Many Californians in the area hit hardest by this week's deadly mudslides did not heed warnings for hours and days by emergency officials encouraging them to evacuate their homes — and then received cellphone alerts of imminent slides when the massive streams of debris were already heading toward them or had already hit their neighborhoods. Wireless emergency alerts are cellphone messages sent to everyone in a region, similar to the Amber alerts that are sent to cellphone users in specific areas when authorities are trying to find missing children. The alert sent by Santa Barbara County officials to all those in mandatory and voluntary evacuation areas went out around 3:50 a.m. Tuesday because of deteriorating conditions, Rob Lewin, the county's emergency management director said Thursday.