Noise in urban land seismic surveys

Land seismic surveys are most often acquired in remote areas, thus the predominant noise source is often the wind. In urban areas, however, noise sources abound, including electrical cables, mechanical equipment, aircraft, and traffic. We recorded seismic data continuously over three days at a test site located in suburban Perth, Western Australia (32° 0’ 40”S, 115° 53’ 22”E). and found that the highest amplitude noise was mechanical (centred on 75 Hz), but the most consistent noise was traffic related (10-25 Hz). Electrical noise was identified but given its moderate amplitude and relatively consistent frequency it should be easily removed in processing. Aircraft flying over the test site resulted in moderately high level of noise with a wide bandwidth (30-200 Hz) but the noise generally lasted only a minute. Based on these results we recommend that: acquisition should be carried out during the late night/early morning; receiver locations should be chosen with care to avoid sources of noise; analogue cabling should be as short as possible to avoid electrical noise; real-time QC should be in place to identify short-duration high-amplitude noise periods during which acquisition should cease.