Long-period Ground Motions Research Articles

Time Series Evaluation of Vibration Characteristics of a High-Rise Building Under Long-Period Seismic Ground Motions

Time Series Evaluation of Vibration Characteristics of a High-Rise Building Under Long-Period Seismic Ground Motions

Proposition of isolation system applicable to the long-period earthquake ground motion (Method of changing natural frequency of isolation system with additional spring)

Proposition of isolation system applicable to the long-period earthquake ground motion (Method of changing natural frequency of isolation system with additional spring)

Fundamental Study on Applicability of Long-period Ground Motion Class for Super High-rise Residential Buildings Based on Structural Response Records and Questionnaire Survey

Fundamental Study on Applicability of Long-period Ground Motion Class for Super High-rise Residential Buildings Based on Structural Response Records and Questionnaire Survey

Propagation Characteristics of Long-period Ground Motion in the Kanto Plain and Variation due to Source Location

Propagation Characteristics of Long-period Ground Motion in the Kanto Plain and Variation due to Source Location

Fling Effects from Near‐Source Strong‐Motion Records: Insights from the 2016 Mw 6.5 Norcia, Central Italy, Earthquake

We propose a semiautomatic processing scheme (extended BASeline Correction [eBASCO]) for recovering the tectonic fling from near-source records. The method, based on a piecewise linear detrend of the strong-motion (SM) recordings, is applied to reconstruct the ground displacement field of the 30 October 2016 M w 6.5 earthquake in central Italy. The robustness of the results is checked against geodetic measurements, remote sensing data, ground-motion simulations, and existing empirical models for fling amplitude. The outcomes of eBASCO are analyzed with the goal of testing its capability to preserve long-period content in near-source SM recordings affected by tectonic fling, different from standard processing schemes based on bandpass filtering. Comparison of peak ground displacements, peak ground velocities, and spectral displacements shows that long-period ground motion recorded over and in proximity of the fault can be underestimated by standard processing. Spectral displacement ordinates can diverge up to the 25% for periods longer than 5 s when an appropriate baseline correction is made.

Evidence of strong long-period ground motions of engineering importance for Nankai Trough plate boundary earthquakes: comparison of ground motions of two moderate-magnitude earthquakes

We analyzed strong-motion and broadband recordings of two moderate-magnitude earthquakes that occurred in the Nankai Trough. The first event was the 2004 Mw 6.5 southeast off-Kii peninsula earthquake, an aftershock event inside the Philippine Sea Plate near the Nankai Trough axis. The second event was the 2016 Mw 5.8 southeast off-Mie Prefecture earthquake, an independent event in the rupture area of the 1944 Mw ~ 8 Tonankai earthquake. The centroid depths were 11 and 14 km for the 2004 and 2016 events, respectively. Despite a large difference in the moment magnitude between the two events, the JMA magnitude (Mj) was 6.5 for both the events. We found that the short-period ground motions (e.g., response spectra at periods < 1 s) as well as the much longer-period ground motions (> 20 s) for the 2016 event scaled generally well with the moment magnitude of the event. In contrast, the ground motions from the 2016 event were comparable to those for the larger-moment-magnitude 2004 event at equal distances at periods of about 2–20 s in wide areas and the observed acceleration response spectra at those periods were noticeably underestimated for the 2016 event by the ground motion prediction equation (GMPE) that employs Mw. An examination of the existing subsurface velocity model suggested that the difference in the relative location of the two events with respect to the thick accretionary prism of low seismic velocity most probably caused the comparable amplitude of the seismic waves at those periods. As a result, we posit that the values of Mj are equal for the two events because Mj is estimated using the displacement amplitude of ground motions at periods smaller than about 6 s. On the other hand, GMPE employing Mj generally described the observed data well. The results suggested that the plate boundary earthquakes in the Nankai Trough may excite strong long-period ground motions of engineering importance, and these ground motions appear to be better explained by Mj than by Mw in GMPEs for moderate-magnitude earthquakes in the Nankai Trough subduction zone.

Adaptive base isolation system to achieve structural resiliency under both short- and long-period earthquake ground motions

Base isolation system is widely used to protect important and essential buildings from seismic hazards. The use of high damping is effective in reducing the resonance effect under long-period earthquake ground motions. However, high damping increases the acceleration demand under short-period ground motions, leading to a higher risk of damage of nonstructural components. Actually, low damping is beneficial to reduce the acceleration demand under short-period ground motions, suggesting the use of adaptive damping control, that is, high damping under long-period motions and low damping under short-period motions. In order to implement this concept, a semi-actively controlled base isolation system is provided in this article along with a new control law based on the transmissibility theory. Unlike existing studies, the proposed method enables a systematic design procedure for base isolated structures with semi-active dampers, which is called the simplified design procedure in this article. The performance of the proposed system is evaluated with numerical simulations for a base isolated three-story building with magneto-rheological dampers. It was shown that the proposed system achieves a high level of performance under long-period ground motions, while maintaining the exceptional performance of a conventional base isolation system with low damping under short-period ground motions.

The effect of composite-elastomer isolation system on the seismic response of liquid-storage tanks: Part I

A typical viable technique to decrease the seismic response of liquid storage tanks is to isolate them at the base. Base-isolation systems are an efficient and feasible solution to reduce the vulnerability of structures in high seismic risk zones. Nevertheless, when liquid storage tanks are under long-period shaking, the base-isolation systems could have different impacts. These kinds of earthquakes can damage the tanks readily. Hence, the seismic behaviour and vibration of cylindrical liquid storage tanks, subjected to earthquakes, is of paramount importance, and it is investigated in this paper. The Finite Element Method is used to evaluate seismic response in addition to the reduction of excessive liquid sloshing in the tank when subjected to the long-period ground motion. The non-linear stress-strain behaviour pertaining to polymers and rubbers is implemented while non-linear contact elements are employed to describe the 3-D surface-to-surface contact. Therefore, Nonlinear Procedures are used to investigate the fluid-structure interactions (FSI) between liquid and the tank wall while there is incompressible liquid. Part I, examines the effect of the flexibility of the isolation system and the tank aspect ratio (height to radius) on the tank wall radial displacements of the tank wall and the liquid sloshing heights. Maximum stress and base shear force for various aspect ratios and different base-isolators, which are subjected to three seismic conditions, will be discussed in Part II. It is shown that the composite-base isolator is much more effective than other isolators due to its high flexibility and strength combined. Moreover, the base isolators may decrease the maximum level pertaining to radial displacement.

Polarization of Near-fault Long-period Ground Motion

Through the analysis of typical near-fault ground motion, the inhomogeneity of the spatial distribution of long-period ground motion intensity on the fault parallel component (FP) and normal component (FN) is revealed. The study shows that the intensity of long-period ground motion on the fault parallel component is higher than that of on the fault normal component. This may be due to the fact that the velocity pulse is more easily formed on the fault parallel component higher than that of on the fault normal component, and the velocity pulse is more intense. The study is of great significance to the establishment of the attenuation relationship of near-fault ground motion and the seismic fortification of near fault structures.

Modeling of Long-Period Ground Motions in the Nankai Subduction Zone: Model Simulation Using the Accretionary Prism Derived from Oceanfloor Local S-Wave Velocity Structures

The accretionary prism in the subduction zone, which consists of thick low-velocity oceanic sediments, significantly affects the propagation of seismic waves for shallow, offshore earthquakes, including large interplate earthquakes. In order to simulate long-period (> 5 s) ground motions in the Nankai subduction zone, we constructed a three-dimensional (3D) seismic velocity structure model of the accretionary prism by interpolation/extrapolation of local S-wave velocity structures beneath 46 oceanfloor seismic stations (DONET), which are deployed just above the accretionary prism off the southern Kii and eastern Shikoku regions. We modeled local S-wave velocity structures using a simple two-parameter depth-varying velocity function. To investigate the effects of the accretionary prism on ground and seafloor motions, we conducted numerical simulations of seismic wave propagation for three local earthquakes that occurred in southwestern Japan. The simulations reasonably reproduced the observed seismograms, not only for the period ranges of the moment tensor inversion (~ 50 s), but also for the strong, long-period ground motions in the sedimentary basins (~ 5 s), especially in the region where DONET stations are densely deployed. Since depth-varying, local S-wave structures significantly improve the reproducibility of long-period ground motions, our modeling procedure is useful for modeling long-period ground motions of local and regional offshore subduction zone earthquakes.

An improved defining parameter for long-period ground motions with application of a super-tall building

This paper focuses on defining long-period ground motions and analyzing the effect of them on building structures. Increasing attention has been paid to the effect of long-period ground motions on building structures. However, long-period ground motions are not quantitatively defined due to the lack of numerous ground motion investigations. In this paper, based on the statistical analysis of 39,744 ground motions, an improved frequency-domain defining parameter, namely βl, is firstly proposed to identify long-period ground motions without the necessity of seismological information. Then, based on the definition, long-period ground motions are selected for the time history analysis of a super-tall building structure. The structural responses are obtained under three scenarios: the original ground motion record, the ground motions scaled to minor earthquakes and major earthquakes. To assess the validity of the proposed parameter βl in identifying long-period ground motions, correlation between the structural response and the defining parameter is obtained.

Cluster Analysis of Long-Period Ground-Motion Simulation Data with Application to Nankai Trough Megathrust Earthquake Scenarios

We developed a clustering method combining principal component analysis and the k-means algorithm, which classifies earthquake scenarios based on the similarity of the spatial distribution of earthquake ground-motion simulation data generated for many earthquake scenarios, and applied it to long-period ground-motion simulation data for Nankai Trough megathrust earthquake scenarios. Values for peak ground velocity and relative velocity response at approximately 80,000 locations in 369 earthquake scenarios were represented by 15 principal components each, and earthquake scenarios were categorized into 30 clusters. In addition, based on clustering results, we determined that extracting relationships between principal components and scenario parameters is possible. Furthermore, by utilizing these relationships, it may be possible to easily estimate the approximate ground-motion distribution from the principal components of arbitrary sets of scenario parameters.

A Simple Response Evaluation Method for Base-Isolation Building-Connection Hybrid Structural System under Long-Period and Long-Duration Ground Motion

An innovative hybrid control building system of base-isolation and building-connection has been proposed in the previous study. This system has two advantages, (i) to resist an impulsive earthquake input through the base-isolation system and (ii) to withstand a long-duration earthquake input through the building-connection system. A simple response evaluation method without the need of nonlinear time-history response analysis is proposed here for this hybrid building system under a long-period and long-duration ground motion. An analytical expression is derived in the plastic deformation of an elastic-perfectly plastic single-degree-of-freedom (SDOF) model with viscous damping under the multi impulse which is the representative of long-period and long-duration ground motions. A transformation procedure of a base-isolation building-connection hybrid structural system into an SDOF model is proposed by introducing two steps, one is the reduction of the main base-isolated building to an SDOF system and the other is the reduction of the connecting oil dampers supported on a free wall to an oil damper with a newly introduced compensation factor on a rigid wall. Application of the analytical expression of the plastic deformation to the reduced SDOF model including the compensation factor on the connecting oil dampers enables the development of a simplified, but rather accurate response evaluation method. The time-history response analysis of the multi-degree-of-freedom (MDOF) model and the comparison with the proposed simplified formula make clear the accuracy and reliability of the proposed simplified response evaluation method.

Simulation of the microtremor H/V spectrum based on the theory of surface wave propagation in a layered half-space

Subsurface velocity structures must be estimated to predict long-period ground motions and seismic hazards. Subsurface velocity structures can be constructed via an inversion of the horizontal-to-vertical (H/V) spectral ratio of microtremor (MHV) curves; thus, a method of simulating the MHV curves is key. In this study, we use the H/V spectral ratio of the surface wave (SHV) based on the surface wave propagation theory in a layered half-space to simulate the MHV curves at sites A and B of the Yuxi basin. Then, we attempt to analyze the features of the SHV curves. We find the H/V ratio of the microtremor loading source to be independent of the peak frequency of the SHV curve, but it has some relation to the amplitude of the SHV curve. Moreover, to reduce the error in subsurface velocity structures obtained by the MHV curves, we suggest that the SHV curves at near-peak frequencies should not be considered in the inversion, because the amplitude deviation is higher at the peak frequency of the MHV curve. In addition, the best frequency ranges for the inversion of the microtremor H/V spectrum are between the peak and trough frequencies of the microtremor H/V spectrum.

The damage mechanism of water tower in Shaanxi Provence during Wenchuan Earthquake

Through the collection, collation and analysis of the data about damage of Water tower in Shaanxi Provence during 12 May 2008 Wenchuan Earthquake, the mechanism of long-period damage of the water tower is given. The analysis shows that, in Hanzhong basin, Ankang basin, and Weihe basin, serious damage should be caused by the long-period effect of basin of large earthquake in the far field. That magnitude of Wenchuan Earthquake is high, three basins are at the direction where the Wenchuan Earthquake wave propagated, and the epicentre is from 400 to 600km determines that the Wenchuan earthquake has the condition producing long-period effect in the three basins. In addition, the basins have very thick deposits, as well as possible basin edge effect may enhance long period damage. The damage of long-period of water tower results from the resonance between water tower and long-period ground motion.

Mechanical Performance and Design Method of Improved Lead Shear Damper with Long Stroke

The paper presents experimental study on an improved plate lead shear damper with long stroke (ILSD‐LS) which is developed to meet the engineering requirements for high‐rise structures with long periods subjected to the long‐period earthquakes. Finite element analysis is also carried out to investigate the proposed damper. Based on the ideal rigid‐plastic constitutive law of lead, a mechanical model of the ILSD‐LS is established. Compared with ordinary dampers, ILSD‐LS has better damping force, energy dissipation capacity, and stability according to the results of simulation and experiments. The method of calculating damping force is reasonable and accurate. In order to verify the damping effect of ILSD‐LS for the structures with long periods under long‐period ground motions, the nonlinear time history analysis of a typical high‐rise structure with ILSD‐LS is carried out. The numerical results indicate that the seismic responses of the high‐rise structure with ILSD‐LS are significantly reduced when subjected to long‐period ground motion.

Spatial Variation of Long-Period Strong Ground Motion Observed in the Kanto Plain during the 2016 Kumamoto Earthquake

Spatial Variation of Long-Period Strong Ground Motion Observed in the Kanto Plain during the 2016 Kumamoto Earthquake

Retrofit Plan Using Dampers for an Existing High-Rise Building in Tokyo Metropolitan Area Using Maximum Considered Earthquake Ground Motions Consisting of Long-Period Strong Ground Motions and Near-Fault Ground Motions

Retrofit Plan Using Dampers for an Existing High-Rise Building in Tokyo Metropolitan Area Using Maximum Considered Earthquake Ground Motions Consisting of Long-Period Strong Ground Motions and Near-Fault Ground Motions

The Performance of Slender Monuments during the 2015 Gorkha, Nepal, Earthquake

This paper studies damage to a few specific monuments in the Kathmandu Valley that were either partially or completely destroyed during the 2015 Gorkha earthquake. Three of these structures—namely, the Basantapur Column, the Dharahara Tower, and the Narayan Temple—were modeled both analytically using rocking dynamics and computationally using discrete element modeling (DEM). The results emphasize the importance of large low frequency content within the ground motion, demonstrating that the Dharahara Tower could have collapsed due to the primary long-period ground motion pulse alone. In addition, comparison of analytical and computational modeling to the observed response enables evaluation of structural behavior, including discussion of the importance of elastic amplification and column embedment on performance during the earthquake.

Basic characteristic parameters and influencing factors of long-period ground motion records

199 earthquake records with reliable information are selected from the PEER and NIED firstly, and the Seismo Signal software is applied to correct the baseline of original earthquake records. Then the basic characteristics and strength parameters under near-fault/far-field long-period ground motions and common ground motions are compared. Moreover, the influence on basic strength parameters affected by earthquake magnitude, rupture distance (or epicenter distance) and site condition under near-fault/far-field long-period ground motions is analyzed one by one. Study results are obtained as follows: Near-fault earthquake has high amplitude intensity and short strong-shock duration, and its energy release process is concentrated in a short time. A Far-field earthquake has a small peak of acceleration, velocity, displacement and long strong-shock duration, and its energy release process is mild. The strength parameter index PGV/PGA under long-period ground motions is beyond 0.2, and its frequency distribution is concentrated within the low-frequency band (0.1-1.0 Hz) while the frequency distribution of common ground motions is concentrated within a relatively high-frequency band (1.0-2.3 Hz); The strength parameter indexes IA, Eρ, P, IC and CAV under near-fault earthquake are greater than those under far-field earthquake. For a near-fault earthquake, the parameter index PGA decreases, and the strong-shock duration increases with the earthquake magnitude from Mw 6.6 to Mw 7.3, while the parameter index PGA, PGV decreases and PGV/PGA, strong-shock duration increase with the increases of rupture distance. Site-soil condition is the key factor affecting the basic strength parameter index under far-field earthquake, and the PGA, PGV parameter indexes increase under far-field earthquake with the site soil condition from class C to D and E. It is suggested to be related to the effect of filtering out high-frequency components and amplifying low-frequency components in soft site-soil.