." >> kit miyamoto is a california seismic safety commissioner and a structural engineer. his company strengthens buildings, like this one, in downtown la. >> before this was reinforced, if this big earthquake happened here, this will have major, major, major damage, even collapse. >> even though it's all concrete? built prior to 1980s, it could be really dangerous. >> the city of los angeles alone has identified 13,500 small residential apartment buildings that need strengthening which can cost tens of thousands of dollars each. but miyamoto says it's okay to start small. >> you don't have to fix everything, you don't have to be perfect about it. >> but every little thing you do. >> that's right. >> makes a difference. >> that's exactly correct. reporter:experts say even many of the are only earthquake "resistant." is that means they're built to allow people to get out alive. but may not necessarily be in happennable afterwards. >> reporter: in prescott, arizona, a playground was dedicated in memory of kayla mueller. she was a 26-year-old humanitarian aid worker captured