Russo, R. M., H. Li, B. M. Gomer, A. Montilla, C. R. Bina, and W. P. Richardson, Variability of seismic attenuation in the source region of the July 9, 1997, Cariaco, Venezuela, earthquake, Report to Universidad de Oriente, Cumaná, Venezuela, 2000.
Abstract. We measured Q for 733 earthquake-to-station paths in northeastern Venezuela, making use of 181 well-located crustal aftershocks of the July 9, 1997, Cariaco earthquake. Q was determined via the drop in slope with frequency of the log of the spectral ratio of S to P waves from the events. We find that crustal Q in the study region varies significantly as a function both of source-station distance and backazimuth, indicating that Q increases generally with depth in the crust, and that it is a strong function of local and regional geology. We find that Q in the schists of the costal Paria-Trinidad terrane is generally 300-600, Q is 150-250 in deformed strata of the Venezuelan foreland fold and thrust belt, and Q is low, 100-150, in the eastern Gulf of Cariaco and Cariaco Lagoon. Low Q in this small sedimentary basin probably reflects the lack of compaction and induration of these sediments.