Security Pacific Corp. has set its sights on buying its second bank holding company this year. Security said it signed a letter of intent to purchase La Jolla Bancorp, agreeing to pay $15 of its own stock for each share of La Jolla. Based on the current number of La Jolla shares, that gives the transaction a value of $104 million. La Jolla is the parent company of La Jolla Bank & Trust Co., which has 12 branches in San Diego County. As of Sept. 30, the bank had assets of $511 million and deposits of $469 million, Security Pacific said. Earlier this month, Security Pacific, which is among the 10 largest bank holding companies in the U.S., completed the acquisition of San Diego-based Southwest Bancorp.