, the change law of daily average apparent stress difference and b value were analyzed based on microseismic event data. In addition, a three-dimensional numerical simulation software (RFPA3D) was used to simulate the damage distribution around the tunnel, and a relationship between spatial position of tunnel damage and direction of the maximum principal stress was qualitatively analyzed. The study results showed that advance speed of the tunnel working face was an important factor affecting the state of stress redistribution in surrounding rock mass, and the change law of b values of microseismic events could be used to predict activity state inside the surrounding rock effectively, which reflected mechanical properties and stress state of surrounding rock. In particular, field falling blocks became more serious with increasing b value, and field surrounding rock was relatively stable with minor b value. A risk of surrounding rock instability was relatively high with small b values. It provided an efficient method of predicting and assessing slight rockburst like falling blocks. The study results can provide significant guidance for field construction and later construction planning. [ABSTRACT FROM AUTHOR]

Gambusia holbrooki Girard, 1859 has established very strong populations in freshwater resources in Turkey after being introduced into Amik Lake (Hatay/Antakya) at the beginning of the 1920s. In this study, it was aimed to determine the female:male ratios and length-weight relationships of G. holbrooki populations in Turkey, which are considered as a threat, especially for endemic species. G. holbrooki specimen were sampled at total of 66 locations, including 39 lentic and 27 lotic locations, between 2016 and 2017. The female:male ratio was 1:0.39 for all of the investigated localities. Length-weight relationships were investigated at 44 sampling locations for the females and 34 sampling locations for the males. The sampled specimens ranged between 12.7 and 57.2 mm in total length, and 0.03 and 2.88 g in total weight. The length-weight relationship of the female and male G. holbrooki specimens indicated mostly isometric growth, whereas the b values varied between 1.755 and 4.009, and 2.154 and 3.665 for the females and males, respectively, in terms of the sampling locations. [ABSTRACT FROM AUTHOR]

In this paper, uniaxial compression tests are conducted on fissured red sandstone specimens to predict fracture damage (large‐scale events). The acoustic mission (AE) coupled with digital image correlation (DIC) technologies are used to monitor and record the real‐time cracking process of tested specimens. The AE characteristics are analysed during the cracking process. Moreover, three types of b‐value methods based on the AE parameters are adopted to predict the occurrence of large‐scale events (macro‐cracking). The results show that every macro‐cracking leads to a rapid decrease in three types of b value. When the fissured specimens reach to ultimate failure, all three types of b value reach to the minimum. The b value based on the AE parameters can be used as a predictor of large‐scale events during the cracking process of fissured rocks. [ABSTRACT FROM AUTHOR]

Changes in the stress state of faults and their surroundings is a highly plausible mechanism explaining earthquake interaction. These stress changes can impact the seismicity rate and the size distribution of earthquakes. However, the effect of large earthquakes on the earthquake size distribution along the Longmenshan fault has not been quantified. We evaluated the levels of the b value for the stable state before and after the large earthquakes on 12 May 2008 (Wenchuan, MS 8.0) and 20 April 2013 (Lushan, MS 7.0) along the Longmenshan fault. We found that after the mainshocks, the size distribution of the subsequent earthquakes shifted toward relatively larger events in the Wenchuan aftershock zone (b value decreased from 1.21 to 0.84), and generally remained invariable in the Lushan aftershock zone (b value remained at 0.76). The time required for the b value to return to stable states after both mainshocks was entirely consistent with the time needed by the aftershock depth images to stop visibly changing. The result of the temporal variation of b values shows decreasing trends for the b value before both large earthquakes. Our results are available for assessing the potential seismic risk of the Longmenshan fault as a reference.

Many studies have shown that b values tend to decrease prior to large earthquakes. To evaluate the forecast information in b value variations, we conduct a systematic assessment in Yunnan Province, China, where the seismicity is intense and moderate–large earthquakes occur frequently. The catalog in the past two decades is divided into four time periods (January 2000–December 2004, January 2005–December 2009, January 2010–December 2014, and January 2015–December 2019). The spatial b values are calculated for each 5-year span and then are used to forecast moderate-large earthquakes (M ≥ 5.0) in the subsequent period. As the fault systems in Yunnan Province are complex, to avoid possible biases in b value computation caused by different faulting regimes when using the grid search, the hierarchical space–time point-process models (HIST-PPM) proposed by Ogata are utilized to estimate spatial b values in this study. The forecast performance is tested by Molchan error diagram (MED) and the efficiency is quantified by probability gain (PG) and probability difference (PD). It is found that moderate–large earthquakes are more likely to occur in low b regions. The MED analysis shows that there is considerable precursory information in spatial b values and the forecast efficiency increases with magnitude in the Yunnan Province. These results suggest that the b value might be useful in middle- and long-term earthquake forecasts in the study area.