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Joint inversions of ERS-InSAR and long-period seismic data

Gareth Funning(1) and Eric Fielding(1)

(1) COMET, Parks Rd, Oxford OX1 3PR, United Kingdom

Abstract

The ERS archive is a rich source of information about earthquakes in the recent past. With acquisitions continuing to the present day it is possible, using the technique of SAR interferometry (InSAR), to revisit seismic events that may have escaped attention at the time, or to re-analyse previously studied events with new data. However source models obtained from these data using elastic dislocation modelling can often be subject to tradeoffs between key parameters (such as rake, fault slip and seismic moment), especially in areas where data from only a single look direction are available -- as is the case in much of the Alpine-Himalayan Belt and parts of the Andes.

In such situations additional constraints can be useful in reducing tradeoffs between key parameters. We demonstrate here the joint inversion of ERS-InSAR data and long-period (135--150 s) seismic data to better constrain earthquake source models. Long-period seismic data are an ideal complement to InSAR data for earthquake studies as they record only the energy released during the earthquake, whereas InSAR records all deformation occurring between the two image acquisitions. They can also, like InSAR, be used `remotely', that is, without the need for field visits.

We use as examples two earthquakes from the ERS archive -- the 1998 Aiquile, Bolivia and 1998 Fandoqa, Iran events. Each earthquake is modelled simultaneously as a rectangular elastic dislocation and a seismic point source, or centroid, whose normalised misfits to the data are scaled so as to have equal weighting. Monte Carlo error analyses using realistic noise show that in both cases uncertainties in rake and moment are significantly reduced, as are related tradeoffs. We believe that this technique could be a valuable tool for improving estimates of source parameters in areas of limited data coverage.

 

Workshop presentation

Keywords: ESA European Space Agency - Agence spatiale europeenne, observation de la terre, earth observation, satellite remote sensing, teledetection, geophysique, altimetrie, radar, chimique atmospherique, geophysics, altimetry, radar, atmospheric chemistry