Why is the radio not affected by the earthquake to receive signals?

The signals received by the radio can travel hundreds to thousands of kilometers along the surface, so the number of broadcast towers is very small. As long as the transmission tower is not damaged by the earthquake and the radio is within the emission range of radio waves, the radio can receive the broadcast normally. However, the mobile phone signal depends on the base station to receive and forward, and the service range is very small. Many base stations were destroyed in the Sichuan earthquake, so the mobile phone can't be used. If the mobile phone signal is forwarded by satellite, it will not be affected by the earthquake, but the cost is too high.