Saturday's search is the largest so far. More than 90 professional search and rescue members from four counties looked for Sierra, within a 12-mile radius of her home. They checked urban and rural areas, looking for clues, evidence, anything that might help.
Sgt. Jose Cardoza of the Santa Clara County Sheriff's Office said: "We're still out here, anything can happen. We could get a lead overnight, in the next 24 hours, a good tip may change everything."
Sierra was on her way to Sobrato High School when she disappeared a little more than a week ago. She was supposed to have caught her bus to school at 7:25 on March 16. Last week her cell phone was found 20 to 30 feet off the road away from the bus stop, and search teams also found her purse, with clothes inside, even further away.
Teams searched that same field again Saturday just to make sure they didn't miss anything.
"Every time you do a search like this, it's about probabilities you can never be entirely certain so sometimes you want to take more than one look at something to gain more confidence that there's nothing there to be found," Jeff Thomas, a member of the search and rescue team, said.
But so far no new leads have turned up. The rain doesn't help. It could wash away evidence of clues.
Her neighbors want to do something -- anything -- to help. They're tired of feeling helpless and so they're walking the streets, posting signs and tying ribbons.
"It's kind of dangerous out here because nobody saw her leave or anything so we want to come together and maybe nothing like this will happen ever again," said 17-year-old Mandy Stanley.
A vigil will be held for Sierra Sunday at 6 p.m. at the Crossroads Christian Center on Wright Avenue in Morgan Hill.