Publication Date:
2017-04-04
Description:
Abstract—We have measured group delays of the spectral components of high-frequency P-waves
along two portions of the North Anatolian Fault Zone (NAFZ) in Turkey and in a region of southern
Germany. Assuming that the observed dispersion is associated with attenuation in the crust and that it can
be described by a continuous relaxation model, we obtained Q and the high-frequency relaxation times for
those waves for each of the three regions. Individual P-wave Q values exhibit large scatter, but mean values
in the NAFZ increase from about 25 to 60 over the distance range 5–90 km. Mean Q values are somewhat
higher in the eastern portion of the NAFZ than in the western portion for measurements made at distances
between 10 and 30 km. P-wave Q values in Germany range between about 50 and 300 over the hypocentral
distance range 20–130 km. In that region we separated the effects of Q for basement rock (2–10 km depth)
from that of the overlying sediment (0–2 km depth) using a least-squares method. Q varies between 100
and 500 in the upper 8–10 km of basement, with mean values for most of the distance range being about
250. Q in the overlying sediments ranges between 6 and 10. Because of large scatter in the Q determinations
we investigated possible effects that variations of the source-time function of the earthquakes and
truncation of the waveform may have on Q determinations. All of our studies indicate that measurement
errors are relatively large and suggest that useful application of the method requires many observations,
and that the method will be most useful in regions where the number of oscillations following the initial P
pulse is minimized. Even though there is large scatter in our Q determinations, the mean values that we
obtained in Turkey are consistent with those found in earlier studies. Our conclusions that Q is significantly
higher in the basement rock of Germany than in the basement rock of Turkey and that Q is lower in
western Turkey than in eastern Turkey are also consistent with results of Q studies using Lg coda.
Description:
Published
Description:
73-91
Description:
4.1. Metodologie sismologiche per l'ingegneria sismica
Description:
JCR Journal
Description:
reserved
Keywords:
Q, attenuation, dispersion, Turkey, Germany.
;
04. Solid Earth::04.07. Tectonophysics::04.07.99. General or miscellaneous
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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