Abstract:

In our country, 4.5Hz vertical geophones are generally used for multi-channel surface wave measurement in geophysical studies or field studies controlled by public institutions. However, some public institutions do not allow using 4.5Hz vertical geophones in seismic refraction studies to identify the first arrivals and believed that the first arrivals could not be reliably picked from the seismic refraction data obtained with these geophones. Within the scope of this study, the effect of geophone center frequency on first arrivals of seismic refraction data was investigated. In study, synthetic seismic traces calculated for three different vertical component geophones with 4.5, 14 and 40 Hz center frequencies and real seismic refraction data collected in two different areas with 4.5-14 Hz, 4.5-40 Hz geophone pairs produced by different companies were used. The first arrival time analysis on synthetic and both real data significantly indicated that the first arrival times are independent of the center frequencies of the used geophones. Therefore, the first arrival times of seismic refraction data collected with same field parameters but with different center frequency geophones do not demonstrate changing. The only difference seen for these data is increasing of amplitudes in spectrum around center frequency of geophone, however it could not affect the first arrivals. Consequently, it has been shown in the proposed study that a single geophone set (e.g., 4.5 Hz) will be adequate in acquisition of both multi-channel surface wave and traditional seismic refraction data, and logistics of different geophone sets are not needed.

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