Microtremor exploration at strong motion stations in Aydin and Denizli provinces, western Turkey

Abstract

This paper reports the results of a case study of the application of the microtremor exploration method in western Turkey. We have conducted microtremor surveys at strong motion stations in Aydin and Denizli provinces to derive shallow S-wave velocity profiles. Array records of vertical microtremor motion were acquired at 12 and 15 stations in Aydin and Denizli provinces, respectively. A spatial autocorrelation analysis was applied to the records to estimate Rayleigh wave phase velocities in the frequency range of 3–30 Hz. Then, the phase velocity dispersion at each station was inverted to a one-dimensional S-wave profile down to a maximum depth of about 50 m. The soil models at 5 and 11 stations in Aydin and Denizli provinces, respectively, have a bedrock with an S-wave velocity of 400–600 m/s at depths less than 10 m. The spatial distribution of average S-wave velocities in the top 30 m of the revealed profiles shows low values in the Büyük Menderes Graben and the Denizli Basin, and high values in the surrounding hill or mountain areas. We compared our S-wave profiles with those from previous surface-wave studies. S-wave velocities in shallow parts to a depth of 5–10 m are similar in the two studies. However, S-wave velocities in deep parts are different at some of the stations.

KEYWORDS:

• Microtremors
• phase velocity
• Rayleigh wave
• S-wave velocity

Acknowledgements

We thank Toshiyuki Tokota and two reviewers for their comments which improved the draft. We also acknowledge the suggestions by Lindsay Thomas to improve draft. We express our sincere thanks to Earthquake Research Department, AFAD, for their valuable support and advice during our study. This study was partly supported by RONPAKU (Dissertation PhD) Program of the Japan Society of the Promotion of Science (JSPS) and by the Joint Research Project under the Bilateral Program of the JSPS and the Türkiye Bilimsel ve Teknolojik Araştırma Kurumu (TÜBITAK).

Disclosure statement

No potential conflict of interest was reported by the author(s).