Introduction

Earthquakes are consequence of the interaction between the tectonic plates that the earth's lithosphere is divided in, which are in contact to each other and move in different directions.

The origin of the earthquakes in Nicaragua is the subduction of the Cocos plate under the Caribbean plate. As a consequence, seismicity in Nicaragua is more intense in the Pacific region, where most of the population is concentrated. Therefore earthquakes are capable to produce great damages in this area, as it has actually happened several times in the history of the country.

Of major influence on damages caused by earthquakes is the soil behaviour, because it supports the structures and is transmitting agent of the seismic excitement, and in this way it induces forces and displacements in all kind of structures, besides affecting the structure of the soil itself.

Ground surface movement characteristics depend on the dynamic properties of the materials present along the routes through which the seismic waves travel from the focus, the local geologic conditions at the site under study inclusive. This is because the soil operates as a filter, so that it adjusts some characteristics from the wave to its own dynamic properties, with amplification or attenuation effects on the movements, in combination with other factors, such as the thickness of the soil, and the amplitude and frequency of the original movements.

The soil response to earthquakes, expressed as the amplitude of accelerations, in combination with its frequency components, is properly represented by means of an acceleration spectrum showing the maximum accelerations induced by the seismic movement in single degree of freedom oscillators with fundamental periods varying from zero to several seconds.

Its most important application is the calculation of the maximum dynamic lateral force acting upon a structure during an earthquake.

Response Spectra in Managua, Nicaragua

Introduction