A methane gas infilling fault theory is presented to refine and upgrade
the conventional earthquake theory of elastic rebound of active
geological faults. It adds the infilling of highly compressed methane
gas mass into the deep geological fault zones. Such gas infilling makes
the fault active and accumulate the elastic energy. With time, the gas
in the fault traps has more and more mass and high and high pressure.
The gas pressure can rupture the trap along the geological fault and
release some gas mass to migrate along the fault, which causes tectonic
earthquakes. The theory shows that the earth-quaking process is a
cooling process because of gas expansion. The earthquake magnitude
estimated from the seismic waves can have a quantitative relationship
with the gas volume from the trap is quantified. The theory can explain
mega earthquakes along subducton zones.