Active crustal deformation in the Jalisco block, Mexico: evidence for a great historical earthquake in the 16th century

Abstract

On December 27th, 1568, a large earthquake occurred to the southwest of Guadalajara, Mexico, near the northeastern corner of the Jalisco block, in an area where no great earthquakes have been reported before. It caused heavy damage in the region where the Colima and Tepic-Zacoalco grabens intersect. Many churches, houses and convents in the neighboring towns collapsed and severe deformation of the ground was observed in the area. Landslides apparently dammed the Ameca River for several days and the opening of large cracks was reported in the lowlands. The flow of natural springs and the level of Lake Zacoalco changed dramatically after the earthquake. All of these reports strongly suggest that a local fault was the source of this large and destructive earthquake. Based on the intensity data inferred from the historical reports, the 1568 event is perhaps the largest earthquake to date in the Trans-Mexican Volcanic Belt. Compared to other well documented, large earthquakes that occurred in the volcanic belt in 1875, 1912 and 1920, the magnitude appears to be greater than 7.0 ( M W ). The Jalisco block is presumed to be rifting away from the North American plate. The Colima and Tepic-Zacoalco grabens, which bound the Jalisco block to the east and north, respectively, are apparently the boundaries where rifting is taking place in a complex and highly faulted environment. Based on the data available, it is impossible to identify the specific fault ruptured during the earthquake unequivocally. However, the occurrence of this large event in 1568 confirms that active deformation is still taking place in the Jalisco block. The apparently long recurrence times of these large events suggest that tectonic deformation is slow.