Are event sourcing and CQRS the same pattern, or is it possible to use one without the other?

Event sourcing and CQRS are separate, independently adoptable patterns that happen to pair very well together, but they solve different problems. Event sourcing is a decision about how the write side stores its history — as a sequence of events instead of just the latest state. CQRS is a decision about whether reads and writes get separate models and code paths at all, regardless of how either side stores its data. A system can use CQRS with traditional state storage on its write side and no events involved, and a system can use event sourcing without a separately optimized read side, though that's rarely a good idea since every read would then have to replay events from scratch. They travel together often in practice because they solve complementary halves of the same larger problem, not because they're actually the same idea.