The western part of the city of Valdivia is more severely damaged than the eastern part. This is because the eastern part is underlain by a firm continuous bed, actually a terrace, of cancagua, a fine-grained soil composed of volcanic ash. The western part consists of a discontinuous surface marked by isolated mesa-like remnants of this terrace, surrounded by soft, incompetent fill. Vibration of the mesa-like columns was severe because of the lack of contiguous support at the contact with the incompetent fill material. Construction on artificial fill was very seriously damaged.