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This paper introduces a new low-damage hybrid steel–timber rocking braced frame with self-centring capability and proposes a design methodology in the framework of Canadian design standards. This system consists of a gravity load-resisting timber frame and a steel concentrically braced frame acting as the lateral load-resisting system that is connected using U-shaped steel fuses. The self-centring capability is achieved by post-tensioning strands and rocking bases within the lateral load-resisting system. The system, along with its components, is first introduced. The proposed design method and system performance objectives are then presented. The seismic performance of the system and the proposed design procedure are validated through numerical analyses considering the interaction between the lateral and gravity load-resisting systems. The results of dynamic analyses confirm the enhanced seismic performance of the proposed hybrid system with almost no residual deformations after the earthquake. Moreover, the proposed design guidelines can accurately predict the system's seismic response and demands imposed on the members. [ABSTRACT FROM AUTHOR]

Many existing buildings fail to meet the requirements of current earthquake resistance codes. Therefore, it is necessary to strengthen and/or upgrade such buildings. Strengthening and/or upgrading include adding new floors, parts, elements, etc. Modern codes usually do not reflect upgrading of existing buildings. These buildings may be damaged and require maintenance and repairs, which may change the original material and structural properties. Design of such buildings is based on dominant vibration periods obtained by empirical dependences according to the building codes or from dynamic numerical analysis using available software. In both cases, the results usually do not consider the present state of the structure, influence of nonstructural elements, and possible differences in material properties in various elements of the building due to construction problems, concrete creep, etc. Such evaluation can be done just based on dynamic analysis, experimental and numeric, whereas the first one is essential. Therefore, the present research is aimed at numerical and experimental investigation of an existing real multistory residential reinforced concrete building before its strengthening and/or upgrading according to the requirements of modern seismic codes. The present study is a first stage of the research. It is focused on obtaining the dynamic parameters of the building before its strengthening and upgrading. Experimental values of natural vibration periods and damping ratios are compared with those obtained numerically. Following these values, the design spectrum of the seismic code is updated and the building is designed using this updated spectrum. The findings of this study form a basis for the second research stage that will be aimed at monitoring and analyzing of this building at each stage of its strengthening and upgrading. This approach iaimed at improving the available techniques for strengthening and upgrading the building. It will also be the basis for further research in this direction. [ABSTRACT FROM AUTHOR]

Seismic risk is one of the biggest challenges for tunnel safety, and several mitigation techniques have been proposed to enhance the seismic performance of existing tunnels. This paper aims to investigate the effectiveness of an innovative approach for reducing the seismic risk of existing tunnels by using soft material walls (SMW) symmetrically installed in the surrounding soils. The investigation is performed with a two-dimensional numerical model and the effectiveness of SMW in mitigating the seismic-induced lining forces is quantitatively evaluated by reduction ratio. The influences of nonlinear properties of soil, SMW and tunnel lining on the isolation effectiveness are also discussed. The parametric studies show that the computed reduction ratio is strongly affected by the modulus ratio between the SMW and the soil, the wall geometric parameter, and the flexibility ratio. It is more effective for the thick and soft isolation walls that are inserted near a stiff tunnel in the soft soil. The tunnel seismic response can be reduced by up to 50% for the scenarios investigated. Notably, the parametric study identifies an optimum normalized depth of SMW and recommends a relation between the maximum isolation effect and the flexibility ratio. Finally, simple charts are suggested in this work for estimating the isolation effect in specific conditions of the soil and the tunnel. Along these lines, the results of this work may be used in the seismic retrofitting of an existing tunnel, aiding the preliminary design of the isolation walls. [ABSTRACT FROM AUTHOR]

For extended structure, the seismic load has a spatiotemporal variation that simultaneously changes with time and space. The incorporation of the seismic wave spatial random variability effect is especially important when large structures such as long bridges, dams, and large buildings are analyzed. The effect of spatially varying earthquake ground motion (SVEGM) on the seismic response of earth dams is analyzed in this paper. To this end, a parametric study is conducted to investigate the effects of length to height ratio (H L) on the 3D seismic response of the studied dams. Ground motions, consistent with the three-directional lagged coherency model, are generated at different discretized cells at the base of the dam. The dams are assumed to sit on trapezoidal and V-shaped canyons and vibrate in all three directions, upstream-downstream, vertical, and longitudinal. The average coherency of different frequencies is calculated and used for the generation of SVEGM. The time histories are simulated using a spectral representation-based method. The separation distance between the cells is determined in such a way that 90% of correlation between seismic input motions can be captured. For each case of H L ratio, a numerical model of the dam and its foundation is constructed using the finite difference numerical method. The 3D seismic behavior of the earth dams is evaluated under the artificially generated three-directional components of SVEGM. Generally, it is concluded that with increasing H L ratio, at the midpoint of the dam crest, the difference between maximum of acceleration values obtained by applying uniform and SVEGM excitations decreases. In all cases of analyses, SVEGM has decreasing effect on the vertical displacement of dam crest. [ABSTRACT FROM AUTHOR]

This paper represents the analysis and interpretation of the airborne magnetic data of central and northern Egypt to delineate the subsurface faults and other structures and also the tectonic framework of the area. First, the total observed magnetic field data was reduced to the north magnetic pole (RTP) and using the power spectrum, the regional and residual magnetic fields were separated using the Butterworth filter to isolate the anomalies caused by each of them. Then, the airborne magnetic data was subjected to several filters to enhance the signals from the different magnetic sources for better delineation and edge detection. Additionally, Euler deconvolution was applied to estimate the depth of the different magnetic sources. The final outputs show a wide variety of magnetic anomalies reflecting different magnetic sources and subsurface features. The main subsurface structures are the linear NNW-SSE parallel to the Red Sea trend and the Gulf of Suez and the NE-SW faults and lineaments surrounding the basins in the northern and western area, the deeply rooted basic intrusions, and the depo-centers (basins) in the western and central parts of the area. Moreover, the area shows several basement uplifts and consequently faulted basins of different directions and displacements. [ABSTRACT FROM AUTHOR]

This paper discusses continuum models for simulating earthquake sequences on faults governed by rate-and-state dependent friction. Through detailed numerical analysis of a conventional strike-slip fault, new observations regarding the use of various continuum earthquake models are presented. We update a recently proposed plasticity-based model using a consistently linearized formulation, show its agreement with discrete fault models for fault thicknesses of hundreds of meters, and demonstrate mesh objectivity for slip-related variables. To obtain a fully regularized fault width description with an internal length scale, we study the performance and mesh convergence of a plasticity-based model complemented by a Kelvin viscosity term and the phase-field approach to cohesive fracture. The Kelvin viscoplasticity-based model can introduce an internal length scale and a mesh-objective response. However, on grid sizes down to meters, this only holds for very high Kelvin viscosities that inhibit seismic slip rates, which renders this approach impractical for simulating earthquake sequences. On the other hand, our phase-field implementation for earthquake sequences provides a numerically robust framework that agrees with a discrete reference solution, is mesh objective, and reaches seismic slip rates. The model, unsurprisingly, requires highly refined grids around the fault zones to reproduce results close to a discrete model. Following this line, the effect of an internal length scale parameter on the phase-field predictions and mesh convergence are discussed. [ABSTRACT FROM AUTHOR]

Underground structures are susceptible to float and move upward during earthquakes when located in a liquefiable soil deposit. There are examples of this phenomenon in past major earthquake events. In this study, the uplift of circular tunnels in a liquefiable sand layer was investigated with a series of shaking table tests. The research has focused on the buried depth of the tunnel, tunnel diameter, tunnel weight, liquefaction extent, uplift mechanism, and factor of safety against liquefaction-induced uplift. According to the test results, the shallow buried depth, larger diameter, and lower weight can intensify the tunnel uplift, so the displacement in post-liquefaction time continues at the same rate as during the shaking time. Due to the shear-induced dilation, pore water pressure generation around the tunnel was reduced compared with that of the free field. The excess pore water pressure dissipation in the soil overlying the uplifted tunnel was significant, which leads to suction in the soil deposit. Furthermore, the acceleration response of overlying soil with the uplifted tunnel was similar to that of the free field. However, the soil acceleration response around the tunnel without uplift was similar to the base motion. [ABSTRACT FROM AUTHOR]

The sloped bottom tank generates higher sloshing-induced base shear with less liquid mass compared to rectangular tanks. Due to the improved sloshing characteristics, sloped bottom TLD achieves better performance than its conventional flat-bottom counterpart. These improvements in sloshing characteristics are due to the modified tank configuration, which reduces the impulsive liquid mass and results in higher convective participation of liquid mass during sloshing. To further increase the convective characteristics, a sloped bottom tank with internal object is proposed. A velocity potential-oriented finite element model has been adopted for the numerical analysis where a combination of three-node triangular and four-node quadrilateral finite elements is used to discretize the liquid domain. Seismic characteristics of liquid sloshing inside a ground-supported sloped bottom tank with internal object are investigated under six different seismic motions categorized as low-, intermediate-, and high-frequency contents. Also, the influence of the internal object on slosh dynamics is investigated suitably for different heights of the object under all earthquakes considered. The dynamic impulsive and convective components of base shear force and hydrodynamic pressure are quantified successfully. The developed numerical model in this study can be utilized in tuning and designing structures coupled with sloped-bottom TLD. [ABSTRACT FROM AUTHOR]

The paper illustrates the construction of abacuses for the semi-quantitative assessment of stratigraphic seismic amplification phenomena, applicable in the eastern Abruzzo region (central Italy). The abacuses provide three expected Amplification Factors (Fas): Fa0.1-0.5, Fa0.4-0.8, Fa0.7-1.1, performed as the ratio between the integral of output and input, in the mentioned time intervals, considering the acceleration response spectra. The choice derives from the fact that these parameters are better correlated to the response of the buildings, characterised by their own different periods. To prepare the abacuses, a procedure was adopted that took into consideration the geological analysis of the area, the collection of all the available geophysical and geotechnical data, the choice of the seismic inputs representative of the seismic hazard, the identification of the main seismic stratigraphic sequences and the numerical analysis aimed at evaluating the Fa. The abacus consists of a series of tables prepared in order to take account of the stratigraphic variability in the area, as a function of the basic seismic hazard level and the vibration period interval to calculate the Fa. By knowing the stratigraphic and mechanical characteristics of the site and using the abacuses, the values of the Fa are obtained. [ABSTRACT FROM AUTHOR]

The review focuses on three main essentials of numerical analyses, namely soil behavior and constitutive model, pile and pile-soil interface modeling and computational framework. This paper presents a critical review of the current challenges in analyzing large, realistic pile groups in soft clay soil under earthquake shaking. [Extracted from the article]

Offshore platforms located in seismically active areas may be subjected to different seismic effects during service. The seismic performance of offshore platforms under different earthquakes was studied using shaking table tests and finite element analysis (FEA). The dynamic properties, acceleration, displacement and strain responses of the scale model under near-field, far-field and offshore earthquakes were studied. On this basis, more consideration was given to soil-pile-structure interactions (SPSIs), and this finite element (FE) model was analyzed for seismic fragility using incremental dynamic analysis (IDA). By combining the results of the tests and FEA, it was found that the dynamic response of the platform was significantly larger under offshore earthquakes than under onshore earthquakes. The collapse resistance of offshore platform under offshore earthquakes was inferior to that under onshore earthquakes. Therefore, seismic performance assessment of long-period offshore platforms based on onshore earthquakes may overestimate its seismic capacity and pose potential risks to platforms in service. • An existing jacket platform in the Bohai Gulf is simulated was ANSYS software. • Numerical simulations were validated using shaking table tests data. • The effect of uncertainties associated with soil–pile, structure modeling, and the ground motions were considered. • The collapse resistance of jacket platform under offshore earthquakes is inferior to that under onshore earthquakes. • Seismic design of offshore platforms is recommended to consider seafloor earthquakes. [ABSTRACT FROM AUTHOR]

Following the Cephalonia, Greece, 2014 earthquake sequence (Mw=6.1 and Mw=6.0), liquefaction of gravelly earthfill materials at the ports of Lixouri and Argostoli resulted in the manifestation of ground cracking and coarse-grained soil ejecta, and the quay walls in these ports exhibited lateral ground displacements ranging from 0.1 to 1.5 m. To evaluate the seismic performance of the port quay walls, numerical analyses using the finite-difference method were performed, and the results compared with the observed response. Three commonly used constitutive models (PM4Sand, UBCSand, and URS/ROTH) calibrated based on in situ site investigation data were considered in modeling the liquefiable earthfills. The results of the numerical analyses at both ports using the best-estimate parameters indicate that taller walls exhibit smaller lateral ground displacements than shorter walls, something that is in line with field observations. For the shorter walls, liquefaction-induced lateral spreading played an important role in the observed response, whereas for the taller walls, the seismic behavior is dominated predominantly by the dynamic response of the structural system. PM4Sand and UBCSand models seem to yield very similar deformational results, but the URS/ROTH model, which assigns residual shear strength parameters once liquefaction is triggered, resulted in horizontal displacements that are closer to the observations for short-wall geometries but overpredict the response when the effect of liquefaction on the overall displacements is small. Finally, the numerical analyses demonstrate the strong influence of the pulselike characteristics, as well as the polarization of the input motion on the seismic response of the Lixouri quay walls, indicating that forward directivity contributed significantly to the observed quay wall deformations. [ABSTRACT FROM AUTHOR]

In earthquake engineering practice, the liquefaction potential of soils is commonly evaluated through simplified procedures. These approaches are suitable for sands with very low to no fines content, which have been traditionally thought to be the only liquefiable materials. However, field observations and experimental research have extensively demonstrated that low plasticity silty sands can also be highly liquefiable. Thus, this paper investigates the effect of nonplastic fines contents on the liquefaction potential of soils, taking the 2010–2011 Canterbury Earthquake Sequence as a case study. The validity of standard simplified procedures for high fines content soils is critically evaluated and compared with a finite element model based on a full solid–fluid coupled formulation. The model includes a state parameter-based constitutive law within the generalised plasticity theory, which allows the fines content to be taken into account explicitly. The standard simplified procedures are shown to be less effective in the evaluation of liquefaction potential in soils with high fines content but are still indispensable tools for evaluating the performance of soils over large urban areas. As the main conclusion, it is recommended that empirical models are complemented with an advanced numerical analysis in those cases where silty sands with high fines content are identified, as its outcomes can more realistically represent the soil behaviour during a seismic event. [ABSTRACT FROM AUTHOR]

To gain a deeper understanding of post-earthquake fire behaviour, 100 reinforced concrete (RC) frames representative of a building stock designed without considering seismic loading were modelled using the software SAFIR. A total of 4400 numerical analyses were performed to investigate the impact of different assumptions, such as the type of damage, damage location, number of sides of the RC elements exposed to fire, location of the fire and different fire curves on the post-earthquake fire resistance of the RC frames. Results showed that heavily damaged frames have significantly lower fire resistance compared to undamaged frames. Variations in the number of heated sides and fire locations were found to lead to significant differences in the time until the collapse of the RC frames. Moreover, due to increased demand for assistance following a large earthquake, rescue teams are likely to experience prolonged response times, exacerbating the potential for loss of life and infrastructure. Assuming parametric fire curves without firefighting efforts is a reasonable approach in post-earthquake events. This approach led to quicker collapse times compared to the standard fire curve ISO 834. This aspect combined with a lower fire resistance of the damaged structures can ultimately lead to the loss of lives and infrastructures. Therefore, a comprehensive understanding of post-earthquake fire behaviour becomes crucial for developing recommendations that can ensure the safety of RC structures in such events. • RC frames representative of a building stock designed without seismic concerns were studied. • The impact of type of seismic damage, damage location, number of fire frontiers was investigated on the post-earthquake fire resistance of the RC frames. • Heavily damaged frames have considerably lower fire resistance when compared with undamaged frames. • different fire frontiers and different fire locations can lead to significant differences in the time until collapse of the RC frames. [ABSTRACT FROM AUTHOR]

This study performed numerical analysis and shaking table tests to investigate the seismic performance of a damped-outrigger system with buckling-restrained braces (BRB-outrigger). A 9-m tall specimen was used to perform the shaking table tests. The specimen with the BRB-outrigger located at either the sixth or the eighth floors was tested in three phases of tests. The buckling-restrained brace (BRB) specimens were kept elastic during Phase I tests to confirm the specimen's response under service-level earthquakes. Phase II tests utilized the ground motions similar to the friction damper–outrigger (FD–outrigger) tests for comparison. Meanwhile, Phase III tests utilized two ground motions with a peak ground acceleration of up to 1.04 g to determine whether the BRB specimens developed stable strength and exhibited energy dissipation performance under the design basis earthquake (DBE) level. In addition, this study utilized OpenSees numerical model to perform nonlinear response spectral analysis. Based on the Phase I experimental results, when compared with the specimen without equipping damped-outrigger system, the roof drifts can be reduced by around 47% to 34% when the BRB-outrigger was located at the sixth and eighth floors, respectively. During Phase III tests, the BRB specimens dissipated around 18% of the total input energy. The specimen with the BRB-outrigger located at the sixth floor performed better in reducing the floor lateral displacement responses in all three phases of tests. Based on the test results, the BRB specimens' high strength and stable energy dissipation capacity make the BRB-outrigger specimen more capable in resisting the earthquakes above the DBE levels. • Performance of damped-outrigger with BRB was verified through shaking tests. • BRB inelastic response evaluated by equivalent damping in spectral analysis was verified. • Optimal elevation of damped-outrigger with BRB locates at 60% of building height. • BRB dissipated 20% energy under DBE level with roof drifts reduction up to 40%. [ABSTRACT FROM AUTHOR]

The preparation, initiation and occurrence dynamics of earthquakes in Italy are governed by several frequently unknown physical mechanisms and parameters. Understanding these mechanisms is crucial for developing new techniques and approaches for earthquake monitoring and hazard assessments. Here, we develop a first-order numerical model simulating quasi-static crustal interseismic loading, coseismic brittle episodic dislocation and post-seismic relaxation for extensional and compressional earthquakes in Italy based on a common framework of lithostatic and tectonic forces. Our model includes an upper crust, where the fault is locked, and a deep crust, where the fault experiences steady shear. The results indicate that during the interseismic phase, the contrasting behaviour between the upper locked fault segment and lower creeping fault segment generates a stretched volume at depth in the hangingwall via extensional tectonics while a contracted volume forms via compressional tectonics. The interseismic stress and strain gradients invert at the coseismic stage, with the interseismic dilated volume contracting during the coseismic stage, and vice versa. Moreover, interseismic stress gradients promote coseismic gravitational subsidence of the hangingwall for normal fault earthquakes and elastic uplift for reverse fault earthquakes. Finally, the post-seismic relaxation is characterized by further ground subsidence and uplift for normal and reverse faulting earthquakes, respectively, which is consistent with the faulting style. The fault is the passive feature, with slipping generating the seismic waves, whereas the energy activating the movement is stored mostly in the hangingwall volume. The main source of energy for normal faulting and thrust is provided by the lithostatic load and elastic load, respectively. [ABSTRACT FROM AUTHOR]

The Loess Plateau is one of the most tectonically and seismically active areas in the world. Observations from past strong earthquakes, particularly the Minxian–Zhangxian and Wenchuan earthquakes, have shown distinctive evidence of seismic site effects in the mountainous area of southeastern Gansu province. In this study, seismic damage in the loess areas of southeastern Gansu province induced by these earthquakes was investigated and briefly described. Different types of ground motion were selected, and the one-dimensional equivalent linear method was used for numerical analysis of the ground motion effects in the loess regions. Moreover, seismic response analysis of a typical loess tableland was conducted. The results showed that the seismic responses of a typical loess tableland under different seismic excitations have totally different dynamic characteristics. Moreover, the seismic damage in loess regions was more serious under far-field seismic excitation compared with near-field seismic excitation with the same peak acceleration. Through this study, the quantitative assessment of ground motion effects can be approximately estimated and the mechanism of site amplification effects on ground motion is further explained. [ABSTRACT FROM AUTHOR]

Mudflow is often associated with seismic activities. The present study applied a seismic based detection of the surface waves generated by the mudflow of Brumadinho dam collapse using records of Brazilian Seismographic Network. The signal envelope and time-frequency spectrograms of the mudflow signals were used in the analysis. As a result, the mudflow signals were successfully detected from the data recorded at a nearby seismic station. The findings of this study provide a good basis for future research to develop a flood early warning system based on cost-effective, remote and contentious seismic monitoring approaches. [ABSTRACT FROM AUTHOR]

• Based on a single degree of freedom Spring-Friction equivalent seismic isolation system with shear keys, this article considers the mutual independence of each shear key being sheared off under collision effect and achieves accurate simulation of each collision between FPS and the shear key under earthquake. • By reasonably designing the spring stiffness coefficient and the shearing force of FPS, the negative impact of collision on the displacement response of FPS under earthquake can be effectively reduced. • Increasing the spring stiffness and friction will weaken the FPS displacement amplification phenomenon caused by the collision, and the impact of the collision on the displacement is closely related to the moment of the collision happening and the number of collisions. Complex collision phenomena can occur between the Friction Pendulum System (FPS) and shear keys under earthquake, potentially resulting in shear keys sheared off. Based on a single-degree of freedom Spring-Friction Isolation System with shear keys, this article considers the independent shearing of each shear key due to collision effects, enabling precise simulation of each collision between FPS and shear keys under earthquakes. Additionally, the study investigates how this collision phenomenon affects the displacement response of FPS under various conditions. The findings reveal that collisions do not merely lead to displacement amplification effects on FPS. Instead, these effects depend closely on the spring stiffness and friction coefficient of FPS. Increased spring stiffness mitigates the displacement amplification caused by collisions. The timing of collisions occurrence also influences their impact on displacement. In cases where a structure exhibits resonance with substantial spring stiffness, frequent collisions can disrupt the resonance, significantly reducing the structural displacement response of FPS. Furthermore, friction plays a role in attenuating the collision's effect on FPS displacement amplification. However, when friction effect dominates in FPS, collisions can cause fluctuations in the FPS displacement time-history curve. The magnitude of this change is determined by the velocity increment resulting from the collision and the duration of this increment. [ABSTRACT FROM AUTHOR]

Highlights • An optimal design procedure for nonlinear fluid viscous dampers is developed. • Nonlinear power law behavior is incorporated a priori in the optimal design process. • An improved stochastic linearization technique is used in the optimal design. • The procedure identifies the optimal dampers from an energy-based perspective. • Comparison with other methods proves key aspects and effectiveness of the procedure. Abstract The earthquake protection of structures equipped with energy dissipation devices in the form of nonlinear fluid viscous dampers (FVDs) is investigated. Most of the optimal design strategies from the literature either address a simplified linear (Newtonian) idealization of the devices, or identify the characteristics of the nonlinear FVDs in a later stage, by invoking the concept of "energy-equivalent" dampers to compromise between the nonlinear power law force-velocity behavior and a simplified (equivalent, in terms of energy dissipation) linear modeling. In this paper, the nonlinear power law behavior of the devices is incorporated a priori in the optimal design process. The proposed strategy, based upon a numerical approach to a constrained optimization problem, invokes a performance criterion that is derived from the energy balance equation of the system, expressed in stochastic terms. To handle the nonlinear constitutive behavior of the FVDs, a novel equal-energy non-Gaussian stochastic linearization technique is integrated in the optimal design process. For a given power-spectral-density function of the seismic excitation, the most effective set of nonlinear FVDs that maximize the energy dissipation behavior can be identified. By stochastic dynamic analysis and by nonlinear response-history-analysis with an ensemble of ground motions, the proposed energy-based design philosophy is found to be better able to control the overall seismic response of the structure than alternative procedures that are not based on energy concepts and that minimize other performance indices. [ABSTRACT FROM AUTHOR]

Highlights • Shaking table tests are conducted to estimate SSI effect on an isolated structure. • Isolation ability of isolation layer should be weaken by the softening soil layer. • Rotation response laws of isolator on different soil foundations are different. • Isolation of softening soil can compensate for the lost isolation ability of isolator. Abstract Soil-structure interaction (SSI) has a significant effect on the earthquake response of a base-isolated structure, particularly on the rotation response of the SSI system and the isolation performance of the isolation layer, as demonstrated by previous shaking table tests (Zhuang et al., 2014). On a softer soil foundation, the SSI should have a greater influence on the seismic response of an isolated structure. To this end, a new shaking table test is conducted to estimate the effect of SSI on the dynamic characteristics of a base-isolated structure on a multi-layered soil foundation including a soft clay layer. As expected, the isolation efficiency of the isolation layer is reduced by the SSI effects, especially with increasing peak ground acceleration (PGA) of the input motion. Compared with the test results for an isolated structure on a harder soil foundation, the rotation responses of the pile cap and the isolation layer in this study are stronger. Additionally, the rotation responses of the pile cap are significantly amplified by the isolation layer. This type of amplification effect can become stronger with increasing PGA of the input motion, which differs from the results for previous tests with a base-isolated structure on a harder sand foundation. Meanwhile, when the natural isolation property of the softening soil layer is considered, the seismic responses of a base-isolated structure are reduced by the SSI effects because the natural isolation of the soft soil layer can compensate for the lost isolation ability of the isolation layer. [ABSTRACT FROM AUTHOR]

Highlights • This paper presents results of shaking table testing for full-scaled CLT building and a design procedure. • This building system is suitable for midrise CLT building with high ductility produced through rocking. • The structure was shown to behave well during severe strong motion as specified in the Japanese building standard law and to have survived the 1995 Kobe earthquake despite the occurrence of a compressive rupture in its shear wall as well as a support element against the vertical load. • Element tests and connection tests for various types of shear wall were conducted to define a numerical model and its parameters, and a shaking table test was conducted to confirm the model and its parameters and to evaluate structural performance. • A target Structure composed of narrow shear walls and high ductile tensile bolts was designed so as to satisfy the minimum requirement of Japanese building standard law. • Story shear capacity calculated from a numerical model and element tests (such as connections) were safely evaluated; but to evaluate the capacity correctly, further research is required in the element and system levels. • Though a variety of undetermined issues and challenges remains, the Building Standard Law and Notification for three different CLT construction systems was enforced in April 2016 to ensure the construction of safe CLT buildings. Abstract A national research project to investigate proper structural design methods for cross-laminated timber (CLT) buildings has been initiated by a subsidiary of the Ministry of Land, Infrastructure, Transport and Tourism of Japan since 2011. In the final stage of the project, shaking table tests were conducted for CLT buildings designed according to a proposed structural design procedure which confirmed damage limit state, safety limit state, allowable stress, and ductile factors, etc. This paper presents results of shaking table testing for full-scaled CLT building and a design procedure. The three different systems examined are buildings composed of narrow panels, wide panels with an edge tensile connection, and wide panels with an edge tensile connection for each no-window shear part. The focus of this paper is the building of narrow panels. This building system is suitable for midrise CLT building with high ductility produced through rocking. The structure was shown to behave well during severe strong motion as specified in the Japanese building standard law and to have survived the 1995 Kobe earthquake despite the occurrence of a compressive rupture in shear walls which are support elements against the vertical load. Story shear capacity calculated from a numerical model and element tests (such as connections) were safely evaluated; but to evaluate the capacity correctly, further research is required in the element and system levels. Though a variety of undetermined issues and challenges remains, the Building Standard Law and Notification for three different CLT construction systems was enforced in April 2016 to ensure the construction of safe CLT buildings. [ABSTRACT FROM AUTHOR]

This study attempts to develop empirical correlations between average penetration resistance (), averaged velocities over depth up to bedrock depth () and 30 m () for shallow depth sites (having bedrock at a depth less than 25 m). A total of 63 shallow sites were assessed for penetration resistance values up to the bedrock from Standard Penetration Tests (SPT) and dynamic soil property analysis, i.e., Shear Wave Velocity (VS) from Multichannel Analysis of Surface Waves. The study shows that 30 m averaged shear wave velocities are more than the average velocity up to bedrock depth in shallow bedrock sites because of inclusion of rock site velocity. Furthermore, averaged SPT-N() and average VS () up to bedrock depth were correlated with the 30 m average() values. This is the first attempt in developing empirical relationships of this kind for seismic site classification. These correlations can be made useful for seismic site classification of sites in regions with Standard Penetration Test (NSPT) values and limited VS values. Further surface and bedrock motion recordings of 12 selected KiK-net shallow depth sites were collected and amplifications were estimated with the respective peak ground acceleration, spectral acceleration and thereby related to the average shear wave velocity up to bedrock and 30 m. The results show that the amplification is better correlated to the than for shallow depth sites, and more data can be added to strengthen this correlation. [ABSTRACT FROM AUTHOR]

• System-level numerical analysis is conducted on a self-centring frame under post-earthquake fire. • Combined effects of pre-damage and temperature are integrated into the proposed material model. • Various earthquake-fire combinations on single and multiple storeys compose the considered scenarios. • Quantitative assessment is provided by comparing structural responses with a conventional frame. • Target self-centring system exhibits favourable performance throughout the earthquake-fire sequence. Post-earthquake fire is a multi-hazard combination with cascading effects, of which catastrophic consequences are not only caused by the earthquake but exacerbated by the triggered fire. Only a few studies focused on the system-level structural analysis in earthquake-fire sequence, mostly on the conventional moment-resisting frame. Despite the self-centring system being a novel structure with excellent seismic performance, its post-earthquake fire response is still unclear due to limited research. Accordingly, this study aims to investigate the system-level behaviour of a self-centring system under post-earthquake fire. A numerical model of the six-storey prototype frame is established, and a two-stage bilinear material model is proposed to reflect the combined effects of pre-induced damage and temperature on material properties. A total of 11 ground motions (DBE and MCE levels) followed by 3 fires on different storeys compose the post-earthquake fire scenarios. A welded moment-resisting frame with reduced beam sections (WR-MRF) is selected for comparison, with the DBE response designed the same as the self-centring frame (SC-MRF). Results show that the SC-MRF exhibits smaller responses to the preceding earthquake and subsequent fire than the WR-MRF. Post-earthquake fire mainly affects two inter-storey drift ratios in each scenario, while it has a negligible effect on others which remain unchanged from the residual status after the earthquake. An obvious increase in structural responses can be found from fire-only (FO) to post-MCE fire (P-MCE-F) scenarios, and deformation is slightly larger in multi-floor fires than in single-floor ones. The findings unveil the post-earthquake fire responses of a seismic-resilient system with self-centring mechanism and provide a comparative assessment against the conventional structure. The methodology, including the proposed material model, can be further extended for analysis on other systems to understand and enhance the comprehensive performance in earthquake-fire sequence. [ABSTRACT FROM AUTHOR]

Specific architectural elements can be identified in constructions located in regions frequently exposed to earthquakes. These earthquake resistant features were developed empirically by local communities to protect their built-up environment. Research in these traditional practices, resulting from a local seismic culture, is a relevant and positive approach, since it focuses on the strength of the system rather than on its weaknesses. Its integration into current vernacular building practices can help to preserve and retrofit surviving in-use examples while respecting their authenticity. The main goal of the present work is to assess numerically the efficiency of traditional earthquake resistant solutions to mitigate the seismic vulnerability of vernacular architecture. The paper thus presents the results of a detailed numerical study based on finite element modeling and nonlinear static (pushover) analysis intended to quantitatively evaluate the influence of each technique on the seismic behavior of vernacular constructions and to better understand their structural role under seismic loading. [ABSTRACT FROM AUTHOR]

Ground motion characteristics, deformation and surface breaks of earthquakes depend upon the causative faults. Their effects on the seismic design of engineering structures are almost not considered in the present codes of design although there are attempts to include in some countries (i.e. USA, Japan, Taiwan, and Turkey). In this study, the authors first describe ground motions, crustal deformation and surface break observations caused by earthquakes having different faulting mechanism. Then some laboratory experiments were carried out to simulate the motions during normal and thrust faulting and their effects on model structures. And then, the effects of surface ruptures and deformations due to earthquake faulting on the response and stability engineering structures through observations in recent great earthquakes are presented. Finally, some recommendations for the design of structures with the consideration of permanent ground deformation in addition to ground shaking, which may be used in the development of seismic codes incorporating the effect of permanent deformation on structures, are proposed. [ABSTRACT FROM AUTHOR]

As a result of the disaster of nuclear power plant caused by the 2011 off the pacific coast of Tohoku Earthquake, establishment of a method to estimate the influence of slopes on the seismic safety of nuclear facilities has become necessary. The creation of such a method can yield important information regarding potential risk as well as risk management regarding seismic safety. The existing guidelines used to evaluate landslide risk provide guidance for landslide zoning as well as how landslide risk can be reduced and avoided. According to these guidelines, either people or houses are typically used as targets of risk evaluation. Particularly, for a specific slope, it is necessary to evaluate the damage of the potentially affected structures quantitatively and systematically. Therefore, the definition and basic assessment procedure of three limit states (stability limit, reachable limit and damage limit) are herein described. Furthermore, an evaluation case for a slope model describes the influence of slope collapse due to an earthquake. In this case, the fragility curves, as well as the occurrence probability for each limit state are described and an evaluation example is provided. Regarding new ideas and methods to evaluate the conditional reachable probability and the conditional damage probability as well as a method to evaluate the total probability of all three limit states are proposed. From the results obtained in our example case, it is found that systematical assessment of the risk information of facilities damaged due to slope collapse is useful, and is made possible via numerical analysis. [ABSTRACT FROM AUTHOR]

Evaluating the seismic stability of a rock slope typically involves searching for the minimum value of calculated safety factors (SF) for each supposed sliding block. Because only the transient equilibrium is evaluated, the likelihood of any slope failure can be deemed negligible if all the calculated SFs are greater than unity. However, even if some of the calculated SF are less than unity, it cannot be assumed that the slope will collapse. Recently, in the wake of extremely large earthquakes in Japan, the design earthquake standards for nuclear power plants (NPP) have been extended. After the experience of the 2011 off the Pacific coast of Tohoku Earthquake, the designer is expected to consider beyond design basis earthquakes to determine whether more can reasonably be done to reduce the potential for damage, especially where major consequences may ensue [IAEA (2011). IAEA international fact finding expert mission of the Fukushima dai-ichi NPP accident following the Great East Japan Earthquake and Tsunami, Mission report, IAEA]. With this in mind, the method employed to evaluate the seismic performance of the slope surrounding an NPP needs to be capable of doing more than determining the likelihood of failure: it must also consider the process toward failure in the event of an earthquake beyond the design basis. In this paper, a new evaluation flow which considers the failure process is proposed to evaluate the seismic performance of slopes surrounding an NPP. This is followed by confirming the validity of the concepts in the proposed flow chart by re-evaluating centrifuge tests in past literature and the numerical simulations designed for those tests. [ABSTRACT FROM AUTHOR]

Once a large deformation appears on the ground surface due to faulting during an earthquake, it may cause severe damage to infrastructure systems. A numerical simulation method that provides accurate prediction on the deformation of the ground surface is very useful for examining the performance of infrastructure systems subjected to a deformation of surrounding ground. The Finite Element Analysis (FEA), which is popular for practical engineers, would be applied to this problem. However, there are some difficulties on dealing with a discontinuity of fault displacement and, therefore, its application is still limited. In the present study, we employed the Smoothed Particle Hydrodynamics (SPH) method that requires no predefined computational mesh. A new computational model was introduced into the SPH for prediction of surface dislocation on the ground. The surface dislocation evaluated by the SPH with the developed computational model showed good agreement with our experimental results. [ABSTRACT FROM AUTHOR]

In recent years, a new demand has appeared for evaluations of earthquake fault displacements, to address the need to evaluate the soundness of underground structures. Fault displacements are caused by the rupturing of earthquake source faults, and are investigated through the use of methods such as the finite difference method and the finite element method (FEM). We conducted dynamic rupture simulations on the Kamishiro Fault Earthquake using a nonlinear FEM, focused on time history of fault displacement and response displacement, and demonstrated an ability to simulate observed values to a certain extent. During these simulations, we created models of homogeneous faults using the ground as the solid element and fault planes as joint elements. Although we were able to roughly simulate displacement time histories, obstacles to achieving more precise simulations still exist. In this research, we conducted investigations to model strong motion generation areas (SMGA). We conducted a searching analysis using Bayesian optimization with SMGA distribution within faults as parameters, and estimated the optimal parameters for simulating time histories of displacement. In addition, we compared our results with estimations of SMGA derived from different methods, and demonstrated that our distributions qualitatively matched. In addition, we evaluated the stochasticity of response displacement considering the randomness of the parameter of the fault. To conduct the simulation, we introduced joint elements from Goodman et al. that had been expanded to the FEM code FrontISTR, which makes it possible to analyze large-scale models. [ABSTRACT FROM AUTHOR]

A conventional "recipe" for strong ground motion prediction has been applied to the seismic fault (deep fault; located within seismogenic layer). In order to perform assessments of strong ground motions and permanent displacements at sites very close to the fault trace, we proposed the method of modeling that takes the entire ruptured fault from the ground surface to the seismic fault into account. Our approach was validated by the simulation of observed records obtained at stations very close to the fault trace of the mainshock of the 2016 Kumamoto Japan, earthquake (Mw7.1). Also, through the ground motion assessment performed for a hypothetical strike-slip fault with a 90 ∘ dip angle, we found that adding the shallow fault had virtually no effect on acceleration time history, but it had a clear effect on the fault-parallel component of velocity and displacement time histories in the area close to the fault trace. [ABSTRACT FROM AUTHOR]

This study investigated the applicability of a nonlinear analysis method that considers progressive failure to evaluating the stability of rock slopes, including post-earthquake residual displacement. The vibration step of the nonlinear analysis, which begins after residual displacement occurs, was found to match that of a dynamic centrifugal model test. The nonlinear analysis was concluded to be relatively conservative because it calculated a slightly larger residual displacement than that observed during the model test. A real-scale soft rock slope was analyzed, and the results showed that the proposed analysis method is useful for evaluating slope seismic stability, including post-earthquake residual displacements. [ABSTRACT FROM AUTHOR]

Understanding the variation of seismic site response plays a crucial role in mitigating a future earthquake disaster. The spatial variation of site response is caused primarily due to varying amplification of the seismic wave by the ground surface layers. In practice, the spatial variation of site response is projected on maps. Site responses are correlated with some parameters and the variation of these parameters are mapped in advance of preparing the site response map. However, in conventional mapping, the observations recorded over events at a site are generally reduced to a single averaged value. Although the site responses at two sites with some difference in their average value are visually considered to be different, the statistical significance of this difference is directly ungraspable without any information on the distribution of the data. This study addresses the issue of site response uncertainty in mapping. A mapping methodology termed as uncertainty projected mapping (UPM) has been proposed which reflects the data insignificance on the map resolutions, based on the uncertainty. In UPM, a hierarchical Bayesian model has been adopted for the spatial distribution of site responses as it incorporates uncertainties and allows modelling variabilities as parameters. In this paper, the theory of UPM is introduced at first. The UPM methodology is then validated with certain numerical experiments. The validated UPM is then applied to make a site response map for a case-study area in Furukawa, Japan. The results are then discussed in comparison to a conventional mapping method. [ABSTRACT FROM AUTHOR]

On 8 May 1939, an earthquake (Ms7.1) occurred near the Azores archipelago, with an epicentre located close to the western end of the Gloria fault. Previous studies present different epicentre locations spreading over a large area, and two different types of focal mechanisms. Given these uncertainties, the interpretation of the seismological information in a complex tectonic environment between the Gloria Fault and the Terceira Ridge is a matter of debate. The event caused a small tsunami recorded in the Azores Islands. In this study, we use the tsunami observations and tsunami numerical modelling to select the earthquake fault rupture that best fits the tsunami observations. We consider the different focal mechanism solutions, perform tsunami numerical modelling, and compute synthetic tsunami waveforms at the tide gauge locations. We find that an earthquake caused by a low-angle dipping fault with dominant strike–slip movement generates a tsunami that reproduces well the record at Ponta Delgada tide gauge. Finally, in areas where earthquakes are rare, the study of ancient earthquakes must use all information available, namely tsunami observations and mareograph data. [ABSTRACT FROM AUTHOR]

The foundation might be separated from the supporting soil if the earthquake is big enough, which is known as base mat uplift. This paper proposed a simplified calculation model in which spring element is adopted to simulate the interaction between soil and structure. The load-deformation curve (F-D curve) of the spring element can be designated to represent the base mat uplift, in which the pressure can be applied while tensile forces are not allowed. Key factors, such as seismic wave types, seismic wave excitation directions, seismic wave amplitudes, soil shear velocities, structure stiffness, and the ratio of structure height to width (H/B), were considered in the analysis. It is shown that (1) seismic wave type has significant influence on structure response due to different frequency components it contained; (2) the vertical input of seismic wave greatly affected structure response in vertical direction, while it has little impacts in horizontal direction; (3) base mat uplift is easier to take place in soil with higher shear velocity; (4) structure H/B value has complicated influence on base mat uplift. The outcome of this research is assumed to provide some references for the seismic design of the structure due to base mat uplift. [ABSTRACT FROM AUTHOR]

This paper presents a three-dimensional non-linear finite element (FE) approach to analyse the dynamic soil-structure interaction (SSI) phenomena observed at the Lotung Large-Scale Seismic Test (LSST) site. The numerical study is carried out in the time domain by a commercial FE code, taking into account the non-linear behaviour of soil and the multi-directional nature of real seismic events. The soil response is simulated by an isotropic hardening elasto-plastic hysteretic model (HSsmall) implemented in the material model library of the code. This model allows to describe the non-linear cyclic response ranging from small to large strain amplitudes and to account for the variation of the initial stiffness with depth. In the paper, the FE numerical approach is first validated through a series of parametric analyses simulating simplified cases (i.e. linear visco-elastic structures founded on a homogeneous linear visco-elastic soil deposit) for which analytical solutions exist. Then, it is adopted to back-analyse the behaviour of the 1/4-scale nuclear power plant containment structure constructed at the Lotung LSST site which was shook by several earthquakes of different intensities and frequency contents. The FE results are thus compared to the recorded in-situ free-field and structural motions, highlighting the satisfactory performance of the numerical model in replicating the observed response. The overall outcome of this research proves that nowadays complex dynamic SSI phenomena can be tackled by direct approach, overpassing the strong simplifications of the well-established substructure approaches. [ABSTRACT FROM AUTHOR]

This paper investigates the slope failure along the Karakorum Highway near Sim Elahi Jung Village, District Mansehra Khyber Pakhtunkhwa, Pakistan by using numerical back analysis method. The slope face was ~80m high with a cut angle of 80 degree in quartz mica schist of Tanawal formation. The failure was triggered by 26th October 2015 earthquake of moment magnitude (Mw) of 7.5. The slope was investigated thoroughly for the geological conditions, slope geometry and the slid mass. During field studies, discontinuity surveys were conducted for onward assessment of the rock mass quality and orientation data for kinematic analyses. In view of rock mass quality determined from discontinuity surveys, back analyses were conducted considering slope material as Hoek-Brown material with the help of computer code Slide 6.0. The rock mass input parameters were adopted in the light of field and laboratory studies at the verge of failure. Back analysis conducted using estimated value of peak ground acceleration (PGA) have indicated that the geological strength index (GSI) value and the uniaxial compressive strength of the slope forming material were 24.0 and 29.0 MPa respectively at the time of failure. The analyzed slip surface and the observed ground slip surface were found consistent with each other, thus, confirming the validity of the model. The derived rock mass parameters are presented here for the evaluation of remaining slopes in the area having similar geological conditions and geometries. [ABSTRACT FROM AUTHOR]

The incident direction of earthquake waves has significance on the seismic responses of long lined tunnels. In this study, based on the equivalent node force method and together with the viscous-spring artificial boundary, the 3-D input method of SV and SH-waves with arbitrary incident angles is studied firstly. The input method is introduced within the framework of ABAQUS software and is verified by two numerical examples. Consequently, the proposed input method is employed to investigate the impact of the incident angles of SV and SH-waves on the seismic responses of a long lined tunnel. The numerical results indicate that the non-linear seismic responses of long lined tunnels are highly affected by the incident angles of S-waves. As the incident directions of SV and SH-waves being not perpendicular to the tunnel longitude, non-uniform motions appear along the tunnel longitude, as well as the longitudinal internal forces. The plastic deformation and strain components along the tunnel cross-section are also influenced by the incident angles of SV and SH-waves. It is thus important to include the incident angles of earthquake waves in mapping the seismic risk of tunnels. [ABSTRACT FROM AUTHOR]

Cable-stayed bridges are quite sensitive to large amplitude oscillations from earthquakes and seismic damage was observed for Shipshaw Bridge and Chi-Lu Bridge during past earthquakes. In order to investigate seismic damage of cable-stayed bridges, a 1 : 20 scale model of a single-tower cable-stayed bridge with A-shaped tower was designed, constructed, and tested on shake tables at Tongji University, China. One typical near-field ground motion was used to excite the model from low to high intensity. Test result showed that severe structural damage occurred at the tower of the model including parallel concrete cracks from bottom to nearly half height of the tower, concrete spalling, and exposed bars at top tower 0.2 m above the section where two skewed legs intersect. Posttest analysis was conducted and compared with test results. It is revealed that the numerical model was able to simulate the seismic damage of the test model by modeling nonlinearity of different components for cable-stayed bridges, namely, the tower, bents, superstructure, cables, and bearings. Numerical analysis also revealed that cable relaxation, which was detected during the test, had limited influence on the overall seismic response of the bridge with maximum error of 12%. [ABSTRACT FROM AUTHOR]

Nonlinear dynamic numerical simulations of infinite slopes are used to examine the effects of spatial variability in penetration resistances on liquefaction-induced settlement and lateral spreading for gently sloping ground and to develop guidance on selecting representative properties for uniform models. Simulation results for models having uniform properties (uniform models) are compared to results for models having spatially correlated Gaussian random field property distributions (stochastic models). Results are presented for sets of stochastic model realizations and a set of ground motions scaled to a range of peak ground accelerations. Computed responses and ground deformations (settlements and lateral displacements) for these uniform and stochastic models are used to identify representative properties (as a percentile of the stochastic distributions) for which the uniform models produce reasonable agreement with the median of the stochastic model responses. The effects of the scales of fluctuation, nonliquefiable crust layer thickness, sand layer thickness, ground motion characteristics, sand density, and other factors are evaluated. Implications for engineering practice are discussed. [ABSTRACT FROM AUTHOR]

The roof slab of the nuclear reactor supports all the components of the reactor. Roof slab is essentially a box structure with top and bottom plates interconnected by vertical shells and radial stiffeners welded to them. The gap between the top and bottom plates is filled with concrete that provides biological and thermal shielding in the top axial direction of the reactor. The 500 MWe Prototype Fast Breeder Reactor (PFBR) is designed based on the Operating Basis Earthquake (OBE) and Safe Shutdown Earthquake (SSE) which are categorized under level A and level D loadings respectively. The primary objective of this work is to optimize the design of the roof slab and to predict and ascertain the structural integrity of the optimized roof slab under static, harmonic and seismic loading conditions. Regression models for critical design parameters are developed and are used in the optimization algorithm. [ABSTRACT FROM AUTHOR]

The evolution of fault strength and behavior during the initial stages of slip plays an important role in driving the onset of instability and fault weakening. Using small-displacement triaxial experiments on quartz sandstone, this study highlights the rapid onset of microstructural change on fault interfaces and identifies new evidence for an evolution in physical processes with increasing slip and velocity. Pre-ground fault surfaces have been slipped over a range of velocities (0.36 μm s-1 to 18 cm s-1) and at normal stresses comparable to upperto mid-crustal conditions (92-287 MPa). Microstructural analysis of the fault interfaces reveals the formation of amorphous material at displacements <170 μm and slip durations < 1 ms. Mechanical and microstructural observations have been combined with numerical modeling to present the first documented examples of a transition from mechanical amorphization to flash heating, then frictional melting, with changes in slip conditions. The sequence of processes activated during the initial stages of fault movement may provide new insights into factors that influence the onset of slip in the seismogenic crust. [ABSTRACT FROM AUTHOR]

• Post-earthquake damage assessments of URM building are considered. • Shake table test are conducted for experimental investigation. • Numerical simulations are used to validate the experimental results. • Ambient vibration tests performed to determine the damage effect. Masonry structures are one of the structures most affected by earthquakes. In addition, since masonry structures constitute a large part of the building inventory, it is important to determine the dynamic characteristics of these structures. The present study is aimed to evaluate the seismic performance of a half-scale hollow brick unreinforced masonry (URM) building considering different damage states. Shake table test was conducted with seven loading conditions. In order to obtain different damage states, seismic excitations were applied incrementally to structure. After each loading, the damage conditions and the corresponding damage patterns were examined comparatively, and the structure collapsed in the last loading condition. To experimentally observe the damage, the modal parameters for un-damaged and damaged situations of the building were identified by ambient vibration tests performed before and after the seismic loadings. The experimental results obtained were then compared with the analyses made in numerical softwares, and similar results were obtained. [ABSTRACT FROM AUTHOR]

The first part of the paper presents a brief description of the material point method (MPM) including the governing equations, solution scheme and a benchmark problem of soil collapse simulated using the method. In the second and third part of the paper, the post-failure runout process of the Wangjiayan landslide is simulated and analyzed. The landslide's final topography and information from post-failure in-situ survey and laboratory tests are used to constrain the accuracy of computational results. The kinematic behaviors of the failure mass are investigated in terms of displacement, velocity, effective plastic strain fields and topography changes during the movement. Comparisons are made between conditions with and without buildings on the deposition area. Numerical computations demonstrate that the presence of buildings on the sliding path strongly governs the flow regime, run-out distance, velocity, strain field and final deposition topography of the landslide. So it is very essential to incorporate the effects of buildings in the modelling and analyses. Numerical results considering buildings show that the slide lasts about 30 s with the most rapid phase occurring between 6 and 12 s, and that the maximum simulated velocity among the sliding particles in the landslide is 43.5 m/s, indicates that the moving of the landslide mass was very fast. The run-out distance simulated with MPM matches the measured post-earthquake topography well, whereas the shape of the simulated deposition zone is a little differs. The buildings influence the sliding by shortening the overall run-out distance, decelerating the movement of the bottom layer, and increasing the internal deformation and mixing among deposition layers. [ABSTRACT FROM AUTHOR]

The damping effect of the vertical baffles inside a liquid storage tank is studied in this paper. A numerical model based on the finite volume method is established and used to evaluate the accuracy of an analytical model developed to estimate the hydrodynamic damping caused by the vertical wall bounded baffles. For this purpose, several full scale baffled tanks with different aspect ratios are numerically analyzed. The numerical results were then used to validate the analytical model. The reduction in sloshing wave height caused by the baffles is estimated for selected tanks subjected to the seismic excitations. Finally, a simple procedure to estimate the reduction in sloshing amplitude due to the presence of baffles is proposed and validated using the time history numerical results. [ABSTRACT FROM AUTHOR]

Stimulated by the recent advances in computational tools for the simulation of seismic wave propagation problems in realistic geological configurations, this paper presents a 3D physicsbased numerical analysis of near-source ground motion during the MW 6.0 2012 May 29 earthquake in the Po Plain, Northern Italy. To reproduce with sufficient accuracy some of the most peculiar features of the near-source strong-motion records and of the spatial variability of damage distribution, this study required a sequence of investigations, starting from the analysis of a wide set of near-source records, to the calibration of an improved kinematic seismic source model, up to the development of a 3D numerical model of the portion of the Po Plain interested by the earthquake. The latter includes the basin geometry, characterized by sediment thickness sharply varying from few tens of metres to some kilometres. The spatial resolution of the numerical model is suitable to propagate frequencies up to about 1.5 Hz. Numerical simulations were performed using the open-source high-performance code SPEED, based on the Discontinuous Galerkin Spectral Elements method. The 3D numerical model, coupled with the updated slip distribution along the rupturing fault, proved successful to reproduce with good agreement, measured through quantitative goodness-of-fit criteria, the most relevant features of the observed ground motion. These include: (i) the large fault normal velocity peaks at the near-source stations driven by updip directivity effects; (ii) the small-scale variability at short distance from the source, resulting in the out-of-phase motion at stations separated by only 3 km distance; (iii) the propagation of prominent trains of surface waves, especially in the Northern direction; (iv) the map of earthquake-induced ground uplift with maximum values of about 10 cm, in substantial agreement with geodetic measurements and (v) the two-lobed pattern of the peak ground velocity map, well correlated with the distribution of macroseismic intensity. [ABSTRACT FROM AUTHOR]

We have developed a new method to retrieve seismic surface wave phase velocity using dense seismic arrays. The method measures phase variations between nearby stations based on waveform cross-correlation. The coherence in waveforms between adjacent stations results in highly precise relative phase estimates. Frequency-dependent phase variations are then inverted for spatial variations in apparent phase velocity via the Eikonal equation. Frequency-dependent surface wave amplitudes measured on individual stations are used to correct the apparent phase velocity to account for multipathing via the Helmholtz equation. By using coherence and other data selection criteria, we construct an automated system that retrieves structural phase-velocity maps directly from raw seismic waveforms for individual earthquakes without human intervention. The system is applied to broad-band seismic data from over 800 events recorded on EarthScope's USArray from 2006 to 2014, systematically building up Rayleigh-wave phase-velocity maps between the periods of 20 and 100 s for the entire continental United States. At the highest frequencies, the resulting maps are highly correlated with phase-velocity maps derived from ambient noise tomography. At all frequencies, we observe a significant contrast in Rayleigh-wave phase velocity between the tectonically active western US and the stable eastern US, with the phase velocity variations in the western US being 1-2 times greater. The Love wave phase-velocity maps are also calculated. We find that overtone contamination may produce systemic bias for the Love-wave phase-velocity measurements. [ABSTRACT FROM AUTHOR]

In the Umbria-Marche (Central Italy) region an important earthquake sequence occurred in 1997, characterized by nine earthquakes with magnitudes in the range between 5 and 6, that caused important damages and causalities. In the present paper, we separately estimate intrinsic and scatteringQ-1 parameters, using the classical multiple lapse timewindowanalysis (MLTWA) approach in the assumption of a half-space model. The results clearly show that the attenuation parameters Qi-1 and Qs-1 are frequency dependent. This estimate is compared with other attenuation studies carried out in the same area, and with all the other MLTWA estimates obtained till now in other tectonic environments in the Earth. The bias introduced by the half-space assumption is investigated through numerical solutions of the energy transport equation in the more realistic assumption of a heterogeneous crust overlying a transparent mantle, with a Moho located at a depth ranging between 35 and 45 km below the surface. The bias introduced by the half-space assumption is significant only at high frequency. We finally show how the attenuation estimates, calculated with different techniques, lead to different peak ground acceleration decay with distance relationships, using the well-known and well proven Boore's method. This last result indicates that care must be used in selecting the correct estimate of the attenuation parameters for seismic risk purposes. We also discuss the reason why MLTWA may be chosen among all the other available techniques, due to its intrinsic stability, to obtain the right attenuation parameters. [ABSTRACT FROM AUTHOR]

Differences between 3-D numerical predictions of earthquake ground motion in the Mygdonian basin near Thessaloniki, Greece, led us to define four canonical stringent models derived from the complex realistic 3-D model of theMygdonian basin. Sediments atop an elastic bedrock are modelled in the 1D-sharp and 1D-smooth models using three homogeneous layers and smooth velocity distribution, respectively. The 2D-sharp and 2D-smooth models are extensions of the 1-D models to an asymmetric sedimentary valley. In all cases, 3-D wavefields include strongly dispersive surface waves in the sediments. We compared simulations by the Fourier pseudospectral method (FPSM), the Legendre spectral-element method (SEM) and two formulations of the finite-difference method (FDM-S and FDM-C) up to 4Hz. The accuracy of individual solutions and level of agreement between solutions vary with type of seismic waves and depend on the smoothness of the velocity model. The level of accuracy is high for the bodywaves in all solutions. However, it strongly depends on the discrete representation of the material interfaces (at which material parameters change discontinuously) for the surface waves in the sharp models. An improper discrete representation of the interfaces can cause inaccurate numerical modelling of surface waves. For all the numerical methods considered, except SEM with mesh of elements following the interfaces, a proper implementation of interfaces requires definition of an effective medium consistent with the interface boundary conditions. An orthorhombic effective medium is shown to significantly improve accuracy and preserve the computational efficiency of modelling. The conclusions drawn from the analysis of the results of the canonical cases greatly help to explain differences between numerical predictions of ground motion in realistic models of the Mygdonian basin. We recommend that any numerical method and code that is intended for numerical prediction of earthquake ground motion should be verified through stringent models that would make it possible to test the most important aspects of accuracy. [ABSTRACT FROM AUTHOR]

Since centroid moment tensor (CMT) solution is not enough to describe the mechanism variations of large earthquakes, multiple CMTs were investigated in recent years by inverting seismic waveforms to retrieve the mechanism complexities. However, a problem in these waveform inversions is the trade-off between spatial mechanism variation and temporal rupture process, which may lead to ambiguous results. In this work, we propose a simple but practical approach to invert geodetic coseismic data for spatial mechanism variation. Because there is no need to solve for rupture velocity, geodetic inversion is generally more efficient and robust than waveform inversion. This approach was used to investigate the mechanism variation of the 2008 Wenchuan earthquake. In the case study, a line fault, whose position had been optimized through a 3-D grid search, was used to approximate the rupture fault, aiming to determine the mechanism variations along the strike direction. From the inversion results, there are thrust-slips and strike-slips in the southwest and northeast, respectively. The mechanism change appears at 160–200 km to the northeast of the epicentre, where compensated linear vector dipoles (CLVDs) have a local maximum and also support a significant mechanism change. By testing eight line faults with different positions, it is found that the inversion results do not strongly depend on the fault position, suggesting that the mechanism and its variations are robustly constrained in coseismic data inversion with our approach. Compared to waveform inversions, this work provides a more effective way to explore the mechanism complexities, and lays a foundation for future joint inversion of seismic and geodetic data sets. [ABSTRACT FROM AUTHOR]