Coda‐Q Distribution In the Iberian Peninsula

Abstract

Several attenuation studies have established a frequency dependence law of the anelastic attenuation factor Q in the form Q=Qo(f/fo)v for the approximate 1–10 Hz frequency range. We propose a method that leads to the determination of Qo, which is a function of the reference frequency fo, and the real exponent v with a single station. to carry out the problem we determine a set of master curves as a function of v. We discuss the method, and the different features of the master curves, when it is applied to the complicated regions of the Iberian Peninsula and to several instruments with different responses. Using this new method and the seismographic stations available in the Iberian Peninsula we have mapped iso‐Q0 lines, at a reference frequency of 1 Hz, applying inversion methods. the Q0 values determined for Iberia vary between about 100 and about 600. Values close to 100 correspond to the southern part of Iberia. In general, Qo values increase from south to north with values about 600 near the NW part of Iberia. the Pyrenees Mountains and adjacent areas present Q0 values between about 200 and about 350. These results suggest a strong Q0 lateral variation in Iberia. A considerable frequency dependence of coda‐Q has also been determined. the v values vary between 0.3 and 0.8. the Q0 values obtained in the Iberian Peninsula show very good agreement with several Q0 values obtained in other regions of the world. Comparison between the iso‐Q0 lines and other geophysical parameters, like regional variations of Pn velocities, heat flow, isoseimal intensity distribution and crustal thickness, indicates that lower Q0 values are associated with higher isoseismal intensity attenuation, higher heat flow, lower Pn velocities and thinner crust. Copyright © 1990, Wiley Blackwell. All rights reserved