1. Geometrics/OYO Corporation, 2190 Fortune Drive, San Jose, California 95014, USA.(corresponding author).
2. California State University, East Bay, 25800 Carlos Bee Blvd., Hayward, California 94542, USA..
3. School of Geophysics and Measurement Control Technology, ECUT and Institute of Geology, CAGS, No. 26 Baiwanzhuang Street, Beijing 100037, China..
4. OYO Corporation, 1-66-2, Miyahara-cho, Kita-ku, Saitama, Saitama 331-0812, Japan..
5. OYO Corporation, 1-10-2, Sakuragi-cho, Omiya-ku, Saitama, Saitama 330-0854, Japan..
6. Geometrics, 2190 Fortune Drive, San Jose, California 95014, USA..
7. Laurel Geophysical Instruments LTD, Qikeshu Innovation Park B5-1, NO.55 Banjieta Road, Chaoyang District, Beijing, China..