Submitted on: 23 June 1999.
Revised on: 29 September 1999.
Accepted on: 26 November 1999.
___________________JOURNAL OF APPLIED GEOPHYSICS---ELSEVIER
Submitted on: 26 July 2005.
Revised on: 21 September 2005.
Accepted on: 18 October 2005.
___________________JOURNAL OF APPLIED GEOPHYSICS---ELSEVIER
http://reply.papertrans.cn/2/154/15316/15316-33.png
http://reply.papertrans.cn/2/154/15316/15316-34.png
http://reply.papertrans.cn/2/154/15316/15316-35.png
Submitted on: 13 July 1999.
Revised on: 07 September 1999.
Accepted on: 30 September 1999.
___________________JOURNAL OF APPLIED GEOPHYSICS---ELSEVIER