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The establishment of a unified earthquake catalog is a basic requirement for attaining a detailed seismological analysis and an improved seismic hazard assessment. Accordingly, the current research paper aims to present a reliable instrumental unified earthquake catalog for the northern part of Algeria. This unified catalog is compiled using regional empirical relationships derived from converting different magnitude scales to an advanced physical-based moment magnitude scale suggested in the recent literature and denoted by Mwg. The regression methodology used in this study is called the New General Orthogonal Regression approach (N.GOR), which was selected since it is the most trustworthy procedure for scaling the magnitudes to Mwg. To highlight the significance of using the N.GOR, the obtained outcomes of the scaling relations were compared with those issued from the conventional general orthogonal regression (GOR) method, which is deemed to be the most dependable methodology used worldwide for magnitude conversion problems. The unified earthquake catalog was assembled from 1954 to 2022. Reliably converting the original magnitudes into homogenized moment magnitude leads to a complete and consistent unified earthquake catalog. Indeed, the unified moment magnitude catalog presented in this paper could provide reliable data for studying earthquakes distribution and the assessment of seismic hazards in the north of Algeria. [ABSTRACT FROM AUTHOR]

Because of the scarcity of recorded seismic ground motions from Vrancea intermediate-depth source that can be used in designing a structure, engineers are bound to use scaled, artificial, or simulated accelerograms. Out of these options, the first two might incompletely account for the phenomena that may appear. Although complicated, simulated accelerograms provide one of the best options for defining the seismic demand in engineering design, but further research is needed to adapt the simulation methods to the source, path, and site-specific characteristics. As some parameters used in simulations were not addressed yet specifically for the Vrancea-intermediate seismic source, the specific path duration is investigated in this paper. Using a database with the recorded ground motions from March 4, 1977, August 30, 1986, May 30 and May 31, 1990, October 27, 2004 Vrancea earthquakes (the only five recorded earthquakes with moment magnitudes at least equal to 6), the path and magnitude dependent duration specific to Vrancea intermediate-depth seismic source to be used in the stochastic simulation is developed. [ABSTRACT FROM AUTHOR]

According to theory, earthquakes may produce disturbances in surrounding areas and affect the major earthquake occurrence rate of surrounding faults. The MS 6.6 Jinghe Earthquake on 9th August, 2017 occurred in the Tienshan Seismic Belt where there is much tectonic activity and many strong earthquakes occur. The impact of this earthquake on major earthquake activity of surrounding areas is worth studying. This paper attempts to combine two models: the Brownian passage-time (BPT) model, which describes the quasi-periodic recurrence of major earthquakes, and the Coulomb Failure Stress model, which describes rock failure on faults. The amount of change in the rate of major earthquake occurrence caused by a nearby earthquake was calculated, and changes in major earthquake activity in the surrounding areas after the Jinghe Earthquake were re-estimated. There are few differences in major earthquake occurrence rate change by stress disturbances calculated with the BPT model or the Coulomb Failure Stress model. Calculation results are consistent with actual earthquake cases. The 2017 Jinghe Earthquake increased major earthquake activity on the Boluokenu Fault and Yili Basin North Fault, and the expected major earthquake recurrence times of the two faults were advanced by 11 years and 59 years, respectively. Conclusions of this paper provide a reference for time-dependent seismic hazard assessments in related areas. [ABSTRACT FROM AUTHOR]

Statistical quantification of observed seismicity is important for understanding earthquake dynamics and future risk in any seismic-prone region. In this paper, we implement the idea of nowcasting (Rundle et al. in Earth and Space Science 3:480–486, 2016) to examine the current uncertain state of earthquake hazard assessment in the seismically active Bay of Bengal (BoB) and adjacent regions. First, we utilize the concept of "natural time" (Varostos et al. in Physical Review E 71:032102, 2005), rather than clock time, to develop a statistical distribution of inter-event counts of "small" earthquakes occurring between "large" earthquakes. Using relevant statistics of natural time, we then calculate the earthquake potential score (EPS) as the cumulative number of small earthquakes since the last large event in the selected region. The EPS, which provides the nowcast value for a region, reveals the current state of earthquake hazard in that region. Therefore, by indirect means, the EPS provides us with a simple yet transparent estimation of the current level of seismic progress through the regional earthquake cycle of recurring events in a geographical area. To illustrate the nowcasting approach in the study region, we computed EPS values for the two most seismically exposed megacities, Dhaka and Kolkata, considering events of M ≥ 4 within a radius of 250 km around their respective city centers. We found that the current EPS values corresponding to M ≥ 6 events in Dhaka and Kolkata were approximately 0.72 and 0.40, respectively. The practical applicability of these values is discussed in conjunction with sensitivity analysis of the threshold magnitudes. [ABSTRACT FROM AUTHOR]

The paper considers Poisson temporal occurrence of earthquakes and presents a way to integrate uncertainties of the estimates of mean activity rate and magnitude cumulative distribution function in the interval estimation of the most widely used seismic hazard functions, such as the exceedance probability and the mean return period. The proposed algorithm can be used either when the Gutenberg-Richter model of magnitude distribution is accepted or when the nonparametric estimation is in use. When the Gutenberg-Richter model of magnitude distribution is used the interval estimation of its parameters is based on the asymptotic normality of the maximum likelihood estimator. When the nonparametric kernel estimation of magnitude distribution is used, we propose the iterated bias corrected and accelerated method for interval estimation based on the smoothed bootstrap and second-order bootstrap samples. The changes resulted from the integrated approach in the interval estimation of the seismic hazard functions with respect to the approach, which neglects the uncertainty of the mean activity rate estimates have been studied using Monte Carlo simulations and two real dataset examples. The results indicate that the uncertainty of mean activity rate affects significantly the interval estimates of hazard functions only when the product of activity rate and the time period, for which the hazard is estimated, is no more than 5.0. When this product becomes greater than 5.0, the impact of the uncertainty of cumulative distribution function of magnitude dominates the impact of the uncertainty of mean activity rate in the aggregated uncertainty of the hazard functions. Following, the interval estimates with and without inclusion of the uncertainty of mean activity rate converge. The presented algorithm is generic and can be applied also to capture the propagation of uncertainty of estimates, which are parameters of a multiparameter function, onto this function. [ABSTRACT FROM AUTHOR]

Real-time integration of multi-parametric observations is expected to accelerate the process toward improved, and operationally more effective, systems for time-Dependent Assessment of Seismic Hazard (t-DASH) and earthquake short-term (from days to weeks) forecast. However, a very preliminary step in this direction is the identification of those parameters (chemical, physical, biological, etc.) whose anomalous variations can be, to some extent, associated with the complex process of preparation for major earthquakes. In this paper one of these parameters (the Earth's emitted radiation in the Thermal InfraRed spectral region) is considered for its possible correlation with M ≥ 4 earthquakes occurred in Greece in between 2004 and 2013. The Robust Satellite Technique (RST) data analysis approach and Robust Estimator of TIR Anomalies (RETIRA) index were used to preliminarily define, and then to identify, significant sequences of TIR anomalies (SSTAs) in 10 years (2004-2013) of daily TIR images acquired by the Spinning Enhanced Visible and Infrared Imager on board the Meteosat Second Generation satellite. Taking into account the physical models proposed for justifying the existence of a correlation among TIR anomalies and earthquake occurrences, specific validation rules (in line with the ones used by the Collaboratory for the Study of Earthquake Predictability-CSEP-Project) have been defined to drive a retrospective correlation analysis process. The analysis shows that more than 93 % of all identified SSTAs occur in the prefixed space-time window around ( M ≥ 4) earthquake's time and location of occurrence with a false positive rate smaller than 7 %. Molchan error diagram analysis shows that such a correlation is far to be achievable by chance notwithstanding the huge amount of missed events due to frequent space/time data gaps produced by the presence of clouds over the scene. Achieved results, and particularly the very low rate of false positives registered on a so long testing period, seems already sufficient (at least) to qualify TIR anomalies (identified by RST approach and RETIRA index) among the parameters to be considered in the framework of a multi-parametric approach to t-DASH. [ABSTRACT FROM AUTHOR]

We performed a study to test the performances of the Hybrid Heuristic Search (HHS) algorithm (Nagashima et al. 2014) using earthquake recordings at 23 instrumented sites in Switzerland. The HHS algorithm is based on the diffuse field theory and estimates the P- and S-wave velocity profiles by inverting horizontal-to vertical spectral ratio (H/V) curves of earthquake recordings. In this study we inverted the H/V curves computed using the arrivals of local and regional earthquakes with a maximum local magnitude of 4.6. We compared the results of the inversion technique to the information available for each investigated site (e.g., site characterization analysis). Our results emphasize the importance of site characterization data for the definition of the parameter space in the near surface, and the potential to extend the investigated depth to much higher depths than the standard site characterization measurements. The additional constraints in the inversion are important to drive the inversion towards a unique solution. Our analysis confirms the potential of the HHS algorithm to invert the full earthquake H/V curve for subsurface investigation and its applicability to areas with low magnitude earthquakes. In addition, the HHS algorithm can be a useful technique to investigate deeper structures and extend the velocity profile to depths that are not resolved by classical site characterization techniques. [ABSTRACT FROM AUTHOR]

A devastating earthquake (Mw 7.4) struck near Izmit city, northwestern Turkey, on 17 August 1999. The relatively large size of this earthquake and site amplification conditions caused severe damage in the Marmara region as well as the city of Istanbul. The disastrous outcome of this large earthquake requires careful analysis of the seismic hazard including local site effects in this region. Therefore, the present work addresses the issue of local site effects and modelling of strong ground motion for this earthquake. We have estimated the soil effects using the horizontal-to-vertical (H/V) ratio. Furthermore, high-frequency records are simulated using a modified semi-empirical technique (MSET) by including estimated site effects. This modification will provide more reliable and precise simulated strong motion records. In the present study, strong ground motions are simulated at nine seismic stations in the epicentral range of 40–99 km. These stations were selected based on their recorded data quality. To validate the technique, we have compared the synthetic records with the observed records in terms of root mean square error (RMSE). This comparison includes time records, pseudo-acceleration spectra, mean period and predominant period. This comparison shows MSET has successfully simulated the 1999 Izmit earthquake. [ABSTRACT FROM AUTHOR]

The southwest Iberian Margin (SWIM) hosted a series of tsunamigenic earthquakes. However, strong magnitude earthquakes M > 7.0 are scarce and geological and geophysical evidence suggest that slow deformation occurs on a large area without a discrete plate boundary. The reanalysis of this event is crucial because of its location in a possible transition zone between the diffuse plate boundary and the stable continent regime. The 11 November 1858 earthquake in Setúbal, Portugal, with an estimated M ~ 7, ruined a large part of the city and was felt all over Portugal and large parts of the Iberian Peninsula. Earlier studies suggest an epicentre close to the shore, less than 50 km away, and there exists a description of a tsunami in Setúbal. We use macroseismic intensities and present a reevaluation of the event parameters: depth, epicentre, magnitude, and fault orientation. We select the candidate faults according to the epicentral area and plate kinematics and use scaling laws for the magnitude range. We use tsunami numerical modelling to check the tsunamigenic potential of the event. Finally, we compute the tsunami propagation and inundation for Setúbal for seven candidate scenarios and analyze waveform data obtained at virtual tide gauges. Our results favour an offshore inverse fault compatible with the tsunami observation corresponding to a reverse fault with a 40° strike angle at 13 km depth and a magnitude range of 6.8 ± 0.3. [ABSTRACT FROM AUTHOR]

Pakistan and its surroundings are among the most seismically active regions in the world. Occurrence of major earthquakes in Pakistan is a real hazard for life. In this study, an attempt has been made to estimate the seismic hazard in terms of earthquake occurrence conditional probabilities in different zones of Pakistan. We assumed that the temporal data of earthquakes, that occurred in different regions of Pakistan follow a certain probability distribution. In present study, the 10 probability models that include the exponential, gamma, generalized Pareto, inverse Pareto, kappa, log-logistic, lognormal, Pareto, transformed gamma and Weibull are used to analyze the interevent times of the earthquakes with M w ≥ 5.5 in different regions of Pakistan. In current study, Pakistan territory has been divided into five different seismic zones based on their tectonic settings. Parameters of the considered distributions are estimated by using the maximum likelihood method using the reviewed earthquake catalogue compiled by Centre for Earthquake Studies (CES), Pakistan. The best suitable model in each seismic zone is selected through various model selection criteria. The results show that the log-logistic distribution provides the best representation of earthquake temporal data of plate convergence zones; while the gamma distribution best explains the temporal seismicity of other tectonic regimes including the transform plate boundary, fold and thrust belts and stable plains. The most suitable gamma and log-logistic models are used for the earthquake occurrence probabilities in different regions of Pakistan. The highest (> 96 %) and the least (> 30 %) earthquake occurrence conditional probabilities are respectively observed for Zones I and V among five seismic zones for different combinations of elapsed time (τ) and time interval (υ) . The estimated probability of M w ≥ 5.5 event reaches (60–98)% in next (3–9) years time interval without any elapsed time (τ = 0) in Zones II to IV (the time periods corresponding to 3–9 years time interval are 2016–2022, 2020–2026 and 2019–2025 in Zones I, II and III respectively) since the last event occurrence time in each of these seismic zone. The mean values of the interevent time for an earthquake occurrence of M w ≥ 5.5 in Zone-I to Zone-V are respectively calculated as 0.90, 1.78, 4.52, 3.35 and 11.76 years, respectively. The results of the present study indicate that Zone-I has potential capability of producing an earthquake of magnitude 5.5 or higher in next 3 years (2019–2021) time interval since the last event occurrence in May 2018. The earthquake hazard curves associated with earthquake occurrence probabilities are also developed in order to understand the current and future earthquake mechanism in the study region. [ABSTRACT FROM AUTHOR]

The possibilities of statistical estimation of quantiles of predicted maximum peak ground acceleration are discussed. The estimation is based on the theory of extreme values. The quantiles of maximum peak ground acceleration are calculated for a spatial grid covering the territory of high seismicity regions of Japan, Kuril Islands, and Kamchatka. A new phenomenon is observed: spatial spots of increased ground acceleration showing essential inhomogeneity not only across the deep ocean trench, but as well along its extension. Some spots exist during all observation time (130 years), whereas some other can disappear or appear during this time interval. The position of majority of spots is correlated with the concentration of underwater sea mounts at the adjacent part of the oceanic plate. The subduction of these sea mounts could induce an increased seismicity. A correlation of spots with sites of increased (Mb − Mw) values is observed also, which can be caused by an increased friction between the plates. Stable spots of higher acceleration are observed for different earthquake catalogs and various time periods. Our results make advisable using the extreme values theory technique for statistical estimation of seismic hazard, in particular, for characterization of seismic activity spots. [ABSTRACT FROM AUTHOR]

To adaptively forecast forthcoming large aftershocks of the 2008 Mw7.9 Wenchuan, China, earthquake, we construct a new hazard model to describe the occurrence rate of aftershocks in a study region along the Longmenshan fault. The model is denoted by SRJ since it is a combination of the Reasenberg–Jones (RJ) model and a spatial hazard model that is obtained by taking a reference of previous earthquakes in the study region. We employ the maximum likelihood (ML) method to estimate the SRJ model based on aftershocks that occurred within 1 or 2 days after the Wenchuan earthquake. The probabilities of M ≥ 5.0 aftershocks at each of the grids in the study region during next few days are then computed according to the estimated SRJ model, and hence the corresponding relative aftershock hazard (RAH) map is constructed. Finally, according to a variety of criteria for evaluating the hazard maps on depicting possible rupture area of forthcoming large aftershocks, the SRJ-based RAH map is demonstrated to be more efficient than the RAH maps constructed based on the RJ model incorporated with the gridding method using a fixed radius or varying radii. [ABSTRACT FROM AUTHOR]

Seismogenic nodes capable of generating shallow earthquakes with M ≥ 5.0 have been identified in the northeast part of Egypt using the pattern recognition approach. The study region includes the Sinai Peninsula and the northern part of the Eastern Desert between the Nile River and the Red Sea, which comprises the new capital of Egypt and Suez Canal projects and represents a place for much future development. We apply a phenomenological approach based on pattern recognition for identifying seismogenic nodes. The methodology is based on the idea that earthquakes nucleate at nodes: specific structures forming around fault intersections. Morphostructural zoning (MZ) is applied to map nodes over the entire study region without using a priori knowledge of regional seismicity. The pattern recognition is employed to pinpoint seismogenic nodes where earthquakes with M ≥ 5.0 may occur in the future. As a result, seismogenic nodes capable of generating earthquakes with M ≥ 5.0 have been defined in the Sinai Peninsula and the northern part of the Eastern Desert. We also found characteristic geological-geophysical features that discriminate seismogenic nodes (D) from non-seismogenic ones (N). Information on the potential seismic sources represents the main issue in seismic hazard evaluation. Seismogenic nodes prone to earthquakes with M ≥ 5.0, as described in this work, may contribute to the definition of earthquake source zones in the northeast of Egypt because some of the D nodes are potential sources of seismic risk for critical facilities (e.g., Ismailia Tunnels) and large metropolitan areas (e.g., Nile Valley). This information can contribute to the revision of seismic zoning or microzoning and improve the performance of seismic hazard studies of Egypt by adding a new source of information about seismogenic nodes to the seismogenic zones. [ABSTRACT FROM AUTHOR]

The casualties and financial losses caused by large earthquakes have led to an awareness of prediction importance of such earthquakes. The earthquake prediction is divided into four categories: long term, intermediate term, short term, and immediate. The M8 algorithm is one of the intermediate-term middle-range prediction algorithms primarily used to predict earthquake of magnitude 8 or more and is applied later for smaller magnitudes. The Iranian Plateau is less exposed to earthquake with magnitude 8 or more and it is observed that the seismicity rate in this region is generally low. Thus; the original M8 is not suitable for applying in this region. The objective of this study is to modify the M8 algorithm for Prediction of Major M7.0+ Earthquakes in the Iranian Plateau. The major earthquake of magnitude 7 or more in the Iranian plateau from 1975 to 2018 is considered as the target earthquakes. The hit rate times 1 minus alarm rate is defined as objective function and the particles swarm optimization meta-heuristic algorithm is used to maximize it. The optimum M8 could predict 14 out of 17 large earthquakes in the Iranian plateau while occupying 31.7% of the spatio-temporal space as the alarm. The results show that by employing an optimization algorithm, we can modify the M8 algorithm for efficient prediction of the target magnitudes less than 8 in the regions with low seismicity rate. [ABSTRACT FROM AUTHOR]

Seismicity induced in geo-reservoirs can be a valuable observation to image fractured reservoirs, to characterize hydrological properties, or to mitigate seismic hazard. However, this requires accurate location of the seismicity, which is nowadays an important seismological task in reservoir engineering. The earthquake location (determination of the hypocentres) depends on the model used to represent the medium in which the seismic waves propagate and on the seismic monitoring network. In this work, location uncertainties and location inaccuracies are modeled to investigate the impact of several parameters on the determination of the hypocentres: the picking uncertainty, the numerical precision of picked arrival times, a velocity perturbation and the seismic network configuration. The method is applied to the geothermal site of Soultz-sous-Forêts, which is located in the Upper Rhine Graben (France) and which was subject to detailed scientific investigations. We focus on a massive water injection performed in the year 2000 to enhance the productivity of the well GPK2 in the granitic basement, at approximately 5 km depth, and which induced more than 7000 earthquakes recorded by down-hole and surface seismic networks. We compare the location errors obtained from the joint or the separate use of the down-hole and surface networks. Besides the quantification of location uncertainties caused by picking uncertainties, the impact of the numerical precision of the picked arrival times as provided in a reference catalogue is investigated. The velocity model is also modified to mimic possible effects of a massive water injection and to evaluate its impact on earthquake hypocentres. It is shown that the use of the down-hole network in addition to the surface network provides smaller location uncertainties but can also lead to larger inaccuracies. Hence, location uncertainties would not be well representative of the location errors and interpretation of the seismicity distribution possibly biased. This result also emphasizes that it is still necessary to properly describe the seismic propagation medium even though the addition of down-hole sensors increases the coverage of a surface network. [ABSTRACT FROM AUTHOR]

Adaptive neuro-fuzzy inference systems (ANFIS) are used here to obtain the robust ground motion prediction model (GMPM). Avoiding a priori functional form, ANFIS provides fully data-driven predictive models. A large subset of the NGA-West2 database is used, including 2335 records from 580 sites and 137 earthquakes. Only shallow earthquakes and recordings corresponding to stations with measured Vs30 properties are selected. Three basics input parameters are chosen: the moment magnitude (Mw), the Joyner-Boore distance (RJB) and Vs30. ANFIS model output is the peak ground acceleration (PGA), peak ground velocity (PGV) and 5% damped pseudo-spectral acceleration (PSA) at periods from 0.01 to 4 s. A procedure similar to the random-effects approach is developed to provide between- and within-event standard deviations. The total standard deviation (SD) varies between [0.303 and 0.360] (log10 units) depending on the period. The ground motion predictions resulting from such simple three explanatory variables ANFIS models are shown to be comparable to the most recent NGA results (e.g., Boore et al., in Earthquake Spectra 30:1057-1085, 2014; Derras et al., in Earthquake Spectra 32:2027-2056, 2016). The main advantage of ANFIS compared to artificial neuronal network (ANN) is its simple and one-off topology: five layers. Our results exhibit a number of physically sound features: magnitude scaling of the distance dependency, near-fault saturation distance increasing with magnitude and amplification on soft soils. The ability to implement ANFIS model using an analytic equation and Excel is demonstrated. [ABSTRACT FROM AUTHOR]

The 2014 ML 5.9 Fanglin earthquake occurred at the northern end of the aftershock distribution of the 2013 ML 6.4 Ruisui event and caused strong ground shaking and some damage in the northern part of the Longitudinal Valley. We carried out the strong-motion simulation of the 2014 Fanglin event in the broadband frequency range (0.4–10 Hz) using the empirical Green’s function method and then integrated the source models to investigate the source characteristics of the 2013 Ruisui and 2014 Fanglin events. The results show that the dimension of strong motion generation area of the 2013 Ruisui event is smaller, whereas that of the 2014 Fanglin event is comparable with the empirical estimation of inland crustal earthquakes, which indicates the different faulting behaviors. Furthermore, the localized high PGV patch might be caused by the radiation energy amplified by the local low-velocity structure in the northern Longitudinal Valley. Additional study issues are required for building up the knowledge of the potential seismic hazard related to moderate-large events for various seismogenic areas in Taiwan. [ABSTRACT FROM AUTHOR]

The Xianshuihe fault zone consists of left-lateral, segmented strike-slip faults, which produce strong and relatively frequent earthquakes, and exposes millions of people to the risk of strong motion and earthquake-induced geologic hazards in Southwest China. Seismicity in this fault zone exhibits typical features of characteristic earthquakes. The stochastic finite-fault model was used to generate time-histories and peak values of strong ground motion at near-fault locations for the characteristic earthquakes. First, the source parameters were determined and verified by comparing them with the simulated time-histories and intensity distribution and observations from the 2014 Kangding earthquake (Mw 6.0). Then, scenario-based ground-motion hazard maps were produced from simulated ground motions of characteristic earthquakes. The scenario-based ground-motion hazard maps can be directly compared with historical and future earthquakes in the Xianshuihe fault zone. Scenario-based seismic hazard analysis also has other advantages. Our results show that current design ground motion for the Xianshuihe Fault area is not adequate. [ABSTRACT FROM AUTHOR]

The Himalayan Main Frontal Thrust is the most active fault in the Himalayan subduction zone, with a high degree of locking and a large thrust rate. Gaps on the Himalayan Main Frontal Thrust have been free of strong earthquakes for hundreds of years and the surrounding areas are densely populated, so it is significant to study the evolution law and the current status of stress along the Himalayan Main Frontal Thrust. Based on a lithospheric viscoelastic layered medium model, we analyzed the interseismic stress accumulation along the Himalayan Main Frontal Thrust and the coseismic and postseismic stress disturbance on the fault surface caused by nine Mw ≥ 7.5 earthquakes since 1803. The results showed that the stress disturbance along the Himalayan Main Frontal Thrust caused by historical earthquakes have promoted most of the subsequent earthquakes, but the coseismic and postseismic stress changes caused by the historical earthquakes on the faulty surface of subsequent earthquakes are not significant, because of the long distance between strong earthquakes. Interseismic stress enhanced the stress level of the majority of fault planes in the study area and played a dominant role in the stress evolution and strong earthquake preparation along the Himalayan Main Frontal Thrust. The recurrence interval of Mw 7.5-7.9 earthquakes on the Himalayan Main Frontal Thrust is 70-250 years and the recurrence interval of Mw > 8 earthquakes which rupture the whole seismogenic layer may be longer than 500 years. This agrees with historical seismic records. The elapsed time of strong earthquakes in the four seismic gaps is between 460 and 915 years and the possibilities of Mw 8 earthquakes in the future 10 years always exist, including a probability of higher than 50% in three seismic gaps. The peak of cumulative Coulomb stress in the seismic gaps is more than 1 MPa, and the seismic hazard on the Himalayan Main Frontal Thrust needs further attention. [ABSTRACT FROM AUTHOR]

The seismic spectrum can be constructed by assuming a Brune spectral model and estimating the parameters of seismic moment ( M ), corner frequency ( f ), and high-frequency site attenuation ( κ). Using seismic data collected during the 2010-2011 Canterbury, New Zealand, earthquake sequence, we apply the non-linear least-squares Gauss-Newton method, a deterministic downhill optimization technique, to simultaneously determine the M , f , and κ for each event-station pair. We fit the Brune spectral acceleration model to Fourier-transformed S-wave records following application of path and site corrections to the data. For each event, we solve for a single M and f , while any remaining residual kappa, $$\kappa_{\text{r}}$$ , is allowed to differ per station record to reflect varying high-frequency falloff due to path and site attenuation. We use a parametric forward modeling method, calculating initial M and f values from the local GNS New Zealand catalog M magnitudes and measuring an initial $$\kappa_{\text{r}}$$ using an automated high-frequency linear regression method. Final solutions for M , f , and $$\kappa_{\text{r}}$$ are iteratively computed through minimization of the residual function, and the Brune model stress drop is then calculated from the final, best-fit f . We perform the spectral fitting routine on nested array seismic data that include the permanent GeoNet accelerometer network as well as a dense network of nearly 200 Quake Catcher Network (QCN) MEMs accelerometers, analyzing over 180 aftershocks M ≥ 3.5 that occurred from 9 September 2010 to 31 July 2011. QCN stations were hosted by public volunteers and served to fill spatial gaps between existing GeoNet stations. Moment magnitudes determined using the spectral fitting procedure ( M ) range from 3.5 to 5.7 and agree well with M , with a median difference of 0.09 and 0.17 for GeoNet and QCN records, respectively, and 0.11 when data from both networks are combined. The majority of events are calculated to have stress drops between 1.7 and 13 MPa (20th and 80th percentile, correspondingly) for the combined networks. The overall median stress drop for the combined networks is 3.2 MPa, which is similar to median stress drops previously reported for the Canterbury sequence. We do not observe a correlation between stress drop and depth for this region, nor a relationship between stress drop and magnitude over the catalog considered. Lateral spatial patterns in stress drop, such as a cluster of aftershocks near the eastern extent of the Greendale fault with higher stress drops and lower stress drops for aftershocks of the 2011 M 6.2 Christchurch mainshock, are found to be in agreement with previous reports. As stress drop is arguably a method-dependent calculation and subject to high spatial variability, our results using the parametric Gauss-Newton algorithm strengthen conclusions that the Canterbury sequence has stress drops that are more similar to those found in intraplate regions, with overall higher stress drops that are typically observed in tectonically active areas. [ABSTRACT FROM AUTHOR]

Northeast India bounded by latitudes 20°-30°N and longitudes 87°-98°E is one of the most seismically active areas in the world. This region has experienced several moderate-to-large-sized earthquakes, including the 12 June, 1897 Shillong earthquake ( M 8.1) and the 15 August, 1950 Assam earthquake ( M 8.7) which caused loss of human lives and significant damages to buildings highlighting the importance of seismic hazard assessment for the region. Probabilistic seismic hazard assessment of the region has been carried out using a unified moment magnitude catalog prepared by an improved General Orthogonal Regression methodology (Geophys J Int, 190:1091-1096, 2012; Probabilistic seismic hazard assessment of Northeast India region, Ph.D. Thesis, Department of Earthquake Engineering, IIT Roorkee, Roorkee, 2013) with events compiled from various databases (ISC, NEIC,GCMT, IMD) and other available catalogs. The study area has been subdivided into nine seismogenic source zones to account for local variation in tectonics and seismicity characteristics. The seismicity parameters are estimated for each of these source zones, which are input variables into seismic hazard estimation of a region. The seismic hazard analysis of the study region has been performed by dividing the area into grids of size 0.1° × 0.1°. Peak ground acceleration (PGA) and spectral acceleration ( S ) values (for periods of 0.2 and 1 s) have been evaluated at bedrock level corresponding to probability of exceedance (PE) of 50, 20, 10, 2 and 0.5 % in 50 years. These exceedance values correspond to return periods of 100, 225, 475, 2475, and 10,000 years, respectively. The seismic hazard maps have been prepared at the bedrock level, and it is observed that the seismic hazard estimates show a significant local variation in contrast to the uniform hazard value suggested by the Indian standard seismic code [Indian standard, criteria for earthquake-resistant design of structures, fifth edition, Part-I. Bureau of Indian Standards, New Delhi, 2002]. Not only holistic treatment of earthquake catalog and seismogenic zones has been performed, but also higher resolution in spatial distribution could be achieved. The COV maps have been provided with the strong ground-motion maps under various conditions to show the confidence in the results obtained. Results obtained in the present study would be helpful for risk assessment and other disaster mitigation-related studies. [ABSTRACT FROM AUTHOR]

The Bayesian method is used to evaluate earthquake hazard parameters of maximum regional magnitude ( M), β value, and seismic activity rate or intensity ( λ) and their uncertainties for the 15 different source regions in Western Anatolia. A compiled earthquake catalog that is homogenous for M ≥ 4 was completed during the period from 1900 to 2013. The computed M values are between 6.00 and 8.06. Low values are found in the northern part of Western Anatolia, whereas high values are observed in the southern part of Western Anatolia, related to the Aegean subduction zone. The largest value is computed in region 10, comprising the Aegean Islands. The quantiles of functions of distributions of true and apparent magnitude on a given time interval [0 ,T] are evaluated. The quantiles of functions of distributions of apparent and true magnitudes for future time intervals of 5, 10, 20, 50, and 100 years are calculated in all seismogenic source regions for confidence limits of probability levels of 50, 70, and 90 %. According to the computed earthquake hazard parameters, the requirement leads to the earthquake estimation of the parameters referred to as the most seismically active regions of Western Anatolia. The Aegean Islands, which have the highest earthquake magnitude (7.65) in the next 100 years with a 90 % probability level, is the most dangerous region compared to other regions. The results found in this study can be used in probabilistic seismic hazard studies of Western Anatolia. [ABSTRACT FROM AUTHOR]

We developed a synth esis approach to augment current techniques for seismic hazard evaluation by combining four previously unrelated subjects: the pattern informatics (PI), load/unload response ratio (LURR), state vector (SV), and accelerating moment release (AMR) methods. Since the PI is proposed in the premise that the change in the seismicity rate is a proxy for the change in the tectonic stress, this method is used to quantify localized changes surrounding the epicenters of large earthquakes to objectively quantify the anomalous areas (hot spots) of the upcoming events. On the short-to-intermediate-term estimation, we apply the LURR, SV, and AMR methods to examine the hazard regions derived from the PI hot spots. A predictive study of the 2014 earthquake tendency in Chinese mainland, using the seismic data from 1970-01-01 to 2014-10-01, shows that, during Jan 01 to Oct 31, 2014, most of the M > 5.0 earthquakes, especially the Feb 12 M7.3 Yutian, May 30 M6.1 Yingjiang, Aug. 03 M6.5 Ludian, and Oct 07 M6.6 earthquakes, occurred in the seismic hazard regions predicted. Comparing the predictions produced by the PI and combination approaches, it is clear that, by using the combination approach, we can screen out the false-alarm regions from the PI estimation, without reducing the hit rate, and therefore effectively augment the predictive power of current techniques. This provided evidence that the multi-method combination approach may be a useful tool to detect precursory information of future large earthquakes. [ABSTRACT FROM AUTHOR]

In 1991, a new seismic monitoring network named SIL was started in Iceland with a digital seismic system and automatic operation. The system is equipped with software that reports the automatic location and magnitude of earthquakes, usually within 1-2 min of their occurrence. Normally, automatic locations are manually checked and re-estimated with corrected phase picks, but locations are subject to random errors and systematic biases. In this article, we consider the quality of the catalogue and produce a revised catalogue for South Iceland, the area with the highest seismic risk in Iceland. We explore the effects of filtering events using some common recommendations based on network geometry and station spacing and, as an alternative, filtering based on a multivariate analysis that identifies outliers in the hypocentre error distribution. We identify and remove quarry blasts, and we re-estimate the magnitude of many events. This revised catalogue which we consider to be filtered, cleaned, and corrected should be valuable for building future seismicity models and for assessing seismic hazard and risk. We present a comparative seismicity analysis using the original and revised catalogues: we report characteristics of South Iceland seismicity in terms of b value and magnitude of completeness. Our work demonstrates the importance of carefully checking an earthquake catalogue before proceeding with seismicity analysis. [ABSTRACT FROM AUTHOR]

An important part of the preparation and homogenization of the seismic catalog used in the recent seismic hazard assessment study of Spain is the development of relationships among the different scales used to measure earthquake size. The objective is to convert all earthquake size data in the original catalog to a single magnitude scale, the moment magnitude M, in order to have a set of events with an uniform comparable size measurement. These new relationships are based on regression analysis between M and the other units used in the catalog in different epochs. The reduced major axis regression scheme is used, because it is the most suitable method for symmetric treatment of the variables involved in the fits. The new relationships obtained for Spain, M as a function of m; M as a function of m; and M as a function of I, are presented and their applicability limits and accuracy are discussed. The results obtained could have other practical uses in regional seismicity analysis. [ABSTRACT FROM AUTHOR]

In order to analyze observed seismicity in central Japan and Venezuela, we applied a new method to identify semi-periodic sequences in the occurrence times of large earthquakes, which allows for the presence of multiple periodic sequences and/or events not belonging to any sequence in the time series. We also explored a scheme for diminishing the effects of a sharp cutoff magnitude threshold in selecting the events to analyze. A main four-event sequence with probability P = 0.991 of not having occurred by chance was identified for earthquakes with M ≥ 8.0 in central Japan. Venezuela is divided, from West to East, into four regions; for each of these, the magnitude ranges and identified sequences are as follows. Region 1: M ≥ 6.0, a six-event sequence with P = 0.923, and a four-event sequence with P = 0.706. Region 2: M ≥ 5.6, a five-event sequence with P = 0.942. Region 3: M ≥ 5.6, a four-event sequence with P = 0.882. Region 4: M ≥ 6.0, a five-event sequence with P = 0.891. Forecasts are made and evaluated for all identified sequences having four or more events and probabilities ≥0.5. The last event of all these sequences was satisfactorily aftcast by previous events. Whether the identified sequences do, in fact, correspond to physical processes resulting in semi-periodic seismicity is, of course, an open question; but the forecasts, properly used, may be useful as a factor in seismic hazard estimation. [ABSTRACT FROM AUTHOR]

Starting on 14 May 2010 and lasting several months, the village of Beni-Ilmane (Msila District, North-Central Algeria) and its surroundings were struck by an important seismic crisis marked by three successive moderate shocks (5.0 ≤ M ≤ 5.2). This sequence of events caused severe damage in the Beni-Ilmane village and in the epicentral area. The poor quality of masonry construction and the cumulative effects of the large number of aftershock events played a key role in the destruction. To follow this earthquake sequence, 11 temporary seismic stations, in addition to the permanent stations of the Algerian seismic network, were deployed in the region. A representative set of well located aftershocks in the period of maximum activity (lasting 18 days) were selected. The horizontal distribution of the aftershocks shows two main earthquake clusters located near Beni-Ilmane village, one cluster oriented E-W and the other oriented NNE-SSW, crossing the first cluster at its eastern tip. The aftershocks distribution suggests that the three main shocks ruptured two distinct and adjacent fault segments of about 8 km length. The focal mechanisms of the first and third events, located in the NNE-SSW cluster, show near-vertical left-lateral strike-slip fault planes. In the second cluster, oriented E-W, focal mechanisms show a high-angle reverse fault. A field survey, initiated immediately after the first main shock, identified surface fissures generated by the three largest events in the sequence. The fissures, concentrated in a narrow area at the western termination of the NE-SW Jebel Choukchot anticline (location of Beni-Ilmane village), showed several orientations which were mainly related to gravity instabilities. The 2010 Beni-Ilmane earthquake sequence, located in the Bibans-Hodna Mountains transition zone, demonstrates that the Tellian Atlas-High Plateaus border region is an active seismic zone marked by moderate and possibly strong earthquakes; thus, a reevaluation of the seismic hazard in the region is needed. [ABSTRACT FROM AUTHOR]