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We present the development and testing of multiple epidemic-type aftershock sequence (ETAS)-based earthquake forecasting models for Switzerland, aiming to identify suitable candidate models for operational earthquake forecasting (OEF) at the Swiss Seismological Service. We consider seven model variants: four variants use parameters obtained through fitting the ETAS model to the Swiss earthquake catalog, and three use generic parameters that were fit to Californian seismicity or global seismicity from regions tectonically similar to Switzerland. The model variants use different pieces of information from the current state-of-the-art time-independent earthquake rate forecast underlying the Swiss seismic hazard model (SUIhaz2015), and one is calibrated on a larger local data set that includes smaller earthquakes by allowing a time-dependent estimate of the completeness magnitude. We test all variants using pseudoprospective short-term (7-day) forecasting experiments and retrospective long-term (30-year) consistency tests. Our results suggest that all ETAS-based models outperform the time-independent SUIhaz2015 forecast in the short term, but two of the model variants overestimate event numbers in the long term. ETAS parameters are found not to be universally transferrable across tectonic regimes, and region-specific calibration is found to add value over generic parameters. Finally, we rank all model variants based on six criteria, including the results of the pseudoprospective and retrospective tests, as well as other criteria such as model run time or consistency with the existing long-term model, using a multicriteria decision analysis approach. Based on this ranking, we propose the ETAS model calibrated on the Swiss catalog, and with the spatial background seismicity distribution of SUIhaz2015 as the ideal candidate for the first Swiss OEF system. All procedures and choices involved in the development and testing of the Swiss ETAS model follow recently established expert recommendations and can act as a reference in the establishment of time-variant earthquake forecasting models for other regions. [ABSTRACT FROM AUTHOR]

Abstract Background The initial phase of earthquake hazard assessment involves the consolidation of diverse magnitude scales, thereby requiring the homogenization of various magnitudes. Moment magnitude (Mw) emerges as the preferred descriptor for a range of magnitudes, encompassing local magnitude (ML), teleseismic magnitude (e.g., mb and MS), duration magnitudes (MD), and other magnitude proxies. Unlike alternative scales, Mw does not exhibit saturation at high magnitudes, enhancing its reliability. To achieve uniformity in magnitude representation, diverse regression techniques are employed, with the General Orthogonal Regression (GOR) method being widely regarded as the most dependable, accounting for uncertainty in both independent and dependent variables. Methods This study utilized the International Seismological Centre (ISC) Catalogue ( http://www.isc.ac.uk/ ) to compile an array of events related to the East Africa Rift System (EARS). Subsequently, the General Orthogonal Regression method was applied to merge and harmonize the collected data. Furthermore, the research computed Gutenberg-Richter b-values using the newly unified magnitude. Results Notably, the conversion relationships between magnitude proxies, including MS-mb, mb-Mw, MS-Mw, and ML-Mw, exhibited robust correlations, with coefficients of 0.86, 0.80, 0.88, and 0.94, respectively. In contrast, the relationship between ML and mb proxies revealed a notably weaker correlation, registering a coefficient of 0.54. Ultimately, the study identified a magnitude of completeness and a b-value of 3.8 and 0.71, respectively, for the EARS region, providing valuable insights for earthquake hazard assessment in this area. Conclusion Generally, the homogeneous catalogue is a step forward in seismicity assessment and geodynamic activities in the EARS. Hence, developing the empirical equations for the area is essential for future studies on seismic hazards and engineering applications due to the peculiarity of EARS’s geological and tectonic characteristics.

Original fracture structures always present discontinuity in the real rock mass, and many invisible fractures hide inside the rock mass, which may cause serious engineering safety issues. To mimic the true 3D fracture structures through the experimental method, the gypsum rock-like samples containing both 2D through-type and 3D internal-type preset flaws are prepared, and multiple sets of inclination angles of the twin parallel flaws are set in the test. By applying the AE and DIC monitoring technologies during the uniaxial compression tests, the main results are as follows: (1) The flaw inclination angle presents a direct influence on the surface cracks distribution, maximum principal strain field, and the density of secondary failure in the middle rock; (2) AE events initially distribute around the internal 3D preset flaw, while the gradient inclination angle shows a slight impact on the events' location before reaching the UCS status of samples; (3) mutations in b-values and S values can serve as evidence for predicting local damage, and the final failures quickly form at various scales and energy levels; (4) when the statistical analysis grid is divided sufficiently, the data window width and moving step length have little impact on the evaluation results, while the recommended bin width of event magnitude is 0.5 or 1.0. [ABSTRACT FROM AUTHOR]

Molybdenum nitride-based composites, specifically the two-dimensional MoN/Mo2N variants, emerge as promising electrode materials for next-generation energy storage devices. This research presents a facile synthesis approach involving a mechanochemical method followed by heat treatment at 900 ֯C in a nitrogen atmosphere to produce the MoN/Mo2N composite material. Crystallographic analysis using X-ray diffraction (XRD) and morphological characterization via high-resolution scanning electron microscopy (HRSEM) were conducted. The electrochemical evaluation demonstrated remarkable supercapacitor performance, with a specific capacitance of 306.7 F/g at 1 A/g, highlighting exceptional charge storage capacity. Even at a higher current density of 2 A/g, the composite maintained substantial reversible capacity (198.6 F/g), higher capacitance retention (95.7 %), and Coulombic efficiency (86.2 %) over 6000 cycles, showcasing its robust stability. At a challenging current density of 10 A/g, the specific capacitance remained high at 85.4 F/g. Detailed charge storage mechanism analysis, employing the Dunn method, revealed a complex interplay of capacitive and diffusive processes. Particularly noteworthy was the predominance of capacitive behavior, constituting 78.4 % at an accelerated scan rate of 100 mV/s. This observation underscores the material's advantageous propensity for a higher proportion of capacitive behavior in the charge storage mechanism at elevated scan rates, making it well-suited for applications requiring rapid energy storage and release.

AbstractThe African continent is one of the few tectonic plates where very few earthquakes have been reported. Sporadic poor data have jeopardized efforts to assess seismic hazards. In light of the tectonic setting, a review of the continent’s seismicity is crucial for predicting seismic hazards. For this study, seismicity data from USGS and ISC catalogs were collected from 1964–2022, in the latitude range of 40oS-40oN and longitude 20oW-52oE, from the surface to 700 km deep. Gutenberg’s parameters as well as the spatial variation of seismic energy were then analyzed as an assessment of Africa’s seismicity. The results show that NE Africa is at a higher stress level in terms of energy release than NW Africa. The Richter and Guttenberg’s constants of a = 5.61, b = 0.59; a = 6.55, b = 0.77; a = 6.44, b = 0.78; a = 7.41, b = 0.92; a = 5.94, b = 0.86; a = 5.97, b = 0.77 with the corresponding magnitude of completeness, mc, observed to be 3.7, 4.1, 4.4, 4.7, 4.8 and 4.6 were found for regions NW, NE, southern, eastern, western and central Africa, respectively. The distribution of focal depths vs. magnitude revealed that most of the seismicity is inherently shallow in its nature with an average focal depth of 21.22 km. In comparison, NW experiences relatively more profound events with an average depth of 32.19 km. A substantial rise in focal depth in North Africa is associated with the collision boundary. This information as a constraint on the tectonic plate near convergent boundary could be useful in plate modeling.Key Policy HighlightsThe higher stress observed in the North Africa and East Africa continent is vital for policy makers for sustainable built environmentThe estimated minimum magnitude cut-off Mw 3.7 reveals that the recording facilities in African continent is now improving.An increased focal depth distribution of events in North Africa infers there is plate convergence and can be used to constrain African tectonic plate for plate modeling.

Background: The initial phase of earthquake hazard assessment involves the consolidation of diverse magnitude scales, thereby requiring the homogenization of various magnitudes. Moment magnitude (Mw) emerges as the preferred descriptor for a range of magnitudes, encompassing local magnitude (ML), teleseismic magnitude (e.g., mb and MS), duration magnitudes (MD), and other magnitude proxies. Unlike alternative scales, Mw does not exhibit saturation at high magnitudes, enhancing its reliability. To achieve uniformity in magnitude representation, diverse regression techniques are employed, with the General Orthogonal Regression (GOR) method being widely regarded as the most dependable, accounting for uncertainty in both independent and dependent variables. Methods: This study utilized the International Seismological Centre (ISC) Catalogue (http://www.isc.ac.uk/) to compile an array of events related to the East Africa Rift System (EARS). Subsequently, the General Orthogonal Regression method was applied to merge and harmonize the collected data. Furthermore, the research computed Gutenberg-Richter b-values using the newly unified magnitude. Results: Notably, the conversion relationships between magnitude proxies, including MS-mb, mb-Mw, MS-Mw, and ML-Mw, exhibited robust correlations, with coefficients of 0.86, 0.80, 0.88, and 0.94, respectively. In contrast, the relationship between ML and mb proxies revealed a notably weaker correlation, registering a coefficient of 0.54. Ultimately, the study identified a magnitude of completeness and a b-value of 3.8 and 0.71, respectively, for the EARS region, providing valuable insights for earthquake hazard assessment in this area. Conclusion: Generally, the homogeneous catalogue is a step forward in seismicity assessment and geodynamic activities in the EARS. Hence, developing the empirical equations for the area is essential for future studies on seismic hazards and engineering applications due to the peculiarity of EARS's geological and tectonic characteristics. Article highlights: The empirical relations developed on the basis of the updated catalogue for the EARS are crucial and strong agreement with global studies for the earthquake hazard analysis in the region. The magnitude of completeness, Mc, for the EARS is significantly low as catalogues are continuously being updated. b-value obtained reveals that the EARS is experiencing active stress field with b-value significantly lower than 1. [ABSTRACT FROM AUTHOR]

The detection of abrupt changes in an evolving pattern of time series in the presence of missing data still poses a challenge to real applications. We formulate the multiple changepoint problem into a latent Markov model on a countably infinite state space. For efficiency‐enhancing, we propose a partially collapsed Gibbs sampler for the inference of the joint posterior of the number of changepoints and their locations. Variants of Viterbi algorithms are suggested for obtaining the MAP estimates of random changepoints in the presence of missing data, which provides better performances in these varying‐dimensional problems. The method is generally applicable for multiple changepoint detection under a variety of missing data mechanism. The method is applied to a case study of the magnitude‐frequency distribution of the 2010 Darfield M7.1 earthquake sequence in New Zealand. We find out some unusual features of the seismic b‐value in the Darfield earthquake sequence. It is noted that two changepoints are detected and in contrast to the background seismic b‐value, relatively low b‐values in the early aftershock propagation period are identified. We suggest that this might be a forewarning of potentially devastatingly strong aftershocks. The advance in the method of b‐value changepoint detection will enhance our understanding of earthquake occurrence and potentially lead to improved risk forecasting. [ABSTRACT FROM AUTHOR]

Original fracture structures always present discontinuity in the real rock mass, and many invisible fractures hide inside the rock mass, which may cause serious engineering safety issues. To mimic the true 3D fracture structures through the experimental method, the gypsum rock-like samples containing both 2D through-type and 3D internal-type preset flaws are prepared, and multiple sets of inclination angles of the twin parallel flaws are set in the test. By applying the AE and DIC monitoring technologies during the uniaxial compression tests, the main results are as follows: (1) The flaw inclination angle presents a direct influence on the surface cracks distribution, maximum principal strain field, and the density of secondary failure in the middle rock; (2) AE events initially distribute around the internal 3D preset flaw, while the gradient inclination angle shows a slight impact on the events’ location before reaching the UCS status of samples; (3) mutations in b-values and S values can serve as evidence for predicting local damage, and the final failures quickly form at various scales and energy levels; (4) when the statistical analysis grid is divided sufficiently, the data window width and moving step length have little impact on the evaluation results, while the recommended bin width of event magnitude is 0.5 or 1.0.

Earthquake sequences are broadly classified into 3 categories by Mogi (1963a, b). The Deccan Volcanic Province (DVP) of India witnessed earthquake sequences belonging Type 1 (Latur earthquake of M 6.2 on 29 September 1993), Type 2 (Koyna earthquake of M 6.3 on 10 December 1967), and Type 3 (Palghar earthquake swarm 2018-2020). It has been proposed that the change in the mechanical properties in the shallow crust due to loading of water reservoir has caused the change from Type 1 to Type 2 earthquake sequence for Koyna. Similarly, intense rain is considered to cause the change to Type 3. However, how these changes occur is not well understood. It is hoped that the detailed near field studies of earthquakes being undertaken at Koyna through deep bore-hole observations in the immediate vicinity of the hypocenters of earthquakes will provide an explanation.

We investigate the dependence of the Gutenberg-Richter b parameter on the crustal thickness quantified by the Moho depth, for nine different regional catalogs. We find that, for all the catalogs considered in our study, the b-value is larger in areas presenting a thicker crust. This result appears in apparent contradiction with previous findings of a b decreasing with the focal depth. However, both the results are consistent with acoustic emission experiments, indicating a b-value inversely proportion to the applied differential stress. Our results can be indeed interpreted as the signature of a larger stress concentration in areas presenting a thinner crust. This is compatible with the scenario where postseismic deformation plays a central role in stress concentration and in aftershock triggering. [ABSTRACT FROM AUTHOR]

The Apparent Diffusion Coefficient (ADC) is considered an importantimaging biomarker contributing to the assessment of tissue microstructure and pathophy- siology. It is calculated from Diffusion-Weighted Magnetic Resonance Imaging (DWI) by means of a diffusion model, usually without considering any motion during image acquisition. We propose a method to improve the computation of the ADC by coping jointly with both motion artifacts in whole-body DWI (through group-wise registration) and possible instrumental noise in the diffusion model. The proposed deformable registration method yielded on average the lowest ADC reconstruction error on data with simulated motion and diffusion. Moreover, our approach was applied on whole-body diffusion weighted images obtained with five different b-values from a cohort of 38 patients with histologically confirmed lymphomas of three different types (Hodgkin, diffuse large B-cell lymphoma and follicular lymphoma). Evaluation on the real data showed that ADC-based features, extracted using our joint optimization approach classified lymphomas with an accuracy of approximately 78.6% (yielding a 11% increase in respect to the standard features extracted from unregistered diffusion-weighted images). Furthermore, the correlation between diffusion characteristics and histopathological findings was higher than any other previous approach of ADC computation. [ABSTRACT FROM AUTHOR]

Ruinous earthquakes have frequently occurred on the border of the Ordos Block, historically. Thus, where is a future disastrous earthquake around the Ordos? This problem is becoming more and more urgent both in the scientific community and the public, particularly after the 2008 Wenchuan earthquake (Ms = 8.0). To this end, we at first compute b-values in and around the Ordos Block based on the updated catalogue with earthquakes (M ≥ 0.0) from 1 January 2010 to 31 December 2020, and presented the spatial distribution of b-values. By examining the distribution feature of b-values, we chose 14 locations on the border of the Ordos Block where the b-value is relatively low and neo-tectonic faults are active. After that, we calculate the temporal variations of b-values in these 14 places, respectively. Comparing the 14 curves of b-variations with seismic precursors on b-values, we found that four of fourteen b-variations have characteristics of earthquake precursors. Therefore, these four places, located in the western end of the Weihe Graben, both the eastern and western ends of Hetao Graben, and the northeastern front of the Tibet, are considered to be seismically dangerous in the future. Naturally, the seismic damage in these areas is more serious than other places. Hence, the study is helpful in earthquake prediction and also can provide important clues for earthquake hazard assessment around the Ordos Block.

The gravitational pulls from the moon and the sun result in tidal forces which influence both Earth's solid and water mass. These stresses are periodically added to the tectonic ones and may become sufficient for initiating rupture in fault systems critically close to failure. Previous research indicates correlations between increased seismicity rates and low tides for fast‐ and intermediate‐spreading mid‐ocean ridges in the Pacific Ocean. Here, we present a microseismicity data set (4,719 events) recorded by an ocean bottom seismometer deployment at the equatorial Mid‐Atlantic Ridge. We show that low, as well as decreasing ocean water level, result in relatively elevated seismicity rates at higher magnitudes (lower b‐values), translated into increased probabilities of stronger event occurrence at or towards low tides. Moreover, seismic bursts (enhanced activity rate clusters), occurring at rates well above the reference seismicity, are exclusively present during values of either high tidally induced extensional stresses or high extensional stress rates. Although the b‐value differences are not significant enough to be conclusive, the seismicity rate variations exhibit statistical significance, supporting the previous findings for tidal triggering at low tides within normal‐faulting regimes and extending the range of observations to slow‐spreading ridges. Observed triggering of slip on low angle faults at low tides is predicted by Coulomb stress modeling. The triggering of slip on high angle faults observed here, is not easily explained without another factor. It may be related to the presence of a shallow magma body beneath the ridge, as supported by previous seismic imaging in the region. Plain Language Summary: The Earth is periodically subjected to tidal forces due to the combined influence of solar and lunar gravity. Solid Earth tides dominate in the continents, whereas in particular marine sites ocean tides are strong enough to generate considerable stress. Although theoretically plausible, tidal triggering of earthquakes has been only occasionally observed in the Pacific Ocean, with the results often being controversial. The deployment of ocean bottom seismometers (OBS) in combination with modern earthquake detection techniques, offer better chances to study the remote oceanic environments, making it possible to recognize a tidal footprint on small earthquakes. Here we present a dense data set of small earthquakes from the equatorial Mid‐Atlantic Ridge, recorded by a temporary OBS network operated from March 2016 to February 2017. We find that the majority of the earthquakes occurred during or towards low tides, corresponding to high extensional stressing. We show that seismicity bursts (very high activity rates) exclusively occur at low tides. There is also evidence that a larger proportion of stronger events occur during or just before low tides. We interpret our results in terms of stress change modeling, considering faulting properties and the potential existence of a magma chamber beneath the study area. Key Points: Tidal triggering is investigated for a microseismicity data set from the equatorial Mid‐Atlantic RidgeSeismicity rates are increased and b‐values are decreased during and towards low tidesCoulomb stress modeling suggests additional factors are required, for example, a shallow magma chamber beneath the ridge [ABSTRACT FROM AUTHOR]

Abstract We applied the epidemic type aftershock sequence (ETAS) model, the two-stage ETAS model and the non-stationary ETAS model to investigate the detailed features of the series of earthquake occurrences before and after the M6.7 Hokkaido Eastern Iburi earthquake on 6 September 2018, based on earthquake data from October 1997. First, after the 2003 M8.0 Tokachi-Oki earthquake, seismic activity in the Eastern Iburi region reduced relative to the ETAS model. During this period, the depth ranges of the seismicity were migrating towards shallow depths, where a swarm cluster, including a M5.1 earthquake, finally occurred in the deepest part of the range. This swarm activity was well described by the non-stationary ETAS model until the M6.7 main shock. The aftershocks of the M6.7 earthquake obeyed the ETAS model until the M5.8 largest aftershock, except for a period of several days when small, swarm-like activity was found at the southern end of the aftershock region. However, when we focus on the medium and larger aftershocks, we observed quiescence relative to the ETAS model from 8.6 days after the main shock until the M5.8 largest aftershock. For micro-earthquakes, we further studied the separated aftershock sequences in the naturally divided aftershock volumes. We found that the temporal changes in the background rate and triggering coefficient (aftershock productivity) in respective sub-volumes were in contrast with each other. In particular, relative quiescence was seen in the northern deep zones that includes the M5.8 largest aftershock. Furthermore, changes in the b-values of the whole aftershock activity showed an increasing trend with respect to the logarithm of elapsed time during the entire aftershock period, which is ultimately explained by the spatially different characteristics of the aftershocks.

Abstract The Ethiopian rift which is part of East African Rift system passes through the middle of the country making it one of the most seismically active regions in the world. Thus, significant and damaging earthquakes have been reported and recorded in the past in this region. A homogeneous earthquake catalog is of basic importance for studying the earthquake occurrence pattern in space and time and for many engineering applications including assessment of seismic hazard, estimation of peak ground accelerations and determination of long-term seismic strain rates. The first earthquake catalogue for Ethiopia was prepared by Pierre Gouin and later, different authors attempted to compile a catalogue using different time period intervals and different earthquake magnitude scales. The b-value mapping and its implication never done for Ethiopia and its environs. The main purpose of the study is therefore first compile and homogenize earthquake catalog of Ethiopia including Read Sea and Gulf of Aden regions into Moment magnitude Mw scale through completeness analysis in time and magnitudes. Secondly, mapping b-values for different Seismgenic regions and understand its implications for magma induced Seismicity in the regions. During the present study, a new homogenized earthquake catalog in moment magnitude scale (Mw), covering about 3814 events is prepared for Ethiopia including Red sea and Gulf of Aden regions. The present study area is bounded within Latitude (40N − 200)N and Longitude (340N − 480)N E and have a magnitude range of Mw (3.0–7.1) with a total coverage period of 56 years (1960 to 2016). The catalog has been analyzed for magnitude completeness (Mc) using Gutenberg’s Frequency Magnitude Distribution law and it is found to be complete respectively for Mc ≥ 4.6 ± 0.03, Mc ≥ 4.6 ± 0.03, Mc ≥ 3.2, Mc ≥ 3.1 and Mc ≥ 5.1 for Afar including red sea and Gulf of Aden, Afar rift and Dabbahu Volcano, Northern, Central, and Southern Main Ethiopian Rifts. Further, the corresponding average b-value of the regions Afar including Red Sea and Gulf of Aden, Afar and Dabbahu Volcano separately, Northern Main Ethiopian Rift, Central Main Ethiopian Rift and Southern Main Ethiopian Rift respectively are estimated to be 1.17 ± 0.05, 1.15 ± 0.05, 0.843, 0.826 and 1.03 with respective period of completeness from 2003 to 2014, 2005 to 2014, 2001 to 2003, 2001 to 2003 and 1960 to 2016 for the regions. Later, mapping of the b-values in the Gutenberg-Richter relation from the newly developed catalog was performed by binning the regions into minimum of 0.050x0.050 for Afar and Dabbahu region, 0.10x0.10 for Main Ethiopian rifts and 0.20x0.20 for the other regions. Thus, the b-value characteristics of various seismogenic zones within the area have been discussed. Hence, in this study, we clearly observed that magma chamber movement including mapping of volcanic centers and magmatic segments are mapped using b-values.

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Diffusion kurtosis imaging (DKI) is a diffusion-weighted MRI technique that probes the non-Gaussian diffusion of water molecules within biological tissues. The purpose of this study was to investigate the DKI model optimal b-values combinations in invasive ductal carcinoma (IDC) versus ductal carcinoma in situ (DCIS) breast lesions. The study included 114 malignant breast lesions (64 IDC and 50 DCIS). Patients underwent a breast MRI examination which included a diffusion-weighted sequence (b = 0–3000 s/mm2). For each lesion, the b-values were combined among each other (109 combinations) and each mean kurtosis (MK) parameter was obtained. Differences between the lesion groups and b-values combinations were assessed. Also, the diagnostic performance of the combinations was determined through receiver operating characteristic (ROC) curve analysis, and compared. Root mean square error (RMSE) was also obtained. All the b-values combinations showed significant differences between the lesion groups (p < 0.05). The combination 0, 50, 200, 750, 1000, 2000 s/mm2 showed the best performance (AUC = 0.930, sensitivity = 95.3%, specificity = 82.0%, accuracy = 89.5%), with a RMSE of 17.65. The b-values combinations with the worst performance were composed of only high or ultra-high b-values, or with b = 1000 s/mm2 as the maximum b-value. Better results were obtained when zero b-value was included in the DKI model fitting with at least one b-value below 1000 s/mm2 and one b-value above 1000 s/mm2 (conserving b = 1000 s/mm2). Six was the optimal number of b-values, nonetheless other combinations with less b-values may be considered, but with a consequent diagnostic performance loss. [ABSTRACT FROM AUTHOR]

• CMTs for 46 events are computed by applying a waveform inversion method. • The geometry of focal mechanisms reveals a normal stress regime. • It is performed to obtain a more precise picture of the TGFZ stress field. • The b -value changes are computed to identify the expanded stress distribution. • High-resolution hypocenter relocation of the TGFZ seismic sequence is examined. We investigate significant earthquake sequences in the observation period between 2000 and 2018 along the Tuz Gölü Fault Zone in Central Anatolia. These sequences include a series of strong events with moment magnitudes (M w) >5.0, e.g. 30 July 2005 Bala-Ankara M w 5.2, 20 December 2007 Bala-Ankara M w 5.7 and 26 December 2007 M w 5.6 Afşar-Ankara earthquakes. The mainshocks are shallow focus strike-slip events with minor normal component at depths of 12–15 km. Focal depths of aftershocks range from 2 to 30 km. The focal mechanisms of the aftershocks are mainly normal faulting with variable strike-slip components. The geometry of focal mechanisms reveals a normal faulting regime with E-W and also NE-SW trending directions of T -axis in the entire activated region. A stress tensor inversion of focal mechanism data is performed to acquire a more accurate picture of the Tuz Gölü Fault Zone stress field. The stress tensor inversion results display a predominant normal stress regime with a NNE–SSW oriented maximum horizontal compressive stress (S H). According to high-resolution hypocenter relocations of the Tuz Gölü Fault Zone seismic sequences, eight clusters are revealed. The aftershock activities in the observation period between 5 March 2000 and 2 June 2018 extend from NW to SE direction. Seismic cross-sections show that a complex pattern of the hypocenter distribution with the activation of Tuz Gölü Fault Zone segments. The western clusters are associated with a fault plane trending mainly N-S and dipping towards almost vertical, while the eastern clusters are related to a fault plane trending NW and dipping towards SE direction. The best constrained focal depths are mainly confined in the crust (depth < 30 km) and range from 2 to 30 km. In this study, we compare the results of an analysis of b -values from seismicity and stress tensors of focal mechanism solutions to understand their coupling in terms of faulting and earthquake hazard implications. In particular, this comparison allows to investigate the spatiotemporal correlation between b -values and stress distributions and it is therefore able to locate fault segments that have a high potential of generating large earthquakes. According to recent seismicity, b -values range from 0.5 to 1.5 along the Tuz Gölü Fault Zone in Central Anatolia. The maximum horizontal compressive stress (S H) indicates N-S and NE-SW directions while the minimum horizontal compressive stress (Sh) displays E-W. These results represent that low stress variances are correlated with high b -values. Low b -values are predominant in areas with high stress rates, consistent with a high heterogeneity of focal mechanisms. [ABSTRACT FROM AUTHOR]

In this study, we compiled the Central Weather Bureau (CWB) data in order to study the Gutenberg-Richter magnitude-frequency slopes (i.e., b-values) and seismicity rates of significant earthquake sequences in the area of Hualien. A total of ten events between 1973 and 2018 were selected for analysis. Using time windows 72 h before and after the main shock, we first examined the existence of detectable foreshocks and then applied the Gutenberg-Richter law and Omori's law to determine the b-value and seismicity rate, respectively. The compiled results were used to assess the abnormalities and other characteristics of the 2018 Hualien earthquake for their forecast potential. We concluded that seismicity rates alone are not sufficient to forecast whether a greater main shock is forthcoming. The foreshock sequence of the 2018 Hualien earthquake was characterized by a low b-value and a high seismicity rate. Another earthquake with a prominent foreshock sequence occurred in 1990, but it showed a different relationship between the magnitude and the seismicity rate. For both the 1990 and the 2018 Hualien earthquakes, we found that the b-values of the foreshocks were lower than those of the respective aftershocks. The b-values for earthquake sequences are depressed relative to the background seismicity in the area. The mechanisms proposed for temporal variation in b-values are briefly reviewed to explain the observed b-value patterns. Finally, we established an empirical relationship with moment magnitude (Mw) in order to estimate the spatial range of aftershock distributions in the area of Hualien for shallow earthquakes (hypocenter depth ≤ 20 km) with Mw ≥ 5.3. [ABSTRACT FROM AUTHOR]

A multiple changepoint model for marked Poisson process is formulated as a continuous time hidden Markov model, which is an extension of Chib's multiple changepoint models (J Econ 86:221-241, 1998). The inference on the locations of changepoints and other model parameters is based on a two-block Gibbs sampling scheme. We suggest a continuous time version of forward-filtering backward-sampling algorithm for simulating the full trajectories of the latent Markov chain without utilizing the uniformization method. To retrieve the optimal posterior path of the latent Markov chain, i.e. the maximum a posteriori estimation of changepoint locations, a continuous-time version of Viterbi algorithm (CT-Viterbi) is proposed. The set of changepoint locations is obtainable either from the CT-Viterbi algorithm or the posterior samples of the latent Markov chain. The number of changepoints is determined according to a modified BIC criterion tailored particularly for the multiple changepoint problems of a marked Poisson process. We then perform a simulation study to demonstrate the methods. The methods are applied to investigate the temporal variabilities of seismicity rates and the magnitude-frequency distributions of medium size deep earthquakes in New Zealand. [ABSTRACT FROM AUTHOR]

We used earthquake catalogs recorded by Guangdong Seismological Network from 2008 to 2014 to resolve the spatial variations of b-values in the coastal area of Guangdong, particularly in three key research areas (Yangjiang, Heyuan, and offshore Nanao Island) with strong seismicity. Our results revealed that b-values exhibited significant spatial variations, and zones with low b-values could indicate the most likely seismogenic area of large earthquakes. We observed three clear low b-value patches in the offshore Nanao Island. We found a distinct high b-value peak at the depth of 11 km and two minimum peaks at about 14 and 7-8 km in the Yangjiang area. The overall b-values generally decrease with depth in the Heyuan area. The spatial variations of b-values reflect tectonic anomalies; that is, the 'low-high-low' distribution of b-values in the offshore Nanao Island and the Yangjiang area may indicate the anomaly of the crustal structure with a weak layer. The b-values of reservoir-induced seismicity are obviously lower than that induced by tectonism. This finding indicates that the reservoir area is generally at high stress state under the condition of high pore pressure. We inferred that large earthquakes might be prone to occur at 10-12 km depth in the offshore Nanao Island, at 12-15 km depth in the Yangjiang area, and at the lower part of the seismic activity zone in the Heyuan area. Moreover, the upstream area of the Xinfengjiang reservoir is the most likely area of future large earthquakes in the Heyuan area. [ABSTRACT FROM AUTHOR]

Highlights: [•] We studied the faults around Izmir of Aegean region by geodetic and seismic data. [•] To increase spatial resolution of velocity field, 3-years GPS data and published velocities combined. [•] The strain field derived from GPS observations is consistent with b-value data. [•] The areas with low b-values have the capacity of stress accumulation. [ABSTRACT FROM AUTHOR]

Analysis of 1275 seismic events recorded at least at 4 seismic stations during 2009–2013, enabled to conduct the analysis of the b- value from the Gutenberg-Richter relation in time and space in the Tres Vírgenes Volcanic and Geothermal Complex (TVVGC). A mean value of 1.64 (b = 1.64 ± 0.08) was calculated for all the TVVC, which is alike to estimations obtained at other geothermal zones and volcanic regions. The spatial distribution can be characterized by four zones with distinctive ranges of b- values. Zone A (b = 2.07 ± 0.2) corresponds to the central part of the TVVC. Zone B (b = 0.63 ± 0.04) comprises El Aguajito caldera, and El Cimarrón Fault. Zone C (b = 2.33 ± 0.3) is centered between the La Virgen Volcano, and La Virgen Fault. The zone west of La Virgen volcano, delimited by the Mezquital, and Bonfil Faults, constitutes zone D (b = 0.946 ± 0.1). A large regional and local tectonic heterogeneity is associated with zones A and C. Zone A comprises the geothermal production operation zone. Zones B and D can be correlated with regional tectonics. Larger seismicity levels are observed in zones A and C (a- values of 6.52 and 7.8 respectively) with respect to zones B (a = 2.81) and D (a = 3.05). The minimum magnitude of completeness (M c) was 2.3 and 2.6 for zones A and C, and 1.2, and 1.5 for zones B and D. At depths of 3.5 and 7.0 km, values of b = 1.47 ± 0.1 and 2.24 ± 0.2 were obtained. For depths less than 2.5 km, and larger than to 7.1 km, we estimated b = 0.93 ± 0.1 and 0.789 ± 0.05. Similarly, the largest values of the a -parameter (i.e., 4.72 and 7.66), are associated with depths between 3.5 and 7.0 km. The lowest values, 3.23 and 3.25, correspond to shallow depths of less than 2.5 km, or larger than 7.1 km. The largest values observed between 3.5 and 7.0 km might indicate that permeability is low at the Mesozoic granitic basement, and intense seismic activity (seismic swarms) is associated with tectonic and geothermal processes. Cylindrical to vertical oblate volumes are associated with four high b -value anomalies which correlate with deep reaching NW-SE regional faults (i.e., El Mezquital, La Virgen-El Campamento, and El Azufre-Reforma). These anomalies stretch along several depth intervals. A recently reported distribution of Vp, and Vp/Vs beneath the volcanic complex further indicates that the combination of tectonic and geothermal process giving rise to two of such anomalies might be due to the presence at depth of partially melted magma. In particular, beneath the northwestern portion of the La Virgen volcano, and north of the geothermal field. This interpretation implies that magma emplacement was controlled, in particular by deep reaching NW-SE regional faults, which were emplaced at different times along the NE-to-SW directed magmatic evolution of this volcanic complex. Another issue is that there are several independent heat sources beneath the TVVC. • B-values at Tres Vírgenes geothermal field (Mexico) correlate with magma bodies, or steam and hot water zones. • It is interpreted that high b-values are associated with regional faults. • The reservoir of the Tres Vírgenes geothermal field is associated with low b-values. • The granitic basement is featured by low permeability. [ABSTRACT FROM AUTHOR]

The aim of our work was to evaluate the apparent diffusion coefficient (ADC) values of normal brain over a wide age range and in different cerebral structures, including the white and grey matter. A population of 89 subjects (39 male, 50 female, age range: 3-69 years) was divided into age groups designated as 1-7 as follows: 3-9; 10-19; 20-29; 30-39; 40-49; 50-59; 60-69 years old. All subjects underwent a head MRI using a 1,5 T GE system with diffusion-weighted imaging using spin echo echo planar imaging (EPI) for b=0, 500, 1000, and 1200 s/mm². The ADC values of the following 10 regions of interest were analysed: head of the caudate nucleus (L=left and R=right side), thalamus (L and R side), centrum semiovale (L and R side), pons, respectively, as well as in cerebellum (L and R side) and vermis of the cerebellum. The ADC values of the studied brain structures showed a polynomial dependence on age indicating a logarithmic decline in children, some stabilisation during adulthood and a small trend of increasing diffusivity for subjects over the age of 50 years old. Significant interhemispheric differences in the ADC values were mainly found for thalamus, especially in older age groups. Moreover, the best differentiation of the examined structures was found in the mature brain. The knowledge of age-dependent diffusion changes in the human brain can be helpful in the proper interpretation of diffusion-weighted images in clinical practice. [ABSTRACT FROM AUTHOR]

We consider some practical issues of the determination of the b-value of sequences of magnitudes with the bootstrap method for short series of length L and various quantization levels $$\Updelta m$$ of the magnitude. Preliminary Monte Carlo tests performed with $$\Updelta m = 0$$ demonstrate the superiority of the maximum likelihood estimator b, and the inconsistency of the, yet often used, b estimator defined as the least-squares slope of the experimental Gutenberg-Richter curve. The Monte Carlo tests are also applied to an estimator, b, which minimizes the Kolmogorov-Smirnov distance between the cumulative distribution of magnitudes and a power-law model. Monte Carlo tests of discrete versions of the b and b estimators are done for $$\Updelta m = \{0.1, 0.2, 0.3 \}$$ and used as reference to evaluate the performance of the bootstrap determination of b. We show that all estimators provide b estimates within 10 % error for L ≥ 100 and if a large number, n = 2 × 10, of bootstrapped sample series is used. A resolution test done with $$\Updelta m = 0.1$$ reveals that a clear distinction between b = 0.8, 1.0, and 1.2 is obtained if L ≥ 200. [ABSTRACT FROM AUTHOR]

Seismicity in the Murindó seismic zone, Colombia (6° to 8° and − 75.5° to − 78.0°) during 1992-2007 included the occurrence of the M 6.6 foreshock on October 17, and M 7.1 mainshock on October 18, 1992, and aftershocks, which caused severe damage throughout the region. We modeled this seismic sequence by means of Coulomb stress changes imparted by slip along two semi-vertical fault planes with left-lateral motion and subdivided slip. Seismicity thereafter (1993-2007) was characterized by earthquakes magnitude in the range 0.7−6.1 for which a magnitude of completeness M = 2.7 was determined. b-values are relatively high to the south of the study region and relatively low to the north and northwest. The relocation of epicenters indicates that recent seismicity may be occurring on a fault that is yet to be mapped under the Atrato river valley. We conclude that the 1992 seismic sequence was a case of a major earthquake facilitated by the stress changes imparted during a strong rupture the previous day and that the aftershocks and background seismicity in the region can be explained by static Coulomb stress changes up to 50.1 bar. Our results have implications for hazard in Colombia and serve as basis to foster future investigations. [ABSTRACT FROM AUTHOR]

Abstract: We investigate the variations in seismicity pattern in the Taiwan region before the 2003 Chengkung, Taiwan, earthquake (M w =6.8) by calculating the standard normal deviate of the Z-values and b-values from the Gutenberg–Richter relation. The Mogi donut-shaped variations in the seismicity can be identified in the Z-value map surrounding the Chengkung earthquake source region. Noticeable decreases in the b-values have also been found around the mainshock region before the Chengkung event. The relatively low-seismicity rate and the decrease in the b-values may be the precursory phenomena associated with the quiescence in overall seismicity and the activation of moderate-sized events occurred around the mainshock region before the Chengkung event. [Copyright &y& Elsevier]

The estimation of arthropod biomass is often important in studies of terrestrial ecosystem structure and function, including analyses of the relative importance of different arthropod taxa in the diet of insectivorous animals. In order to estimate arthropod biomass in eucalypt woodlands and rehabilitated mine-land in the monsoonal tropics of northern Australia, insect morpho-species ( n = 693) and spider morpho-species ( n = 100) were collected, sorted, then weighed and measured. Body length–weight regressions were determined for spiders, nine insect orders and all insects combined. There was a significant relationship between body length and weight for all taxonomic groups, with the power model being a better predictor than linear or exponential models for all groups except Diptera (which was best predicted by the linear model). Whilst Schoener (1980) found that the length–weight regression slopes of neotropical insects (all orders combined, as well as several individual orders) differed from those of their temperate North American counterparts, our comparisons between monsoon-tropical and temperate Australian arthropods suggested differences among Dipterans and spiders only. We conclude that generalised regressions provide adequate estimates of arthropod biomass across Australia, providing that the body proportions of the dominant taxa do not vary substantively. [ABSTRACT FROM AUTHOR]

Abstract: We have proposed that points of future initiation of rupture may be mapped, based on minima in local recurrence times, which are equivalent to local maxima in the probability for main shocks to occur. These minima are often controlled by anomalously low b-values (logN = a − bM). Of the Kanto-Tokai area, approximately 12% showed anomalously short recurrence times and was proposed as asperities, based on seismicity up to 1999. During the period 1999–2003.5, about 75% of the earthquakes with M ≥3.5 fell into the asperities, earlier defined (for example 19 out of 23 M ≥3.8 events). The probability for this to occur by chance is approximately 2 10−14. This supports our idea that the most likely volumes to produce main shocks may be mapped by minima in local recurrence times. [Copyright &y& Elsevier]

Although the parameters used in seismic hazard analyses imply a long-term seismic strain rate, they are usually not checked against such alternative estimates. In this study, we determine hazard parameters for the eastern Mediterranean ( a-value, b-value, and the corresponding long-term seismic moment rate ) consistent with seismicity data, tectonic information and geodetic strain rates. The dense data coverage in this region permits a detailed comparison of the horizontal seismic strain rate field, , as recorded in the 500-yr long historical catalogue and the tectonic strain rate field, , measured geodetically. We find that is very similar in style over all magnitude ranges within each different tectonic regime in the study region. Furthermore, is similar in style to . Except along the Hellenic Arc, is consistent with in amplitude. We verify that for the high strain rates accommodated in the eastern Mediterranean and historical catalogues spanning at least 100–200 yr, should reflect the long-term seismic strain release when averaged over each tectonic zone. To estimate such seismic strain reliably, accurate knowledge about the rates of recurrence of intermediate size events is needed. For , these events can accommodate up to 60 per cent of the strain. The combined analysis of and provides an estimate of the seismic/total strain. The major strike-slip zones in the region, the Northern Anatolian Fault and the Kephalonian Fault, experience little to negligible aseismic deformation. In the remaining eastern Mediterranean up to 10–30 per cent of the total deformation is aseismic. The Hellenic Trench is largely uncoupled, with at least 50 per cent and up to 90 per cent of the compressive strain released aseismically. Only the extensional component of strain at the eastern end of this trench appears significantly seismically active. [ABSTRACT FROM AUTHOR]

Near the seamount Ho´ll in the Tjo¨rnes Fracture Zone (TFZ) north of Iceland two anomalies of high seismic b-values have been found in a depth shallower than 10 km. According to the results of similar b-value anomalies beneath volcanic edifices such as Mt. St Helens a magma chamber was suspected in the region. On first view, the existence of a long-living magma body between the island of Kolbeinsey and Ho´ll seamount appears to be confirmed by reflection seismic surveys conducted in the area with shallow water depths of 400 m. They show a clear deep reflector. However, the reflector is best imaged in a migrated record at 1500 m/s, i.e. the speed of sound in water, and it can be modeled by single scattering from the bathymetry in the area, which leads to the conclusion that the apparent reflection images the seafloor rather than a magma chamber. The recent volcanism along Manareyjar Ridge with the last eruption in 1868/69 and the hydrothermalism east of Grimsey Island would be trivially explainable by a magma chamber in the subsurface. However, there is no evidence for a magma chamber in this more southern part of the Grimsey Lineament (GL). Even in a volcanic area such as the GL as the leaky part of the TFZ, neither the existence of high b-values nor an apparent deep reflector prove the existence of a magma chamber. Instead, the seismic imaging of magma chambers in areas of intermediate to slow spreading ridge areas appears to be questionable. [Copyright &y& Elsevier]

To investigate the characteristics of earthquake hazard parameters as a means of identifying different zones of seismicity, we have compiled a catalogue of about 1850 moderate to large-sized earthquakes with magnitudes m≥4.0 or greater in southern Turkey for the time period from 1900 to 1990. Several methods have been applied to the earthquake catalogue to assess seismic hazard. The study area is divided into 77 overlapping cells of 2° size. Theoretical calculations were made for the prediction of maximum magnitude, intensity, b-values, strain energy release and corresponding m3 and peak ground acceleration levels for a given period of time. The resultant seismic hazard for each parameter is depicted as a contour map to indicate lateral variations in areas of seismic source. A combination and evaluation of various hazard parameters resulted in more reasonable estimates of hazard. It is found that the most hazardous seismic zones are the Rhodes and Burdur zones where the level of peak ground acceleration reaches up to 280 cm s-2 for an average return period of 100 years. [ABSTRACT FROM AUTHOR]

This study uses a commercial reservoir simulator to generate production rate data for shale wells with systematic variations in fracture treatment design parameters using a plausible range of reservoir properties. The synthetic well data is then used to generate diagnostic log-rate log-time plots, which allow for a distinction of four types of flow regimes. Such a distinction of flow regimes is of practical relevance, because of the inverse link with reservoir properties and fracture treatment design parameters. Each flow regime has a characteristic slope, which traditionally has been attributed to typical flow conditions in the reservoir. The synthetic production data from the reservoir simulator are used to constrain b -sigmoid patterns for narrow discrete time increments of production (1 month) throughout the various flow regimes occurring during the economic life of each synthetic well model. Nearly a hundred different models were generated as a basis for our analysis. From the analysis of the DCA parameters for time series, using the difference in inverse of decline rates (loss ratio) for two adjacent time steps, it appears possible to recognize systematic shifts in the instantaneous decline rates and temporal b -values. In particular, the generated b -value patterns (b -sigmoids) appear diagnostic for flow regime changes recognized on diagnostic log-rate log-time plots. The results demonstrate that it is possible, based on well design and reservoir parameters, to establish correlation trends between b -sigmoids and flow regime changes using time series of the DCA parameters. The results are subsequently used to improve the accuracy of a modified 3-segment DCA method based on Arps equation. The proposed method is applied to synthetic production data, generated based on an Eagle Ford shale oil well (with known reservoir and fracture properties), to demonstrate the practical value for production forecasting and reserves estimation. This research paper paves the way for wider, future application of the methods described. • b -sigmoid patterns are linked to flow regimes transitions. • b -sigmoids help improve accuracy of production forecasts of shale wells. • Sensitivity of flow regime changes to reservoir and fracture parameters is quantified. [ABSTRACT FROM AUTHOR]

We applied the epidemic type aftershock sequence (ETAS) model, the two-stage ETAS model and the non-stationary ETAS model to investigate the detailed features of the series of earthquake occurrences before and after the M6.7 Hokkaido Eastern Iburi earthquake on 6 September 2018, based on earthquake data from October 1997. First, after the 2003 M8.0 Tokachi-Oki earthquake, seismic activity in the Eastern Iburi region reduced relative to the ETAS model. During this period, the depth ranges of the seismicity were migrating towards shallow depths, where a swarm cluster, including a M5.1 earthquake, finally occurred in the deepest part of the range. This swarm activity was well described by the non-stationary ETAS model until the M6.7 main shock. The aftershocks of the M6.7 earthquake obeyed the ETAS model until the M5.8 largest aftershock, except for a period of several days when small, swarm-like activity was found at the southern end of the aftershock region. However, when we focus on the medium and larger aftershocks, we observed quiescence relative to the ETAS model from 8.6 days after the main shock until the M5.8 largest aftershock. For micro-earthquakes, we further studied the separated aftershock sequences in the naturally divided aftershock volumes. We found that the temporal changes in the background rate and triggering coefficient (aftershock productivity) in respective sub-volumes were in contrast with each other. In particular, relative quiescence was seen in the northern deep zones that includes the M5.8 largest aftershock. Furthermore, changes in the b-values of the whole aftershock activity showed an increasing trend with respect to the logarithm of elapsed time during the entire aftershock period, which is ultimately explained by the spatially different characteristics of the aftershocks. [ABSTRACT FROM AUTHOR]

The Ethiopian rift which is part of East African Rift system passes through the middle of the country making it one of the most seismically active regions in the world. Thus, significant and damaging earthquakes have been reported and recorded in the past in this region. A homogeneous earthquake catalog is of basic importance for studying the earthquake occurrence pattern in space and time and for many engineering applications including assessment of seismic hazard, estimation of peak ground accelerations and determination of long-term seismic strain rates. The first earthquake catalogue for Ethiopia was prepared by Pierre Gouin and later, different authors attempted to compile a catalogue using different time period intervals and different earthquake magnitude scales. The b-value mapping and its implication never done for Ethiopia and its environs. The main purpose of the study is therefore first compile and homogenize earthquake catalog of Ethiopia including Read Sea and Gulf of Aden regions into Moment magnitude Mw scale through completeness analysis in time and magnitudes. Secondly, mapping b-values for different Seismgenic regions and understand its implications for magma induced Seismicity in the regions. During the present study, a new homogenized earthquake catalog in moment magnitude scale (Mw), covering about 3814 events is prepared for Ethiopia including Red sea and Gulf of Aden regions. The present study area is bounded within Latitude (40N − 200)N and Longitude (340N − 480)N E and have a magnitude range of Mw (3.0–7.1) with a total coverage period of 56 years (1960 to 2016). The catalog has been analyzed for magnitude completeness (Mc) using Gutenberg's Frequency Magnitude Distribution law and it is found to be complete respectively for Mc ≥ 4.6 ± 0.03, Mc ≥ 4.6 ± 0.03, Mc ≥ 3.2, Mc ≥ 3.1 and Mc ≥ 5.1 for Afar including red sea and Gulf of Aden, Afar rift and Dabbahu Volcano, Northern, Central, and Southern Main Ethiopian Rifts. Further, the corresponding average b-value of the regions Afar including Red Sea and Gulf of Aden, Afar and Dabbahu Volcano separately, Northern Main Ethiopian Rift, Central Main Ethiopian Rift and Southern Main Ethiopian Rift respectively are estimated to be 1.17 ± 0.05, 1.15 ± 0.05, 0.843, 0.826 and 1.03 with respective period of completeness from 2003 to 2014, 2005 to 2014, 2001 to 2003, 2001 to 2003 and 1960 to 2016 for the regions. Later, mapping of the b-values in the Gutenberg-Richter relation from the newly developed catalog was performed by binning the regions into minimum of 0.050x0.050 for Afar and Dabbahu region, 0.10x0.10 for Main Ethiopian rifts and 0.20x0.20 for the other regions. Thus, the b-value characteristics of various seismogenic zones within the area have been discussed. Hence, in this study, we clearly observed that magma chamber movement including mapping of volcanic centers and magmatic segments are mapped using b-values. [ABSTRACT FROM AUTHOR]