The man approached a 25-year-old woman from behind as she was jogging on the Seascape Trail in the Fall Creek area of Henry Cowell Redwoods State Park at around 4:30 p.m. on May 2, according to the sheriff's office.
The man attempted to make conversation with the woman, who continued running, and then he began to chase her. She sprinted away and called 911 from a safe location, sheriff's officials said.
Deputies and park rangers searched the trails but could not locate the suspect, who was described as a white man in his 30s, 5 feet 10 inches tall, with a medium build and brown hair.
On the day of the incident, he was wearing a black baseball cap, a black long-sleeve shirt and light-colored pants.
Anyone with information about the case or any similar encounters is asked to call investigators at (831) 454-2311 or dispatchers at (831) 471-1121.
Park-goers are encouraged to be aware of their surroundings, not to use trails alone, and to call 911 about suspicious individuals in the park, according to the sheriff's office.