A Regional Seismic Array of Three-Component Stations in Central Saudi Arabia

Abstract

Seismic arrays are used to enhance signals and suppress noise as well as to estimate the slowness and azimuth of signals. Seismic monitoring traditionally has relied upon seismic arrays to reduce detection (magnitude) thresholds by increasing signal-to-noise ratios (SNR) and to contribute to event formation by improving phase identification and association. A seismic array differs from a local network of seismic stations mainly by the techniques used for data analysis. In principle, a network of seismic stations can be used as an array, and data from an array can be analyzed the same as from a network. However, most array processing techniques require high signal coherency across the array, and this puts important constraints on the array geometry, spatial extent, and data quality. Furthermore, proper analysis of array data is dependent on a stable, highly precise relative timing of all array elements. This is required because the measurement of (usually very small) time differences in the arrival of seismic signals between the different sensors plays an important role in all array processing techniques. The Department of Geology of King Saud University (KSU) has established a small-aperture (∼3.5 km) three-component seismic array in central Saudi Arabia at a hard rock site on the Arabian shield (Figure 1A). The facility consists of well-constructed vaults in hard rock outcrops in a region that has very low background noise. The deployed equipment consists of a broadband three-component sensor (STS-2) at the center element and eight short-period three-component sensors at the outlying elements (Figure 1B). The objectives of this deployment are to provide data for research into three-component seismic array processing and structural studies and are not related to any real-time monitoring efforts ( e.g. , the International Monitoring System). Specifically, the array project is intended to improve constraints on the structure and physical state of …