Enhancement of Detection Capabilities at the Brasília Infrasound Station: Brazil's Contribution to the International Monitoring System (IMS) of the Comprehensive Nuclear-Test-Ban Treaty (CTBT)

Abstract

The Brasília Infrasound Station (designated IS09), the only infrasound station in Brazil, is operated by the Seismological Observatory of the University of Brasilia in collaboration with the Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization (PrepCom/CTBTO). Located in the Brasília National Park, the station comprises a four-element array, forming a triangle approximately 2 km aperture with a central element. The inter-distances and the number of array elements are limiting the effectiveness in detecting local and regional events (distances < 1000 km). To overcome this restriction, PrepCom/CTBTO is modernizing the global infrasound network of the International Monitoring System. This initiative aims to standardize and enhance sensitivity by increasing the array's elements from four to eight (or nine). In this study, simulations utilizing the DTK-GPMCC computational tool, involving the addition of five elements to the former IS09, reveal a significant enhancement in the station's performance. Shorter inter-distances between the new elements (ranging from 150 to 900 meters) lead to increased detections and reduced spatial aliasing effects for frequencies above 1 Hz. Analysis of the array response function demonstrated that the gain achieved with the new array is fivefold compared to the previous configuration, besides expanding the frequency bandwidth, thereby allowing the detection of local and regional events. This work also includes the development of a mechanical filter that reduced the amplitude response noise by a factor of 10 between 0.6 and 10 Hz in the employed temporary stations.