Journal of Earthquake and Tsunami

The effect of soil parameters on basin amplification effect has been widely investigated, especially for the small and medium-sized basins under plane wave incidence or point source ruptures. However, the sensitivities of seismic amplification effect of large-scale basins with respect to soil parameters during great earthquakes with tremendous rupture faults have obtained relatively less attention. In this paper, based on the established three-dimensional Sichuan basin model, the effects of four material parameters of the basin sediments, including the shear wave velocity, Poisson’s ratio, and the shear quality factor of the Quaternary sediment, as well as the velocity of the rock above the basin crystalline basement (which will be referred as SVQS, PRQS, QFQS, and VCBR, respectively), on the long-period wave amplification patterns of the Sichuan basin during the great Wenchuan earthquake are investigated by using the spectral element method and parallel computing technique. The results show the following: (1) SVQS has the greatest influence on the basin horizontal component ground motions, while the vertical component is comparably insensitive to it. (2) PRQS demonstrates comparable effects on the horizontal and vertical basin ground motions. With the increase of PRQS, the amplitudes and regions of the strong shakings both become smaller. However, the influence of PRQS is less significant compared with SVQS and VCBR. (3) QFQS mainly affects the relatively high-frequency motions inside the basin, and the low-frequency motions are generally insensitive to it. With the reduction of QFQS, the amplitudes and regions of the basin strong ground motions turn a little smaller, but the distribution features are generally unchanged. (4) Effects of VCBR on the horizontal and vertical component basin ground motions are opposite. With the growth of VCBR, the amplitudes and areas of strong horizontal motions increase consequently, but they decrease for the vertical component.

On February 6, 2023, two major earthquakes (Mw 7.7 and Mw 7.6) occurred in the province of Kahramanmaraş in southern Türkiye at 9-h intervals, causing a lot of loss of life and destruction in the region where approximately 16% of the country’s population lives. This study provides a comprehensive summary of common structural deficiencies that occurred in reinforced concrete (RC) buildings in earthquake-prone cities and proposes actionable measures systematically for future disasters. The evaluated data are based on the field observations of the authors. The main reasons for damages in RC buildings in the observation field can be classified into two categories: (1) the errors during the design stage (strong beam–weak column, short column, soft story, pounding effects, the existence of short and unconfined lap splices, insufficient transverse reinforcement, column–beam connection failures), and (2) the errors during the construction stage (poor concrete quality, unribbed reinforcing steel bar and corrosion, incorrect placement of reinforcement bars, incorrect end hook angle and length, weak gable walls, workmanship defects). Furthermore, a comparative nonlinear finite element analysis of the seismic impacts caused by the first earthquake on an existing RC building fully collapsed in the earthquake was conducted as a case study considering Türkiye Building Earthquake Code 2018 [TBEC 2018] “Türkiye Bina Deprem Yönetmeliği,” Afet ve Acil Durum Yönetimi Başkanlığı, Ankara (in Turkish)]. The validity and accuracy of the reasons for damages, which were reached by the field observations, were also proven by numerical analysis results. The importance of complying with the regulations, conducting the performance evaluations and controls of the buildings according to the renewed earthquake regulations and, if necessary, repairing–strengthening works were emphasized. The loss of life and property after the earthquakes that we experienced on February 6, 2023, which were called the “Disaster of the Century”, showed that Türkiye’s current building stock, especially those built before a certain date, is insufficient against earthquakes.

Karachi, a sprawling city spanning over 3500sq. km, exhibits significant variability in seismic hazard across its expanse. This study employs a deterministic approach for seismic hazard assessment due to the unavailability of a long-term seismic archive required for a probabilistic approach, given the city’s relatively young age. Furthermore, a novel methodology is employed in this study, utilizing all known faults within Karachi’s seismic vicinity for conducting Deterministic Seismic Hazard Assessment (DSHA). Individual hazards associated with each seismic source are estimated, enabling the determination of the most severe hazard for the development of a seismic zoning map. The resulting DSHA-based seismic hazard assessment categorizes Karachi into four seismic zones, ranging from Zone 2A to Zone 4. This paper concludes that for a vast city like Karachi, relying solely on a single fault source for DSHA does not accurately represent the realistic seismic hazard to the region.

Seismic fragility assessment is the probability of damage exceeding a certain design limit. The dynamic performance of a combined multiple tunnel complex is less explored and requires thorough study. This research is based on the numerical approach to evaluate the damage caused to the two new types of tunnel complexes, i.e. twin and triple tunnel complexes in a soft soil profile. A two-dimensional (2D) finite element analysis is performed to determine the induced bending moments for each of the tunnel complexes and develop the seismic fragility curves. A set of full acceleration-time histories are applied to the soil–tunnel complex system by varying embedment depths in different soft soil profiles. From the results, it is concluded that increasing the embedment ratio results in an increased probability of tunnel damage. The developed fragility curves are also inter-compared for both the tunnel complexes to evaluate the better performer during a seismic event. This study serves as an initial step toward the guidelines to determine the percentage of incurred damage and design the combined multiple tunnel complex in a seismic-prone area.

This study comprehensively investigates the seismic response of a partially filled rectangular liquid tank equipped with a bottom-mounted submerged block under six real earthquakes of varying frequency contents. Based on a velocity potential theory, Galerkin’s method is employed for the liquid domain formulation. A finite element algorithm is developed for the model and the simulated results are validated with the existing solutions. A parametric study is conducted to present the influence of isolator properties on the critical seismic responses. The efficacy of lead rubber bearing is emphasized in the overall dynamic response of the tank–block–isolation systems by varying the location and height of the block. The total and impulsive hydrodynamic pressure of the non-isolated tank decreases when a block is mounted at the base and a subsequent reduction is noticed due to the eccentricity of the block across the tank wall close to the block. Also, the eccentric configuration of the block has shown a typical reduction in the total base shear for most of the earthquake responses when a specific block depth is considered. Furthermore, a significant decrease is noticed in the impulsive and total hydrodynamic pressure and base shear due to the application of lead rubber bearing where the reduction is higher for high-frequency motions and relatively lower for low- and intermediate-frequency content seismic motions. The impulsive response is invariably dominant over the convective one in the overall dynamic responses of different non-isolated tank systems irrespective of the earthquakes whereas the convective response is found to be predominant in the base-isolated tank responses in majority of the earthquakes considered. However, the earthquake’s frequency has noticeably influenced the slosh elevation, total base shear and convective base shear responses.

The inherent energy dissipation ability of the sloshing liquid is effective in vibration control of the supporting structure. Due to the advancement in the construction techniques in structural and mechanical fields, liquid containers of different geometrical configurations were required to avoid tank interference with rigid structural or mechanical components. The quantity of liquid that participates in the connective mode determines the effectiveness of the tuned liquid damper (TLD). To reduce the impulsive liquid mass and to increase the participation of liquid mass in the convective mode, a chamfered bottom tank with a bottom-mounted internal object is proposed in this study. A 2D finite element model developed employing the potential flow theory is used for the present numerical investigation. The effect of the frequency content of ground motion on the slosh dynamics of the chamfered bottom tank has been investigated under six different earthquake ground motions classified based on frequency contents. Also, the dynamic impulsive and convective components of base shear force and hydrodynamic pressure are quantified successfully. A parametric study has been performed to quantify the influence of the bottom-mounted object on the seismic response by altering the object’s height. The developed numerical model in this study can be utilized for tuning and designing structure-coupled chamfered bottom TLDs as well as the irregular liquid containers with internal submerged components.