Sea level acceleration caused by earthquake induced subsidence in the Samoa Islands

Abstract

The anomalous pattern of relative sea levels for the Samoan Islands that followed the 2009 earthquake and tsunami is explained by coupling tide-gauge time series of relative sea levels and GPS time series of absolute geocentric positions of inland fixed domes. The subsidence of the land is responsible for the relative sea level acceleration that followed the earthquake. The pattern of subsidence is characterized by small departures from a linear pattern immediately before the earthquake, an abrupt change at the earthquake, and then a parabolically reducing extra subsidence. The absolute geocentric sea levels obtained clearing the relative sea level signal of the subsidence signal are stable. There is a need to couple GPS monitoring of tide gauge position with tide gauge measurements of relative sea levels without any linearity assumption to produce reliable, accurate, assessments of the pattern of sea level rise to inform policy makers.