Data processing of recorded motion at seven-story hotel in Van Nuys, California during Northridge earthquake 1994

In this paper, we present digital signal processing of recorded earthquake motions. The paper describes all the techniques used for the whole process of signal processing. From the measured displacements at the ground (first) floor and at the roof of typical seven-story building and their processing, we can get valuable information about the strong ground shaking and the structural response. In many cases, Fourier transform from time to frequency domain provides more information about the signal. First, using FFT, we transform the measured displacements at basement and at the roof from time to frequency domain. The transformation at basement level, Fb(f), gives us valuable information about the frequency content of the strong ground motion. On the other side, the ratio of the Fourier transform at the roof and at the basement gives us so called transfer function, which reveals the natural frequencies of the building. To accomplish the above tasks, we use the software Labview. Labview enables constructing graphical environment that represents design and analysis of a DSP system in a very minor compared to text – based programming environments. The graphical environment in Labview consists of VI (virtual instrument) which is represented by a Front Panel (FP) and Block Diagram (BD). The BD incorporates the graphical code and the FP provides the user – interface of the program. The Vis is modular and independent, which means they can be run by itself.