Journal
JOURNAL OF GEODESY
Volume 86, Issue 11, Pages 1029-1041Publisher
SPRINGER
DOI: 10.1007/s00190-012-0563-6
Keywords
Three-dimension displacement; Darfield earthquake; MAI; Ionospheric effects; D-InSAR
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Funding
- National Natural Science Foundation of China [40974006, 40774003]
- Program for New Century Excellent Talents in Universities [NCET-08-0570]
- Fundamental Research Funds for the Central Universities [2011JQ001]
- Research Grants Council of the Hong Kong Special Administrative Region [PolyU 5154/10E]
- Ministry of Education of China [085201001]
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Differential interferometric synthetic aperture radar (D-InSAR) measures ground deformation only along the line-of-sight (LOS) of the radar, which limits the capability of D-InSAR in investigating the surface damages and the focus mechanisms of earthquakes. We do a three-dimensional (3D) decomposition of the coseismic displacement of the Darfield, New Zealand earthquake that occurred on 3 September 2010 by exploiting the Multi-Aperture InSAR (MAI) and D-InSAR measurements from both ascending and descending L-band PALSAR data. Due to the dispersive nature of the ionosphere and the slight Doppler shift between the forward- and backward-looking interferograms, the ionospheric effects can be more serious in MAI measurements than in D-InSAR. We propose mitigating the ionospheric effects in the MAI processing with the directional filtering and interpolation procedure that has been applied in Offset-tracking. The rupture revealed by the 3D surface displacement fits closely to the Greendale fault, which is believed to be responsible for the earthquake. The horizontal ground motions, mostly eastwards in the hanging wall and westwards in the footwall, reached up to 2.5 m and are anti-symmetric with respect to the Greendale fault. Up to 2.5 m subsidence occurred in the hanging wall, while uplift is found in the footwall with an extreme case of 1.6 m in the far left of the fault. This makes us conclude that the Greendale fault is a normal and dextral strike-slip. It is seen that the MAI measurements are very helpful in the derivation of 3D coseismic displacement fields as it provides more accurate displacement estimation in the north-south direction.
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