3-Dimension Deformation Mapping from InSAR & Multiaperture. Hyung-Sup Jung The Univ. of Seoul, Korea Zhong Lu U.S. Geological Survey, U.S.A.

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1 3-Dimension Deformation Mapping from InSAR & Multiaperture InSAR Hyung-Sup Jung The Univ. of Seoul, Korea Zhong Lu U.S. Geological Survey, U.S.A.

2 Outline Introduction to multiple-aperture InSAR (MAI) 3-D deformation reconstruction by combining descending and ascending InSAR and MAI images Mapping 3D deformation associated with the 2007 eruption at Kilauea Mapping 3D deformation associated with the 2010 Haiti EQ 3-D deformation mapping from Sentinel-1 Conclusions

3 Why Mapping 3D Deformation A 3D deformation field allows for better resolution of the parameters of deformation models for volcanic activity, earthquake, and other processes, including the geometry of the deformation source. Source geometry in deformation modeling can be ambiguous if it is estimated from vertical deformation data alone [Dieterich & Decker, 1975].

4 Why Mapping 3D Deformation InSAR is a powerful technique in mapping surface deformation, but is limited to the measurement of ground surface deformation along the radar line ofsight (LOS) direction. Because SAR satellites have near-polar orbits, it is difficult to determine 3D surface deformation from LOS InSAR data alone, even when multiple independent interferograms with different viewing angles are used jointly [Wright et al., 2004]. The objective is how to resolve the along-track (~ N-S direction) deformation.

5 Mapping Along-track Deformation Pixel offset method - Cross correlation of two or more SAR (or optical) images [Michel et al, 1999; Fialko et al., 2001] Reduced sensitivity to along-track deformation: 3-4% of azimuth pixel size. Multiple aperture InSAR (MAI): Split-beam InSAR processing that create forward- and backward-looking interferograms [Bechor & Zebker, 2006; Jung et al., 2009]. Better sensitivity to along-track deformation: 1-2% of azimuth pixel size.

6 Multiple Aperture InSAR Using the difference of squint angles between forward- and backward-looking SLC images For ERS, about 0.3 deg Estimation of along-track deformation from the phase difference between forward- and backward-looking interferograms: Modifying the Doppler centroids Limiting the integration time

7 Multiple Aperture InSAR What is Multiple Aperture Interferometry? (Jung et al., IEEE TGRS, 2009)

8 Multiple Aperture InSAR MAI Phase MAI 4 nx l x : along-track displacement l : the effective antenna length n : a normalized squint changing the aperture width. MAI phase is proportional to the along-track displacement. Better along-track displacement can be achieved with shorter effective antenna length.

9 Multiple Aperture InSAR Measurement uncertainty x l 4 n, MAI : std. of displacement measurement : std. of the phase 1 1 2, MAI N L N : the effective number L of looks for MAI : total correlation for MAI The effective number of looks (N L ) is reduced by (1-n), because the azimuth resolution degrades with aperture loss. MAI interferogram requires higher coherence than conventional interferogram in order to get high precision.

10 d d, d, d x y T z 3D Deformation Mapping r u T i d i R r r,..., 1, 2 : one LOS InSAR or MAI measurement r T n d d, d, d x u u, u, u x : a total of n InSAR and MAI measurement y y u u T z T z sin cos,sin sin, cos : 3D deformation vector (east, north, up) : unit LOS or along-track vector sin, cos,0 T T : along-track vector : LOS vector dˆ T 1 1 U U T 1 Σ U Σ R : weighted solution of 3D deformation vector

11 Application of MAI to Kilauea volcano June 2007 intrusion and eruption at Kilauea s East Rift Zone Jung et al., IEEE GRSL 2011

12 LOS InSAR LOS InSAR and MAI Images MAI LOS InSAR MAI Jung et al., 2011

13 East 3D Deformation Reconstruction North Up 3D Jung et al., 2011

14 InSAR/MAI-derived 3D Displacements vs GPS Measurements East North Up Jung et al., IEEE GRSL, 2011

15 Application of MAI to 2010 Haiti EQ

16 Application of MAI to 2010 Haiti EQ LOS InSAR LOS InSAR MAI Across-track 39 o Across-track 39 o Along-track (cm) (cm) (cm)

17 Application of MAI to 2010 Haiti EQ East North Up

18 3D Deformation Field of 2010 Haiti EQ

19 Comparison with GPS measurements East North Up GPS from Calais et al., 2010

20 3D Deformation Mapping From Sentinel-1 IW Mode Parameters ERS/EV Sentinel-1 Effective Azimuth Antenna Dimension (m) Effective Doppler Bandwidth (Hz) Satellite Velocity (m/s) Chirp Bandwidth (MHz) Carrier Frequency (GHz) Mean incidence angle (degree) Azimuth Resolution (m) 5 20 Ground Range Resolution (m) 25 5 Characteristics of Sentinel-1 w.r.t. ERS/Envisat Effective antenna dimension is larger Azimuth resolution is lower Chirp bandwidth is larger Ground range resolution is higher

21 Multiple Aperture InSAR Measurement uncertainty x l 4 n, MAI : std. of displacement measurement : std. of the phase 1 1 2, MAI N L N : the effective number L of looks for MAI : total correlation for MAI The effective number of looks (N L ) is reduced by (1-n), because the azimuth resolution degrades with aperture loss. MAI interferogram requires higher coherence than conventional interferogram in order to get high precision.

22 Precision of Along-track Displacement Measurement Along-track Displacement Std. (cm) Expected Range of Sentinel-1 for Correlation Method l ERS = 1,000 cm l SEN = 4,000cm n=0.5 N L,SEN = 50 looks Published Range of ERS for Correlation Method N L,ERS = 40 looks Decorrelation

23 Simulation of Sentinel-1 IW MAI processing Pairs Master Slave f DC,f (Hz) f DC,c (Hz) f DC,b (Hz) f D,S (Hz) Bp (m) Bp (m) ERS-2 Pair Synthetic Sentinel-1 Pair 15/09/ /10/ /09/ /10/ Sentinel-1 Simulation ERS-2 raw data spanning 1999 Hector Mine EQ Doppler bandwidth of 380 Hz is applied to ERS-2 raw data and a complex average of 5 azimuth pixels is carried out.

24 Application of MAI to Hector Mine EQ -2 Along -track LOS 2 InSAR Interferogram - /20 /20 MAI Interferogram

25 InSAR and MAI interferograms of Sentinel-1 IW Mode -2 Along -track LOS 2 InSAR Interferogram - /80 /80 MAI Interferogram

26 Along-track Along-track 50cm 50cm MAI v.s. Offset Track 2m -2m Along-track Along-track Sentinel-1 MAI ERS MAI Sentinel-1 Offset ERS Offset GPS from Agnew et al. (2002)

27 GPS v.s. MAI or offset measurements Sentinel-1 MAI ERS MAI Sentinel-1 Offset ERS Offset

28 Conclusions Combination of ascending/descending MAI and LOS InSAR images allow for 3D deformation mapping at an uncertainty of several centimeters. Measurement accuracy from MAI is about 2-3 times better than the offset tracking method. MAI-derived along-track deformation from Sentinel-1 IW can reach ~10 cm (~0.5% pixel size), while offset tracking is ~30 cm (>1.5% pixel size). Poster: Lee, Jung and Lu Ionosphere correction in InSAR imagery with MAI

29 Acknowledgements Lei Zhang for providing automated offset tracking codes Mike Poland and Asta Miklius for GPS over Kilauea Eric Calais for GPS over Haiti EQ ESA and JAXA for SAR imagery

Detecting the Source Location of Recent Summit Inflation via Three-Dimensional InSAR Observation of Kīlauea Volcano

Remote Sens. 2015, 7, 14386-14402; doi:10.3390/rs71114386 Article OPEN ACCESS remote sensing ISSN 2072-4292 www.mdpi.com/journal/remotesensing Detecting the Source Location of Recent Summit Inflation via