The earthquake generally originates deep within the earth at a point on the fault where the stress that produces the slip is a maximum. This point is called the hypocenter or focus and the point on the earth's surface directly above this point is called the epicenter. The main or greatest shock is usually followed by numerous smaller aftershocks. These aftershocks are produced by slippage at other points on the fault or in the fault zone.

Types of earthquake faults

Faults are classified in accordance with the direction and nature of the relative displacement of the earth at the fault plane. Probably the most common type is the strike-slip fault in which the relative fault displacement is mainly horizontal across an essentially vertical fault plane. The great San Andreas fault in California is of the type. Another type is termed a normal fault — when the relative movement is in an upward an downward direction on a nearly vertical fault plane. The great Alaskan earthquake of 1964 was apparently of this type. A less common type is the thrust fault — when the earth is under compressive stress across the fault and the slippage is in an upward and downward direction along an inclined fault plane. The San Fernando earthquake was generated on what has usually been classified as a thrust fault, although there was about as much lateral slippage as up and down slippage due to thrust across the inclined fault plane. Some authorities refer to this combined action as lateral thrust faulting. The compressive strain in the earth of the San Fernando Valley floor just south of the thrust fault was evidenced in many places by buckled sidewalks and asphalt paving.

抗侧向荷载的结构体系

常用的结构体系

若已测出荷载量达数千万磅重，那么在高层建筑设计中就没有多少可以进行极其复杂的构思余地了。确实，较好的高层建筑普遍具有构思简单、表现明晰的特点。

这并不是说没有进行宏观构思的余地。实际上，正是因为有了这种宏观的构思，新奇的高层建筑体系才得以发展，可能更重要的是：几年以前才出现的一些新概念在今天的技术中已经变得平常了。源:自*优尔~·论,文'网·www.youerw.com/

如果忽略一些与建筑材料密切相关的概念不谈，高层建筑里最为常用的结构体系便可分为如下几类：

1． 抗弯矩框架。

2． 支撑框架，包括偏心支撑框架。

3． 剪力墙，包括钢板剪力墙。

4． 筒中框架。

5． 筒中筒结构。

6． 核心交互结构。

7． 框格体系或束筒体系。

特别是由于最近趋向于更复杂的建筑形式，同时也需要增加刚度以抵抗几力和地震力，大多数高层建筑都具有由框架、支撑构架、剪力墙和相关体系相结合而构成的体系。而且，就较高的建筑物而言，大多数都是由交互式构件组成三维陈列。文献综述

将这些构件结合起来的方法正是高层建筑设计方法的本质。其结合方式需要在考虑环境、功能和费用后再发展，以便提供促使建筑发展达到新高度的有效结构。这并不是说富于想象力的结构设计就能够创造出伟大建筑。正相反，有许多例优美的建筑仅得到结构工程师适当的支持就被创造出来了，然而，如果没有天赋甚厚的建筑师的创造力的指导，那么，得以发展的就只能是好的结构，并非是伟大的建筑。无论如何，要想创造出高层建筑真正非凡的设计，两者都需要最好的。

 虽然在文献中通常可以见到有关这七种体系的全面性讨论，但是在这里还值得进一步讨论。设计方法的本质贯穿于整个讨论。设计方法的本质贯穿于整个讨论中。