Crustal anisotropy of Taihang Mountain Range using azimuthal variation of receiverfunctions
Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing
Abstract
We discussed the possibility of studying crust anisotropy by analyzing azimuthal variation of the receiver functions英语论文范文and presented a technique for computing the transmission response of a flat-layered medium with arbitrarily oriented
hexagonally symmetric anisotropy using the reflectivity algorithm. Using this method we investigated the
crust anisotropy of Taihang Mountain Range (TMR). Our result shows that there is significant anisotropy with aslow symmetry axis in the upper crust and a fast symmetry axis in the lower crust. The anisotropy magnitude ofabout 8%~15% is found in the upper crust and a smaller magnitude of about 3%~5% in the lower crust. Orientationof the symmetry axes and the depth of anisotropy appearance as deduced from the seismic records of fourindividual seismic stations are different from each other. The crust anisotropy beneath the four stations may beassociated with the local crustal fabrics in a small area.
Key words: receiver function; anisotropy; azimuthal pattern; Taihang Mountain Range
Introduction
Seismic anisotropy is the property of the dependence of seismic velocity upon angle. The
history of studying on seismic anisotropy is only about half a century, but various scholars have
achieved many constructive results. Anderson (1961) and some others studied the principle of
seismic wave propagation systematically since 1950s. Hess (1964) discovered the phenomenon of
azimuthal anisotropy at Pacific mid-ocean ridge, and provided important geophysical evidences
for ocean-floor spreading hypothesis in 1960s. Since Crampin and Booth (1985) discovered the
phenomenon of shear wave splitting in 1980s, the technique of shear-wave splitting has become a
main and effective method in studying the crust and mantle anisotropy. Anatomizing anisotropy
information contained in the seismic waves can provide useful information about the Earth’s interior
structure, deformation (Tommasi et al, 1999), dynamic processing (Montagner, 1998) and
mantle convection (Karato, 1998). Therefore, seismic anisotropy plays an increasingly important
role during earth science research, such as theoretical seismology, exploring seismology, geodynamics
and earthquake catastrophology.
The evolution of the North China Craton (NCC) is a hot issue of present researches. The different
ideas about the history of NCC, such as lithosphere thinning, require urgently other moreFoundation item: National Natural Science Foundation of China (40774042 and 90714012).
Author for correspondence: [email protected]
No.4 TIAN Bao-feng et al: CRUSTAL ANISOTROPY OF TAIHANG MOUNTAIN RANGE 359
results from geochemistry and geophysics for verification. Seismic anisotropy gives a new way to
get knowledge of the interior structure and status of stress within the plate. Furthermore, we can
have a good understanding of mantle convection and plate motion. The most common method at
present to study seismic anisotropy is the shear-wave splitting technique (ZHENG and GAO, 1994;
LIU et al, 2001; LUO et al, 2004; WU et al, 2007; Iidaka and Niu, 2001; Zhao and Zheng, 2005).
The shear-wave splitting technique is developed from a simple principle, but the results obtained
by various scholars in the same region or obtained by one scholar with different earthquake records
using this technique sometimes are dramatically contradictory to each other. Liu et al (2008) gave a
more comprehensive overview of the shear-wave splitting results. They thought that the inconsistency
of the previous studies was mostly due to the limited amount of events and different
shear-wave splitting measurements. They also gave a reliable research on the seismic anisotropy of
North China using much more events records that satisfy one standard defined by them. Though errors
can be reduced by improvement of the processing technique, the shear-wave splitting
