著者

三雲 健

出版者

日本自然災害学会

雑誌

自然災害科学 (ISSN:02866021)

巻号頁・発行日

vol.22, no.1, pp.49-57, 2003-05-30

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A large earthquake (Mw7.4) occurred on January 22, 2003 off the Pacific coast of the state of Colima, Mexico, which was felt strongly throughout the state and its adjacent regions. The hypocenter was located near the suggested boundary between the Rivera and Cocos plates both subducting beneath the North American plate, and close to the southeastern rim of the source region of the 1995 Colima-Jalisco earthquake (Mw8.O). From a centroid moment tensor (CMT) inversion of teleseismic waveforms, the 2003 earthquake has been shown to have a thrust fault shallowly dipping toward NNE. The ruptured source region estimated from the aftershock area with a radius of about 30 km extended over part of the seismic gap left unbroken between the source areas of the 1973 and 1995 previous large earthquakes, and overlapped the southeastern part of the 1932 and 1995 source regions. The earthquake has been recorded at various seismograph stations not only in Mexico but also worldwide. The maximum ground acceleration recorded at hard sites during this earthquake exceeded 100 gals in the epicentral region, and was 2-3 gals at inland stations 800 km away from the epicenter. The seismic intensity in the cities of Colima and Tecoman was reported to be VIII on the modified Mercali scale. The state of Colima and the adjacent states suffered extensive damage, including 15,000 damaged houses which were mostly unreinforced masonry and brick structures. Landslides and liquefactions were also reported near the epicentral region and along the coast.