The third-seeded Goerges notched a 6-4, 7-5 win over 2006 Seoul champ Eleni Daniilidou of Greece, while the sixth-seeded Martinez Sanchez claimed a 7-6 (7-5), 6-2 victory over Czech qualifier Kristyna Pliskova.
Goerges and Martinez Sanchez will meet in one of Friday's quarterfinals.
It's been a solid year for Goerges, who captured her second career WTA title with a triumph in Stuttgart back in April. She beat world No. 1 Caroline Wozniacki for the clay court title, and has also reached the semifinals in two other tournaments. In addition, Goerges advanced to the third round in each of the four Grand Slam events, marking her best finish in each.
Martinez Sanchez also has one title this year, taking the clay court event in Bad Gastein back in July.
Russia's Vera Dushevina and Kazakhstan's Galina Voskoboeva also won Thursday and will meet in the quarterfinals. Dushevina, who began the tournament with an upset of top-seeded Italian Francesca Schiavone, cruised to a 6-3, 6-1 rout of Romania's Alexandra Dulgheru. Voskoboeva knocked out eighth-seeded Russian Ekaterina Makarova in the first round and toppled Czech Iveta Benesova, 6-4, 6-4, on Thursday to advance.
The other quarterfinals on Friday will pit fourth-seeded Dominika Cibulkova of Slovakia against fifth-seeded Polana Hercog of Slovenia and American Vania King against Klara Zakopalova of the Czech Republic. All four women claimed second-round wins on Wednesday, with King taking out second-seeded Marion Bartoli of France.
This week's champion will earn a first prize of $37,000.