SKS and SKKS waveforms from 16 events occurring between 2003 and 2005 in the Tonga Trench that were recorded by the BOLIVAR array are analyzed to determine the structure of the D＂ layer beneath the Galapagos Islands....SKS and SKKS waveforms from 16 events occurring between 2003 and 2005 in the Tonga Trench that were recorded by the BOLIVAR array are analyzed to determine the structure of the D＂ layer beneath the Galapagos Islands. 248 differential travel-time residuals of SKKS-SKS are measured and reveal a region of positive residuals of differential travel times in the northeast portion of the sampled region. Analyzing correlation statistics between the measured SKKS-SKS residuals and the observed absolute travel time delay of the individual SKS and SKKS phases for two events with high data quality, we determine that the residual differential travel time is due to excess low velocity along the SKKS raypaths. First order modeling of three potential low velocity structures, ultra-low velocity zones （ULVZ）, plume conduit, D＂ structure, indicates that the observed SKKS-SKS residuals can be best explained by a low velocity anomaly within the D＂ layer. To determine the presence of lower mantle anisotropy, amplitude ratios of the radial and transverse component of SKS and SKKS waveform are calculated and compared. Regions with significant presence of seismic anisotropy are interpreted as the edge of the flow field associated with a hypothetical mantle upwelling.展开更多
Systematic analyses of seismic data recorded by the Yunnan regional seismograph network reveal significant crustal and upper mantle anisotropy. Splitting of the S phase of local earthquakes and teleseismic SKS, PKS, a...Systematic analyses of seismic data recorded by the Yunnan regional seismograph network reveal significant crustal and upper mantle anisotropy. Splitting of the S phase of local earthquakes and teleseismic SKS, PKS, and SKKS phases indicates time-delays from 1.60 ms/km to 2.30 ms/km in the crust, and from 0.55 s to 1.65 s in the upper mantle which corresponds to an The polarization orientations of fast shear waves in direction, and the mantle anisotropy has a nearly styles and mechanisms exist between the crust and anisotropic layer with a thickness about between 55 165 km. the crust are complicated with a predominantly north-south west-east direction. Our results show different deformation upper mantle.展开更多
The effect of La addition in Fe-P-N upon Snoek-Ke-Kster(SKK)damping peak was studied.It was found that the damping depends on the atomic concentration ratio between La and P(C_(La)/C_P).When the ratio is comparatively...The effect of La addition in Fe-P-N upon Snoek-Ke-Kster(SKK)damping peak was studied.It was found that the damping depends on the atomic concentration ratio between La and P(C_(La)/C_P).When the ratio is comparatively high in the alloy(for example,4.56 on 2.6),La will appreciably enhance SKK damping,whereas in the alloy saturated with P at a lower C_(La)/C_P ratio of 0.27 La will no longer exert any effect on SKK peak.展开更多
文摘SKS and SKKS waveforms from 16 events occurring between 2003 and 2005 in the Tonga Trench that were recorded by the BOLIVAR array are analyzed to determine the structure of the D＂ layer beneath the Galapagos Islands. 248 differential travel-time residuals of SKKS-SKS are measured and reveal a region of positive residuals of differential travel times in the northeast portion of the sampled region. Analyzing correlation statistics between the measured SKKS-SKS residuals and the observed absolute travel time delay of the individual SKS and SKKS phases for two events with high data quality, we determine that the residual differential travel time is due to excess low velocity along the SKKS raypaths. First order modeling of three potential low velocity structures, ultra-low velocity zones （ULVZ）, plume conduit, D＂ structure, indicates that the observed SKKS-SKS residuals can be best explained by a low velocity anomaly within the D＂ layer. To determine the presence of lower mantle anisotropy, amplitude ratios of the radial and transverse component of SKS and SKKS waveform are calculated and compared. Regions with significant presence of seismic anisotropy are interpreted as the edge of the flow field associated with a hypothetical mantle upwelling.
基金supported by National NaturalScience Foundation of China Project(No.41174042)China National Special Fund for Earthquake Scientific Research in Public Interest(No.201008001)Basic Research Project of Institute of Earthquake Science,CEA(No.2009-21)
文摘Systematic analyses of seismic data recorded by the Yunnan regional seismograph network reveal significant crustal and upper mantle anisotropy. Splitting of the S phase of local earthquakes and teleseismic SKS, PKS, and SKKS phases indicates time-delays from 1.60 ms/km to 2.30 ms/km in the crust, and from 0.55 s to 1.65 s in the upper mantle which corresponds to an The polarization orientations of fast shear waves in direction, and the mantle anisotropy has a nearly styles and mechanisms exist between the crust and anisotropic layer with a thickness about between 55 165 km. the crust are complicated with a predominantly north-south west-east direction. Our results show different deformation upper mantle.
文摘The effect of La addition in Fe-P-N upon Snoek-Ke-Kster(SKK)damping peak was studied.It was found that the damping depends on the atomic concentration ratio between La and P(C_(La)/C_P).When the ratio is comparatively high in the alloy(for example,4.56 on 2.6),La will appreciably enhance SKK damping,whereas in the alloy saturated with P at a lower C_(La)/C_P ratio of 0.27 La will no longer exert any effect on SKK peak.
