Change of crustal gravitational potential energy in orogenic belts: example of the 1999 Taiwan Chi-Chi earthquake sequence

In orogenic belts, due to the plate convergence a gain of crustal gravitational potential energy (GPE) is generally associated with the mountain uplifting. In contrast, a loss of crustal GPE is associated with a post-collisional mountain collapsing. The Taiwan orogeny is actively undergoing on account of the convergence between the Philippine Sea Plate and Eurasian Plate. The direct consequences are the uplifting of the Taiwan mountain belt and the numerous earthquakes. The crustal GPE is therefore accumulated. Here we demonstrate the mode of crustal GPE change caused by the 1999 Chi-Chi earthquake sequence in the Taiwan mountain belt. During the earthquake sequence, the crust was in fact going up and down randomly, but overall a cumulative gain of the crustal GPE was rapidly stabilized in one month after the main shock. The crustal GPE gain is mainly distributed in central Taiwan, rather than in the more hazardous western Taiwan.