ESTIMATION OF SITE RESPONSE CHARACTERISTICS AT FOUR SITES OF SEISMIC MONITORING NETWORK IN PAKISTAN
Abstract
The widely used approach proposed by Nakamura was adopted for the assessment of site response characteristic parameters namely; resonance frequency and amplification factor that are important for seismic hazard assessment and yield assessment in case of explosions. The technique involves calculation of spectral ratios of the horizontal to vertical components (H/V) of ambient noise recorded at sites of seismic monitoring network. The resonant frequency and amplification factor for four selected sites were estimated. The ambient noise at these sites have ground amplification factor of 1.2 – 3.75 over the frequency range of 1.05 – 4.90 Hz. The normalized spectral ratio reflects the dominant frequency and relative amplification of the selected sites. The amplification factors estimated for Sakesar and Fatehjang sites are higher than Nilore and Nurpur sites. These results are fully supported by the fact that calculated magnitudes of seismic events (local, regional and teleseismic) recorded at Sakesar and Fatehjang show higher values as compared to Nilore and Nurpur sites.References
S. Bonnefoy-Claudet, C. Cornou, P.-Y. Bard, F. Cotton, P. Moczo, J. Kristek and D. Fäh, Geophysical Journal International, 167, No. 2 (2006) 827.
Sesame, Guidelines for the implantation of the H/V spectral ratio technique on ambient vibrations, measurements, processing and interpretation, European Commission Res-earch General Directorate project no. EVG1-CT-2000-00026 (2004).
Guo Xun, Y. L. Wong and Y. Yifan, Earthquake Engineering and Engineering Vibration, 1, No. 1 (2002) 45.
A. Köhler, M. Ohrnberger, F. Scherbaum, M. Wathelet and C. Cornou, Geophysical Journal International, 168, No. 2 (2007) 827.
K. Kanai and T. Tanaka, Bulletin of the Earthquake Research Institute 39 (1961) 97.
K. Konno and T. Ohmachi, Bulletin of the Seismological Society of America, 88, No. 1 (1998) 228.
K. Kudo,. Practical estimates of site response. State-of-art report. Proceedings of the fifth International Conference on Seismic Zonation. Nice, France (1995) 1878.
C. Lachet and P.Y. Bard, Journal of Physics of the Earth, 42, No. 4 (1994) 377.
J. Lermo and F. J. Chavez-Garcia, Bulletin of the Seismological Society of America, 83, No. 5 (1993) 1574.
J. Lermo and F. J. Chavez-Garcia, Bulletin of the Seismological Society of America, 84, No. 5, (1994) 1350.
M. Massa, G. Ferretti, A. Cevasco, L. Isella, and C. Eva, Earthquake, Spectra, 20 (1989) S107.
Y. Nakamura, Quarterly Report Railway Tech. Res. Inst. 30, No. 1 (1989) 25.
Y. Nakamura, Real-time information systems for hazards mitigation. Proceedings of the 11th World Conference on Earthquake Engineering. Acapulco, Mexico (1996).
Y. Nakamura, Clear identification of fundamental idea of Nakamura’s technique and its applications. Proceedings of the 12th World Conference on Earthquake Engineering. Auckland, New Zealand (2000).
M. Nogoshi and T. Igarashi, Journal of Seismological Society of Japan, 24 (1971) 26 (in Japanese with English abstract).
S. Parolai, S. M. Richwalski, C. Milkereit and P. Bormann, Tectonophysics 390 (2004).
K. Wakamatsu and Y. Yasui, Possibility of estimation for amplification characteristics of soil deposits based on ratio of horizontal to vertical spectra of microtremors. Proceedings of the 11th World Conference on Earthquake Engineering. Acapulco, Mexico (1996) 1526.
P. Goldstein, D. Dodge, M. Firpo and L. Minner, SAC: Signal processing and analysis tools for seismologists and engineers: Lawrence Livermore National Laboratory, Livermore, CA 94550 (2003).
Scream 4.4: Designed and Manufactured by Guralp Systems Limited, 3 Midas House, Calleva Park Aldermaston RG78EA England.
