Contribution of coseismic deformations on the current expansion of the Earth

In this paper, the effects of earthquake source parameters (especially the rake angle and the dip angle) on changes in the overall volume and mean radius of the Earth are discussed, and it is herein concluded that dip-slip earthquakes produce the maximum changes in the Earth’s mean radius. We computed almost 40 years of changes in the Earth’s mean radius induced by approximately 41,064 events (Mw ≥ 4.0) from 1976 to 2014 and estimated the change rates of the Earth’s mean radius from 1976 to 2014 and 1994–2014, which were 0.02 mm/yr and 0.06 mm/yr, respectively. It is worth noting that the expansion of the Earth’s mean radius is dominated by thrust-type earthquakes, and earthquakes in the northern hemisphere have caused the Earth to expand faster. Compared to the expansion rate evaluated using geodetic data, the expansion rate caused by earthquakes can account for approximately 10–30% of the current expansion rate, which may demonstrate that earthquakes can be considered to be additional physical processes that are responsible for the current expansion of the Earth. We also discuss the expansion rate induced by plate motions on geological time scales, which is similar to the expansion rate derived using geodetic data.