abstract

Determination of Q structures are made using a new method which matches observed surface wave spectra with theoretical spectra computed for earthquakes with known fault-plane solutions. The importance of the method lies in its ability to utilize relatively short paths between a single source and receiver, both of which are preferably located within a single geological province.

The method has been applied to study the regions of the Eastern United States, the Colorado Plateau, and the Basin and Range Province. Q models have been obtained through trial-and-error procedures and with an inversion scheme developed for that purpose. Models for each region obtained from these two procedures are in good agreement. Qβ values in the upper crust, as obtained from inversions, are 275 for the Eastern United States, 160 for the Colorado Plateau, and 85 for the Basin and Range Province. Qβ values in the lower crust, although not well determined, must be much higher than upper crustal values in all three regions. The conclusions are consistent with those of previous work in which Qβ values in the upper crust of a broad region of the Western United States are lower than those of the Eastern United States. These new results show that substantial variations of Qβ occur in different regions of the Western United States. The upper crustal Qβ values show an inverse relationship to heat flow values.

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