Occurrence Of Seismic Events Research Articles

Подземная исследовательская лаборатория: преодоление неопределенностей в оценке сейсмических условий участка «Енисейский»

The article presents the basic principles and an algorithm allowing to arrange a seismological monitoring system for the Yeniseiskiy site selected for deep geological disposal of high-level waste. It describes the seismological monitoring system developed by NO RAO in 2018 also briefly considering the seismotectonic conditions of the area. The paper describes the process that has been followed to select the corresponding sites and equipment layouts in the areas fitted with seismological monitoring stations with relevant instrumental characteristics being provided. It shows that considering the current stage of research, higher sensitivity was provided in the area as compared to the one associated with available regional seismological observations. It demonstrates the efficiency of the built-up monitoring system with its sensitivity assessment provided both based on the calculated model and under real conditions. The long-term safety assessment performed for such a facility relies upon many factors with the seismic hazard level within the area of the monitored facility also taken into consideration. To provide most reliable evaluation of seismic parameters, continuous seismological monitoring should be performed over a several years’ period along with the sensitivity assessment of the selected monitoring system. The seismological monitoring system should focus not only on the general study of the monitored territory, but also on the areas assumed as zones of most probable seismic event occurrence, i.e. areas involving tectonic faults. The relevance of this task has been repeatedly emphasized in the course of multiple discussions on this issue featuring the representatives from SC Rosatom and the Scientific and Engineering Centre for Nuclear and Radiation Safety. The monitoring system fitted within the repository area meets relevant regulatory requirements. In accordance with the existing requirements, to reduce the uncertainties in the seismic hazard assessment of the territory, the implementation of certain measures was recommended during further development of the local seismological monitoring network to identify and assess the potential of hazardous geodynamic zones.

Quantitative assessment of seismic risk in hydraulic fracturing areas based on rough set and Bayesian network: A case analysis of Changning shale gas development block in Yibin City, Sichuan Province, China

The growing maturity of hydraulic fracturing and horizontal drilling techniques has made shale gas production the core energy strategy for many countries. However, it is also bringing along increasing concerns about hydraulic fracturing-induced seismicity (HFIS). In fact, how to effectively assess the seismic risk in hydraulic fracturing areas, identify the key HFIS factors and safeguard people's lives and property has become a scientific problem in need of immediate solution. In this study, a quantitative seismic risk assessment model for hydraulic fracturing areas is built based on rough set and Bayesian network. First, five factors most relevant to HFIS are identified based on existing research experience and the geological and engineering background of the study area. Then, knowledge acquisition on HFIS is performed using the rough set method. Next, the initial Bayesian network is built with the knowledge acquired and a geospatial correction model is constructed by introducing a “latent factor” into it. Finally, the seismic risk level in the study area is quantitatively assessed with the geospatial correction model. Besides, through sensitive analysis of the Bayesian network, it is established that injection volume is the most sensitive risk factor for HFIS and it plays a crucial role in the occurrence of seismic events. Through backward inference of the Bayesian network, the most probable combination of risk factors when the study area is in medium or high seismic risk is identified as injection volume, depth, b value, and fault. Experiments show that our new model is effective; the results obtained can provide scientific basis for predicting seismic risk in hydraulic fracturing areas, improving the hydraulic fracturing construction plans, thereby achieving the goal of resource exploitation and seismic disaster avoidance.

Методы групповой классификации на основе теории мультимножеств в задаче локализации зон с различным уровнем сейсмической активности при ведении горных рабо

The work is dedicated to assessing the applicability of supervised group classification methods developed on the basis of multiset theory for solving the problem of identifying zones with different degrees of seismic activity (using the example of one of the sections of the highly stressed rock massif of the Kukisvumchorr apatite-nepheline deposit). The initial objects for classification procedures are spatial cells into which the fieldis divided. Each spatial cell is described by a certain set of factors that, according to experts, have an impact on the occurrence of seismic events in a given cell. An original representation of spatial cells (their groups) as a set of multisets is proposed. Studies have been carried out aimed at identifying the influence of various options for presenting the initial data on the result of classification procedures. Representation of objects described by quantitative and / or qualitative features and existing in several versions (copies) in the form of multisets makes it possible not to transform qualitative features into numerical ones when performing clustering procedures and use methods of group classification of objects. Generalized decision rules of group classification for assigning objects (spatial cells) to four classes of seismic hazard are obtained. In contrast to the currently widely used technologies based on the neural network approach, in this work, the training result is not a “black box” in the form of a trained neural network, but a set of rules that can be easily interpreted, which increases the confidence of end users in decision-making procedures.

Numerical simulation of the possibility of seismic event occurrence in hard rock mine

This article presents the problem of seismic and rockburst hazard in underground hard rock mines. Types of rockbursts and their mechanisms as well as the causes of dynamic phenomena are discussed. The possibility of using numerical modeling to simulate the occurrence of a high-energy tremor, as a result of sudden shear rupture, is also shown. Results of numerical simulations are presented for a model mining field in a hard rock mine at high depth, in which the deposit is mined in a room-and-pillar mining system. General geological and mining conditions characteristic for Polish underground copper mines in Legnica-Glogow Copper Mining District belongs to KGHM Polska Miedz S.A. were adopted in the models. The typical lithological cross-section of the polish copper mines is characterized by rigid, high-strength rock layers in the roof, capable of accumulating elastic energy, while layers with much lower strength parameters are present in the floor. In the analyzed mining field, the remaining undisturbed rock, with a width of 40 m, was left. Numerical simulations were conducted in a plane strain state by means of Phase2 v. 8.0 software. An elastic-plastic model with softening was accepted for the rock mass. The results of numerical modeling showed that sudden (one computational step in the model) collapse of roof strata may occur over the excavated space on the edge of the remaining undisturbed rock, as a result of exceedance of shear strength, above all. This may cause a very high-energy tremor, and under the appropriate conditions, may result in the rockburst phenomenon.

Disaster preparedness for metro projects: a social-cognitive perspective of Pakistan

During the last decade, 2.4 billion individuals, the majority of which were residing in low economic growth countries, became victim of global disasters. As economic growth is correlated with the resilience of a nation against a disaster, therefore developing and underdeveloped nations significantly face higher magnitude of losses. With Pakistan being a developing country, the present study takes into account the most recently accomplished mega project of METROBUS service that is currently operational in the twin metropolitan cities of Pakistan i.e. Islamabad and Rawalpindi to study the pre and post development perspectives of project in terms of the hazard perception, prospect disaster threats it poses towards the society in case of major seismic activity and the magnitude of disaster preparedness associated to the potential hazardous circumstances as result of seismic event occurrence. Statistical evaluations for the current study were conducted utilizing the SmartPLS 3.0, being based upon the information collected through 336 self-supervised surveyed responses. The results of the current study indicated, the respondents to be highly in favor of the commute service project, but at the same time, they highlighted the concerns regarding socio-economic adversities faced during the project development phases as well as after its completion. Further, the respondents expressed major reservations regarding the disaster management measures taken by the potential stakeholders of the project. Despite the fact that most of the respondents were well educated, the lack of awareness regarding preparedness against any possible project related disastrous situation, was observed. To mitigate the potential disaster losses associated to the project, respondents suggested that the national authorities should proactively provide awareness to the public and assure the availability of all necessary facilities, in case of any hazardous situation; seismic in particular. Considering the practical implications, the current study may be useful for other developing countries, which too faced similar concerns during development of comparable megaprojects and share similar environmental conditions.

Tracing the seismic history of Sant’Agata del Mugello (Italy, Tuscany) through a cross-disciplinary approach

Historical seismicity is mainly defined from historical sources which are not always available. Yet historical buildings are a unique opportunity to record and study effects of past earthquakes at a given place. An innovative methodology is defined to improve knowledge of local historical seismicity. Such a methodology is based on an interdisciplinary approach combining: analysis of historical sources, stratigraphic analysis and structural analysis of an historical building. The church of Sant’Agata del Mugello (Italy, Tuscany) is considered as a case of study. The stratigraphic analysis is performed by identifying the repairs using the RECAP methodology. 80 repairs units using 13 building techniques are identified in the church. The identified repairs are associated with unknown events, earthquakes or routine reconstructions. When post-earthquake reconstructions are found, damage mechanisms are associated with them. 13 constructive phases of the church have been traced combining stratigraphic analysis and historical sources. A proto-church was built before 948 A.D. and is nowadays below the current one. The first phase of the current church appears between the 9th and the 12th century. A significant event of unknown origin occurred during the 12th century which probably led to an important collapse and then a significant reconstruction of the church. The church is then deeply affected by the 1542 seismic event (epicentral macroseismic intensity 9, deduced magnitude 6.02) which resulted in the collapse of the upper part of the bell tower and the two lateral chapels as well as the overturning of the front wall and of the two lateral walls of the nave. The 1611 seismic event (epicentral macroseismic intensity 7, deduced magnitude 5.1) damaged the upper part of the bell tower as described in historical records. In spite of the confirmed occurrence of seismic events in the area from the middle of the 17th century and the beginning of the 20th century, no information relating seismic damage of the church has been found in historical records nor in the startigraphic analysis. The most important earthquake which struck the area on June 19th, 1919, produced only some small cracks in the church (magnitude 6.38).

Numerical analysis of fault-slip behaviour in longwall mining using linear slip weakening law

Coal burst induced by fault-slip in longwall mining can adversely influence underground mining activities. This paper analyses the source mechanisms of fault-slip behaviour using a numerical fast Lagrangian analysis of continua in three dimensions (FLAC3D) model. The fault was simulated by the build in zero-thickness interface elements. The post failure process of fault-slip was studied using the linear slip weakening law which was implemented in a user-defined FISH program. The numerical results showed that the fault-slip presented significantly different trends at different positions along the fault. Seismic events mainly occurred at the fault area where the normal stresses reduced drastically. Few seismic events occurred when the distance between the longwall face and the fault was less than 20 m. For the parameters of the linear slip weakening law, the influence of the dynamic friction and the critical slip distance were analysed. These two parameters have significant impact on the occurrence of seismic events and the source parameters of fault-slip. The parametric study showed that fault-slip with around 0.1 m of critical slip distance was able to release larger seismic energy than fault-slip with both less and greater than 0.1 m of critical slip distance. The outcomes of this paper help to better understand the seismic fault-slip process in longwall mining and the influence of the critical parameters of the linear slip weakening law on seismic fault-slip behaviour.

Numerical modelling of the dynamic response of threadbar under laboratory-scale conditions

The development of mining and underground excavations under high stress conditions, where the occurrence of seismic events may induce sudden energy release, has generated new challenges and additional research related to the dynamic response of reinforcement systems. To ensure safety of underground excavations, the development of new reinforcement elements able to resist dynamic events and yielding during the loading process has advanced in the last 30 years as a result of research studies and testing programs carried out by recognized institutions. The execution of these testing programs involves a considerable time and requires validation. In Chile, the development of a new laboratory-scale dynamic test facility has required several studies in which numerical modelling is considered as an important part of the design process. This paper presents the implementation and results of a numerical model used to simulate the dynamic response of threadbar under laboratory-scale test conditions. A comprehensive calibration of the numerical model using the results of laboratory-scale dynamic tests available from the literature is presented. The continuous and split configurations for the encapsulating tube are tested and compared. A parametric analysis is performed with the calibrated model. The verification of the model is established with an additional laboratory-scale result not considered in the calibration process. A summary of the results in terms of the dissipated energy and the maximum displacement is presented. The results indicates a linear trend between the dissipated energy and the maximum displacement, and a significant improvement of the dynamic response of threadbar when the steel grade or the diameter of the rockbolt is increased.

Seismic emergency system evaluation: The role of seismic hazard and local effects

The emergency management system is a complex network consisting of structural components, such as buildings, infrastructure and emergency areas, and non-structural elements, such as procedures, emergency workers, information management, etc. This document describes the evaluation of only its structural components. The system was adopted at the territorial scale and is defined by a multi-municipality area extension. This paper presents a methodology for the probabilistic evaluation of operating the emergency structural system in the case of a seismic event occurrence and, in detail, it highlights the methodology for calculating the seismic hazard including seismic local effects (amplification and permanent co-seismic effects). Systemic seismic risk and associated impact were considered in a rigorous and unified way. Moreover, the importance of the interconnection and interdependence between elements at risk belonging to the same system and between different networks at urban or territorial scales is well known. The aim of the proposed methodology is to evaluate the operational losses of an emergency system considering the connections between the components of the system, contributing, in an original way, to the estimation of the seismic effects. The fundamental characteristics of this calculation are:•Estimating ground motion amplification at the territorial scale using a Vs30 from a probabilistic map obtained with the seismic microzonation national database;•Estimating shaking scenarios in terms of PGA and PGV depending on the Vs30;•Co-seismic permanent failure and deformations (landslide and liquefaction) evaluated with regression logistic methods.Finally, a case study is presented showing the application of the methodology on a real emergency system in an area of southern Italy.

Operational and geological controls of coupled poroelastic stressing and pore-pressure accumulation along faults: Induced earthquakes in Pohang, South Korea

Coupled poroelastic stressing and pore-pressure accumulation along pre-existing faults in deep basement contribute to recent occurrence of seismic events at subsurface energy exploration sites. Our coupled fluid-flow and geomechanical model describes the physical processes inducing seismicity corresponding to the sequential stimulation operations in Pohang, South Korea. Simulation results show that prolonged accumulation of poroelastic energy and pore pressure along a fault can nucleate seismic events larger than Mw3 even after terminating well operations. In particular the possibility of large seismic events can be increased by multiple-well operations with alternate injection and extraction that can enhance the degree of pore-pressure diffusion and subsequent stress transfer through a rigid and low-permeability rock to the fault. This study demonstrates that the proper mechanistic model and optimal well operations need to be accounted for to mitigate unexpected seismic hazards in the presence of the site-specific uncertainty such as hidden/undetected faults and stress regime.

Disaster risk management in secondary education teachers in Chincha Province, Peru [Gestión de riesgo de desastres en docentes de educación secundaria de la provincia de Chincha, Perú

The objective of the research was to identify the levels of knowledge in Risk Management in teachers of secondary education in the province of Chincha. Basic research was carried out, descriptive level, cross section and non-experimental design. The population was constituted by teachers of educational institutions of secondary level of the city of Chincha. The sample size was calculated probabilistically, being constituted by 298 teachers from seven schools, between State and Private. A Questionnaire with thirty-three questions was applied. The results show a deficient level of knowledge about the prevention of disaster risks among the teachers of the investigated schools. It is concluded that the levels of knowledge of teachers facing earthquakes do not reach optimal or adequate levels, which is very worrying, considering that there is a high probability of occurrence of seismic events of high magnitude in the context of the Province of Chincha, as in the entire Ica Region.

Application of Seismic Monitoring and Numerical Modelling in the Assessment of Possibility of Seismic Event Occurrence in the Vicinity of Ore Remnant

Seismic and rockburst hazard is one of the basic problems associated with deposit exploitation in many underground mines. Rockbursts are responsible for many mining accidents, and their effects, which include damaged excavations, destroyed equipment and machinery, generate financial losses and disrupt the operational continuity of the mining facility. Dynamic phenomena occurrence is one of the major natural hazards in Polish underground copper mines in the Legnica-Glogow Copper Belt (LGCB). The degree of seismic hazard in the LGCB results, among others, from the great depth of the copper deposit exploitation, high-strength rock layers in the roof strata and the ability of rock mass to accumulate elastic energy, as well as from an increasing amount of mining works to be carried out in difficult geological and mining conditions, for instance in the vicinity of remnants. The purpose of this paper is to show the influence of ore remnant on the possibility of seismic event occurrence by seismic activity analysis and numerical modelling. The possibility of using numerical modelling to back-calculate the occurrence of a seismic event due to sudden shear rupture is also presented. Analyses were conducted for the case study of the Polkowice-Sieroszowice Polish underground copper mine for the room-and-pillar mining system with room deflection. For the selected mining field, quantitative analysis of seismic activity was performed in connection with the assessment of the mining situation in this field. The location of tremor epicentres in the context of the existing geological and mining situation was also analysed, with special attention paid to the impact of remnants and dynamic phenomena in their vicinity. Subsequent investigations focused on the back analysis of deposit exploitation by room and pillar mining system with roof deflection in the selected mining field. Numerical simulations were conducted in a plane deformation state by means of Phase2 v. 8.0 software, which is based on the finite element method. The results of seismic and numerical analyses show that undisturbed rock remnants may have a negative impact on the seismic and rockburst hazard in the mining field. The analyses also show that on the edge of a rigid remnant, sudden fracturing of roof strata may occur, as a result of exceedance of shear strength (shear rapture). This may cause a high-energy mining tremor, and under appropriate conditions, may result in a rockburst phenomenon.

Cyclic soft stimulation (CSS): a new fluid injection protocol and traffic light system to mitigate seismic risks of hydraulic stimulation treatments

Hydraulic stimulation treatments are standard techniques to access geologic resources which cannot economically be exploited with conventional methods. Fluid injection into unproductive formations may increase their permeability by forming new fractures and activating existing ones. A major risk of this process is a possible occurrence of seismic events that can potentially be felt on the surface or even cause minor damage. In this paper, an advanced fluid injection scheme is proposed that aims to mitigate these unwanted events and to improve the permeability enhancement process. Amongst other procedures, it involves different types of cyclic injection and a traffic light system specifically designed for cyclic injection schemes. The concept is applied to develop a stimulation design for the Pohang enhanced geothermal system site in Korea, where it was first deployed in the field in August 2017.

Heliogeodynamics and seismicity in Pribaikalie

The field of earthquake epicentres of Pribaikalie (Russia) is reconstructed from the data of historical and instrumental monitoring of earthquakes. The analysis shows that seismic events in the study area are distributed irregularly in space and time. The seismic process in Pribaikalie is investigated through the prism of seismic structures in the lithosphere; the irregular occurrence of seismic events in time is considered with reference to seismic weather and climate; and the causes of periodic activations of the seismic process are discovered in relation to the external effects on the Earth's physical fields from cosmic and solar processes. It is proposed to classify the seismic structures as specific geometric objects located in the lithosphere. Such objects are viewed as abstract structural elements. Some regular features are noted in the occurrence of seismic events. It is revealed that the seismic process in time shows a similarity with the course of hydrometeorological processes, which is reflected in the periodicity of elastic energy release, if only the change in the number of earthquakes (of different energy classes) in time is analysed by years. An evidently regular time pattern of seismically active periods suggests that the seismic process is influenced by some external factors. In this study, we apply the concepts of heliogeodynamics, space climate and weather to investigate such factors.

The particle swarm modified quasi bang-bang controller for seismic vibration control

The frequent occurrence of seismic events results in the damage to the structures. Structural control is one of the popular methods to prevent these damages. In structural control, the main objective is to impart an adequate counterforce. This required counter force is determined by a suitable control algorithm. In this work, an optimized and adaptive control algorithm is proposed based on modified quasi bang-bang control algorithm to generate the adequate counterforce. The constant output weights used in the modified quasi bang-bang controller are optimized for best performance in dynamic loading such as earthquake using the particle swarm optimization (PSO). The proposed optimized controller is then applied to a three storey prototype structure fixed with an MR damper. This structure has been subjected to various seismic events for performance evaluation. The results thus obtained are compared with best performing clipped optimal linear quadratic Gaussian (LQG) controller, quasi bang-bang and modified quasi bang-bang controller. The results establish that the PSO modified quasi bang-bang controller is superior to the other controller in reducing the structural responses i.e. relative displacement, interstorey drift and the absolute accelerations. Further, the voltage comparison shows that the power consumption is less for the proposed controller in attaining better performance.

Evaluating Micro-Seismic Events Triggered by Reservoir Operations at the Geothermal Site of Groß Schönebeck (Germany)

This study aims at evaluating the spatial and temporal distribution of 26 micro-seismic events which were triggered by hydraulic stimulation at the geothermal site of Gros Schonebeck (Germany). For this purpose, the alteration of the in-situ stress state and the related change of slip tendency for existing fault zones due to stimulation treatments and reservoir operations is numerical simulated. Changes in slip tendency can potentially lead to reactivation of fault zones, the related movement can lead to the occurrence of seismic events. In the current numerical study, results obtained based on the thermal–hydraulic–mechanical coupled simulation are compared to field observations. In particular, the study focuses on describing the fault reactivation potential: (1) under in-situ stress conditions; (2) during a waterfrac stimulation treatment; and (3) during a projected 30 years production and injection period at the in-situ geothermal test-site Gros Schonebeck. The in-situ stress state indicates no potential for fault reactivation. During a waterfrac stimulation treatment, micro-seismic events were recorded. Our current evaluation shows an increase of slip tendency during the treatment above the failure level in the direct vicinity of the micro-seismic events. During the projected production and injection period, despite increased thermal stress, the values for slip tendency are below the threshold for fault reactivation. Based on these results, and to prove the applied method to evaluate the observed micro-seismic events, a final discussion is opened. This includes the in-situ stress state, the role of pre-existing fault zones, the adopted criterion for fault reactivation, and a 3D rock failure criterion based on true triaxial measurements.

Tetra‐stage cluster identification model to analyse the seismic activities of Japan, Himalaya and Taiwan

From the decades, due to the independent and Poisson nature of background seismicity, they are extensively used for hazard analysis, modelling of prediction phenomenon and also used for earthquake simulations. In this study, a tetra-stage cluster identification model is proposed for accurate estimation of background seismicity and triggered seismicity. The proposed method considers a seismic event's occurrence time, location, magnitude and depth information available in the given catalogue to classify the event as a background or aftershock. The model has flexible threshold parameters which can be tuned to a proper value according to the specific seismic zone to be analysed. It exploits the current seismic activities of the region by taking care the past samples of the region over last 25 years. The analyses of Japan, Himalaya and Taiwan catalogues are carried out using the proposed model. Superior results with the proposed model are achieved, compared with benchmark models by Nanda et al., Gardner–Knopoff and Uhrhammer et al. in terms of percentage of background seismicity, lambda plot and cumulative plot. The ergodicity present in the original seismic catalogue and catalogue after de-clustering are compared using Thirumalai-Mountain metric to justify the stationary and linearity.

Depth to the bottom of magnetic layer in South America and its relationship to Curie isotherm, Moho depth and seismicity behavior

We have estimated the DBML (depth to the bottom of the magnetic layer) in South America from the inversion of magnetic anomaly data extracted from the EMAG2 grid. The results show that the DBML values, interpreted as the Curie isotherm, vary between ∼10 and ∼60 km. The deepest values (>∼45) are mainly observed forming two anomalous zones in the central part of the Andes Cordillera. To the east of the Andes, in most of the stable cratonic area of South America, intermediate values (between ∼25 and ∼45 km) are predominant. The shallowest values (<∼25 km) are present in northwestern corner of South America, southern Patagonia, and in a few sectors to the east of the Andes Cordillera. Based on these results, we estimated the heat flow variations along the study area and found a very good correlation with the DBML. Also striking is the observation that the thermal anomalies of low heat flow are closely related to segments of flat subduction, where the presence of a cold and thick subducting oceanic slab beneath the continent, with a virtual absence of hot mantle wedge, leads to a decrease in the heat transfer from the deeper parts of the system.After comparing our results with the Moho depths reported by other authors, we have found that the Curie isotherm is deeper than Moho in most of the South American Platform (northward to ∼20°S), which is located in the stable cratonic area at the east of the Andes. This is evidence that the lithospheric mantle here is magnetic and contributes to the long wavelength magnetic signal. Also, our results support the hypothesis that the Curie isotherm may be acting as a boundary above which most of the crustal seismicity is concentrated. Below this boundary the occurrence of seismic events decreases dramatically.

A New Numerical Approach to the Structural Analysis of Masonry Vaults

The present paper concentrates on the numerical modelling of masonry vaults, adopting a type of analysis first developed at the University of Parma for applied mechanics, based on the use of non-smooth dynamics software, through a Differential Variational Inequalities (DVI) formulation specifically developed for the 3D discrete elements method. It allows to follow large displacements and the opening and closure of cracks in dynamic field, typical of the masonry vaulted structures. Once the modelling instrument was calibrated, thanks to the comparison with the recurrent damage mechanisms previously analysed, it was also applied to foresee the behavior of the same structure with different actions and with different types of strengthening. The development of damage mechanisms, both in quasi-static cases (for insufficient lateral confinement or for possible soil settlements) and in the occurrence of seismic events, make this type of structures very difficult to be modelled precisely with other methods. Given the three-dimensional CAD model of a vault modeled with a great number of masonry units with specific positions and pattern, the method proved to be able to reproduce the behavior of the structure under both static and seismic loads, showing the mechanism of collapse, the network of contact forces, the displacements and other useful data. The aim is to inspect the possible influences in the structural behavior given by the discrete geometry and the changes in the mechanisms development given by different strengthening interventions. Once the modeling instrument will be calibrated, also through the comparison with real cases and with the results obtained through limit analysis, it will be possible to adopt it as a base also for the prevision of the future behavior of the vaults subjected to strengthening, avoiding uncalibrated and uncritical applications of materials based more on trends rather than on a thorough analysis for the specific case.

Assessment of seismic hazard of the Japanese islands based on fractal analysis of GPS time series

Based on the fractal analysis of the time series of the Earth’s surface vertical displacements in the region of the Japanese Archipelago, the maps of the estimates of seismic activity in the region over 2015 are constructed. The analysis of the maps revealed several segments of the territory which are prone to the emergence of significant earthquakes. The characteristic peculiarity is noted in the change of the behavior of the geophysical dynamic system—the Earth’s crust—before the occurrence of seismic events: the mechanism of transition to the critical state demonstrates the energy preservation of the low frequencies with the simultaneous energy decay of the middle and high frequencies, which differs from the behavior of the other dynamical systems.