%0 Journal Article %1 braun_etal:2004 %A Braun, Thomas %A Schweitzer, Johannes %A Azzara, Riccardo M. %A Piccinini, Davide %A Cocco, Massimo %A Boschi, Enzo %D 2004 %J Annals of Geophysics %K geophysics seismology %N 5 %P 1557--1568 %R 10.4401/ag-3359 %T Results from the temporary installation of a small aperture seismic array in the Central Appennines and its merits for local event detection and location capabilities %U http://www.annalsofgeophysics.eu/index.php/annals/article/view/3359 %V 47 %X In order to evaluate the detection and localisation improvement of a small aperture array in the Northern Apennines, we installed an irregularly spaced test configuration in the vicinity of Città di Castello (CDC) for a period of two weeks. The experimental array consisted of nine 3-component stations with inter-station distances between 150 m and 2200 m. Seismic data were digitised at 125 Hz and telemetered to a mobile acquisition, processing and storage centre. The data could only be recorded in trigger mode. The peculiarity of the test array installation was the exclusive use of 3-component sensors at all array sites, which also allowed beamforming for S-phases on the horizontal components. Since the altitudes of the single array sites differed considerably among each other, for f-k analysis and beamforming an elevation correction was included. During the two weeks of operation about 20 local earthquakes with magnitudes ML<2.6, 1 regional, and several teleseismic events were recorded. In addition to these events, the array occasionally triggered on coherent noise-signals generated by local industrial activity. The data analysis was performed by means of f-k analysis and beamforming, providing wavenumber characteristics of the incident plane wave. Typical apparent velocities were determined to be 4.8 km/s and 6 km/s for Pg-phases and \~10 km/s for Pn-phases. We observed local seismic events, which occurred just beneath the array. In these cases wavefronts with unusual high apparent velocities, similar to those found for the Pn-phase, were observed. Since no continuously recorded array data were available, we extrapolated the lower detection magnitude threshold as a result of the SNR improvement due to array beamforming. Compared to the actual detection threshold of MT \~1.6 reached by the national seismic network in this area, a nine element array would improve this value up to MT \~0.8.

@article{braun_etal:2004, abstract = {In order to evaluate the detection and localisation improvement of a small aperture array in the Northern Apennines, we installed an irregularly spaced test configuration in the vicinity of Citt\`{a} di Castello (CDC) for a period of two weeks. The experimental array consisted of nine 3-component stations with inter-station distances between 150 m and 2200 m. Seismic data were digitised at 125 Hz and telemetered to a mobile acquisition, processing and storage centre. The data could only be recorded in trigger mode. The peculiarity of the test array installation was the exclusive use of 3-component sensors at all array sites, which also allowed beamforming for S-phases on the horizontal components. Since the altitudes of the single array sites differed considerably among each other, for f-k analysis and beamforming an elevation correction was included. During the two weeks of operation about 20 local earthquakes with magnitudes ML<2.6, 1 regional, and several teleseismic events were recorded. In addition to these events, the array occasionally triggered on coherent noise-signals generated by local industrial activity. The data analysis was performed by means of f-k analysis and beamforming, providing wavenumber characteristics of the incident plane wave. Typical apparent velocities were determined to be 4.8 km/s and 6 km/s for Pg-phases and \~{}10 km/s for Pn-phases. We observed local seismic events, which occurred just beneath the array. In these cases wavefronts with unusual high apparent velocities, similar to those found for the Pn-phase, were observed. Since no continuously recorded array data were available, we extrapolated the lower detection magnitude threshold as a result of the SNR improvement due to array beamforming. Compared to the actual detection threshold of MT \~{}1.6 reached by the national seismic network in this area, a nine element array would improve this value up to MT \~{}0.8.}, added-at = {2012-09-01T13:08:21.000+0200}, author = {Braun, Thomas and Schweitzer, Johannes and Azzara, Riccardo M. and Piccinini, Davide and Cocco, Massimo and Boschi, Enzo}, biburl = {https://www.bibsonomy.org/bibtex/28bf78c779fd062e9713ffa1be6a5fca5/nilsma}, doi = {10.4401/ag-3359}, interhash = {f14d5a5c173303e317d1dd4fd2a7ea3c}, intrahash = {8bf78c779fd062e9713ffa1be6a5fca5}, journal = {Annals of Geophysics}, keywords = {geophysics seismology}, number = 5, pages = {1557--1568}, timestamp = {2021-02-09T13:23:09.000+0100}, title = {Results from the temporary installation of a small aperture seismic array in the Central Appennines and its merits for local event detection and location capabilities}, url = {http://www.annalsofgeophysics.eu/index.php/annals/article/view/3359}, volume = 47, year = 2004 }