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The new accelerograph network for Santa Fe De Bogota, Colombia and implications for microzonation |
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| Authors: | Anibal Ojeda Samuel Martinez Maria Bermudez Kuvvet Atakan |
| Institution: | a Institute of Solid Earth Physics, University of Bergen, Allégaten 41, N-5007, Bergen, Norway b Instituto de Investigación e Información Geocientífica, Minero-Ambiental y Nuclear, INGEOMINAS, Diagonal 53 # 34-53, Santafé de Bogotá, Colombia |
| Abstract: | The new accelerographic network of Santa Fe de Bogotá is composed of 29 three-component stations with sensors at the surface and three additional six-component borehole stations with three sensors at the surface and three at depth (115, 126 and 184 m). In total, 32 stations have been operative in the metropolitan area of Bogotá since 1999. During this period of time, a significant number of weak motion are recorded and used for a preliminary analysis of local site effects. Using the SH-wave response spectra we verify the behavior of the different seismic zones proposed by the previous microzonation study of the city. A comparison between normalized SH-wave response spectra and the normalized design spectra for each zone clearly depicts that parts of the design spectra should be revised, as well as the boundaries between different zones may require some changes. The spectral amplification levels reach up to a factor of 5. The predominant periods obtained by the amplification spectra in different stations in the city, show variability from 0.3 to 3.0 s. A comparison is also made between the predominant periods obtained using H/V spectral ratios of microtremors and those using weak motion. In general, microtremors tend to predict slightly lower values of dominant periods than those calculated by the weak motion spectra. However, there is a general correlation between the two data sets. Using the data recorded by one of the borehole station, an equivalent linear seismic response analysis was conducted. The modeled and recorded response spectra show similarities in period peaks, however, the modeled soil amplification is underestimated for periods less than 0.8 s. Since the available record is weak motion which represents mostly the linear response of the soils, further analysis is required. |
| Keywords: | Accelerographic Network Borehole accelerometers Soil response modeling Microtremors Bogotá Colombia |
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