Who do hammered (percussive) messages travel throught the rubble while wireless signals from the cellular base stations do not penetrate only a short distance?
Many of those trapped in recent earthquakes were saved because rescuers heard them tapping, shouting or making other loud signal. Seismic signals (vibrations through the earth) can be detected by iPhone applications such as iSiesmo or Seismometer. Professional rescue teams use sensitive seismometers designed for oil exploration, to hear hammered and other percussive signals from deep within the earth. Sensitive seismometers have long been used to listen for the tapings of miners who are trapped far below the surface. The sound of a hammered percussive pulse travels in the air gaps between the rubble to the surface. A rescuer on the surface heard the percussive sounds of those trapped persons under the World Trade Center. Rescue professionals listen for the percussive pulses they input into the RescueMe Phone application using sensitive audio microphones .
