Frequency dependence of Q sub Lg and its relation to crustal anelasticity in the Basin and Range province

Journal Article · Mon Apr 01 00:00:00 EST 1991 · Geophysical Research Letters (American Geophysical Union); (United States)

DOI:https://doi.org/10.1029/91GL00821· OSTI ID:5399887

Mitchell, B J ^[1]

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1. Saint Louis Univ., MO (United States)

The high observed frequency dependence of Q for 1-hz Lg waves (f{sup 0.4 - 0.6}) in the Basin and Range province can be explained by a frequency-independent layered model of intrinsic Q for shear waves (Q{sub mu}) which has very low values in the upper crust and rapidly increasing values at greater depths. By contrast, earlier work in the eastern United States indicated Q{sub mu} values in the upper crust which are high and which vary with frequency. The Q{mu} model which best explains reported values of Q{sub Lg} and its frequency dependence in the Basin-and-Range consists of an 8-km thick low-Q layer (60 or less) overlying Q values as high as 1,000 or more at mid-crustal depths. This Q{sub mu} distribution is best explained by an upper crust which contains fluids in interconnected cracks overlying a lower crust where higher lithostatic pressure has closed those cracks. These results indicate that whereas the frequency dependence of Q{mu} is an intrinsic property of crustal material, the frequency dependence of Q{sub Lg} arises from both the intrinsic frequency dependence of crustal material and its layered structure. A notation is suggested which distinguishes between the frequency dependence of Q{sub Lg} and Q{sub mu}.

• OSTI ID: 5399887
• Journal Information: Geophysical Research Letters (American Geophysical Union); (United States), Vol. 18:4; ISSN 0094-8276
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
CALIFORNIA
GEOLOGIC FORMATIONS
GEOLOGIC STRUCTURES
CONTINENTAL CRUST
DATA ANALYSIS
DEPTH
FREQUENCY DEPENDENCE
GEOLOGIC MODELS
GEOLOGIC STRATA
RESERVOIR FLUIDS
RESERVOIR PRESSURE
SEISMIC SURVEYS
SEISMIC WAVES
STANDARDIZED TERMINOLOGY
THICKNESS
DEVELOPED COUNTRIES
DIMENSIONS
EARTH CRUST
FLUIDS
GEOPHYSICAL SURVEYS
NORTH AMERICA
SURVEYS
USA
580000* - Geosciences