 HOUSTON, May 05, 2021 GLOBE NEWSWIRE -- ION Geophysical Corporation NYSE: IO today reported total net revenues of 14.0 million in the first quarter 2021, a 49 decrease compared to 27.3 million in the fourth quarter 2020 and a 75 decrease compared to 56.4 million one year ago. At March 31, 2021, backlog, which consists of commitments for multi-client programs and proprietary imaging work, was 21.4 million or 9 higher compared to December 31, 2020. 