Spectral ratio of short-period S<i>cP</i>and S<i>cS</i>phases in relation to the attenuation in the mantle beneath the Tasman Sea and the Antarctic Region

Choudhury, Mansur A.; Dorel, J.

doi:10.1029/jb078i002p00462

Cited by 8 publications

(3 citation statements)

References 5 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…These values are consistent with the very high value we have found beneath the subduction zones in our region 3. A rather high Q has also been found beneath station DRV at Dumont d'Urville on the Antarctic margin (Choudhury & Dorel 1973). Frohlich & Barazangi (1980) have estimated Q in the lower mantle between Fiji-Tonga and Australia from a comparison of (ScP-PcP) and (ScS-PcS) waves, and obtain a value of 1050 at 1 Hz.…”

Section: Comparison With Previous Q-results From Body Wave Analysesmentioning

confidence: 97%

“…This method has several advantages: it directly takes into account source and propagation effects, it allows us to work at a single frequency, and it provides a good control on possible undesirable contributions due to nearby phases, scattered phases, high noise or strong focusing–defocusing effects. This method is applied to the Australian–Antarctic region, where global attenuation models retrieved from surface waves have a limited resolution, and where only few short period ScS wave studies have been performed (Choudhury & Dorel 1973; Frohlich & Barazangi 1980). The region is well sampled by high quality ScS n waves thanks to the deep focus events of the nearby subduction zones, and to the availability of data from several permanent broad‐band stations.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Seismic attenuation in the eastern Australian and Antarctic plates, from multiple ScS waves

Souriau¹,

Rivera

Maggi

et al. 2012

Geophysical Journal International

View full text Add to dashboard Cite

SUMMARY The attenuation of seismic shear waves in the mantle beneath the eastern Australian and Antarctic plates is analysed using a large data set of multiple ScSn waves, reflected n times at the core–mantle boundary and (n–1) times at the surface. The data are the transverse components of deep earthquakes from the subduction zones north and east of Australia, recorded at stations in Antarctica, Australia, Indonesia, New Caledonia and New Zealand. The data are filtered with narrow bandpass filters at five frequencies in the range 0.013–0.040 Hz. The ScSn+1/ScSn amplitude ratios of successive ScS phases are compared to the ratios computed for synthetic seismograms for the same paths and same focal mechanisms, to eliminate the effects of source radiation and geometric attenuation. The synthetic seismograms are computed from a summation of toroidal modes for the 1‐D reference model PREM. The observed to computed spectral ratios appear consistent for similar paths. They reveal that the attenuation is not frequency dependent, that the contribution of scattering to attenuation is low, and that the PREM model is a valuable reference model for the study region at the considered frequencies. An inversion of the data at 0.026 Hz is performed to retrieve the quality factor Q in the upper mantle, in regions defined using a priori constraints inferred from seismic shear velocities. Q‐values close to those of PREM are found beneath the Australian and Antarctic cratons, lower values beneath the Eastern Australian Phanerozoic margin, and very low values beneath the oceanic region between Australia and Antarctica, where ridges and a triple junction are present. The Australian–Antarctic Discordance along the South‐Indian ridge appears as an exception with a Q‐value close to those of stable continents. The highest Q‐values are found beneath the subduction zones, a feature which is not apparent in global attenuation models possibly because of its narrow lateral extension, and because it extends at depths larger than those sampled by surface waves. Despite limitations due to the uneven distribution of the ScSn bounce points at the surface and to the difficulty of collecting a large number of high quality data, our approach appears very promising. It is complementary to the more widely used determination of seismic attenuation using surface waves because it provides increased depth coverage, and a broader spectral coverage. It therefore has a considerable potential in future investigations of mantle structure and dynamics.

show abstract

Section: Comparison With Previous Q-results From Body Wave Analysesmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

Seismic attenuation in the eastern Australian and Antarctic plates, from multiple ScS waves

Souriau¹,

Rivera

Maggi

et al. 2012

Geophysical Journal International

View full text Add to dashboard Cite

show abstract

“…Other methods have involved measuring the spectral content of direct P and S waves from long-period seismometers (Solomon and ToksSz, 1970;Mikumo and Kurita, 1968;Teng, 1968). A few studies have used P waves recorded on shortperiod instruments (Kanamori, 1967a;Frasier and Filson, 1972) and fewer still have used short-period S waves (Marshall et al, 1975;Kanamori, 1967b;Choudhury and 1013 Dorel, 1973). Marshall et al (1975) pointed out that the short-period teleseismic S waves merited much closer examination because the effect of anelastic attenuation on them is overwhelming.…”

Section: Introductionmentioning

confidence: 99%

t* for S waves with a continental ray path

Burdick

1978

Bulletin of the Seismological Society of America

View full text Add to dashboard Cite

The purpose of this study was to determine t* for S waves with ray paths under the continental United States. The data set consists of long- and short-period body waves from the Borrego Mountain earthquake as observed in the northeastern U.S. The P wave forms are dominated by the sP phase and the SH wave forms by the sS. It is assumed that there are no losses in pure compression so that the relative attenuation rate of P and S waves is known. The initial source radiation is determined from the sP phase and the value of tβ* from the spectral content of the S wave. The results indicate that tβ* is 5.2 ± 0.7 sec along this ray path. Long- and short-period body waves from some deep South American events are used to test for lateral asymmetry of the Q distribution under the U.S. No lateral amplitude variation exists in this data, but this result is difficult to correlate with many previous results. The t°* value for a 600-km deep earthquake appears to be about 3 sec. A comparison of these values with values computed from current models of the Earth's Q distribution indicates that the models are slightly too high in Q overall and that more of the total body-wave attenuation occurs above 600 km than is indicated by the models.

show abstract