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Introduction
Published in Sreevalsa Kolathayar, T.G. Sitharam, Earthquake Hazard Assessment, 2018
Sreevalsa Kolathayar, T.G. Sitharam
An earthquake is a sudden vibration of the earth caused by an immediate release of energy during rupture of rock that creates seismic waves. The place within the earth’s crust where an earthquake originates is called the hypocenter, or focus, of the earthquake (Fig. 1.1). The point vertically above this, on the surface of the earth, is known as the earthquake’s epicenter.
Dynamic proper ties of soil
Published in Hsai-Yang Fang, John L. Daniels, Introductory Geotechnical Engineering, 2017
Hsai-Yang Fang, John L. Daniels
Hypocenter and epicenter: The origin of an earthquake in the Earth’s crust or upper mantle is the “focus,” or sometimes referred to as the hypocenter. The epicenter is defined as the point on the Earth’s surface directly above the focus or hypocenter as illustrated in Figure 11.4. The epicenter is that point on the Earth’s surface that is intersected by a radial line drawn from the center of the Earth and passing through the hypocenter. When an energy release occurs at the hypocenter this energy is dissipated in the form of waves that travel through the crustal media to the surface and create a dynamic oscillatory motion at the surface. Two groups of seismic waves are generally named; (a) body waves and (b) surface waves.
Elements of dam engineering
Published in P. Novak, A.I.B. Moffat, C. Nalluri, R. Narayanan, Hydraulic Structures, 2017
P. Novak, A.I.B. Moffat, C. Nalluri, R. Narayanan
Evaluation of seismic risk for an important dam requires identification of the regional geological structure, with particular attention being paid to fault complexes. Activity or inactivity within recent geological history will require to be established from study of historical records and field reconnaissance. If historical records of apparent epicentres can be matched to key geological structures it is possible to make a probabilistic assessment of seismic risk in terms of specific intensities of seismic event. In the absence of reliable historical information it will be necessary to monitor microseismic activity as a basis for the probabilistic prediction of major seismic events. Either process is imprecise and will at best provide only an estimate of the order of seismic risk. As a measure of reassurance over seismicity it has been suggested that most well-engineered dams on a competent foundation can accept a moderate seismic event, with peak accelerations in excess of 0.2g, without fatal damage. Dams constructed with or on low-density saturated cohesionless soils, i.e. silts or sands, are, however, at some risk of failure in the event of seismic disturbance due to porewater pressure buildup and liquefaction with consequent loss of stability.
A spatial evaluation method for earthquake disaster using optimized BP neural network model
Published in Geomatics, Natural Hazards and Risk, 2023
Hanxu Zhou, Ailan Che, Xianghua Shuai, Yi Zhang
The distance to the epicentre is used to measure the relative distance between the study region and the epicentre. In previous studies, it was found that with an increase in distance to the epicentre, the impacts of earthquake disasters were gradually reduced. The distance to the epicentre was calculated using the ArcMap software buffers (Figure 3(c)).
Reconnaissance Report on Geotechnical Engineering Aspect of the 2015 Gorkha, Nepal, Earthquake
Published in Journal of Earthquake Engineering, 2019
The earthquake shaking intensity depends on not only the magnitude and distance to the epicenter but also the local soil conditions and topography. The effects of local soils and topography on the geotechnical or structural damages were manifest during the reconnaissance. This section illustrates case studies in the areas where these effects were observed.