Experience with the Design of an Air Ionization Monitoring Station for Earthquake Prediction

Although the prediction of earthquakes is currently not reliable, there are networks of measuring stations around the world located at critical points for early warning. In addition to conventional geophones that sense the vibrations of the earth’s subsurface, animals that respond to changes in the earth’s magnetic and electric fields are often used. For the proposed use in Indonesia, it was crucial to replace the use of animals with electronic sensors, so that it was not necessary to feed the animals and provide for their care. The proposed station focused on the use of a gerdien tube to measure air ionization, as the example of several earthquakes showed a significant change in air ionization several hours before the earthquake. Significant technical issues had to be resolved, especially the ability of the gerdien tube to operate during high relative humidity in the rainforest, the ability to withstand heavy rains, storms. The leakage resistance of the Gerdien tube can be significantly reduced by living organisms such as insects, spiders and fungi residing in the tube. To eliminate these influences, the gerdien tube must be automatically zeroed periodically. A built-in microcomputer automatically ensures the operation of the measurement setup, the output is an analog voltage processed by a 24-bit converter in the industry PC measurement card. Despite the use of all techniques, the gerdien tube will need to be cleaned in about three months and completely disassembled and reassembled twice a year. The advantage of measuring air ionisation over, for example, radon measurements is the faster reaction time. The designed and assembled station has been in trial operation near Vienna.