Relationship of pore pressure with power and intensities of quakes

Correlaciones de la presión de poros con potencia e intensidades del sismo

Abstract

In this article, the intensity of the strong sector of the accelerogram and the Arias intensity are considered representatives of the power of the earthqueke to cause damage. In this context damage is consider the excess pore water pressure to produce liquefaction in sands. Power acceleration of strong part of the accelerogram is defined as the average of accelerarion square values within the strong part, which becomes the intensity when multiplied by the duration of the strong part. The Arias intensity utilizes the average of all acceleration values in the acceleration record multiplied by the total duration and other factors to transform it into the energy dissipated by a single degree of freedom oscilator. Both intensities are well correlated and one is a fraction of the other one. However, an important limitation to measure the power and the intensity of the strong sector of the accelerogram is the definition of such strong part itself. In this article a new simplified method is presented to define the strong sector of the accelerogram. In this article it is also evaluated if the pore pressure build up and liquefaction occur only during the strong sector of the accelerogram using a software available for research on ground response during earthquakes. It is demonstrated that efectively, the increase of pore water pressure occurs during the strong part of the record, which also indicates that it is the acceleration power the resonsible of such behavior and not intensity. It is also demonstrated that pore water pressure build up is identical at the end of the strong sector with that at the end of the quake with Arias intensity.

Keywords: dynamic response, geotechnical profile, pore water pressure, strong part of accelerogram intensity, Arias intensity, intensity amplification, power of acceleration.