INTRODUCTION

We address the puzzle of seismic polarity. Why do we rarely observe it clearly and how could we be more systematic about trying to observe polarity? This puzzle will lead us to long prediction-error filters. Being long, they require many data samples. If such a filter is nonstationary, we might have an inadequate number of fitting equations. Then we need regularization. Here we consider some examples and consider an efficient way to regularize the filter estimation.