International help for Christchurch

After the major earthquake in Christchurch on Tuesday, many countries offered help. Britain, the US, Australia, Singapore, Japan and Taiwan have all sent Search and Rescue people to help find those who are buried under collapsed buildings. They brought special search and rescue dogs and tonnes of special equipment to help find those who are missing. We now know that they are searching for bodies because it is impossible for anyone to survive under all the steel and concrete.

Australia has also sent a field hospital with 75 beds because some of Christchurch hospital was damaged and many people have been badly injured. When the Prime Minister of Australia, Julia Gillard, visited New Zealand recently she said that Australia and New Zealand are like a family. We are very close to each other. Australia is giving $5m in aid and has also sent 300 police to help with security in Christchurch.

Question
What kind of person would do a job like Search and Rescue? What are the skills needed? What are the dangers?