Horizontal Ground Displacements Research Articles

Simple approach to obtain ground amplification motion of surface soil deposits with a radical change of depth

Earthquake observations at different sites within alluvial soil deposits have demonstrated that the motion of buried underground structures closely follows that of the surrounding soil. Therefore, it is usual in a seismic design process to apply free-field ground displacements through Winkler-type soil springs to an underground structure to evaluate stress patterns induced within its structural members. Using a simplified approach, this paper provides a clear understanding of resonant horizontal ground displacement of and strain in a surface soil deposit with a radical change of depth and of where they occur.Key words: simple approach, seismic design, earthquake, resonance, underground structures.

Evaluation of lateral spreading using artificial neural networks

Liquefaction-induced lateral spreading has been a very damaging type of ground failure during past strong earthquakes. Although the occurrence of liquefaction and lateral spreading at a given site can be predicted, the methods to estimate the magnitude of resulting deformations is still the focus of many researches. In this study, using professional software called STATISTICA, a neural network model is developed to predict the horizontal ground displacement in both ground slope and free face conditions due to liquefaction-induced lateral spreading. The database, implemented in this work, is the one compiled by Youd and his colleagues in their revised MLR model. The influence of seismological, topographical and geotechnical parameters on resulting deformations and their degrees of importance are investigated. The results indicate that the model presented in this research serves as a reliable tool to predict horizontal ground displacement. The correlation factors and the root mean square errors obtained in this model show the superiority of the Neural Network approach over the traditional regression analysis.

Improving Structural Response to Permanent Ground Displacement

Structural damage due to permanent ground displacement is a common occurrence during seismic events. Light-frame structures, typical of residential construction, seem both particularly susceptible to and easily reinforced against moderate ground failure. Because the foundations of these structures typically receive little or no engineering attention, a spreadsheet capable of quickly checking the capacity of a foundation to resist anticipated lateral and vertical displacement might encourage residential designers to require more appropriate foundation cross sections. Unfortunately, a simple strengthening of the foundation elements is generally insufficient. Designs must also eliminate noncontinuous interior bearing supports, which are highly vulnerable to horizontal ground displacement. Site remediation, including the installation of free-draining base materials, may also be needed to enable placement of the footer at or near grade. Finally, we should strive for more efficient designs: smaller, more compac...

A neural network model for liquefaction-induced horizontal ground displacement

The horizontal ground displacement generated by seismically induced liquefaction is known to produce significant damage to engineered structures. A backpropagation neural network model is developed to predict the horizontal ground displacements. A large database containing the case histories of lateral spreads observed in eight major earthquakes is used. The results of this study indicate that the neural network model serves as a reliable and simple predictive tool for the amount of horizontal ground displacement. As more data become available, the model itself can be improved to make more accurate displacement prediction for a wider range of earthquake and site conditions.

Near-shore ocean wave measurement using a very low frequency folded pendulum

A very low frequency folded pendulum has been used to measure the horizontal ground displacement at a site near the Indian Ocean. The results show a close correlation between the displacement and ocean wave height. This suggests that such a pendulum can provide a simple land-based wave measurement system and, in an array, can provide tomographic images of the wave height along extended shorelines.

Empirical Prediction of Liquefaction-Induced Lateral Spread

This paper presents an empirical model for predicting the amount of horizontal ground displacement resulting from liquefaction-induced lateral spread. The model was developed from multiple linear regression analyses of U.S. and Japanese case histories of lateral spread. Two general types of lateral spread are differentiated herein: (1) lateral spread towards a free face and (2) lateral spread down gentle ground slopes where a free face is absent. Ground displacement associated with free-face conditions is strongly correlated with the height of and distance from the free face. Similarly, ground displacement associated with ground slope conditions is strongly correlated with the slope of the ground surface. Other factors such as earthquake magnitude, distance from the seismic energy source, thickness of the liquefiable sediments, and the fines content and particle size of those sediments also are correlated with ground displacement. Because the final model presented herein has been adjusted for a wider range of seismic and site conditions than used in previously proposed empirical models, it is more general and will provide better results, if properly applied.

Behavior of near-source peak horizontal and vertical ground motions over SMART-1 Array, Taiwan

Abstract Over 700 accelerograms recorded from 12 earthquakes in northeast Taiwan have been analyzed for investigating the behavior of vertical and horizontal peak and spectral ground motion in the near-source region. Peak horizontal and vertical ground acceleration (PGA), velocity (PGV), and displacement (PGD) in the range of engineering interest have been subjected to a two-step nonlinear regression procedure in terms of magnitude and hypocentral distance. In comparison with a number of other studies of global PGA observations, our predictions show lower far-field attenuation, lower near-source amplitudes, higher magnitude saturation for the vertical component, lower magnitude saturation for the horizontal component, and higher magnitude scaling. The 2 / 3 ratio of vertical to horizontal ground motion, commonly used in engineering applications, may be unconservative in the very near-field for high-frequency ground motion. It falls below 1 / 2 at distances greater than 50 km. The same ratio for PGV and PGD tends to increase with distance, the latter at a faster rate. For SMART-1 data the major source of uncertainty appears to be inter-event rather than intra-event randomness. The predominance of the inter-event uncertainty in ground motions near the source is expected to be a characteristic of all dense arrays.

Building Response to Excavation‐Induced Settlement

Analytic models and field data are used to develop procedures to evaluate the tolerance of brick‐bearing‐wall and small frame structures to the ground displacements that develop during opencutting and tunneling. The role of horizontal and vertical ground displacements are discussed and the effects of grade beams, building orientation and building location relative to excavation are examined. Case studies of structures adjacent to opencuts and tunnels are used to verify procedures for estimating potential for structures adjacent to excavations to sustain damage.

Relevance of Afar seismicity and volcanism to the mechanics of accreting plate boundaries

The seismicity, the horizontal and vertical ground displacements, and the geometry of active faults and fissures during the seismic and volcanic events of November 1978 in Southern Afar are consistent with an accentuation of the pre-existing topography of the Ghoubbet–Asal rift. The zone of sizeable permanent deformation is restricted to several hundred square kilometres. Elastic rebound models seem to explain the observations. The events occurred in the vicinity of the suggested location of the tip of a lithospheric crack which may have been responsible for the progressive opening of the western Gulf of Aden.

Waves Generated by Horizontal Oscillations in Bays

The waves generated in a coastal basin by the horizontal components of ground motion (e.g., during an earthquake) are studied. Special emphasis is placed on the resonant response of the basin of arbitrary boundary shape and uniform depth for idealized motions. An integral equation technique with numerical solution is presented. Results show that the waves generated at resonant frequencies are significant in a semi-enclosed coastal basin with horizontal ground displacement amplitudes typical of large earthquakes.