Site response in Tecoman,Colima, Mexico—II. Determination of subsoil structure and comparison with observations |
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Authors: | Francisco J Chávez-García Juan Tejeda-Jácome |
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Institution: | 1. Instituto de Ingeniería, Universidad Nacional Autónoma de México, Ciudad Universitaria, Coyoacán 04510, México D.F., Mexico;2. Facultad de Ingeniería Civil, Universidad de Colima, Mexico |
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Abstract: | In a companion paper local transfer functions were estimated at Tecoman using earthquake and microtremor data. In this paper, the subsoil structure at this city is investigated using seismic refraction and cross-correlation of noise records as a case study. P- and S-wave refraction profiles were measured at five sites within the city. Standard analysis constrained only very shallow layers. The P-wave refraction deployment was also used to record ambient vibration. These data were processed using an extension of the SPAC (SPatial AutoCorrelation (Aki, 1957) 1]) method; cross-correlation is computed between station pairs and the results are inverted to obtain a phase velocity dispersion curve. Penetration depth was larger than that from the refraction experiments but the shear-wave velocity of the basement could not be determined. For this reason, additional microtremor measurements were made using broad band seismometers with a larger spacing between stations. The results allowed to constrain the shear-wave velocity of the basement. Site amplification computed for the final profiles compare well with observed ground motion amplification at Tecoman. The case of Tecoman illustrates that even a simple subsoil structure may require crossing data from different experiments to correctly constrain site effects. |
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Keywords: | Subsoil exploration Seismic refraction Microtremors SPAC method |
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