Southern Peru desert shattered bv the great 2001 earthquake: Implications for paleoseismic and paleo-El Nino-Southern oscillation records

In the desert region around the coastal city of Ilo, the great southern Peru earthquake of June 23, 2001 (8.2-8.4 moment magnitude), produced intense and widespread ground-failure effects. These effects included abundant landslides, pervasive ground cracking, microfracturing of surficial hillslope materials, collapse of drainage banks over long stretches, widening of hillside rills, and lengthening of first-order tributary channels. We have coined the term shattered landscape to describe the severity of these effects. Long-term consequences of this landscape shattering are inferred to include increased runoff and sediment transport during postearthqualke rainstorms. This inference was confirmed during the first minor postearthquake rainstorm there, which occurred in June and July of 2002. Greater amounts of rainfall in this desert region have historically been associated with El Nino events. Previous studies of an unusual paleoflood deposit in this region have concluded that it is the product of El Nino-generated precipitation failing on seismically disturbed landscapes. The effects of the 2001 earthquake and 2002 rainstorm support that conclusion.