Strong Seismic Events Research Articles

Shaking table test of prestressed high-strength concrete pipe piles reinforced with non-prestressed steel reinforcement

Prestressed high-strength concrete piles reinforced with non-prestressed steel reinforcement (PRHC piles) have been developed to improve their seismic performance. In this study, the seismic response and failure mechanism of PRHC piles was investigated using a shaking table test. The dynamic characteristics, dynamic soil pressure, superstructure response, acceleration magnification factors, maximum curvature ductility demand, bending moment response, and failure mode identification of the PRHC piles were determined. The performance of PRHC piles was compared with that of prestressed high-strength concrete pipe (PHC) piles, which showed that the PRHC piles experienced higher energy dissipation and lower maximum curvature ductility demands than PHC piles. In addition, the PRHC piles suffered bending failure at the upper-middle positions, and the plastic zones were higher than those of the PHC piles. The adverse effects of long-period and pulse-type ground motions on pipe piles should be considered in designing for strong seismic events. The addition of non-prestressed reinforcement to a pipe pile allows longer segments of the pipe pile to be involved in providing resistance.

Design procedure and seismic performance assessment of structures equipped with bar-fuse dampers

The application of metallic yielding dampers (MYDs) to enhance the seismic performance of a structure has been a focus of attention in recent years. One recently introduced MYD is the bar-fuse damper (BFD). Its advantages include ease of installation, simple construction method, cost effectiveness (including replacement and repair costs) and shorter required repair time after strong seismic events. However, the most important benefits of the BFD are its high energy dissipation capacity, which can improve collapse safety and enhance the seismic performance of a structure. Despites its benefits, BFDs have been less studied than other types of MYDs. The present research provides a simple and efficient method for designing structures equipped with BFDs. Moreover, the mechanical characteristics of differently shaped BFDs made with different types of steel has been investigated using finite element analysis. Finally, the seismic performance of three model structures was evaluated using nonlinear time-history analysis. The results indicate that structures equipped with BFDs experience less inter-story drift and are less likely to undergo severe damage compared to similar bare moment-frame buildings.

Soft sediment deformation structures from the Brahmaputra Basin: A window to the eastern Himalayan paleoseismicity and tectonics

The Brahmaputra foreland basin, is one of the most dynamic in terms of tectonism and sediment load, revealed a variety of seismically generated soft sediment deformation structures (SSDS) in the form of clastic dikes, sand sills and related micro-faults. The qualitative and quantitative parameters of these SSDS in the study area such as dimension, angle of intrusion to capping layer, cross-cutting relations, wall shattering, sand sills, and micro-faults seem to be caused by multiple strong seismic events. The causative earthquake with intensity (VIII-X), paleo-peak ground acceleration (0.55 g) and magnitude (M ≥ 7.0) might have caused liquefaction features in the study area. Along with the geometry of various SSDS and Optically stimulated luminescence (OSL) dates derived for the clastic dikes indicate the oldest possible age for the seismic event as 0.94 ka. Further, the intensity and age obtained for the present study indicates a possible near seismic source like Kopili Fault Zone, Mishmi Thrust, and neotectonic lineament with trend NW-SE, which can be traced as micro faults and in clastic dikes. Liquefaction potential studies in the area indicate the likelihood of very high liquefaction potential (>45) with ground failures regardless of earthquake size or epicentral distance. The present study highlights the importance of SSDS for establishing paleoseismology in tectonically active regions where surface ruptures are sporadic due to dense alluvial cover and most of the active faults are blind.

Nonlinear shallow water investigation of atmospheric disturbances generated by strong seismic events.

The upper portions of the Earth's atmospheric layer, e.g., the ionospheric plasma layer, can be significantly affected by perturbations generated in the lower layers. In fact, all perturbations formed within the troposphere can easily propagate, not only horizontally within the layer but also vertically reaching the highest regions of the atmosphere far from the Earth's surface, as depicted by the Wentzel-Kramers-Brillouin (WKB) approximation of atmospheric waves. Because all perturbations generated in the atmospheric boundary layer must take into account the effects of the medium's nonlinearity and thus the effects of atmospheric turbulence, in this work the impact of a strong seismic event and the disturbances generated in the flow are analyzed by means of a fully nonlinear model which incorporates a simple parametrization of the seismic event and is based on the classical shallow water. A strict dependence was observed between the model control parameters and the vertical nonvanishing modes from the WKB approximation, and only few specific bands of excited modes are nonvanishing and can eventually propagate to the ionosphere. Moreover, the flow disturbance, generated by a seismic event, presents a multiscale nature characterized by two fixed wavelengths, and the excited modes are harmonics of such distinctive scales.

METHODOLOGY FOR A KINEMATIC MODEL OF SEISMIC EARLY WARNING SYSTEM ABOUT CRITICAL INFRASTRUCTURE

The destructive earthquakes generated huge losses and human victims. As for the moment the time of impending strong seismic event is unpredictable, during the last years – new global innovation is under development – the seismic early warning systems (SEWS). All of them signalize the population and/or governmental bodies and after the earthquake starts just providing information that the seismic event is fact, to expect stronger shakings and some very fast measures to be performed – for example NPP’s reactors stop, as well as superfast trains, chemical production, gas and oil pipeline disconnection, etc. In lucky cases some people can react (especially in the areas of low buildings) and to evacuate effective in the time domain of few seconds, thus saving their lives. Such system is in operation in Japan since 2007 and some other countries also develop their own SEWS. The present investigation is targeted to the methodology development of so called kinematic SEWS. They are using a fundamental property of the body seismic waves P and S. As it is well known from the theory, the P-waves are faster and less destructive than S-waves. This property gives the possibility to use the detection of the P waves as important signal that after a while (the time domain depends on the distance between the seismic source and the investigated site) the slower (1.41 times) more destructive S waves will arrive and struck the infrastructure. Our previous experience of the developed SEWS (for example for Baku and Venice) gives the possibility to upgrade the modeling methodology extending to the formalized algorithm and accuracy estimations, especially for the critical infrastructure (for example NPP).

Active seismogenic faulting in the Tehran Region, north of Iran; state-of-the-art and future seismic hazard assessment prospects

This study summarizes the state-of-the-art investigation into active-seismogenic faulting in the Tehran Region, and presents new complementary data to provide an overall view on potential seismic sources to strike the capital of Iran. The study region lies in the central portion of the Arabia-Eurasia collision zone. The Tehran Region is located in a transitional zone between the seismically active regions of Central Iran to the south and Alborz to the north and exhibits a tectonic context characterized by both dip-slip and strike-slip E-striking fault systems such as the Mosha, Parchin, Garmsar and North Tehran faults. Seismic catalogues record numerous strong and moderate earthquakes in the Tehran Region. Although the mapping of active faults and paleoseismological records have defined the seismic sources of several historical and prehistorical earthquakes, still many of them need to be constrained. Based on successive fault displacements and related microseismicity, five previously unknown or poorly understood major active seismogenic fault zones in the Tehran Region were introduced. From the west to the east, and in both near- and far-field contexts, the Qezel Hessar, Mahdasht-South Karaj, Kuhak-Lavizan, Arakuh, and Kajan define the fault zones. Critically, in the last decades, the rapid urban development in Tehran, including the new settlements of Karaj, Hashtguerd, Pardis, and Parand, has covered some of the surface expressions of these fault zones. The Kuhak-Lavizan fault zone, however, is known to cut across inner city parts of Tehran. Within the Tehran Region, seismicity on these faults demonstrates ongoing active structural evolution. The active faults of Tehran City are generally discussed in three northern, central and southern ∼E-striking basement zones. The major zones, which contain deep-seated faults, are capable of producing moderate to strong seismic events near and within the metropolitan areas of Tehran and Karaj and nearby settlements.

A Rapid Seismic Damage Assessment (RASDA) Tool for RC Buildings Based on an Artificial Intelligence Algorithm

In the current manuscript, a novel software application for rapid damage assessment of RC buildings subjected to earthquake excitation is presented based on artificial neural networks. The software integrates the use of a novel deep learning methodology for rapid damage assessment into modern software development platforms, while the developed graphical user interface promotes the ease of use even from non-experts. The aim is to foster actions both in the pre- and post-earthquake phase. The structure of the source code permits the usage of the application either autonomously as a software tool for rapid visual inspections of buildings prior to or after a strong seismic event or as a component of building information modelling systems in the framework of digitizing building data and properties. The methodology implemented for the estimation of the RC buildings’ damage states is based on the theory and algorithms of pattern recognition problems. The effectiveness of the developed software is successfully tested using an extended, numerically generated database of RC buildings subjected to recorded seismic events.

2D FEM Numerical Prediction of Local Seismic Effects at San Salvador Municipality (El Salvador) Induced by 2001 Earthquakes

San Salvador Metropolitan Area (MASS) is an urbanized territory in the country of El Salvador, located between the San Salvador volcano and the Ilopango caldera, in a sub-flat area called “Valle de las Hamacas” (Valley of the Hammocks). The high seismicity of this area is due to the subduction zone of the Cocos plate that causes strong seismic events such as the earthquakes that occurred on 13 January (7.6 Mw) and 13 February 2001 (6.6 Mw). As part of the international cooperation project between Italy (AICS) and El Salvador University, the CASTES project focussed on natural hazards in the territory of El Salvador was launched. Therefore, 2D simulations are carried out along two sections to evaluate the Local Seismic Response (LSR) in the Southeast part of MASS territory. Results show spatially variable amplifications (from 3 to 6.5) in the period ranging 0.1–0.7 s and evidence of lateral FA variations that can be calculated only through 2D numerical analyses. Two amplified periods are recognised, 0.1–0.5 s and 0.4–0.8 s, due to the presence of two types of subsoil volcanic deposits: the shallow and soft Tierra Blanca deposits and the deeper and stiffer Volcanic ash and Tuff.

Detection of electromagnetic anomalies over seismic regions during two strong (MW > 5) earthquakes

Ionospheric disturbances (such as electromagnetic emissions) in connection to strong earthquakes have been reported in literature for over two decades. In order to be reliable, the identification of such disturbances requires a preliminary robust definition of the ionospheric background in the absence of both seismic activity and any other possible input (e.g., transient change in solar activity).In this work, we present a new technique for the assessment of the electromagnetic (EM) background in the ionosphere over seismic regions. The background is estimated via a multiscale statistical analysis that makes use of most of the electric- and magnetic-field datasets (2019–2021) from the China Seismo-Electromagnetic Satellite (CSES-01).The result is a map of the average relative energy in a 6° x 6° LAT-LON cell centered at the earthquake epicenter (EE). Only EM signals that statistically differ from the background should be considered as events suitable for investigation.The method is tested against two strong seismic events, the 14 August 2021 Haitian earthquake (7.2 MW) and the 27 September 2021 Cretan earthquake (6.0 MW). In the former case, a signal (with characteristic frequency of 250 Hz) can be identified, which emerges from the background. In the latter one, the concurrent strong geomagnetic activity does not allow to tell any distinct signal apart from the background.

Сейсмотектонические деформации Алтае-Саянской горной области. Часть 1

Seismotectonic deformations (STD) of the Earth’s crust in the Altai-Sayan mountain region were studied. The STD calculation was performed on the basis of the approaches proposed in the works of Yu.V. Riznichenko and S.L. Yunga. Estimation of seismicity distribution and calculation of the average annual STD velocity (STD intensity) IƩ were made on the basis of the catalog of earthquakes that occurred in 1997–2020 (15 669 seismic events). Areas of manifestation of intense seismotectonic deformations and seismic activity are identified. A high level of seismicity and the average annual STD velocity (10–7 year–1) is noted in the areas where strong seismic events occurred (Chuya earthquake on September 27, 2003, Tuva earthquakes on December 27, 2011 and February 26, 2012). The study of STD directionality is based on data on the focal mechanisms of earthquake sources (591 events) that occurred from 1963 to 2021. The classification of STD modes was used to construct the STD map. According to the STD maps, the direction of the shortening axes was determined, which changes from west to east from northwest to northeast. The study area is characterized by a variety of deformation conditions: compression, transpression, strike-slip, transtension, tension, etc. Based on the averaged strain tensors, the distributions of the Lode–Nadai coefficient, angle of generalized plane strain, and vertical component are calculated and plotted. The zones where various modes of deformation, such as simple compression, the predominance of simple compression, shear, the predominance of simple tension and simple tension are manifested, are distinguished in the study area. Both uplift and subsidence of the Earth’s crust are noted in the study area depending on the deformation mode.

A comparative study on the seismic performance of RC beam-column joints retrofitted by ECC, FRP, and concrete jacketing methods

Reinforced concrete (RC) beam-column joints in many old buildings do not have appropriate seismic detailing that allows them to provide sufficient strength and stiffness in strong seismic events. To improve the seismic performance of these deficient beam-column joints, this study proposes a new retrofitting method based on high-strength steel bar mesh and Engineering Cementitious Composite (ECC), a fiber-reinforced cementitious material that shows high tensile ductility and damage tolerance. The proposed method reduces the required size of the retrofitting jacket through the combined use of ECC jackets and high-strength steel bar mesh. The performance of the proposed ECC jacketing method was compared with that of concrete jackets and fiber-reinforced-polymer (FRP) jackets. Experimental program included cyclic testing of four exterior beam-column joints, i.e., one control specimen and three others retrofitted using ECC, concrete, and FRP jacketing. Results showed that (1) reinforced ECC jackets confined the joint core and prevented localized damage in the joint zone via formation of dense and fine cracks, (2) the beam-column joint retrofitted using ECC jackets with high-strength steel mesh exhibited the favorable beam flexural failure, while the other three joints showed joint shear failure, (3) compared to other two retrofitting methods, the reinforced ECC jacket more effectively increased the strength, stiffness retention, energy dissipation capacity, deformation capacity, and collapse drift. In addition to experimental study, suitable strength models were suggested to evaluate the strength and failure patterns of the retrofitted exterior beam-column joints.

Synthetic seismicity obtained by block movements modeling for the territory of Bulgaria: preliminary results

The Bulgarian Region is located in the Southeastern Europe, with not so frequent recent seismicity. Several strong seismic events in the beginning of the XX century evidenced the capability of the main faults to accumulate significant energy. In this study, we investigate the seismicity in the region using the numerical block-and-fault dynamics (BAFD) model of lithosphere dynamics and seismicity. The morphostructural zoning outlines major crustal blocks, and external driving motions are prescribed using GPS data. We performed preliminary test for the simplified block structure to compile the synthetic earthquake catalogue for the Bulgarian region.

Experimental evaluation of SMA-based multi-ring damping devices

This paper investigates the performance of shape memory alloy (SMA)-based multi-ring (SBMR) damping devices through an extensive experimental program. SBMR devices were recently proposed for the seismic damage mitigation of building structures. These devices combine the shape recovery capability of austenitic NiTi rings with the high energy dissipation of a ring made of other metals, such as mild steel or martensitic NiTi, to achieve a balanced performance in terms of energy dissipation and self-centering. The experimental program consisted of two phases: (I) material testing, and (II) device testing. Phase I aimed at selecting the optimal heat treatments of austenitic and martensitic NiTi alloys for potential application in SBMR devices. To this end, 24 NiTi rod samples with various heat treatments were tested under uniaxial cyclic loading. With an optimal heat treatment, the residual strain of austenitic NiTi rods could be limited to less than 0.1% after 6% of elongation. In phase II, three rings made of austenitic NiTi, martensitic NiTi, and A36 steel, as well as a double-ring device and a triple-ring device, were tested under various bidirectional loading protocols. The test results showed that the austenitic NiTi ring with an optimized heat treatment could provide more than 93% of self-centering, but only less than 5% of effective damping ratio. However, both the double- and triple-ring devices provided at least 64% of self-centering and up to 16% of effective damping ratio. SBMR devices were also found capable of remaining usable after at least three strong seismic events with different durations.

An Integration Method of Bursting Strain Energy and Seismic Velocity Tomography for Coal Burst Hazard Assessment

Abstract The occurrence of coal burst in underground coal mines is complex, abrupt, and diverse, and the evaluation and prediction of coal burst hazard is the premise of effective prevention and control of coal burst. In this study, a coal burst carrier system model under the synergistic action of roof, coal seams, and floor was established, and the evolution of coal burst in underground coal mines was discussed based on the stress-vibration-energy coupling principle. On this basis, an integration method of bursting strain energy and seismic velocity tomography for coal burst assessment was proposed. With the deep and complex panel in a mine as the research object, the coal burst risk of the panel during excavation was evaluated in time and space domains, respectively. Results showed that the bursting strain energy and the active seismic velocity tomography technology can accurately identify both the positive anomalies and the negative anomalies of stress field and energy field in the mining period. Moreover, the method can not only evaluate the coal burst risk of the panel in the temporal domain but also predict the area with potential strong seismic events in the spatial domain. The research conclusions can accurately illustrate the whole complex evolution process of coal burst in underground coal mines.

Experimental investigation of the seismic performance of caisson foundations supporting bridge piers

Allowing the transitory attainment of bearing capacity of caisson foundations supporting bridge piers during strong seismic events can lead to substantial optimisation in their design and major cost savings. If the approach of capacity design is applied to geotechnical systems, the temporary triggering of plastic mechanisms may be permitted if the resulting permanent displacements are smaller than given threshold values. To validate this design approach, the seismic performance of caisson foundations was assessed through dynamic centrifuge testing on reduced-scale models. This paper presents the results of two tests in which a caisson–pier–deck system was embedded in a typical alluvial deposit and subjected to a series of earthquakes of different intensities. The caissons were founded on soft and very soft clay, to either avoid or induce the attainment of plastic soil behaviour under the same seismic inputs. It is shown that both yielding and failure of the layer of very soft clay limit inertial forces transmitted to the superstructure, validating the design approach and some useful empirical relations available in the literature. In contrast, inelastic soil behaviour implies accumulation of permanent rotation and settlement of the system, which must be carefully evaluated to check for fulfilment of performance requirements.

Propuesta para obtener las máximas aceleraciones de piso usando la norma sísmica peruana e.030

The collapse of some floor diaphragms during earthquakes was due to failures in connection with vertical elements or because those were not designed for seismic forces in its plane. This has made that the design of diaphragms is an issue that has been incorporated in many seismic codes. For its design, it is necessary the maximum acceleration on each floor during a strong seismic event. The seismic Peruvian code E.030 does not include any methodology about how to calculate those accelerations floor, it only refers to acceleration on floors but due to maximum base shear which does not correspond to maximum acceleration in each level.
 In this paper, a simplified procedure for obtaining maximum floor accelerations is shown. This procedure is based on First Mode Reduced method [1] to which a factor rW was included to consider higher modes participation in dual systems (frames / walls). The rW factor corresponds to the ratio of base moment in walls and base moment in the building. In the validation of the procedure, it was observed that the proposed procedure agrees with the results of experimental and analytical models.

Reassessing the seismic hazard in the Cusco area, Peru: New contribution coming from an archaeoseismological survey on Inca remains

Devastated by two earthquakes in historical times (1650 and 1950 CE), the Cusco Basin is now characterized by dense and chaotic urbanization that makes it even more vulnerable. Unfortunately, the large recurrence intervals of the local crustal earthquakes, the shortness of the historical record (∼500 yr) and the persistent lack of palaeoseismological studies hamper considerably the seismic hazard assessment. In such context, the outstanding archaeological heritage of the Cusco area turns out to be a relevant marker of past seismic activity.We carried out a systematic archaeoseismological survey in nine Inca sites close to Cusco and registered almost 3,000 Earthquake Archaeological Effects. Thanks to a semi-quantitative approach, we show a clear anisotropic seismic deformation on the Inca fine stonework, consistent at the regional scale. In Cusco, the architecture exhibits the impact of two different and strong ancient seismic events (M.M. intensity > VII).By combining these results with the analysis of historical photographs, our work supports, the occurrence of an unreported event during Inca times (∼1400–1533 CE). More broadly, by providing new data on the destructive potential of past earthquakes, this study urges us to conduct further research on the faults near Cusco.

A Holistic Approach to Study Groundwater-Surface Water Modifications Induced by Strong Earthquakes: The Case of Campiano Catchment (Central Italy)

Carbonate aquifers are characterised by strong heterogeneities and their modelling is often a challenging aspect in hydrological studies. Understanding carbonate aquifers can be more complicated in the case of strong seismic events which have been widely demonstrated to influence groundwater flow over wide areas or on a local scale. The 2016–2017 seismic sequence of Central Italy is a paradigmatic example of how earthquakes play an important role in groundwater and surface water modifications. The Campiano catchment, which experienced significant discharge modifications immediately after the mainshocks of the 2016–2017 seismic sequence (Mmax = 6.5) has been analysed in this study. The study area is within an Italian national park (Sibillini Mts.) and thus has importance from a naturalistic and socio-economic standpoint. The research strategy coupled long-period artificial tracer tests (conducted both before and after the main earthquakes), geochemical and discharge analyses and isotope hydrology with hydrogeological cross-sections. This study highlights how the seismic sequence temporarily changed the behaviour of the normal faults which act predominantly as barriers to flow in the inter-seismic period, with water flow being normally favoured along the fault strikes. On the contrary, during earthquakes, groundwater flow can be significantly diverted perpendicularly to fault-strikes due to co-seismic fracturing and a consequent permeability increase. The interaction between groundwater and surface water is not only important from the point of view of scientific research but also has significant implications at an economic and social level.

Evolution Characteristics of Seismic Detection Probability in Underground Mines and Its Application for Assessing Seismic Risks-A Case Study.

Seismic hazards are typical mining hazards causing dynamic failure of coal and rock mass, which greatly threatens the safety of personnel and equipment. At present, various seismic analysis methods are used to assess seismic risks but their accuracy is significantly limited by the incompleteness of seismic data. The probability of detecting earthquakes (PDE) method has been proven as a powerful means for retrieving missed seismic events and enhancing the seismic data integrity in mines. However, to date, the reliability of the results of the PDE method has not been assessed and the highly integrated seismic data have not been linked with the actual hazard potential. To fill these gaps, this paper investigated the impacts of the seismic data volume used for calculation and the modification of the layout of sensors on the reliability and robustness of the PDE method. The event counts and seismic energy were compensated using the PDE method, correlated with strong seismic events. The results indicated that the compensated seismic data presented higher accuracy in locating future hazardous events than before. This research provides references on enhancing the performance of seismic analysing methods for seismic risk assessments.

The Role of Disaster Risk Governance for Effective Post-Disaster Risk Management—Case of Croatia

Risk governance is mostly viewed through the lens of disaster or emergency management departments, agencies, or organizations. Visible in times of crises, risk governance is rarely seen as part of everyday public or private functions such as planning, social welfare, investments, or fiscal responsibilities. This paper emphasizes the importance of disaster risk governance in disaster risk management activities on the example of the post-disaster recovery of Croatia after a series of strong seismic events in mainland Croatia. The analysis is made based on a thorough review of national documents of Croatia and other selected countries overlapped with the national journals reporting on the situation from the affected areas. In accordance with the authors’ opinion, the necessary elements of disaster risk governance are clearly stated through the four Sendai framework priorities, and this statement is supported by the facts from the case study. Without either the political will or the enabling surrounding the disaster, risk management is next to impossible. The Croatian case study emphasizes the importance of disaster risk governance, showcasing the adaptation process for the post-disaster recovery process to start.