Inverting for source parameters using a genetic algorithm applied to deformation signals observed at the Auckland Volcanic Field

Abstract

The city of Auckland is located in the Auckland Volcanic Field in northern New Zealand, where the most recent volcanic activity occurred only 600–800 years ago. Surface deformation is a likely precursor to the resumption of volcanic activity in the field. To investigate the potential for satellite-borne InSAR measurements to detect ground deformation signals of the scale and areal distribution likely to be associated with magma ascent, interferometric processing was carried out on 26 ENVISAT ASAR images acquired between 18 July 2003 and 9 November 2007. The average rate of deformation and its corresponding errors were found by calculating and stacking several differential interferograms. Four regions of subsidence and three regions of uplift were observed in the vertical component of the ground deformations. The sources were modeled with a Mogi point source model, whose parameters (location, depth, and strength) were found using a genetic algorithm inversion. On the whole, the genetic algorithm performed well in finding the optimal solution of the source models from the ground deformation data. The location of ground deformation was compared with the location of present and past groundwater wells, and it was determined that most deformation is groundwater related. Future work includes using a groundwater model instead of a Mogi source to derive groundwater-related parameters.