Spiral-arm seismic arrays

Seismic arrays havemany uses for signal enhancement, from surface-wave characterization of the near surface to teleseismic detection in the context of monitoring nuclear tests. Many variants of the geometrical configuration of stations have been used with the objective of maximizing potential resolution of the incoming wavefronts direction of arrival. Aversatile class of array configurations, with good resolution properties, can be constructed with multiple spiral arms. The array response is comparablewith the same number of full circles, but with far fewer stations and is robust to minor position changes in emplacement. The desirable properties of the spiral-arm arrays are illustrated for a permanent array in the Precambrian Pilbara craton in northwestern Australia and for a temporary array on ancient sediments in southern Queensland, Australia. In each case, the practical array response is very good and matches the theoretical expectations. The spiral-arm configuration allows the deployment of relatively large aperture arrays with a limited number of stations, which is advantageous in a broad range of seismic applications, including near-surface characterization.