engleski

Attenuation of high-frequency body waves in the crust of the Central External Dinarides

The Central External Dinarides are known as a tectonically complex region of moderate seismicity where several strong earthquakes occurred in the last century. In order to gain insight into the attenuation of seismic waves in the area, the extended coda-normalization method was applied to band-pass filtered seismograms of local earthquakes recorded at seven seismological broadband stations. Obtained results indicate strong attenuation of direct body waves: Q0, P = QP (1 Hz) is found between 21 and 120 and Q0, S = QS (1 Hz) is between 46 and 113, whereas the exponent n in the power law of frequency dependence of the quality factor is found in the range of 0.63–1.52 and 0.65–0.97 for nP and nS, respectively. P-waves are on the average attenuated more than S-waves. The three island stations (DUGI, ZIRJ, HVAR) are distinguished by the strong low-frequency P-wave attenuation and more pronounced frequency dependence of the QP-factor (Q0, S/Q0, P > 1.7, Q0, P < 60, nP > nS). The remaining four inland stations (UDBI, MORI, KIJV, CACV) all exhibit similar qualitative attenuation properties for P- and S-waves (nP and nS are almost equal 1 ; Q0, S and Q0, P are almost equal), although individual values of the Q-factors vary notably within this group. Low-frequency attenuation of direct S-waves in the crust is stronger than mean attenuation of scattered coda waves in the lithosphere, especially for long coda lapse-times. The results are also qualitatively in agreement with the thermal regime in the area.

External Dinarides ; coda waves ; attenuation

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