HR: 0800h
AN: T11D-1317    [Abstracts]
TI: Earthquake-induced gravitational potential energy change at convergent plate boundary near Taiwan
AU: * Lo, C
EM: lo@oc.gep.ncu.edu.tw
AF: Institute of Geophysics, National Central University, No.300, Jhongda Rd., Jhongli City, Taoyuan County 320, Taiwan, Jhongli, 32054 Taiwan
AU: Hsu, S
EM: hsu@oc.gep.ncu.edu.tw
AF: Institute of Geophysics, National Central University, No.300, Jhongda Rd., Jhongli City, Taoyuan County 320, Taiwan, Jhongli, 32054 Taiwan
AB: The coseismic displacement induced by earthquakes will change the gravitational potential energy ({\bf {\it GPE}}). Okamoto and Tanimoto (2002) have shown that the gain of {\bf {\it {$\Delta$GPE}}} corresponds to the compressional stress regime while the loss of {\bf {\it {$\Delta$GPE}}} corresponds to the extensional stress regime. Here we show an example at a convergent plate boundary near Taiwan. The Philippine Sea Plate is converging against the Eurasian Plate with a velocity of 7-8 cm/yr near Taiwan, which has caused the active Taiwan orogeny and induced abundant earthquakes. We have examined the corresponding change of gravitational potential energy by using 757 earthquakes from the earthquake catalogue of the Broadband Array in Taiwan for Seismology ({\bf BATS}) from July 1995 to December 2003. The results show that the variation of the crustal {\bf {\it $\Delta$GPE}} strongly correlates with the different stage of the orogenesis. Except for the western Okinawa Trough and the southern Taiwan, most of the Taiwan convergent region exhibits a gain of crustal {\bf {\it $\Delta$GPE}}. In contrast, the lithospheric {\bf {\it $\Delta$GPE}} in the Taiwan region exhibits a reverse pattern. For the whole Taiwan region, the earthquake-induced crustal {\bf {\it $\Delta$GPE}} and the lithospheric {\bf {\it $\Delta$GPE}} during the observation period are 1.03$\times$10$^{17}$ joules and -1.15$\times$10$^{17}$ joules, respectively. The average rate of the whole {\bf {\it $\Delta$GPE}} in the Taiwan region is very intense and equal to -2.07$\times$10$^{10}$ watts, corresponding to about one percent of the global {\bf {\it$\Delta$GPE}} loss induced by earthquakes.
DE: 8102 Continental contractional orogenic belts
DE: 8122 Dynamics, gravity and tectonics
DE: 8123 Dynamics, seismotectonics
DE: 8150 Plate boundary--general (3040)
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting