A Preliminary Report on the Tecoman, Mexico Earthquake of 22 January 2003 (Mw 7.4) and Its Effects

Abstract

The Mw 7.4 Tecoman earthquake occurred off the Pacific coast of the state of Colima, Mexico on 22 January 2003 (Figure 1). It was felt very strongly in the city of Colima and the towns of Tecoman and Armeria. The earthquake left 21 persons dead. About 15,000 houses suffered damage; roughly 3,000 of these experienced severe damage. The most significant damage was observed in adobe and unreinforced brick masonry houses. Very few cases of structural failure were recorded in engineered buildings. Ground motion in the lakebed zone of Mexico City, about 540 km from the epicentral zone, was strong enough to cause general panic in the population. Over the last 100 years the coasts of Colima and the adjacent state of Jalisco have been struck by several large earthquakes: 3 June 1932, Ms 8.2; 18 June 1932, Ms 7.8; 22 June 1932, Ms 7.0; 30 January 1973, Mw 7.6; 9 October 1995, Mw 8.0. The earthquakes of 3 and 18 June 1932 devastated the states of Jalisco and Colima. The relatively small event of 22 June 1932 caused a large local tsunami on the coast of Cuyutlan, drowning many persons. The earthquake of 9 October 1995 caused extensive damage to Manzanillo and towns along the coast of Jalisco. These earthquakes had left a small gap between the rupture areas of the 1973 and 1995 events (Figure 1). This gap broke during the Tecoman earthquake. The purpose of this report is to present preliminary results on the earthquake and its effects. The tectonic setting of the region is outlined in Figure 1. In this region, the oceanic Rivera (RIVE) and Cocos (COCOS) Plates subduct below Mexico, which forms part of the large North American (NOAM) Plate. The boundary between the RIVE and COCOS plates, …