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1

Study on safety management in Turkish earthquakes

Stasiak-Betlejewska Renata, Ömek Gökhan

System Safety : Human - Technical Facility - Environment

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2023

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Vol. 5, iss. 1

224--230

EN

Natural disasters affect not only humans but also all living beings and societal elements. The term "disaster “meaning a Great Calamity. Among these calamities, earthquakes stand out as the most significant in terms of the damages they cause. Internationally, all authorities define earthquakes as the disasters that result in the highest loss of life and property. This paper highlights the urgent need for effective debris management measures, drawing on established scientific knowledge and operational experience from scientific studies authored by universities. By highlighting the challenges faced during earthquake debris management and safety management and the associated threats to public health and the environment, this study was undertaken to raise people's awareness against similar negligence in future catastrophic events.

2

Trzęsienie ziemi w Maroku

Wojnarowicz Michel

Inżynieria Morska i Geotechnika

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2023

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nr 5

217--221

PL

Informacja o tragicznym trzęsieniu ziemi o magnitudzie 6,8 w skali Richtera, do jakiego doszło we wrześniu 2023 roku w Maroku, w prowincji Al Haouz. Przyczyny i skutki trzęsienia ziemi w Maroku. Wytyczne Eurokodu 8 dotyczące klasyfikacji stref zagrożonych trzęsieniem ziemi oraz klas podłoża gruntowego i kategorii podatności budynków pod względem ryzyka sejsmicznego. Zalecenia konstrukcyjne budynków zwiększające bezpieczeństwo podczas trzęsień ziemi.

EN

Information about the tragic earthquake with a magnitude of 6.8 on the Richter scale that occurred in September 2023 in Morocco, in the Al Haouz province. Causes and effects of the earthquake in Morocco. Eurocode 8 guidelines for the classification of earthquake hazard zones and subsoil classes and building vulnerability categories in terms of seismic risk. Building design recommendations to increase earthquake safety.

3

Wstrząs w ogóle i szczególe

Królikowski Jerzy

Geodeta : magazyn geoinformacyjny

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2023

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nr 3

8--9

4

Experimental dynamic damage assessment of PUFJ protected brick infilled RC building during successive shake table tests

Kwiecień Arkadiusz, Rakicevic Zoran, Chełmecki Jarosław, Bogdanovic Aleksandra, Tekieli Marcin, Hojdys Łukasz, Gams Matija, Krajewski Piotr, Manojlovski Filip, Soklarovski Antonio, Halici Omer Faruk, Rousakis Theodoros, Vanian Vachan

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2023

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Vol. 71, nr 3

art. no. e144940

EN

It is highly important to determine eigenvalues before and after certain extreme events that may cause damage accumulation, such as earthquake, blasts and mining or seismic tests on research models. Unique experiment design and shake table testing was performed to investigate seismic performance of a 3D RC building model with infill walls and advanced protection with polyurethane-based joints and fiber polymer reinforced light and emergency jackets. For the purpose of wider experimental activities, three methods for determination of the dynamic characteristics were used during multiple successive shake table tests following a dynamic pushover approach, and they are presented in detail. They are: inertance function through impact hammer tests, standard Fourier transformation of measured acceleration time history and digital image correlation. The expected differences in the results are related to the type and intensity of excitation used, the involvement of materials with different mechanical and physical properties, and with the different rate and extent of damage accumulation, as well as to local or global measurements. Y et, all methods lead to reliable results when a consistent methodology is being used, that takes into account locality or globality of measurements, leaving a choice for the most suitable one, depending on the site conditions. The inertance function method presented manifested its high efficiency in analysis of dynamic properties of large-scale structures and in monitoring of their changes caused by the damage and repair process. It offers quite a wide range of useful information, does not require very expensive equipment and its transportation cost is negligible. This method seems to be a proper diagnostic tool for simple experimental modal analysis of real structures and their structural elements, where detection of changes in the structural condition and in dynamic properties is required, also as a non-destructive testing and monitoring method. Digital image correlation proved to be a promising non-contact tool, strongly supporting the conventional instrumentation of shake table testing, while the Fourier transformation was used as a benchmark method yielding the most reliable results.

5

Seismic performance evaluation of a base-isolated steel liquid storage tank with limiting-devices considering soil-structure interaction

Jing Wei, Tian Shuang

Archives of Civil Engineering

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2023

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Vol. 69, nr 4

635--661

EN

Liquid storage tank is widely used in the petrochemical industry, earthquake will lead to structural damage and secondary disasters, and damping control opens up a new way for seismic design of liquid storage tank. Considering soil-structure-fluid interaction, liquid sloshing dynamic behavior and material nonlinearity, a three-dimensional calculation model of shock absorption liquid storage tank is established by combining sliding isolation and displacement-limiting devices. The dynamic responses of the liquid storage tanks under the action of Kobe and El-Centro waves are investigated, and the influence of soil-structure interaction (SSI) on the dynamic response is discussed. The results show that the damping ratio is basically between 30% and 90%. After the SSI is considered, the damping ratio of liquid sloshing wave height is increased, while the damping ratio of the dynamic response of the liquid storage tank is decreased, and the change of elastic modulus has little effect on the damping effect. The sliding isolation with displacement-limiting devices has significant damping control effects on the liquid sloshing wave height and the dynamic responses of the liquid storage tank.

6

Research on the dynamics of lightweight shell and spatial structures with the aid of computational fluid dynamics and a shaking table

Padewska-Jurczak Agnieszka, Cornik Dawid, Walentyński Ryszard, Wiśniowski Maciej, Szczepaniak Piotr

Archives of Civil Engineering

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2023

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Vol. 69, nr 4

379--392

EN

In determining the effects of actions when designing road structures, the influence of the loads caused by the buffeting of the passing vehicles (high-cycle forces) is neglected. Taking into account the fatigue load, they can have a very large impact on the assessment of the load capacity. The subject of analysis is the pressure and velocity distributions around a truck. At the current stage of the work, it can be concluded that the gusts of passing trucks affect the dynamics of the gantry structure and the elements suspended on it, such as platforms or boards. There is a strong suction force. It is possible to simplify the model in such a way that the board and the wind move with the speed of the vehicle while the truck remains stationary. Due to the lack of reliable guidelines for strength calculations of such structures, advanced Computational Fluid Dynamics (CFD) tools were used. This paper also presents a shaking table built by the authors for dynamic loading of structural models. It describes the construction of the shaking table and the kind of movement made by the table deck. It also shows a scheme of the table deck suspension on linear bearings, as well as a scheme of the table motion system.

PL

Przy określaniu skutków oddziaływań przy projektowaniu obiektów drogowych pomija się wpływ obciążeń wywołanych podmuchami od przejeżdżających pojazdów (siły wysokocyklowe). Biorąc pod uwagę również obciążenie zmęczeniowe, mogą one mieć bardzo duży wpływ na ocenę nośności konstrukcji. Przedmiotem analizy są rozkłady ciśnień i prędkości wokół samochodu ciężarowego. Na obecnym etapie prac można stwierdzić, że podmuchy od przejeżdżających ciężarówek wpływają na dynamikę konstrukcji bramownicy i zawieszonych na niej elementów, takich jak pomosty czy tablice. Istnieje duża siła ssąca. Możliwe jest uproszczenie modelu w taki sposób, aby tablica i wiatr poruszały się z prędkością pojazdu, podczas gdy ciężarówka pozostaje nieruchoma. Ze względu na brak rzetelnych wytycznych do obliczeń wytrzymałościowych takich konstrukcji, zastosowano zaawansowane narzędzia obliczeniowej mechaniki płynów (CFD). W artykule przedstawiono również zbudowany przez autorów stół wstrząsowy do dynamicznego obciążania modeli konstrukcyjnych. Opisano w nim konstrukcję stołu oraz rodzaj ruchu, jaki wykonuje płyta stołu. Przedstawiono również schemat zawieszenia płyty stołu na liniowych łożyskach oraz schemat układu ruchu stołu.

7

Simulation of strong ground motions of 1991 Uttarkashi (M 7) and 1999 Chamoli (M 6.6) earthquakes using modified hybrid technique

Sharma Anjali, Kumar Dinesh, Paul Ajay, Teotia Satybir Singh

Acta Geophysica

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2023

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Vol. 71, no. 6

2573--2602

EN

In the present study, 1991 Uttarkashi (M 7) and 1999 Chamoli (M 6.6) earthquakes that occurred on October 19, 1991, at 21:23:14 h and March 28, 1999, at 19:05:11 h, respectively, have been simulated using the modified hybrid technique. Hybrid technique is the combination of two existing techniques, i.e., envelope technique and composite source model technique. In the present modified technique, site amplification functions and kappa factor have also been incorporated. The simulated waveforms and their corresponding response and Fourier spectra for each site have been generated. In this study, simulation has been done at 11 and 9 recorded stations of Uttarkashi and Chamoli earthquakes, respectively. Important frequency - and time-domain parameters, i.e., Fourier spectra, response spectra, peak ground acceleration (PGA) and duration at stations, have been estimated and compared with the observed accelerograms. It has been observed that the simulated PGA (231 cm/s2) at the closest distance Bhatwari (22 km) matched with the observed one (248 cm/s2) for the Uttarkashi earthquake. The same has been observed at the nearest most station Gopeshwar (19 km) of the Chamoli earthquake. The simulated PGA (347 cm/s2) for this station has been found well matched with the observed PGA value (352 cm/s2). Similar matching has been observed for other stations also. The present technique is independent of velocity-Q structure of earth’s layered model and past events data of small earthquakes. This study brings light on the site effect and high-frequency decay parameter. This study can be very helpful in the estimation of seismic hazard in a specific region and designing earthquake-resistant buildings.

8

Seismo ionospheric anomalies related to the Mw 7.5, Kepulauan Alor, Indonesia earthquake

Koklu Kevser

Acta Geophysica

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2023

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Vol. 71, no. 6

2633--2644

EN

Discussions about anomaly in the ionosphere have made significant progress since the great Alaskan earthquake, in 1964. Specifying signs of precursors of an earthquake and traces of the aftershock of its may minimize every kind losses. This study examines the possible effect on the ionosphere of the M7.5 earthquake that occurred at 21:46 UT on November 11, 2004, near Kepulauan, Alor Islands (8,152°S-124,868°E), Indonesia. This effect is observed in TEC (TECU) data. The limits of the TEC data gained from IRI-2016 are determined by the statistical method. Anomalies are marked by means of out-of-bounds data. Anomaly causes are introduced to the reader according to the principle of causality. In this context, a portrait of space climate conditions is drawn with the aid of the earthquake, geomagnetic storm, and solar activity effect. According to this portrait, we perceive on October 15, November 10, and December 1-11. Probably the November 10 anomaly is caused by the earthquake and the other anomaly days may be related to the aftershock of the earthquake.

9

Ionospheric perturbations: a case study of 2007 five major earthquakes using DEMETER data

Thomas Jewel Emem, Ekanem Aniekan Martin, George Nyakno Jimmy, Akpan Anthony Effiong

Acta Geophysica

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2023

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Vol. 71, no. 4

1607--1618

EN

Using the Plasma analyzer (IAP) and Langmuir Probe (ISL) experiments of the Detection of Electromagnetic Emissions Transmitted from Earthquake Regions (DEMETER) lithospheric–atmospheric–ionospheric coupling has been observed before, during and after five major earthquakes with magnitudes greater than 6.5. The aim of this study is to use ionospheric parameters to identify the ionospheric perturbations associated with the five earthquake regions screened. All the three investigated ionospheric parameters of electron density, electron temperature and total ion density recorded perturbations within the investigative period. A total of 36 anomalies were obtained with 18 each for nighttime and daytime readings. The observed anomalies being screened for false alarm using the geomagnetic indices of Kernnifzer digit (kp) and disturbance storm time (Dst.) revealed 27.8% as geomagnetically induced perturbations. Thus, 72.2% of the studied anomalies transpired in quiet geomagnetic conditions, which is linked to seismic events.

10

Probabilistic Liquefaction Analysis Using Standard Penetration Test

Kamel Filali, Badreddine Sbartai

Studia Geotechnica et Mechanica

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2022

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Vol. 44, nr 2

162--174

EN

The Youd etal liquefaction resistance curves developed in 2001 to characterize the cyclic resistance of soil based on SPT test are the most used in the context of the Seed and Idriss simplified procedure as a deterministic model. These curves were developed from a modified database of Seed etal. in 1985 with the assumption that the actual peak shear stress (τd) induced at depth h is always less than that predicted by the simplified procedure (τr) of Seed and Idriss (rd= τd/τr<1). By using a suite of equivalent linear site response analyses to adjust the dynamic and the simplified shear stress at depth h, Filali and Sbartai showed in 2017 that the dynamic peak shear stress for some earthquakes is greater than the simplified peak shear stress (rd>1). As in this case, the assumption of the simplified procedure is not verified, Filali and Sbartai have proposed a corrector factor (RC) in the range where rd>1 to adjust the deformable and rigid body. In this paper, we will present a probabilistic study for the evaluation of the liquefaction potential using a database based on SPT measurement compiled after the Chi-Chi Taiwan earthquake, in which the cyclic stress ratio is evaluated using the proposed corrector factor. The objective of this study is to present a probabilistic shape of the cyclic resistance ratio (CRR) curves based on the original simplified method of Seed and Idriss and the corrected version and a new formulation for computing the probability of liquefaction.

11

Parametric study of the earth dam's behaviour subjected to earthquake

Ayeche H., Zitouni Z., Limam A., Bouafia A.

Studia Geotechnica et Mechanica

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2022

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Vol. 44, nr 4

267--281

EN

Static stability of an earth dam can be established by estimating the static safety factor equal to the ratio of the shear strength to the shear stress along a critical sliding area. In contrast, it is more complicated to evaluate the dynamic stability during an earthquake. The water filling the interstices of the earth dams cannot drain during the short duration of an earthquake. An excess pore water pressure DU develops, and its role is predominant in the destabilisation of the dam. The pore water increase causes a decrease in the soil shear strength. It is, therefore, crucial to evaluate and take into consideration DU in the dam dynamic stability analysis. This research is a contribution to reach this objective. A parametric study was conducted by varying the physical and mechanical soil characteristics constituting the dam, as well as its geometrical values, in order to evaluate their effects on the dynamic safety factor. The dynamic safety factor is calculated using the pseudo-static method, taking into account the excess pore water pressure that develops during cyclic loading into the granular soil of the earth dam upstream face. The results of the parametrical analytical study were also compared to the results of numerical simulations of the dam seismic stability trough pseudo-static method. The numerical simulations were done with three different software: PLAXIS and ABAQUS (based on the finite element method) and GEOSTAB (deals with the problem at the limit equilibrium using the simplified Bishop method). At the end, on one hand, we were able to describe how and at what level of the dam upstream face the sliding occurs, and on the other hand, we were able to underline the adequate combination between the dam geometric parameters and the mechanical soil characteristics which may ensure seismic stability.

12

Performance of Solid Waste Landfills Under Earthquake-Induced Vibrations

Seyedi Marghaki Behnaz, Soltani Fazlollah, Noroozinejad Farsangi Ehsan, Sivandi-Pour Abbas

Civil and Environmental Engineering Reports

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2022

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Vol. 32, no. 2

1--22

EN

The stability inside the waste, internal stability, and co-stability between the elements of the insulation system and the landfill bed should be considered in the landfill design. The stresses and the resulting deformations in both mineral and geosynthetic materials of the insulation system must be controlled in the design, so that an unpredictable flow path is not created. Besides, long-term durability in the insulation system should be considered. An evaluation of the durability of the system requires knowledge of the interaction between the components and the waste as a settling object. The numerical modeling methods can be used to evaluate the local instability. In this study, a landfill constructed in the UK has been modeled in ABAQUS finite element platform and was verified with the results of obtained data from precision instruments at the landfill site. Then, by applying the earthquake excitations, the seismic behavior of the solid waste landfill under Far-Field and Near-Field earthquakes and their effect on the durability of the landfill wall system were investigated. The outputs include maximum displacement, maximum stress, the most critical state, and investigation of yield stress and rupture of the geomembrane layer. The results indicated that in the landfill wall, the maximum displacement occurs in the waste section. It occurs especially between the boundary of natural soil and waste. It was also observed that the geomembrane layer under the earthquake loadings had experienced some ruptures.

13

Probabilistic assessment of the seismic vulnerability of a rammed earth construction: a case study

Jama Balil, Agliz Driss, Abderrahman Atmani, Derife Mina

Archives of Civil Engineering

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2022

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Vol. 68, nr 2

325--335

EN

Rammed earth significantly reduces intrinsic energy compared to concrete construction and has an environmental benefit throughout the life cycle of the building: phases of construction, operation, maintenance, renovation, and demolition. Several studies have recently been carried out to study this material. However, the seismic behavior of rammed earth constructions is still an important topic that needs to be studied in more detail. Through the analysis of non-linear behavior of the rammed earth construction for different wall thicknesses according to the Moroccan earthquake regulation RPS2011, we were able to assess the seismic performance under the corresponding conditions (loads, seismic zone). The results show that the walls studied can have good resistance in areas of seismicity ranging from “very low” to “moderate” and acceptable performance in areas of high seismicity. Furthermore, fragility analysis shows that rammed construction with a wall thickness equal to 50 centimeters exhibits better seismic performance and a low probability of damage, particularly in the case of moderate, severe, and complete damage states.

14

Nonlinear analysis of a hoist tower for seismic loads

Pachla Filip, Tatara Tadeusz

Archives of Civil Engineering

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2022

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Vol. 68, nr 3

177--198

EN

In recent years, the intensity of the loads caused by mining activity has increased in Poland. This exploitation is often carried out in urbanized areas, so their operation on structures is not only a social problem, but also a challenge for engineers. Many of the surface facilities safe use affects the failure-free operation of the mine. The paper presents the results of representative measurements of surface vibrations from mining areas in Poland and earthquakes and their comparison. Particular attention was paid to the values of PGA/PGV ratios and the most commonly used methods for dynamic calculation of the structure. The last part of the work presents an experimentally verified dynamical model of the selected RC skip tower. The forced vibrations of the model were analysed by taking representative earthquakes and mining origin tremors. Time history non-linear analysis and push over methods were used. The nonlinear concrete model was adopted in the analyses. The results show that pushover analysis is not able to capture the seismic demands imposed by far-field or near-fault ground motions, especially for short-period systems for which it can lead to significant errors in the estimation of the seismic demands. The results confirmed the qualitative results of the linear analysis. The carried out inventory of cracks to the skip tower also allowed their location in bearing elements of the skip tower. The results of non-linear numerical analyses allowed us to assess the safety of the structure.

PL

Dodatkowym obciążeniem działającym na konstrukcje budowlane są drgania przenoszone przez grunt. Z reguły takie konstrukcje, gdy znajdują się poza obszarami trzęsienia ziemi, nie są przystosowane do takich dodatkowych obciążeń. Na terenach dotkniętych wstrząsami górniczymi konstrukcje nie były projektowane na takie obciążenia. W projekcie uwzględniono tylko obciążenia stałe i ciężar własny, obciążenia technologiczne oraz obciążenia od podmuchów wiatru. W ostatnich latach w Polsce wzrosła intensywność obciążeń powodowanych działalnością górniczą. Eksploatacja ta często prowadzona jest na terenach zurbanizowanych, dlatego ich eksploatacja i wpływ na budynki staje się nie tylko problemem społecznym, ale także wyzwaniem dla inżynierów. Ich zadaniem jest zapewnienie bezpieczeństwa konstrukcji i osób przebywających w tych budynkach. Wiele obiektów naziemnych znajduje się bezpośrednio na terenach kopalni. Ich bezpieczne użytkowanie wpływa na bezawaryjną prace kopalni. Awarie obiektów powierzchniowej infrastruktury budowlanej kopalni prowadzą do dużych strat finansowych i powodują problemy społeczne. W pracy przedstawiono wyniki reprezentatywnych pomiarów drgań powierzchniowych z terenów górniczych w Polsce. Drgania te były spowodowane najintensywniejszymi wstrząsami górniczymi, jakie wystąpiły podczas podziemnej eksploatacji kopalni węgla kamiennego i rud miedzi w Polsce. Wyniki pomiarów in-situ tych drgań porównano z zapisami drgań z wybranych trzęsień ziemi. Szczególną uwagę zwrócono na wartości wskaźnika PGA/PGV, a także różnice charakteryzujące drgania powierzchniowe indukowane podziemną eksploatacją górniczą i wstrząsy sejsmiczne oraz czas trwania intensywnej fazy drgań. Następnie przedstawiono najczęściej stosowane metody obliczeń dynamicznych konstrukcji. W ostatniej części pracy zaprezentowano numeryczny model dynamiczny wybranej żelbetowej konstrukcji wieży wyciągowej.

15

Seismic running safety assessment for stochastic vibration of train–bridge coupled system

Zhao Han, Wei Biao, Jiang Lizhong, Xiang Ping

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 4

art. no. e180, 2022

EN

With the rapid development of high-speed railway, the seismic running safety problem of high-speed train passing on bridge is becoming increasingly prominent. Since different wheel–rail contact states including uplifting, climbing up, detachment, recontact and derailment have been introduced into the simulation of train–bridge coupled (TBC) system, there are many problems arising for the mainstream derailment index in evaluating seismic running safety and stochastic analysis of train. To this end, a seismic running safety assessment for stochastic response of TBC system was first proposed in this paper. In this system, a detailed wheel–rail contact model was built to calculate the time-varying contact point and the contact force, which can be applied to simulate the detachment and recontact between the wheel flange and rail. Meanwhile, a stochastic analysis framework for derailment of the TBC system is developed. The stochastic vibration of a high-speed train traversing a multi-span prestressed simply supported box-girder bridge under earthquake with random magnitude was studied. In addition, an improved train running safety index, lateral wheel–rail relative displacement, was proposed and compared with the derailment factor and the offload factor to verify its feasibility. It shows an intuitive result as a derailment index in a stochastic train running safety analysis under earthquake. Furthermore, the lateral wheel–rail relative displacement and pertinent derailment probability were significantly affected by the intensity of the earthquake. The methodology herein can be helpful in seismic running safety assessment of high-speed train.

16

Potential of remote sensing data to support the seismic safety assessment of reinforced concrete buildings affected by slow‑moving landslides

Mele Annalisa, Miano Andrea, Di Martire Diego, Infante Donato, Ramondini Massimo, Prota Andrea

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 2

art. no. e88, 1--22

EN

Different forms of hazard can affect structures throughout their existence. The occurrence of a seismic event in areas exposed to different risks or already affected by other phenomena is highly likely, especially in countries characterized by high seismicity and equally high hydrogeological risk, as Italy. Nevertheless, the seismic safety assessment of reinforced concrete (RC) structures is commonly carried out considering the seismic action only, generally applied to an analytical model, neglecting the stress-strain state induced by previous ongoing phenomena. The aim of this work is to highlight the importance of the seismic safety assessment in a multi-hazard analysis, cumulating the action coming from two different hazards: landslide and earthquake. An existing RC building, located in an area affected by an intermittent landslide phenomenon with slow kinematics, that may also be subjected to strong earthquakes, is used as case study. The Differential Synthetic Aperture Radar Interferometry (DInSAR) approach is used to monitor the evolution in time of the landslide. DInSAR deformation data are used to detect surface ground movements applied to building foundations. A non-linear static analysis procedure is implemented for the code-based seismic safety assessment, in two different scenarios. The seismic assessment of the case-study building is implemented in a condition of structure deformed only for gravity loads, and, then, in a state of known landslide-induced deformed configuration. A comparison is proposed between the building seismic safety assessment per-formed in both cases, with or without the consideration of the landslide-induced displacements, showing the importance of a multi-hazard evaluation.

17

Clustering analysis of the seismicity of Van Province and its surroundings via spatial autocorrelation techniques filters

Perihanoglu Güzide Miray, Bilginer Ömer, Akyel Elif

Advances in Geodesy and Geoinformation

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2022

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Vol. 71, no. 2

art. no. e24, 2022

EN

Destructive aftershocks such as the M w 7.2 Van earthquake on October 23, 2011, and the Hoy (Iran) earthquake with M w 5.9 on February 23, 2020, occurred in the province of Van and its surroundings. In earthquake studies, the issue of examining the distribution and homogeneity of earthquake incidences with Geographic Information Systems (GIS) based via spatial autocorrelation techniques is frequently investigated. Van province and its surroundings are among the areas with high earthquake risk due to its location on the East Anatolian Compressive Tectonic Block. The aim of this study is to analyze the spatial patterns of earthquakes with magnitude M w 4 and above that occurred in the province of Van and its surroundings during the instrumental period and to determine to cluster. Spatial cluster analyses play an important role in examining the distribution of seismicity. The data used in the study have been taken from the database system of the Earthquake Department of the Republic of Turkey Ministry of Interior Disaster and Emergency Management Presidency. Moran’s I and Getis-Ord Gi methods from spatial autocorrelation techniques were preferred on the earthquake data set to be used in this research. It has aimed to determine the dangerous areas by testing the earthquake distributions in clustered regions via spatial autocorrelation techniques.

18

Seismo-ionospheric anomalies before M7.2 Haiti earthquake of August 14, 2021, from GPS TEC

Thomas Jewel E., Ben Ubong C., Ekanem Aniekan M., George Nyakno J., Nathaniel Ekong U.

Acta Geophysica

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2022

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Vol. 70, no 6

2621--2627

EN

Satellite-based measurements of total electron content (TEC) have been employed extensively to detect seismo-ionospheric anomalies. In this research, analysis of Global Positioning System (GPS) and TEC data obtained from three stations within seismogenic zone of M7.2 Haiti earthquake (EQ) of August 14, 2021, has been considered. A statistical procedure was used on daily TEC for the detection of anomalous and differential TEC. The study showed both reduction and enhancement in diurnal TEC within the investigative period on days −14,−11,−9,−7,−6, −4, −3, −1, 2, 3, and 4. Based on results, the three stations on days −11, −9, and −6 were concurrently perturbed. The outcomes of the analysis, which were constrained by data of synchronously monitoring geomagnetic indices of Kernnifzer digit (kp), disturbance storm time (Dst), solar indices (sunspot number (SSN) and F10.7 cm), revealed 82% seismic-induced anomalies relating to the EQ. The differential TEC |∆TEC| data were mostly remarkable on −6 and −4 days to the EQ, and this called for spatial mapping of TEC indices for August 8 and 10, 2021, over the epicenter of the EQ in order to check for atypical UT hours. Unusual ionospheric clouds from 16:00 to 20:00 UT enveloped the epicenter. Thus, this study has uncovered strong seismo-ionospheric anomalies from GPS-TEC data related to M7.2 Haiti EQ of August 14, 2021. This work is promising as short-term precursor of EQ in order to alleviate loss of lives and properties associated with this particular seismic event among others.

19

Estimation of local site efects and seismic vulnerability using geotechnical dataset at fyover site Agartala India

Bashir Khalid, Debnath Rajat, Saha Rajib

Acta Geophysica

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2022

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Vol. 70, no 3

1003--1036

EN

Considering future earthquakes, the vulnerability of Agartala city is following an increasing trend mainly due to the recent surge in population density and significant infrastructure developments. The recent moderate intensity earthquake at Tripura, namely the 2017 Dhalai Earthquake (Mw 5.7), with its epicentre being the adjoining district of Agartala, resulted in liquefaction cases, sand blows and lateral spreads, which may be an alarm for the geotechnical engineering fraternity. The present study attempts to evaluate local soil sites’ effect in the form of developing site-specific ground motions using stochastic point-source program SMSIM based on past scenario earthquakes in this region and performing one-dimensional nonlinear ground response analysis (1D GRA) of a recently constructed flyover site of 2.3 km length at Agartala city. Further, the seismic vulnerability of the flyover structure incorporating the local site effect is also assessed herein. The results obtained are explained in terms of surface acceleration time history, the ratio of shear stress to effective vertical stress with depth, acceleration response spectrum, Fourier amplitude ratio with frequency, etc. 1D GRA presented contrasting results with higher values of acceleration in areas with stiffer soils due to attenuation of the seismic waves. In general, the amplification ratio (Af ) evaluated from the present study indicated that the central portion of the flyover yielded high values and a high fundamental frequency value of 6.0 Hz, which might be detrimental for low-lying buildings. The generated synthetic motions of scenario earthquakes will be helpful for researchers and designers for earthquake resistant assessment or design of geotechnical structures in north-eastern India or similar sites in the absence of site-specific data. Finally, this study sheds important observations on seismic design guidelines of the structure located in this region, which may revamp the existing codal procedures.

20

New iterative method of solving nonlinear equations in fluid mechanics

Palivets M., Andreev E., Bakshtanin A., Benin D., Snezhko V.

International Journal of Applied Mechanics and Engineering

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2021

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Vol. 26, no. 3

163--176

EN

This paper presents the results of applying a new iterative method to linear and nonlinear fractional partial differential equations in fluid mechanics. A numerical analysis was performed to find an exact solution of the fractional wave equation and fractional Burgers’ equation, as well as an approximate solution of fractional KdV equation and fractional Boussinesq equation. Fractional derivatives of the order 𝛼 are described using Caputo's definition with 01<α≤ or 12<α≤. A comparative analysis of the results obtained using a new iterative method with those obtained by the Adomian decomposition method showed the first method to be more efficient and simple, providing accurate results in fewer computational operations. Given its flexibility and ability to solve nonlinear equations, the iterative method can be used to solve more complex linear and nonlinear fractional partial differential equations.