学会誌「自然災害科学」

1999年コロンビア・キンディオ地震の現地調査報告(2) コロンビアの地震テクトニクスと本震の破壊過程

Reconnaissance Report on the 1999 Quindio, Colombia Earthquake Part 2: Seismo tectonics in Colombia and Source process of the main shock

梅田 康弘*・西上 欽也*・Nelson PULIDO*・川方 裕則*

Yasuhiro UMEDA*, Kin'ya MISHIGAMI*, Nelson PULIDO* and Hironori KAWAKATA*

Abstract

Colombia is located in the western margin of the South American plate. The Nasca plate subducts under this continental plate from the Pacific Ocean. The plate motion has produced many intra- and inter-plate earthquakes. The 1999 Quindio earthquake also occurred under such tectonic background. The high sensitive seismic observation stations (National Network) in Colombia were used for the determination of the earthquake foci. From the relationship between the epicenter of the main shock and the aftershock distribution, it was confirmed that the rupture propagated from south to north direction. Armenia city is situated in front of rupture propagation in which direction the period and amplitude of seismic wave becomes short and large, respectively. This high-amplitude and high-frequency seismic waves might cause the destructive damage of the building in Armenia city. Immediately after the main shock occurrence, the temporary observation network was established by INGEOMINAS. An accurate aftershock distribution is obtained from this temporary observation data. Most of the aftershocks distributed along the Silvia-Pijao active fault.

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