Apparel chain Pacific Sunwear of California Inc on Thursday posted a 12.9 per cent jump in August same-store sales and revealed a 25.8 per cent surge in total sales to $110.2 million from $87.6m in 2001. The company said same-store sales rose 13.1 per cent at its key PacSun chain and 10.3 per cent in the company's smaller d.e.m.o. division.