“…Fouch and Rondenay (2006) made a detailed review of the methods for studying seismic anisotropy, as well as their advantages and limitations. In the past three decades, many researchers have attempted to use P-wave travel-time data to study anisotropy tomography (e.g., Babuska et al, 1984;Hearn, 1984;Hirahara and Ishikawa, 1984;Hirahara, 1988;Babuska and Cara, 1991;Mochizuki, 1995;Gresillaud and Cara, 1996;Hearn, 1996;Plomerova et al, 1996;Mochizuki, 1997;Lees and Wu, 1999;Wu and Lees, 1999;Bokelmann, 2002;Eberhart-Phillips and Henderson, 2004;Oda, 2005, 2008;Wang and Zhao, 2008;Koulakov et al, 2009;Eken et al, 2010;Plomerova et al, 2011;Tian and Zhao, 2012a;Wei et al, 2013;Koulakov et al, 2015;Menke, 2015;Wei et al, 2015). However, reliable and geologically reasonable results have been obtained only in recent years, thanks to the availability of abundant high-quality arrival-time data recorded by dense seismic arrays of permanent and portable stations at local and regional scales.…”