Shear-wave splitting of Sichuan Regional Seismic Network

Abstract

Using seismic data recorded by the Chengdu Digital Seismic Network from May 1, 2000 to December 31, 2006, we obtain the dominant polarization directions of fast shear-waves at eight digital seismic stations adopting the SAM technique. The results show that the dominant directions of polarizations of fast shear-waves at most of stations are mainly in nearly NE-SW or NW-SE direction in Sichuan. The dominant polarization directions of the fast shear-waves at stations located at the active faults or intersection of several active faults are consistent with the strikes of active faults which control the earthquakes used in the analysis, and are basically consistent with the directions of regional compression axis. However, several stations show that the fast shear-waves are not consistent with the strikes of active faults and the directions of regional compression axis, due to the influence of local complicated crustal structure.

The Shear‐Wave Splitting Study of Sichuan Zipingpu Reservoir Region

“…The dominant fast shear-wave polarization direction of YZP is nearly NS, differs much from the principal compressive stress direction in situ, GPS observations and the Longmenshan fault trend, consistent with the research results obtained by using data of longer time which contain only the regional seismic network waveform data [33] . It has also proved on the other hand that our study may truly reflect the stress-field or fault conditions near the stations.…”

“…Although dominant polarization directions of YZP station's fast shear-wave are discrete, the main dominant direction is nearly NS, which is consistent with the research results obtained by using original waveform data of the earlier time [33] and has a great difference from the principal compressive stress direction and Longmenshan fault trend and is inconsistent with the result that 7 other stations of Zipingpu reservoir have two dominant directions. Other scholars' studies [4,5,23,24] also show that according to fast shear-wave dominant polarization direction's distribution, we can not only determine whether the ground faults are active but may reveal new structural relationships, such as the hidden fault existing at a certain depth.…”

A Study of Seismic Anisotropy of Wenchuan Earthquake Sequence

“…The direction of maximum horizontal principal stress obtained by in situ hydrofracturing stress measurement is the NW direction with slightly different in each segment on the Longmenshan fault belt [18] . According to the seismic data recorded by Si-Chuan Telemetry Seismic Network (SCSN), there is close relation among the polarizations of the fast shear-waves of the stations, the direction of regional principal compressive stress and the strikes of active faults in Sichuan area [19] . The characteristics of anisotropy of stations on the Longmenshan faults reveal the complex geological tectonics.…”

Possible layered lithospheric anisotropy around Longmenshan Faults by teleseismic S wave splitting and receiver functions

“…CD2 station shows lower crustal anisotropy intensity, with XKS wave fast directions primarily indicating upper mantle anisotropy. The close Pms and XKS wave splitting delay times at YZP indicate higher crustal anisotropy levels, but given the station's proximity to the Sichuan Basin edge, its complex waveforms (Zhang et al, 2008) could be influenced by the edge's sedimentary cover.…”