CHANGES IN GLOBAL GRAVITATIONAL ENERGY INDUCED BY EARTHQUAKES

Besides operating its own energy budget, an earthquake acts as an agent transferring a much greater amount of energy among the Earth's rotation, elastic held, gravitational held and internal heat. This paper computes the co-seismic, globally integrated gravitational energy change induced by 11 015 large earthquakes that occurred during 1977 to 1993. The result shows an extremely strong tendency for the earthquakes to decrease the global gravitational energy, Thus, energy is being extracted from the Earth's gravitational held by the action of earthquakes. The average rate of this energy decrease over the period is found to be fairly constant at about 2.0 TW (TW = 10(12) watt), larger by far than the 0.0067 TW for the average rate of the earthquake-induced rotational energy increase and 0.0047 TW for that of total seismic-wave energy release during the same period. Assuming the inability of the Earth to build up elastic energy continuously over time, it is argued that earthquakes, by converting gravitational energy, may make a significant contribution to the global heat flow.