Filter design of eight order butterworth infinite impulse response for earthquake sign

Abstract

Filtering is an important procedure in modern seismology analysis to obtain the best quality result in advanced process. There are many programs of signal processing consisting of signal filtering features, for example Seismic Analysis Code (SAC). Unfortunately, the basic mathematical equations in signal processing are not explained in detail. This research has purposes to design a Butterworth filter and to examine the influence of increasing order on the arrival time, polarity, and first motion amplitude of seismic wave. Filter design was done by computing eight order lowpass analog transfer functions and transforming them into lowpass, highpass, and bandpass digital using bilinear transformation so we have recursive and causal filters. The designed filter was then validated by the result of SAC. Based on the research we have found that the method and algorithm of designed filter are consistent with SAC. Increasing filter order can clarify the phases of seismic wave positions. On the other hand, it can i...