If the condition is fixed, the first thing to do is evacuating people from buildings which have posibility to fall and burry people beneath them on the aftershocks. Then, Trying to find any comunication means which is still working right after the disaster like trying to operate cellphone, radio, internet nearby. If cellphone network is working, reaching related institution is good. Beside, reaching relatives to make a call to the related institutions is also posible. Then, run to phone booth to make a call or police station nearby to ask hel and use their radio system,.
In my place, there is such an organization whose duties is like police department. the name is SENKOM which stands for Sentra Komunikasi or in English we have it communication center. This organization have national communication system through handie talkie. The access is very wide (all over my country) and connected to the police headquarters. This is a professional organization to handle natural disaster since the members have got trainings of evacuating victims and dealing with natural disaster. Calling the call center of SENKOM is one of possible solutions to do after the earthquake.
This is my opinion. there also website of SENKOM but unfortunately it is available in Indonesian language only. there is also a picture of SENKOM's logo,.