The Spectral Characteristics of Seismic Noise Recorded in an Urban Environment

Abstract

Summary “This paper describes a test conducted to identify the characteristics of the major sources of noise for urban seismic surveys. The strongest source of noise was mechanical equipment, although it was intermittent and restricted to a relatively small bandwidth centred on 75 Hz. Traffic-related noise was also high, with a bandwidth (10-25 Hz) within that typically of interest for seismic surveys, although it did decrease during the late evening/early morning. Aircraft resulted in short (∼1 minute) wide bandwidth (30-200 Hz) bursts of noise. We found no relationship with wind, but this is probably a result of the strength of the other sources and the relatively low wind speeds observed. Electrical noise was observed with the amplitude and frequency (∼50 Hz) varying during the study period. Based on these results we recommend that: acquisition should be carried out during the late night/early morning; receiver locations should be chosen to avoid sources of mechanical and electrical noise; cables should be as short as possible to avoid electrical noise. Although nodal systems for urban surveys are logistically advantageous some degree of real-time quality control must be in place to ensure that records are not acquired when high-amplitude, short-duration noise (e.g. from aircraft).”