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Frankel et al. 1990
Frankel, A., McGarr, A., Bicknell, J., Mori, J., Seeber, L. and Cranswick, E. (1990). Attenuation of high-frequency shear waves in the crust: Measurements from New York State, South Africa, and Southern California. Journal of Geophysical Research 95: doi: 10.1029/90JB01346. issn: 0148-0227.

We compare the attenuation of high-frequency (3--30 Hz) shear waves for crystal paths in New York State, South Africa, and southern California over source-Receiver distances of about 10--400 km. The data consist of digital recordings of S waves (Δ=5--100 km) and Lg waves (Δ=100--400) produced by earthquakes. We use a coda normalization method to remove the effects of site amplification and source excitation from the amplitudes of the S and Lg waves. Over the entire distance range studied (10--400 km), the amplitude decay of 3-Hz shear wave energy is considerably less for the tectonically stable area of New York and South Africa than for the tectonically active region of southern California. High-frequency (30 Hz) S wave attenuation is significantly less for New York and South Africa than for southern California, for distances between 15 and 90 km. We parameterize the decay with distance (R) of coda-normalized shear wave amplitudes with a frequency-independent Q and geometrical spreading exponent &ggr;, where geometrical spreading is proportional to R-&ggr;. For New York State the S wave amplitude decay (3--30 Hz) is well described by a frequency-independent Q of 2100+490-330 and &ggr; of 1.3¿0.1. The decay of Lg wave amplitudes from 3 to 15 Hz in the New York State region is fit with a frequency-independent Q of 1600+330-280 and &ggr; of 0.70¿0.2. The S wave amplitudes (3--30 Hz) in South Africa yield a Q of 1500-380190 and &ggr; of 1.3¿0.1. Fixing the geometrical spreading at R-0.5 produces an Lg wave Q estimate at 3 Hz in South Africa of 360+80-50. This Lg wave Q is low considering that South Africa is a cratonic, tectonically stable area. The S wave amplitues from southern California are described with a frequency-independent Q of 800+280-150 and a large geometrical spreading exponent of &ggr; of 1.9¿0.2. We find an Lg wave Q at 3 Hz of 260¿30 for southern California, after constraining the geometrical spreading at R-0.5. ¿ American Geophysical Union 1990

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Abstract

Keywords
Seismology, Body wave propagation, Seismology, Continental crust, Information Related to Geographic Region, North America, Information Related to Geographic Region, Africa
Journal
Journal of Geophysical Research
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Publisher
American Geophysical Union
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