Large-Array Signal and Noise Analysis. Equalization Studies.

摘要

The report reviews the following four tasks pertaining to response equalization problems: evaluating a new technique using large signals for equalizing seismometers; examining the concept of designing regional equalization filters for subarray outputs; analyzing statistically the coefficients used to equalize the noise data; and developing the theory to incorporate statistical phase fluctuations in the correlation statistics. The technique using large signals to equalize seismometers is based on finding the minimum-phase filters which equalize the signal power spectra for a set of seismometers. Four sets of filters are designed to equalize eight channels to the reference channel. The reference channel is subtracted from the other channels before and after equalization and the error traces compared. The equalized signals are significantly more similar for the first few cycles of the arrival. After the first few cycles, there is little difference between the two sets of signals - probably because of interfering scattered energy. Average Levinson filters are designed for three subarray outputs, using three events from the Aleutian Islands region. (Author)