Short-period PKP phases and the anelastic mechanism of the inner core

Cormier, Vernon F.

doi:10.1016/0031-9201(81)90116-3

Cited by 74 publications

(66 citation statements)

References 29 publications

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“…The results suggest that in the proximity of the ultra-low velocity region previously reported in the South Pacific (e.g. ROST and REVENAUGH, 2003;THORNE and GARNERO, 2004;ROST et al, 2005), the attenuation is approximately twice the value predicted by seismograms synthesized in PREM with a full-wave theory technique based on Langer's approximation (CORMIER andRICHARDS, 1977, 1988). This synthesis method accounts for the frequency dependent effects of diffraction and tunneling of the body waves at and near grazing incidence to the CMB.…”

Section: Introductionsupporting

confidence: 53%

“…In order to evaluate the spectral amplitudes (e.g. CORMIER, 1981;NIAZI and JOHNSON, 1992;BHATTACHARYYA et al, 1993;HELFFRICH et al, 2002), the contamination of the processed PKKP time windows by noise or by other waves with near arrivals had to be kept to a minimum. For PKKP phases, recordings showing highamplitude, long codas of SP (or PS) phases were discarded.…”

Section: Observations and Data Processingmentioning

confidence: 99%

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High Frequency PKKPBC Around 2.5 Hz Recorded Globally

Ivan

Cormier

2010

Pure Appl. Geophys.

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Anomalous high frequency PKKP BC signals (displaying a large amount of energy around 2.5 Hz), recorded globally for deep and intermediate depth earthquakes, are compared to PKKP AB signals. The attenuation difference t Ã AB À t Ã BC is evaluated from spectral amplitudes in the range 96-111°, being approximately twice the results provided by full-wave theory and PREM (with no low Q l zone in the lowermost mantle and a nearly infinite Q K in the outer core). Most ray paths for such recordings are piercing the D 00 region in the proximity of regions where ultra-low velocity zones (ULVZ) have been previously reported beneath the North Atlantic Ocean, the Southwest Pacific and the southwestern part of South America. If BC amplitudes around 2.5 Hz and at low frequencies (0.5-1.5 Hz) are comparable, the observed attenuation difference (in the frequency range 0.2-2.5 Hz) is small (around 0.25 s) and close to the PREM value. The particle motion of the high-frequency PKKP BC at 2.5 Hz is quite similar to that of the raw recording, suggesting a deep source. An explanation for this might be scattering of the BC branch in some very restricted areas of the lowermost mantle. Alternately, the presence of a thin layer with high attenuation in the D 00 region would most likely be associated with either the ultra-low velocity zone (ULVZ) or light sediments on the underside of the core-mantle boundary (CMB). Correlated to other methods to investigate the lowermost mantle, the high-frequency PKKP BC can be used to map lateral variations of attenuation above the CMB, possibly associated with the boundary of the superplumes, especially when PKKP AB is observed.

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Section: Introductionsupporting

confidence: 53%

Section: Observations and Data Processingmentioning

confidence: 99%

High Frequency PKKPBC Around 2.5 Hz Recorded Globally

Ivan

Cormier

2010

Pure Appl. Geophys.

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“…However, advances in the seismic research of the inner core attenuation properties have been relatively slower. Two decades ago, several seismic researchers determined that P-wave attenuation is stronger in the inner core than the outer core and the lower mantle [Doornbos, 1974[Doornbos, , 1983Cormier, 1981]. Shearer andMaster [1990] also pointed out that the shear velocity in the upper inner core decreases anomalously.…”

Section: Introductionmentioning

confidence: 99%

Depth‐dependent attenuation in the uppermost inner core from the Taiwan short period seismic array PKP data

Tseng¹,

Huang²,

Chin³

2001

Geophysical Research Letters

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“…(see Jacobs, 1987) and the axi-symmetric bulk anisotropy of P-wave velocity (Morelli et al, 1986;Shearer et al, 1988) (Doornbos, 1974;Cormier, 1981;Choy and Cormier, 1983 (Dratler et al, 1971;Sailor and Dziewonski, 1978) are, however, of great…”

Section: Attenuationmentioning

confidence: 99%