High‐frequency seismic attenuation of oceanic <i>P</i> and <i>S</i> waves in the western Pacific

Butler, Rhett; McCreery, Charles S.; Frazer, L. Neil; Walker, Daniel A.

doi:10.1029/jb092ib02p01383

Cited by 33 publications

(33 citation statements)

References 50 publications

(16 reference statements)

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“…Attenuation limits the frequencies of teleseismic body waves to less than a few hertz, except for Po and So, which travel within the high-Q oceanic lithosphere. These arrivals can have energy at frequencies as high as 15-20 Hz at distances greater than 30 ø [Walker et al, 1983;Butler et al, 1987]. The long (1-2 min) codas associated with these phases have been ascribed to either scattering by small-scale heterogeneities [Richards and Menke, 1983; Menke and Chen, 1984; Novelo-Casanova and Butler, 1986] or as the result of propagation in leaky organ-pipe modes of the lithospheric waveguide Orcutt, 1985, 1987].…”

Section: Vlf Acoustics Band (5-50 Hz)mentioning

confidence: 99%

Broadband seismology and noise under the ocean

Webb¹

1998

Reviews of Geophysics

460

413

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Section: Vlf Acoustics Band (5-50 Hz)mentioning

confidence: 99%

Broadband seismology and noise under the ocean

Webb¹

1998

Reviews of Geophysics

460

413

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“…Estimates of Q p and its frequency dependence for P n in the western Pacific vary widely and are based on a variety of different techniques including falloff rates of the coda, reduction in amplitude with distance along a linear array, maximum distance the phase is observed, and spectral ratios [Oliver and Isacks, 1967;Walker et al, 1983;Butler et al, 1987;Sereno and Orcutt, 1987;Brandsdóttir and Menke, 1988;Mallick and Frazer, 1990;Roth et al, 1999;Kennett and Furumura, 2013;Shito et al, 2013], although the general consensus is that Q p for P n in the lithosphere at 10 Hz is on the order of 1000 or greater. The thickness of the low-attenuation lithosphere is even less clear.…”

Section: 1002/2013jb010589mentioning

confidence: 99%

Upper mantle Q structure beneath old seafloor in the western Pacific

2014

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The Pacific Lithosphere Anisotropy and Thickness Experiment ocean bottom seismometer array south of the Shatsky Rise allows imaging the attenuation structure of the upper mantle in the oldest parts of the Pacific Ocean. The array consisted of eight seismometers with a lateral extent of 200 km by 600 km. Intermediate-and deep-focus earthquake sources in the Mariana and Izu-Bonin subduction zones provide paths that probe different depths beneath the seafloor. Acceleration spectra from the vertical component of P waves are inverted for the attenuation operator and corner frequency. P n propagation indicates very high Q p values in the lithosphere, of order 1000, while path-average Q p values in the upper mantle are on the order of 400. The variety of source epicentral distances and depths enables us to deduce the vertical Q p À1 structure of the upper mantle. Using the amplitude spectra directly in a weighted least squares problem that accounts for the effects of triplications in the traveltime curves, we invert for Q p À1 as a function of depth. We demonstrate that Q p is frequency dependent and adopt a power law dependence with coefficient α = 0.27. We resolve three distinct layers using a reference frequency of 1 Hz with Q p on the order of 145 at depths 100-250 km, Q p on the order of 350 at depths 250-410 km, and very high Q p with attenuation indistinguishable from zero for depths below 410 km. The P waves have a component of scattering, and thus, Q p À1 represents the maximum intrinsic attenuation beneath normal undisturbed oceanic lithosphere.

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“…Butler et al (1987) western Pacific. These Q s values are obviously higher than those of the upper layer and nearly the same as those of the lower layer of the slab near the southern Kurile trench.…”

Section: Discussionmentioning

confidence: 99%

Two-layer Q s structure of the slab near the southern Kurile trench

Maeda

Sasatani

2006

Earth Planet Sp

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We estimate Q s values (quality factor for S-wave) of the slab near the southern Kurile trench by using seismic data observed at ocean bottom seismometer (OBS) stations from selected local earthquakes. The seismic rays pass mainly through the slab and this enable us to directly estimate the slab Q s values. The spectral inversion and coda normalization method are applied to these data. The estimated Q s values from the two methods are nearly the same and increase with frequencies. However, these Q s values are not high enough to explain the abnormal distribution of ground motion that has been recognized as abnormal distribution of seismic intensities at the Japanese arc. Thus we propose a two-layer Q s structure of the slab to explain the both facts, our slab Q s values and the abnormal distribution of ground motion. The two-layer Q s structure consists of the upper layer with not so high Q s values (39 f 1.0 ) and lower layer with very high Q s values (500 f 1.0 ); the upper layer has a thickness of about 50 km. Seismic activity is restricted only within the upper layer of the two-layer Q s structure. This may mean that the two-layer Q s structure reflects the different material property between the upper and lower layer of the slab.

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High‐frequency seismic attenuation of oceanic P and S waves in the western Pacific

Cited by 33 publications

References 50 publications

Broadband seismology and noise under the ocean

Broadband seismology and noise under the ocean

Upper mantle Q structure beneath old seafloor in the western Pacific

Two-layer Q s structure of the slab near the southern Kurile trench

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