| Abstract: | An analysis of the superficial structures related to the Huaytapallana fault is presented. This fault was formed during the Pariahuanca earthquakes of July 24 and October 1, 1969. The fault trends N120E and is 3.5 km long, the displacement is 0.70 m left-lateral slip and 1.6 vertical upthrust. At most places the fault appears as a steep flexure associated with open fractures and mostly gravity folds, all of them almost parallel to it. Oblique, “en échelon” shears, often associated with small folds, are developed in the turf which is partly detached from its substratum. The analysis of these fractures is consistent with a mean N65E shortening direction. The compressional and dilatational quadrants obtained by means of this analysis fit rather well with the focal-mechanism data. On the other hand, some of the en échelon fold and fault systems provide a model of similar features with a magnitude of several kilometers. |
