Publications

Export 3 results:
Sort by: Author Title Type [ Year  (Desc)]
2012
Manzo, M, Fialko Y, Casu F, Pepe A, Lanari R.  2012.  A quantitative assessment of DInSAR measurements of interseismic deformation: the Southern San Andreas Fault case study. Pure and Appl. Geophys.. 169(8):1463-1482.   10.1007/s00024-011-0403-2   AbstractWebsite

We investigate the capabilities and limitations of the Differential Interferometric Synthetic Aperture Radar (DInSAR) techniques, in particular of the Small BAseline Subset (SBAS) approach, to measure surface deformation in active seismogenetic areas. The DInSAR analysis of low-amplitude, long-wavelength deformation, such as that due to interseismic strain accumulation, is limited by intrinsic trade-offs between deformation signals and orbital uncertainties of SAR platforms in their contributions to the interferometric phases, the latter being typically well approximated by phase ramps. Such trade-offs can be substantially reduced by employing auxiliary measurements of the long-wavelength velocity field. We use continuous Global Positioning System (GPS) measurements from a properly distributed set of stations to perform a pre-filtering operation of the available DInSAR interferograms. In particular, the GPS measurements are used to estimate the secular velocity signal, approximated by a spatial ramp within the azimuth-range radar imaging plane; the phase ramps derived from the GPS data are then subtracted from the available set of DInSAR interferograms. This pre-filtering step allows us to compensate for the major component of the long-wavelength range change that, within the SBAS procedure, might be wrongly interpreted and filtered out as orbital phase ramps. With this correction, the final results are obtained by simply adding the pre-filtered long-wavelength deformation signal to the SBAS retrieved time series. The proposed approach has been applied to a set of ERS-1/2 SAR data acquired during the 1992–2006 time interval over a 200 × 200 km area around the Coachella Valley section of the San Andreas Fault in Southern California, USA. We present results of the comparison between the SBAS and the Line Of Sight (LOS)—projected GPS time series of the USGC/PBO network, as well as the mean LOS velocity fields derived using SBAS, GPS and stacking techniques. Our analysis demonstrates the effectiveness of the presented approach and provides a quantitative assessment of the accuracy of DInSAR measurements of interseismic deformation in a tectonically active area.

2010
Pearse, J, Fialko Y.  2010.  Mechanics of active magmatic intraplating in the Rio Grande Rift near Socorro, New Mexico. Journal of Geophysical Research-Solid Earth. 115   10.1029/2009jb006592   AbstractWebsite

We investigate long-term deformation due to the Socorro Magma Body (SMB), one of the largest active intrusions in the Earth's continental crust, using interferometric synthetic aperture radar (InSAR) observations and finite element simulations. InSAR data spanning 15 years (1992-2007) indicate that the magma body is associated with a steady crustal uplift at a rate of about 2 mm yr(-1). Previous work showed that while the pattern of surface uplift is consistent with an elastic inflation of a large sill-like magma body, the SMB could not have formed via steady elastic inflation because the latter would be outpaced by magma solidification. We resolve this problem using coupled thermovisco-elastic models, and place constraints on the intrusion history as well as the rheology of the ambient crustal rocks. We demonstrate that observations rule out the linear Maxwell response of the ductile crust, but are consistent with laboratory-derived power law rheologies. Our preferred model suggests that the age of the SMB is of the order of 10(3) years, and that the apparent constancy of the present-day uplift may be due to slow heat transfer and ductile deformation in a metamorphic aureole of a giant sill-like magma intrusion, rather than due to a steady increase in the magma overpressure. The SMB is a contemporaneous example of "magmatic intraplating," a process by which large volumes of mafic melt stall and spread at midcrustal depths due to density or rheology contrasts.