Historical tsunami deposits in Peru: Sedimentology, inverse modeling and optically stimulated luminescence dating

Spiske M, Piepenbreier J, Benavente C, Kunz A, Bahlburg H, Steffahn J

Zusammenfassung

The entire coast of Perú was surveyed to document deposits of historical tsunami. Evidence of four tsunami was found. At Puerto Casma, in northern Perú, a graded, heavy mineral-rich layer with shell- and rockfragments was detected. OSL dating revealed an age of 0.37 0.03 ka (1615e1667 AD). Inverse modelling of tsunami onshore flow parameters indicates a flow depth of w6 m and a flow speed of w8 m/s at a distance of w60 m from the shoreline. For the Chimbote earthquake of 1619 AD, a tsunami was notlisted in the historical tsunami catalogues, although it is seen as a predecessor of the 1996 Chimbote earthquake and tsunami. Hence, this study may provide the first evidence of a local tsunami triggered by this event. A graded, shell-rich event layer that contains cobbles with attached marine organisms was found at Vila Vila in southern Perú. This layer was dated to 0.17 0.04 ka (1797e1871 AD) and is mostprobably the result of the 1868 Arica tsunami. Two additional event layers found in Boca del Río (southern Perú) were dated 2.26 0.37 ka (615 BCe119 AD) and 1.98 0.23 ka (207 BCe255 AD). Thus, the layers record for the first time tsunami much older than the events listed in tsunami catalogues. These two events exhibit similar parameters with flow speeds of 7e8 m/s and depths of 6 m in a distance of 460 m from the present shoreline. The time that passed between the events is similar to the recurrence interval of the two Arica tsunami of 1604 and 1868 AD, hence giving evidence of another prehistoric earthquake and tsunamicouplet.