The whale was first spotted on shore near Fort Bragg in Mendocino County on Monday night, hours after an ocean survey vessel reported hitting a whale a few miles away, said Joe Cordaro, a wildlife biologist with the National Oceanic and Atmospheric Administration's marine fisheries service.
Blue whales are the world's largest mammals.
Students from California State University, Humboldt, examined the whale's massive body Tuesday as it lay on its side in a rocky cove.
"I was personally jazzed just to see the animal," said Thor Holmes, a lecturer in mammology at the school. He has examined other whale species that washed ashore but never a blue whale.
The whale had two gashes on its back - at least one of which was deep enough to cut through the blubber down to the vertebral column, Holmes said. It otherwise appeared to be in good health.
It's unusual for blue whales to wash ashore, Cordaro said. Last week, another blue whale washed up in Monterey County after being hit by a ship.
Before that, the last time a blue whale washed onto a California beach was 2007.
The whales are "usually far offshore, deep water animals," Cordaro said.
Although blue whales are considered endangered, experts say they have recently made a comeback and now number several thousand.
Some blue whales feed in the waters off Central and Northern California this time of year then migrate elsewhere to breed, said Dawn Goley, an associate professor of zoology at the Humboldt campus.
Researchers have taken skin and blubber samples from the beached animal to see what contaminants it may have been exposed to and what population group it comes from.