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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]

Concrete-filled steel tubular (CFST) columns are frequently used as the main load-bearing components in engineering structures due to their excellent load-bearing capacity. However, the presence of steel tube makes it impossible to accurately detect the damage characteristics of concrete by only relying on traditional mechanical measurement methods. This article quantitatively investigates the concrete damage of circular CFST column during axial compression based on the acoustic emission (AE) technique. Through the cumulative AE parameters including amplitude, count, and energy, the axial compression process of the CFST column can be divided into five main stages (Stage I is divided into two substages) to represent the different damage degree. The damage characteristics of concrete at each stage were explained by combining AE results and mechanical phenomena. A sensitivity analysis of the axial compression process was carried out using the Historic Index (HI) and Severity (Sr) and found that the sudden rise in HI and Sr corresponded to the changes in the different loading stages. The Improved b (Ib) value analysis calculated from the AE amplitudes reflects the evolution mechanism of the crack and can be used for the identification of the final failure moment of the specimen. Finally, a new method for processing and analyzing AE parameters was proposed, which effectively enhanced the dimensionality of real-time monitoring information on the damage of concrete filled in the steel tube. [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]

This study deals with the seismicity analysis of north Pakistan and its surrounding regions (Pamir, Hindu Kush, Karakorum, Kohistan, and Himalaya). For the seismicity analysis, earthquake catalogue is updated and homogenised which reports 14,158 events with magnitude M ≥ 4 from 1900 to 2021. Based on updated catalogue, the seismicity of the study region is analysed with respect to (1) various subdivisions of dataset (Subsets 1–6 based on time-institute), (2) domains based on tectonic setting or tectonic structures that include Pamir, Hindu Kush, Karakorum, Kohistan, and Himalaya, and (3) depth zones (zone-1 0–70 km, zone-2 70–150 km, and zone-3 150–300 km) based on available data and previous study. The various subsets give us Mc4.4–5.8, a value 6.5–13.5 and b value 0.73–1.89. The appropriate Mc for the whole region using various subsets is 4.9, because 4 subsets give this value, and is the average value of subsets. Period from 1900 to 1963 were identified as the low seismic activity period with a value 6.55, and subset 4 (2006–2021) the most active seismic period with a value 13.5. Pre-instrumental period (1900–1963) is dominated by large earthquakes (b value 0.73), while instrumental period (1964–2021) is dominated by small magnitude earthquakes (b value 1.77). Domain-wise Pamir, Hindu Kush, Karakorum, Kohistan, and Himalaya produced a value 11.151, 10.012, 8.091, 9.685, and 6.709, while b value 1.63, 1.36, 1.12, 1.52, and 0.86, respectively. Relatively, the lower b values of Hindu Kush, Karakorum, and Himalaya are due to thrust faults, which reveals that these are high stresses domains and dominated by moderate-to-large magnitude earthquakes. Spatially, Hindu Kush, Karakorum, and Pamir have high variation in b value (Hindu Kush 0.5–2.5, Karakorum 1.2–2.8, and Pamir 0.5–2) and large magnitude earthquake are expected in these domains. The lower b value regions (dominated by large magnitude earthquakes) are south-west of Pamir, the central region of Hindu Kush, Karakoram (almost the Pak-Afghan border), Nanga-Parbat-Haramosh, Hazara-Kashmir Syntaxis, and Kohistan Island Arc. In the depth zones of Pamir, Hindu Kush and Karakorum zone-3 of Hindu Kush and Zone-1 of Karakorum are seismically less active zones and has experienced moderate magnitude earthquakes. Kohistan and Himalaya are characterised by shallow earthquakes, but variation of b value (0.9–1.6) in the Himalaya suggests high stresses. Zone-3 (150–300 km depth) under the Pamir, Hindu Kush, and Karakorum is the zone of large earthquakes and causes deaths and damages in north Pakistan, Afghanistan, and Tajikistan. Also, in zone-1 of Pamir, the low b value approximately less than 1 in the central part of Pakistan–Afghanistan and Tajikistan border reveals that shallow seismicity also causes destruction in these countries. [ABSTRACT FROM AUTHOR]

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Copyright of Nonferrous Metals (Mining Section) is the property of Beijing Research Institute of Mining & Metallurgy Technology Group and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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]

The 14 November 2016, Mw 7.8 Kaikoura, New Zealand earthquake offers an unprecedented opportunity to observe the heterogeneity in stress field over a very complex fault system where the subduction zone converges with the strike-slip faults system. Here, we report the pre- and post-seismic stress field asperity for the first time in terms of the b value variations associated to the Kaikoura earthquake. Pre-seismic disparity of b values indicates the existence of two prominent low b value clusters, one in the neighborhood of the epicenter and the other just to the northeast of the earthquake rupture zone. Owing to the co-seismic stress release near the epicentral area, the pattern of low b value has become negligible in the post-seismic period. However, the pattern of low b value in the northeast of the rupture zone remains unchanged in the post-seismic period and indicates the unreleased strain energy in the province. The stress fields inferred from the inversion of the focal mechanism during pre- and post-seismic periods of the event suggest a strike-slip mechanism with a horizontal maximum stress axis (σ1) in the WNW-ESE direction. Nevertheless, before and after the earthquake, the stress field direction did not change significantly, indicating that the energy released during the Kaikoura event was insufficient to alter the stress orientations in the complex fault system. [ABSTRACT FROM AUTHOR]

The Gutenberg-Richter (GR) b value is a proxy for crustal stress that has been widely applied in earthquake prediction, regional stress analysis and earthquake physics investigation. Following the 2019 Mw 7.1 Ridgecrest earthquake sequence, a large number of aftershocks were well documented along the earthquake faults. We analyzed these aftershocks based on the GR law for the spatiotemporal b value distributions within the fault zone in three dimensions. The results show that the b values are homogeneous in space at a low level of ~ 0.6 immediately after the mainshock, while they increase rapidly within 3 months to ~ 1.0, which was thought to be an average level for California in the interseismic period. Meanwhile, in the first few weeks after the mainshock, the distribution of the b values along the faults is heterogeneous, where the recovery rates of the b values on individual fault cells vary dramatically along both the strike and dip. Considering significant postseismic geodetic observations, the afterslip processes along the faults may be responsible for the time-dependent variation in b values. Given that frictional sliding is a key mechanism for afterslip, the b values could then have potential for fault frictional properties, which deserve special care in the future. [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.

There exists no clear consensus about the effect of fines on the undrained monotonic shear behavior of mixed soil. The contribution of fines in the force transfer mechanism differs compared to sand. There have been conflicting conclusions regarding the role of fines in the undrained shear strength of mixed soil. Some preceding studies completely ignored the role of fines regarding fines as void, whereas some studies applied a factor to consider the role of fines. Therefore, a series of undrained monotonic triaxial tests have been performed on sand containing a small amount of fines content (fc = 0–20%) to scrutinize the effect of fines on the shear behavior of mixed soil. The test results show that the steady/critical-state lines (SSL/CSL) for sand move downwards with increased fines content in terms of global void ratio, e. But, as the void ratio is expressed in terms of equivalent intergranular void ratio e c eq , all the SSL/CSL gets normalized. The contribution factor, b, is computed as 0.21–0.28 for plastic and non-plastic fines, respectively, via the back-analysis method. This suggests that the fines contribute differently to the force transfer mechanism of the mixed soil. Also, fine particles in sand affect the critical internal angle, M, differently. The result reveals that the critical internal angle, M, decreases for plastic fines and increases for non-plastic fines. Finally, triaxial test data from several studies have been combined with the data from this study to propose a simplified method to compute the contribution factor, b. The proposed method is based on the void size distribution of host sand and fine particle, termed grain size ratio, χ . The grain size ratio is a ratio of D 10 , hostsand to D 50 , fines . Finally, an empirical equation, b = 0.8883 - 0.207 ln χ , has been proposed to compute the b value. [ABSTRACT FROM AUTHOR]

Objective: To compare the diagnostic accuracy of diffusion-weighted (DW)-MRI with b-values of 50 s/mm2 and 800 s/mm2 for the detection of bone marrow metastases in children and young adults with solid malignancies. Methods: In an institutional review board-approved prospective study, we performed 51 whole-body DW-MRI scans in 19 children and young adults (14 males, 5 females; age range: 1–25 years) with metastasized cancers before (n = 19 scans) and after (n = 32 scans) chemotherapy. Two readers determined the presence of focal bone marrow lesions in 10 anatomical areas. A third reader measured ADC and SNR of focal lesions and normal marrow. Simultaneously acquired 18F-FDG-PET scans served as the standard of reference. Data of b = 50 s/mm2 and 800 s/mm2 images were compared with the Wilcoxon signed-rank test. Inter-reader agreement was evaluated with weighted kappa statistics. Results: The SNR of bone marrow metastases was significantly higher compared to normal bone marrow on b = 50 s/mm2 (mean ± SD: 978.436 ± 1239.436 vs. 108.881 ± 109.813, p < 0.001) and b = 800 s/mm2 DW-MRI (499.638 ± 612.721 vs. 86.280 ± 89.120; p < 0.001). On 30 out of 32 post-treatment DW-MRI scans, reconverted marrow demonstrated low signal with low ADC values (0.385 × 10−3 ± 0.168 × 10−3mm2/s). The same number of metastases (556/588; 94.6%; p > 0.99) was detected on b = 50 s/mm2 and 800 s/mm2 images. However, both normal marrow and metastases exhibited low signals on ADC maps, limiting the ability to delineate metastases. The inter-reader agreement was substantial, with a weighted kappa of 0.783 and 0.778, respectively. Conclusion: Bone marrow metastases in children and young adults can be equally well detected on b = 50 s/mm2 and 800 s/mm2 images, but ADC values can be misleading. [ABSTRACT FROM AUTHOR]

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.

• The strength effects under various cyclic loads were divided into low-stress weakening, low-cycle weakening, strengthening, and fatigue effects. • The correlation between the axial and circumferential ultimate strain, peak strength, and upper limit stress of cyclic load was established. • The mechanisms of rock strengthening and fatigue effects were revealed by AE energy and sources analysis. The purpose of this paper is to reveal the influence mechanism of various cyclic loads on siltstone strength, by conducting a series of coupled cyclic-monotonic loading tests. Firstly, it was found that the peak strength of rock depends on the upper limit and cycle number of cyclic load. The peak strength of siltstone shows low-stress weakening effect, low-cycle weakening effect, strengthening effect, chaotic effect, and fatigue effect. Secondly, the ultimate strain of siltstone under cyclic load is controlled by the peak strain of uniaxial compression test. The peak strength is linearly with the peak strain, and the peak strain under uniaxial compression can be regarded as the critical threshold for fatigue failure. Then, the decrease of AE b value reflects the aggregation of micro cracks, which can predict the damage and failure of siltstone earlier than the burst of AE signals. The propagation paths of cracks under these strength effects show significant differences, by comparing the evolution of three-dimensional AE sources with different energy levels. Finally, the fracture mechanism of the strengthening and weakening effects was discussed through electron microscopy scanning. The results indicate that the micro structures are adjusted by cyclic loadings, its fracture and energy release mode was changed, resulting in the increase of peak strength. [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.

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]

Summary: The mechanical health of any composite specimen can be monitored by recording the acoustic emissions (AE) from the surface and hence can be used to predict mechanical fracturing of the material. The AE technique, which is a nondestructive and noninvasive technique, is a common method to monitor the mechanical health of a structure/material. The AE data emanated from a specimen under mechanical stress appears to follow power law distribution that can be used to estimate the power exponent (b value). It has been observed that empirical data do not completely follow power law, which in turn makes the estimation to be significantly erroneous. Some attempts have been made by the researchers in the past to filter out the non‐power law parts of the dataset; however, issues such as choice of upper and lower bounds and fixed values of these bounds for different types of datasets remain a challenge for efficient and robust estimation of b value. In the presented work, an attempt has been made to rectify the inherent shortcomings of b value and improved b value (ib value) estimation methodology. The proposed method, which is computationally light to implement, has been verified on some synthetic and experimental datasets. The results show promising improvements in the estimation of b value parameter from the previous reported methods in the literature. [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]

Dense arrays deployed near the hydraulic fracturing (HF) wells greatly enhance the understanding of injection‐induced seismicity. In this study, we revisit the continuous recordings that are acquired by 69 three‐component nodes at an HF site in Alberta, Canada, taking advantage of a machine learning‐based seismic detection and location workflow. The obtained new earthquake catalog contains 21,619 events with relative location errors of <1 m, which exceeds ∼20% of the number of earthquakes (18,040) reported previously (Igonin et al., 2021). This high‐resolution catalog reveals the distribution of earthquake sequences at much improved spatiotemporal resolution and illustrates several previously unmapped faults/fractures. Earthquake frequency‐magnitude distribution reveals that the average b value increases with depth from ∼1.1 above 3.5 km to ∼2.5 at greater depths. Further spatial analysis of seismic clusters indicates that the b value varies laterally (∼1–1.7) at shallow depths and is inversely related to the proximity to injection wells in conjunction with the change in structural types (i.e., reactivated fault and pre‐existing fracture). The seismic sequence on the north‐south oriented faults also shows a distinctive occurrence pattern and temporal affinity to the fracturing network reactivation between the two stages of HF operations. The change in faulting behavior could reflect a shift of dominating triggering mechanisms and physical processes from (a) the rapid diffusion of pore fluid pressure along pre‐existing fracture corridors to (b) the cascade migration of earthquake sequences in response to the cumulative Coulomb stress perturbation on the fluid‐lubricated, critically stressed faults. Plain Language Summary: The potential for fluid‐related industrial activities (e.g., hydraulic fracturing, HF) to induce felt earthquakes has long been recognized. In the past few years, a number of felt events (i.e., M ∼ 4) have occurred in western Canada, which are often linked to HF operations (e.g., Kao et al., 2018, https://doi.org/10.1190/tle37020117.1; Mahani et al., 2019, https://doi.org/10.1785/0220190040). To better understand processes that induce earthquakes, the Tony Creek dual Microseismic Experiment (ToC2ME) deployed a dense seismic array around an HF well in late 2016 (26 October to 30 November). In this study, we utilize a recently developed earthquake detection and location workflow to revisit the ToC2ME data set and build a high‐resolution earthquake catalog. We observe over 20,000 earthquakes with magnitudes down to −2 with high location accuracy at meter scale. The improved earthquake locations allow us to better delineate the fractures and faults activated during the HF. Our results further reveal the complexity of the triggering mechanism of HF‐induced earthquakes according to the statistical analysis of the frequency‐magnitude distribution of earthquakes. Our study suggests that multiple factors, including pore fluid pressure due to fluid injection and perturbation in the stress field caused by earthquakes, can jointly control the spatiotemporal variations of regional seismicity during multi‐stage HF operations. Key Points: We revisited the Tony Creek dual Microseismic Experiment data set and built a high‐resolution catalog with a new earthquake detection and location workflowThe 21,619 events revealed spatially varying b values associated with changes in structural type and pore‐fluid pressureMultiple triggering mechanisms may control earthquake occurrence during multi‐stage hydraulic fracturing operations [ABSTRACT FROM AUTHOR]

The stability of remnant coal pillars is of great significance for safe mining of coal resources around them. The remnant coal pillars are often soaked in mine water with a certain height. Different water levels (or depths) may affect the stability of remnant coal pillar differently. In this paper, uniaxial compression tests were carried out on coal specimens with different water soaked depths. Deformation and damage characteristics of coal specimens under loading were analyzed through acoustic emission (AE) and digital image correlation techniques. The results show that the AE energy curve of each partially soaked coal specimens presents double peak, while that of fully soaked coal specimen has only single peak. As the soaked depth increases, the AE b value gradually decreases, which indicates that the micro-fracture of coal specimens decrease with the increase of water soaked depth. During deformation and damage, partially soaked coal specimens have obvious localized strain, and the local strain concentration area is basically distributed in the dry–wet transition area. While the surface of the fully soaked coal specimen presents relatively uniform deformation. Partially distributed water within coal matrix increases the heterogeneity of the coal specimens. These results reveal the deformation and damage characteristics of coal with different water soaked depths, and provide a useful reference for reasonably evaluating the stability of coal pillars. [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.

Research on the deformation and failure of loaded rocks has a certain reference value in the fields of mining and geological hazard prediction. Here, cylindrical sandstone and metamorphic gabbro samples are taken as the research objects. The sandstone is from a quarry, and the metamorphic gabbro is from a geological exploration core of a metal deposit. Uniaxial and triaxial experiments are carried out by using TAW/GAW-2000 servo presses: TAW-2000 is used for the triaxial testing, whereas GAW-2000 is used for the uniaxial testing. The confining pressure in the triaxial test is provided by the oil pressure. The confining pressure of the triaxial test is set to 20 MPa. In the process of loading, both presses are equipped with pressure sensors to automatically record the pressure. The axial loading rate of all tests is 0.01 mm/min. The circumferential and axial deformations of the rock samples are recorded by extensometers and saved by a computer in real time. The acoustic signals of rock fractures are recorded with a PCI-2 acoustic emission collector. In the uniaxial tests, the acoustic emission probe is directly attached to the sample. In the triaxial tests, the acoustic emission probe is attached to the oil cylinder. The contributions from and conclusions of the analysis of the experimental results are as follows: The circumferential axial strain ratio damage index is defined. This index, combined with the geometry of the rupture shear plane, is considered to determine that the circumferential axial strain ratio corresponding to the triaxial compressive strength of rock is between -1 and -2. The circumferential axial strain ratio corresponding to the uniaxial compressive strength is between -0.25 and -0.4 (the range when Poisson's ratio is negative). Under the confining pressure constraint, the timing of the rapid nonlinear increase in the circumferential axial strain ratio is generally consistent with that of the uniaxial damage limit. The confining pressure constraint prolongs the nonlinear stage of damage evolution. Ignoring the low-amplitude acoustic signals with amplitudes less than 45 dB, there is an obvious difference in the rock fracture mechanisms between the tests with uniaxial and confining pressure constraints. The distribution characteristics of acoustic signals further support the uniaxial and triaxial damage evolutions of rock samples. The evolution of water flow in triaxial experiments is also discussed. The research conclusions can further deepen the understanding of the rock fracture process. [ABSTRACT FROM AUTHOR]

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]

We calculated apparent stresses for 70 earthquakes (MW ≥ 5.0) occurring in the aftershock region of the 2010 MW8.8 Bio-Bío earthquake from January 1990 to September 2019. We identified that the average apparent stress was approximately 0.487 MPa between January 1990 and December 2005 and approximately 1.063 MPa within the period from January 2006 to January 2010. The latter one is 2.2-fold greater than the former, representing a significant difference as determined by a z test, with a 99% confidence level. Moreover, we analyzed the temporal evolution of the apparent stress and found that apparent stress rapidly increased from 0.43 to 1.2 MPa during the pre-event period from March 2006 to the occurrence of the Bio-Bío MW8.8 mainshock, and this increased apparent stress was found to be significant at the 98% confidence level. Furthermore, we calculated the spatial distribution of the apparent stress in the study region and observed two higher-apparent-stress regions, within one of which the epicenter of the MW8.8 event was located. On the basis of the inverse correlation between b value and stress, the temporal evolution and spatial distribution of b values were calculated and compared with those of the apparent stress. The comparison showed that the b values decreased approximately 4 years before the occurrence of the mainshock, while the apparent stress increased substantially; for the region of lower b, the apparent stress is higher, and vice versa. Therefore, the inverse correlation between b value and stress is supported by the results obtained in the present study and can be probably considered as one of the precursors to great earthquakes. [ABSTRACT FROM AUTHOR]