Seismic driving of nationwide changes in geomorphology and prehistoric settlement - a 15th Century New Zealand example

We propose a model for the seismic driving of environmental changes and illustrate it using a case study from New Zealand dated to the 15th Century AD. A seismic staircase shows a chronological progression of environmental outcomes that includes tsunami, rock avalanches, vegetation disturbance, rapid coastal dune building, river aggradation, and abandonment of prehistoric coastal settlements. The 15th Century event appears to be unique in the past Millenium and is most notable for its period of rapid coastal dune building. The coincidence of a catastrophic El Nino episode in the mid 15th Century AD may have served to move sediments rapidly through the terrestrial system thus delimiting clearly separate geomorphological after-effects. We contend that seismic driving is a major factor in determining paleoenvironmental change in tectonically active areas during the Holocene and provides the palaeoenvironmental context within which smaller scale events operate. (C) 2002 Elsevier Science Ltd. All rights reserved.