Search Results (31)

This paper presents the results of statistical analyses carried out for the input energy velocity (equivalent velocity to be used for the determination of the input energy) of equivalent single-degree-of-freedom systems with definite strength. An earthquake ground motion database, which includes 268 far-field records and two horizontal components from 134 recording stations located on firm sites, is employed for nonlinear time–history analysis. The probabilistic distribution of the input energy velocity is investigated for the candidate distribution models through a chi-square test, and the lognormal distribution was found as the most representative distribution model. Furthermore, the data used for analysis are classified with respect to the considered strength reduction factors of SDOF systems as a structural parameter and the effective duration of the considered strong ground motions as a ground motion parameter. The effect of those parameters on input energy velocity is investigated by using probabilistic techniques such as t-tests and ANOVAs. It is concluded that the strength reduction factor influences the input energy velocity along the particular period ranges of SDOF systems. Furthermore, the effective duration of the ground motion is another effective parameter on input energy velocity for almost all the considered period ranges. An equation is proposed for the determination of input energy velocity in terms of the aforementioned parameters. Full article

Understanding how disasters are framed in news media is critical to unpacking the socio-political dynamics of crisis communication. However, empirical research on narrative variation across disaster types and geographies remains limited. This study addresses that gap by examining whether media outlets adopt distinct narrative structures based on disaster type and country. We curated a large-scale dataset of 20,756 disaster-related news articles, spanning from September 2023 to May 2025, aggregated from 471 distinct global news portals using automated web scraping, RSS feeds, and public APIs. The unstructured news titles were transformed into structured representations using GPT-3.5 Turbo and subjected to unsupervised topic modeling using Latent Dirichlet Allocation (LDA). Five dominant latent narrative topics were extracted, each characterized by semantically coherent keyword clusters (e.g., “wildfire”, “earthquake”, “flood”, “hurricane”). To empirically evaluate our hypotheses, we conducted chi-square tests of independence. Results demonstrated a statistically significant association between disaster type and narrative frame (${\chi }^2=25,280.78$, p < 0.001), as well as between country and narrative frame (${\chi }^2=23,564.62$, p < 0.001). Visualizations confirmed consistent topic–disaster and topic–country pairings, such as “earthquake” narratives dominating in Japan and Myanmar and “hurricane” narratives in the USA. The findings reveal that disaster narratives vary by event type and geopolitical context, supported by a mathematically robust, scalable, data-driven method for analyzing media framing of global crises. Full article

Almost two years after the devastating 1999 M_W7.6 Chi-Chi earthquake, a new concept of time termed natural time (NT) was introduced in 2001 that reveals unique dynamic features hidden behind the time series of complex systems. In particular, NT analysis enables the study of the dynamical evolution of a complex system and identifies when the system enters a critical stage. Since the observed earthquake scaling laws indicate the existence of phenomena closely associated with the proximity of the system to a critical point, here we apply NT analysis to seismicity that preceded the 3 April 2024 M_W7.4 Hualien earthquake. We find that in the beginning of September 2023 the order parameter of seismicity exhibited a clearly detectable minimum. Such a minimum demonstrates that seismic electric signal (SES) activity initiated which comprises several low-frequency transient changes of the electric field of the Earth preceding major earthquakes. Full article

The propagation of seismo-traveling ionospheric disturbances (STIDs) is generally observed at one specific altitude layer. On 2 April 2024, a Mw 7.4 earthquake struck Hualien, which was the biggest earthquake since the 1999 Chi-Chi earthquake in the Taiwan region. In this study, a co-located vertical monitoring system combined with the observation of two horizontal layers in the ionosphere was utilized to study the STIDs associated with the Hualien earthquake. The vertical monitoring system can capture disturbances from the ground surface up to a height of ~350 km. In addition, changes in electric currents and the TEC (total electron content) at two horizontal layers, ~100 km and ~350 km, were monitored by permanent geomagnetic stations and a ground-based GNSS (global navigation satellite system) receivers network, respectively. The observations from this four-dimensional (4D) monitoring network show that the STIDs at a height of ~100 km associated with Rayleigh waves can propagate as far as 2000 km from the epicenter, while at an altitude of ~350 km, they can only propagate to about 1000 km. At an altitude of about 200 km, STIDs were also captured by a high-frequency Doppler sounder in a vertical monitoring system, which was consistent with the results in the geomagnetic field. The results from the 4D monitoring network suggest that the STIDs associated with Rayleigh waves exhibit different propagation ranges at various altitudes and prefer to propagate at low ionosphere layers. The vertical propagating waves typically only reach the bottom of the ionosphere and struggle to propagate to higher regions over long distances. Full article

Ensuring sustainability in the production and marketing of agricultural and food products after natural disasters is of critical importance to maintain beneficial nutrition for society. Examining the effects of earthquakes on the agricultural and food sectors is important in terms of drawing attention to the possible risks they may pose to societies that have not experienced large-scale earthquakes. This study examines firms in the agriculture and food sectors of Malatya province that were affected by the devastating earthquakes centered in Kahramanmaraş on 6 February 2023. This study aimed to determine the effects of earthquakes on firms in the agriculture and food sectors, the factors affecting firms’ production and marketing processes, and the priority issues for them. Data obtained from 44 firms registered in the agricultural and food sectors of the Organized Industrial Zone of Malatya province were used. This study reports their general structure and frequency distributions by firm characteristics. In addition, statistical analysis methods, such as the chi-squared test, t-test, and factor analysis, were used for data evaluation. The results showed that 79.5% of firms export and make a significant contribution to Türkiye’s agricultural and food product trade. The primary factors influencing firms, based on their size, included workforce availability, raw material supply, transportation logistics, and financial assistance. Firms’ earthquake insurance, providing earthquake training for their employees, and constructing durable buildings were the most important factors in ensuring sustainability in production and marketing. These results further show that firms in the agriculture and food sectors in Malatya province were greatly affected economically by the earthquakes. Important lessons emerged as a result of these earthquakes experienced in Türkiye. The economic disruption following earthquakes may be overcome with less damage by constructing disaster-resistant buildings, instilling awareness of living with earthquakes in society, and creating safe production environments. This field study will guide sector stakeholders in building a resilient supply, production, and marketing network in preparation for future earthquakes. Full article

The objective of this study is to present a method for developing fragility curves for soil liquefaction that align with seismic hazards using Monte Carlo simulation. This approach can incorporate all uncertainties and variabilities in the input parameters. The seismic parameters, including earthquake magnitude (M) and associated peak ground acceleration (PGA), are jointly considered for the liquefaction assessment. The liquefaction potential and the resulting damages obtained by this method are more realistic. A case study is conducted using data from a sand-boil site in Yuanlin, Changhua County, where liquefaction occurred during the 1999 Chi-Chi earthquake in Taiwan. The findings indicate that the liquefaction potential index, I_L, the post-liquefaction settlement, S_t, and the liquefaction probability index, P_W, are all appropriate parameters for assessing liquefaction damages. The fragility curves for soil liquefaction developed through this method can support the performance-based earthquake engineering (PBEE) approach, provide guidance for liquefaction evaluation to the Taiwan Earthquake Loss Estimation System (TELES), and serve as a foundation for scenario simulation and an earthquake early warning system for liquefaction damages. Full article

An earthquake of magnitude 6.4 occurred in Yangbi County, Yunnan Province on 21 May 2021, with a focal depth of 8 km, and strong ground motion with vertical components was monitored by Yangbi station (53YBX). A total of 14,122 houses were damaged in Yangbi in the earthquake, and 232 of them collapsed. Vertical components of ground motions have been gained more attention for its effect on structure’s seismic response in epicenter or near-fault regions at present. Taking the three earthquake ground motions of Yangbi, Chi-Chi, and Loma Prieta as inputs, and modeling based on Perform-3D, this research carried out the seismic dynamic time history analysis of an RC (reinforced concrete) frame structure and a brick-concrete structure under both horizontal and vertical working conditions. The results showed that vertical components of the three ground motions had no evident impact on the top horizontal displacement and acceleration of the two types of structures. Among the three ground motions, the vertical component of Yangbi ground motion has largely influenced the top vertical displacement, acceleration, and axial force of the frame column bottom (or masonry wall bottom). The vertical component had different amplification effects on the axial pressure and the bending moment of a single column at the bottom of the RC frame structure, thus causing resonance amplification effect of the brick-concrete structure floors and amplifying the vertical acceleration of the top floor. In addition, it considerably increase the maximum axial tensile strain of masonry walls and the possibility of faster tensile failure of the brick-concrete structure. Influence of vertical ground motion on the bearing capacity of RC frame structure’s columns and the brick-concrete structure’s masonry walls should not be ignored. The results of the research may provide a reference for the earthquake-resistant design of building structures, especially the earthquake-resistant design considering the vertical seismic effect. Full article

A five-story moment frame structural model with a base isolation system was tested on a shaking table. The isolation system comprised both linear natural rubber bearing (LNR) and nonlinear viscous dampers (NLVDs). Seven ground motions were employed: including three far-fault (FF) and four near-fault (NF) earthquake ground motions. The performance of the isolation system was evaluated by measuring the displacement and base shear of the isolation bearings. Furthermore, the axial force and displacement of the NLVDs were measured. The evolution of the fundamental dynamic frequency of the frame during the test was also determined. During strong earthquakes, NF ground motions caused larger story drifts and floor accelerations of the superstructure than FF ground motions. The displacement and base shear of the isolation base was very large when the isolated structure was subjected to Kobe_TAK000 and ChiChi_TCU102/278 pulse-like NF ground motions. Furthermore, the LNR s experienced tension and uplift when the PGA of input earthquake ground motions was larger than 0.80 g. Although the NLVDs performed very well in combination with the LNRs, the severe responses of the isolation bearings were caused by NF ground motion with a pulse period T_p neighboring the fundamental period of the isolated structure. Full article

This paper includes the investigation of the soil–structure interaction (SSI) effect on the seismic response of 20 and 30-story reinforced concrete moment resisting frames (MRFs) rested on a piled raft foundation using the direct approach. After that, a study is conducted to show the impact of using a cellular raft instead of the designed solid raft on the dynamic response of the building. A study is introduced to select the best gap size for the cellular raft. The soil model is assumed as a single layer of sandy clay. Time history analysis by the direct integration method is performed under seven earthquake records (El-Centro, Northridge, Kobe, Chichi, Friuli, Kocaeli, and Loma), which are scaled to the Egyptian Code for Loads (ECP-201) response spectrum using a full 3D model by a finite element software named (Midas GTS NX). It is concluded that considering SSI significantly affects the dynamic response of high-rise buildings, and using cellular rafts generally leads to a decrease in their dynamic response. Full article

This paper aims to apply a performance-based earthquake engineering approach to assess the assurance of flexural frames whose members are jointed together by using new modified RBS connections, namely, semi-rigid welded steel connections, which obey a progressive failure mechanism. First, the structural members and connections are modeled and predesigned in ETABS software, and then, using OpenSees software, a series of nonlinear progressive failure analyses are performed on the built models extracted from ETABS. To this end, three types of multi-story structures with 3, 10, and 15 are modeled. The models are subjected to 15 earthquakes, such as Northridge (1994), Kobe (1995), Chichi (1999), Bam (2003), Tabas (1978), and so on. The connections are modeled by a series of rotational springs whose nonlinear behavior is estimated by a three-line curve that is established based on the modified Ibarra–Krawinkler deterioration model. Finally, obtaining the maximum ground acceleration versus the maximum relative drift of the floors, the fragility curves of the structures for a collapse level (CP) are determined, through which the seismic performances of the models are evaluated. The results show that by reducing the number of structural floors, the ductility of structures was reduced, and by increasing the ductility of structures, higher drifts in structures were achieved at the same seismic level. The average amount of ductility reduction coefficient in structures with RBS was 1.06 times those without RBS, which indicates that the energy dissipation capacity in structures without RBS connection is higher than in those with RBS. Local analysis of connections shows a 9% increase in the plastic rotation capacity if RBS connections are used. The ductility of all frames with RBS connection increased slightly compared to frames without RBS. Full article

The 1999 Chichi earthquake and Typhoon Morakot in 2009 caused two serious landslide events in the Chishan river watershed in southern Taiwan. In this study, certainty factor analysis was used to evaluate the effectiveness of landslide occurrence, and spatiotemporal hotspot analysis was used to explain the pattern and distribution of landslide hotspots. The Z-values from the Getis–Ord formula were used to assess the clustering strength of landslide evolution on different scales and with different landslide sizes in different time periods. The landslide-prone area had an elevation of 1000–1750 m, a slope of >40°, and hillslopes with N, NE, E, and SE aspects and was within 100 m of rivers. The main spatiotemporal hotspot patterns of landslide evolution during 1999–2017 were oscillating hotspots, intensifying hotspots, and persistent hotspots, and the three main hotspot patterns occupied 80.1–89.4% of all hotspot areas. The main spatiotemporal landslide hotspots were concentrated in the core landslide areas and the downslopes of riverbank landslide areas, especially in the upstream subwatersheds. The landslide clustered strength in the upstream watershed was 3.4 times larger than that in the Chishan river watershed, and that in large landslides was 2.4 and 6.6 times larger than those in medium and small landslides, respectively. Full article

This paper proposes a framework for screening and evaluating seismic performance of river earth embankments on liquefiable foundation soils. The framework is executed in the order of simplest screening by soil liquefaction potential map to preliminary and detailed evaluation of seismic performance of embankment according to the sufficiency of data and the complexity and accuracy of the methods. The seismic performances of embankments are classified into four levels based on the seismic-induced crest settlement. The method used for preliminary evaluation is based only on the factors of safety of foundation soils against liquefaction and the embankment slope against sliding. The static softening method (SSM) and dynamic effective stress method (DESM) are suggested for detailed evaluation of seismic performance. SSM is a static FDM or FEM analysis for estimating liquefaction-induced settlement by weakening the strength of the liquefied foundation soil under the action of the self-weight of the embankment. However, DESM is a dynamic history analysis for estimating liquefaction-induced settlement by simulating the generation and dissipation of pore water pressure in the liquefaction process of foundation soils under the action of the self-weight of the soil embankment and its seismic inertial force. The damaged embankment of the Maoluo River in the 1999 Chi-Chi earthquake was used as a case to demonstrate the feasibility of this framework. The results showed that the simpler the adopted method is, the more conservative the estimated settlement. Full article

The dynamic soil-structure interaction is a combination of phenomena caused by the flexibility of soil foundation in structure response. The structure response may be changed by embedded basement stories. Thus, this study seeks to assess the dynamic response of seven-story concrete frame type buildings without a basement, one basement story, and two basement stories, considering fixed and flexible bases. For this purpose, the experimental tests on the small shaking table were executed with a small scaling coefficient of 1:50. Consequently, three scaled models of steel skeleton structures with variable embedded depths have been constructed with fixed and flexible bases. These models are exposed to three seismic input motions: Northridge (1994), Kobe (1995), and Chi-Chi (1999) at the base of the structure as a fixed base and the bedrock level in the soil structure system as a flexible base. The finite element technique is carried out for scaled and real models. Both the scaled and real numerical models are in good agreement with the obtained experimental observations with reasonable accuracy. It is concluded that the lateral deflections are overestimated by excluding embedded depths of structural elements. In the flexible prototype model, the lateral deflections of the superstructure with embedded depths (3 m, 6 m) decrease compared with no embedded depth, in which the maximum reduction percentages of 7-story with embedded depths 3 m and 6 m at the roof floor level are 21% and 42% compared with no embedded depth, respectively, under Northridge earthquake. Otherwise, ignoring the SSI effects (fixed base case), the lateral displacements are underestimated compared with the flexible base. The maximum amplification percentages at the roof floor level between flexible and fixed bases models with variable embedded depths are 35%, 37%, and 65% under Northridge, Kobe, and Chi-Chi earthquakes, respectively. The amplification and reduction percentages may be high or low, mainly depending on soil condition (fixed, flexible), variable embedded depths, characteristics of seismic motion, travel pass, and source of seismic motion. These items are summarized as the frequency domain of the coupled system compared with the frequency domain of the earthquake motion. Full article

This study analyzed the support activities that the Disaster Psychiatric Assistance Team (DPAT) in Japan provided following four previous disasters (a volcanic eruption, a mudslide, a flood, and an earthquake) to identify links between the disaster type and the characteristics of acute stage mental disorders observed. Using Disaster Mental Health Information Support System database records of consultations with patients supported by the DPAT during the survey period from 2013 (when DPAT was launched) to 2016, we performed cross-tabulations and investigated significant differences using chi-squared tests. For expected values less than 5, Fisher’s exact test was performed. Frequently occurring acute-stage symptoms after a disaster include anxiety, sleep problems, mood and affect, and physical symptoms. The affected population characteristics, victim attributes, severity of damage sustained, and evacuation status were the chief factors that influenced acute-stage mental health symptoms. The psychiatric symptoms detected in our study together with the results of diagnoses are important for determining the types of early interventions needed during the acute stage of a disaster. By sharing baseline mental health information, together with disaster-related characteristics highlighted in this study, mental health providers are better able to predict future possible mental disorders and symptoms. Full article

Although the study of spatiotemporal variation of a subsurface velocity structure is a challenging task, it can provide a description of the fault geometry as well as important information on the rheological changes caused by fault rupture. Our main objective is to investigate whether rheological changes of faults can be associated with the seismogenic process before a strong earthquake. For this purpose, a 3D tomographic technique is applied to obtain P- and S-wave velocity structures in central Taiwan using travel time data. The results show that temporal variations in the Vs structure in the source area demonstrate significant spatiotemporal variation before and after the Chi-Chi earthquake. We infer that, before the mainshock, Vs began to decrease (and Vp/Vs increased) at the hanging wall of the Chelungpu fault, which may be induced by the increasing density of microcracks and fluid. However, in the vicinity of the Chi-Chi earthquake’s source area, Vs increased (and Vp/Vs decreased), which may be attributed to the closing of cracks or migration of fluid. The different physical characteristics at the junctional zone may easily generate strong earthquakes. Therefore, seismic velocity changes are found to be associated with a subsurface evolution around the source area in Taiwan. Our findings suggest that monitoring the Vp and Vs (or Vp/Vs) structures in high seismic potential zones is an important ongoing task, which may minimize the damage caused by future large earthquakes. Full article