Distortion is inherent in recording seismic data. Although some distortion serves a useful purpose, distortion of desirable seismic events decreases resolution thereby reducing the effectiveness of the seismograph as an exploration tool. This paper describes an experimental‐computational technique to determine the distortion introduced by a seismic recording system. The technique utilizes a piezoelectric shaketable to obtain suitable input‐output pairs from which the velocity impulse response of the system is computed. Distortion introduced by the system is compensated by digital filters that are designed in the frequency domain. Nearly complete phase compensation is achieved by designing filters with phase characteristics that closely approximate the negative phase characteristics of the seismic system. Complete amplitude compensation is intentionally averted because of practical considerations. The degree of amplitude compensation deemed feasible is controlled by the relative frequency content of signal and noise. Synthetic examples which simulate field data indicate that approximate compensation filters are effective in removing much of the signal distortion introduced by the seismic recording system without decreasing the signal‐to‐noise ratio.
Abstract
Design details of a portable, light-weight, seismic recording system are presented together with data concerning sensitivity and frequency response. Field procedures and methods are described with emphasis on coupling the hydrophone detector to waves propagating in the glacier ice. Two of the field-recorded signals are reproduced here: the first resulted from a small serac avalanche in the ice fall and the second was produced by an unusual, local source of glacier noise.
abstract
A multi-channel seismic system which records directly on a nine-track synchronous digital tape is described. Low-noise amplifiers with a band-pass of 0.1 to 50 Hz coupled with a 14-bit A to D converter provide the wide-frequency response and dynamic range necessary for high-quality recording of seismic reflection signals from the deep crust.
Electronic Detection of Serac Avalanches and Glacier Noise at Vaughan Lewis Icefall, Alaska