Papers by Keyword: Strong Ground Motion

Abstract: In recent years, numerical simulation of strong ground motion has been well developed with the progress of earthquake science, and it has become an important approach to estimate strong ground motion. In this research, we improve the original program of EXSIM and the modified program named MEXSIM to calculate the Peak Ground Acceleration (PGA) and Peak Ground Velocity (PGV) which is essential for seismic hazard assessment of Hengshui area. Considering the impact of V₃₀ (the average shear-velocity down to 30 m) we calculate the impact of two scenario earthquakes from the rupture processes of Hengshui fault and Qianmotou fault. Comparing to Qianmotou scenario earthquake, if the instability fault is Hengshui fault, the PGA and PGV could be 200-360gal and 20-35cm/s respectively in Hengshui city.

Abstract: In order to study the characteristics of ground motions at the two dam sites damaged during the great Wenchuan earthquake in 2008, the motions at two observation stations nearby are synthesized in this paper. 30 finite fault based hybrid source models of the great Wenchuan earthquake with magnitude 8.0 is built. The global and local parameters are both generated from the truncated Normal distribution with mean and standard deviation values estimated by a set of semi-experiential calibration laws and from the regional seismo-tectonics, structure of the crust, and seismicity. A representative source model is then chosen from the corresponding response spectrum mostly close to the average one. The result motions are presented, and the characteristics of the time histories, response spectra and the peak accelerations are quite close to the recordings.

Abstract: The ground motions on two dam sites during the great Wenchuan earthquake with magnitude 8.0, motions are synthesized from 30 finite fault based hybrid source models and inversed regional parameters of source spectrum and motion attenuation. The results show that the peak ground acceleration values are less than those estimated directly from the Intensities Ⅹ and Ⅺ at the two sites, with mean values 259 and 716 gals. The motion at Shapai is much stronger than that at Zipingpu, and the spectrum is also wider than the latter, but the corresponding duration is shorter during the earthquake.

Abstract: The influence of vibration on surrounding structures is one of the most important factors considered during blasting demolition of high-rise buildings in metropolitan regions. In the controlled blasting demolition of a 22-story RC building in Kunming, several accelerograms on ground surface were observed. Based on analyses of vertical peak ground velocity which is normally used in blasting vibration evaluation, and horizontal spectral acceleration which is frequently used in earthquake engineering, the ground motion caused by building collapse was evaluated. The results indicated that the adoptive vibration decreasing measures had a good effect, and the slight damages of two nearby buildings could not be due to abnormal strong ground motion caused by collapse.

Abstract: Based on 266 strong ground motions from 15 significant earthquakes in California of America, the attenuation law of hysteretic spectra is established by using nonlinear regression method, and the effects of site class and ductility level on the hysteretic spectra constructed from the attenuation relationship are discussed in the paper. The results show that the site has significant effects on hysteretic energy spectra, and the more soft the site is, the more hysteretic energy structure will suffer from earthquake. Moreover, for ductility level scaled by ductility factor, the results show that structure with greater ductility factor can dissipate more input energy from the earthquake by means of the plastic deformation. The up limit design value of ductility factor for a structure is proposed as 4 because there is little difference between the hysteretic energy demand for ductility factor 4 and larger values. The hysteretic energy demand for structures at a given site in scenario earthquakes can be evaluated according to the results of the paper.

Abstract: Accelerograms recorded by accelerographs are of fundamental importance in seismic engineering, forming the basis of ground shaking employed for anti-seismic design. By analysis on the general solution of wave equation, this article demonstrated that the ground tilting is related with the ground velocity and displacement histories. For accelerograms with co-seismic permanent displacement, this ground tilting would be presented continuously with a tiny constant value after severe shock terminated. The co-seismic permanent displacement might be the reason of baseline drift, which caused that the real velocity and displacement histories could not be achieved by the direct integration of accelerograms. A baseline correction method was also proposed based on this finding, with which the ground velocity and displacement histories of several near-fault stations were given. But this proposed method still needed improvement because of the divergence in its iterative process.

Abstract: Dynamic equations of pendulums in strong motion instrument are analyzed. The equations imply horizontal recordings may be significantly influenced by ground surface tilt while the effects can be ignored for vertical recordings. The difference causes anomaly of horizontal to vertical Fourier amplitude spectra ratio, which is used to identify affected low frequency range.. The low frequency filter based on spectral ratio was employed to estimate the coseismic ground surface tilts in Wenchuan Ms8.0 earthquake. Results show the ground surface tilts are generally less than 1 degree and mainly happened within 30 kilometers to fault surface rupture traces, while rarely discovered in area outside 100 km and squared horizontal peak accelerations less than 200 cm/s². Comparison of ground surface tilts under spectral ratio being 2 and 4, shows ground surface tilting amplitudes usually increased when spectral ratio is decreased, but residual ground surface tilts have small change.

Abstract: Considering the uncertainty and the time variation of frequency contents of real seismic excitation, a new versatile stochastic strong ground motion model named general stochastic seismic ground motion (GSSGM) model is presented in this paper. Some essential assumptions for the earthquake process used in this paper are first given. The intensity and energy of the target seismic ground motion are used to determine the model parameters. The frequency contents are demanded to be agreed with the main characteristics of the target ground motions. The GSSGM model is appropriate to simulate the stationary, intensity non-stationary and fully non-stationary stochastic processes. Additionally, a simple non-stationary stochastic seismic response analysis procedure based on the GSSGM model and the pseudo excitation theory is put forward. The presented non-stationary stochastic seismic response analysis procedure is later applied in the seismic response analysis of a real homogeneous earth dam. The non-stationary analysis results display the effects of non-stationarity on the seismic response of the dam and reflect the main phenomena of dynamic embankment-foundation interaction. The results indicate that the GSSGM model and the presented analysis procedure are effective.

Abstract: It has always been concerned about seismic motion and building materials near faults, but it still remains as an uncertain problem due to insufficiency of case study and information. The paper presents the main cases of seismic disaster by field investigations of M8.0 Wenchuan earthquake, on the relationship among earthquake faults, ground motion and earthquake disasters near fault zone, i.e. the forms of structural damage are very complex in the fault areas, with main forms of shear failure and damage of tension and compression. The brittle materials such as reinforced concrete and masonry materials are prone to partial brittle fracture, and main forms are composed of up and down shake and surface ruptures. The brittle materials are prone to tension and compression damage. By using qualified materials, following building codes, the constructions in urban areas showed good seismic performance. Survey results showed that the framework and the structure of the steel and wood that use the flexible materials with flexible structures possess good seismic performance.