Occidental Petroleum Corp's board of directors cut Chief Executive Officer Stephen Chazen's total compensation by about 75 percent in 2013 as part of the U.S. oil company's overhaul of executive pay, according to a regulatory filing on Thursday.

Chazen received $6.9 million in salary and stock awards last year, compared with $28.5 million in 2012, according to the company's proxy filing with the U.S. Securities and Exchange Commission.

Ray Irani, the longtime chairman of Occidental who was voted out by shareholders last year, received total compensation of $20.6 million, a figure that included a $14 million separation payment and $572,503 for security services, according to the proxy.

After the company's 2013 annual meeting where only 63 percent of shareholders supported the company's executive pay package, the board changed the compensation program significantly for Chazen and other executives, the proxy said.

For example the board decided to "narrow the gap" between the value of Chazen's total compensation with that of other Occidental executives, the filing said.

(Reporting by Anna Driver; Editing by Lisa Shumaker)