Mantle and crust anisotropy in the eastern China region inferred from waveform splitting of SKS and PpSms

Abstract

S-waves converted from P-wave at different boundaries inside the earth, i.e., the Moho discontinuity and CMB, are used to determine the distribution of anisotropy in different layers. A clear later phase at approximately 17 sec after the direct P-wave, which is identified to be PpSms (a phase that is P-to-S converted at the free surface and is reflected by the Moho discontinuity on the receiver side), is observed in the radial component of seismograms recorded by broadband stations in the east China region. Waveform splitting observed from the PpSms and SKS suggests that the crust beneath the eastmost part of China is almost isotropic, and the mantle is weakly anisotropic. Splitting analysis using converted waves is a promising technique for investigating the depth distribution of shear-wave splitting.

P n tomographic velocity and anisotropy beneath the Tibetan Plateau and the adjacent regions

“…Recent studies involving the comparison between GPS-observed plate motion and seismologically-observed anisotropy also support this idea (Xiong et al, 2003;Zhang et al, 2004;Wang et al, 2008). Shear-wave splitting measurement (Iidaka and Niu, 2001;Sol et al, 2007;Chen et al, 2010) was also compared with the P n anisotropy. In region c, the fast direction of P n anisotropy is generally the same as the SKS splitting fast direction.…”

Upper mantle conductivity structure of the back‐arc region beneath northeastern China

“…Such a feature may be due to anisotropy in the mantle conductivity, although a study of seismic wave splitting suggests that the anisotropic feature is very weak in the upper to middle mantle beneath this region [Iidaka and Niu, 2001]. However, it is premature to discuss anisotropy any further at this time.…”

Shear-wave splitting analysis of later phases in southwest Japan —A lineament structure detector inside the crust—

“…The PpSms-phase was first applied for the analysis of crustal anisotropy by Iidaka and Niu (2001). The PpPms Thomson-Haskell method.…”

“…Iidaka and Niu (2001) attempt to use converted waves to obtain the anisotropy of each layer (i.e., crust, upper mantle, and lower mantle). The PpSms (the notation is defined by Bath and Stefansson, 1966) is a laterarriving S-phase, which is converted from P at the earth's surface, and is reflected at the Moho discontinuity before arriving at a seismic station.…”

“…The PpSms (the notation is defined by Bath and Stefansson, 1966) is a laterarriving S-phase, which is converted from P at the earth's surface, and is reflected at the Moho discontinuity before arriving at a seismic station. Iidaka and Niu (2001) first used the PpSms phase for the shear-wave splitting analysis. PpPms is a later S-phase, which is reflected at the surface as a P wave, dives again, and is reflected and converted from P to S at the Moho boundary.…”