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Numerical Integration Methods and Seismic Response Spectra for Single- and Multi-Component Seismic Input
Published in Franklin Y. Cheng, Matrix Analysis of Structural Dynamics, 2017
An earthquake is an oscillatory, sometimes violent movement of the earth’s surface that follows a release of energy in the earth’s crust. This energy can be generated by sudden dislocation of segments in the crust, volcanic eruption, or man-made explosion. Most destructive earthquakes, however, are caused by dislocation of the crust. When subjected to geologic forces from plate tectonics, the crust strains, and the rock in the crust is stressed and stores strain energy. When stress exceeds the rock’s ultimate strength, the rock breaks and quickly moves into new positions. In the process of breaking, strain energy is released and seismic waves are generated. These waves travel from the source of the earthquake, known as the hypocenter or focus, to the surface and underground. The epicenter is the point on the earth’s surface directly above the hypocenter, as shown in Fig. 7.1. An earthquake’s location is commonly described by the geographic position of its epicenter and its focal depth. The focal depth of an earthquake is the distance from epicenter to focus. These terms are illustrated in Fig. 7.1.
Engineering Seismology Overview
Published in Hector Estrada, Luke S. Lee, Introduction to Earthquake Engineering, 2017
The focal depth is used to classify earthquakes as: shallow for focal depths less than 70 km (43 miles), intermediate for focal depths between 70 km (43 miles) and 300 km (186 miles), and deep for focal depths greater than 300 km (186 miles). Focal depths have been known to be as large as 720 km (450 miles). Shallow earthquakes are more destructive than others because the mass of the rock above deeper earthquakes attenuates their shock waves. Shallow earthquakes generally occur near ocean trenches, like coastal California earthquakes, which have focal depths of less than 16 km (10 miles). Most moderate-to-large shallow earthquakes are preceded by smaller quakes, called foreshocks, and followed by smaller quakes called aftershocks. Foreshocks are precursors of the impending fault rupture, while aftershocks result from adjustments to the stress imbalance in the rocks produced during the rupture.
Introduction
Published in George G. Penelis, Andreas J. Kappos, P. E. Pinto, Earthquake-resistant Concrete Structures, 2014
George G. Penelis, Andreas J. Kappos, P. E. Pinto
The potential destructiveness of an earthquake, although partly related to its magnitude, is also a function of other equally important factors, such as the focal depth of the earthquake, the distance from the epicentre, the soil conditions and the mechanical properties of the structures (strength, natural period, ductility and so on). The term intensity of the earthquake is a measure of the consequences that this earthquake has on the people and the structures of a certain area. It is obvious that it is impossible to measure the damage due to an earthquake using a single quantity system. Therefore, the damage is usually qualitatively estimated using empirical intensity scales. The most common macroseismic scales that are used today are the modified Mercalli (MM) scale (Table 2.1) and the Medvedev, Sponheur, Karnik (MSK) scale (Table 2.2), both of which have 12 intensity grades. Figure 2.9 shows the division of Greece into seismic zones (Papaioannou et al., 1994) according to the MM scale. An earthquake has only one magnitude but different intensities from one place to another. The intensity generally attenuates as the distance from the epicentre increases. The soil conditions have a significant effect on the distribution of structural damage. This effect is estimated through so-called microzonation studies.
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 Lushan Ms7.0 earthquake occurred on April 20, 2013 and the epicentre was located at 30°18’N, 103°56’E, in Lushan County, Sichuan Province, China. The focal depth of the earthquake was 13 km. The affected area was the junction of the Qinghai Tibet Plateau and the Sichuan Basin. The Lushan earthquake was caused by a tectonic activity in the Longmenshan fault zone, similar to the 2008 Ms8.0 Wenchuan earthquake. The distance between the epicentres of the Lushan earthquake and the Wenchuan earthquake was approximately 85 km. A total of 196 people were killed, 21 were missing, and 11470 were injured in the Lushan earthquake. The Lushan earthquake affected an area of 12500 km2 and caused a direct economic loss of approximately 185.4 billion yuan. After the earthquake, the Sichuan Province immediately started first-level emergency procedures and sent out an army to carry out emergency rescue work.
Uncertainty Analysis and Spatial Correlation of Ground Motion in the Kanto Basin, Japan
Published in Journal of Earthquake Engineering, 2022
Jinjun Hu, Lei Hu, Hui Zhang, Chaoyue Jin, Zhongwei Wang, Yitian Ding
K-NET and KiK-net are nationwide strong-motion observation networks in Japan that provide high-quality digital strong motion data. These networks provide a good opportunity to study the spatial correlation of peak ground motion and response spectrum. To select the appropriate data set, we collected all the ground motion records of the last 20 years in the Kanto Basin. The earthquake magnitude range is , the focal depth is , and the focal longitude and latitude coordinates are and . The distribution of stations and earthquakes is shown in Fig. 1. The blue triangle and the red triangle represent 87 K-NET and 29 KiK-net stations in the basin, respectively. For the KiK-net data, only the surface ground motions are used.
Multi-level Response Modification Factor Estimation for Steel Moment-Resisting Frames Using Endurance-Time Method
Published in Journal of Earthquake Engineering, 2022
Vahid Mohsenian, Iman Hajirasouliha, Ali Nikkhoo
In order to answer the above questions, the concept of demand response modification factor () is introduced. This parameter greatly depends on the parameters such as ductility, energy absorption capacity, height and vibration period, over-strength, redundancy, number of degrees of freedom as well as the site soil type (Lia and Biggs 1980; Miranda 1991; ATC-19; 1995). However, earthquake magnitude and the focal depth do not considerably affect the “”. In addition, based on the results of previous studies, this factor generally decreases with an increase the height of the buildings (Mohsenian, Nikkhoo, and Hajirasouliha 2019b; Mohsenian, Gharaei-Moghaddam, and Hajirasouliha 2020a; Mohsenian, Padashpour, and Hajirasouliha 2020b). In this study, the response modification factor is derived based on Eq. (2):