FR01_01_GlezetalIGARSS2011.ppt
-
Upload
grssieee -
Category
Technology
-
view
322 -
download
8
Transcript of FR01_01_GlezetalIGARSS2011.ppt
![Page 1: FR01_01_GlezetalIGARSS2011.ppt](https://reader034.fdocuments.in/reader034/viewer/2022042614/55a478091a28abfe268b4778/html5/thumbnails/1.jpg)
Large-scale deformation mapping over Danakil depression (Afar, Ethiopia) from
Wide-Swath SAR interferometric time series
Pablo J. González1, Nicolas d’Oreye2, Eugenio Sansosti3, Kristy F. Tiampo1 and José Fernández4
1. Dept. Earth Sciences, University of Western Ontario, London-Ontario, Canada.2. Musée National d’Histoire Naturelle (MNHN), Luxembourg.3. Istituto per il Rivelamento Elettromagnetico dell’Ambiente (IREA, CNR), Naples, Italy4. Institute of Geosciences (CSIC-UCM), Facultad CC. Matemáticas, Madrid, Spain
![Page 2: FR01_01_GlezetalIGARSS2011.ppt](https://reader034.fdocuments.in/reader034/viewer/2022042614/55a478091a28abfe268b4778/html5/thumbnails/2.jpg)
Outline
Motivation
SCANSAR interferometry time series
Case application: Danakil depression
Conclusions
![Page 3: FR01_01_GlezetalIGARSS2011.ppt](https://reader034.fdocuments.in/reader034/viewer/2022042614/55a478091a28abfe268b4778/html5/thumbnails/3.jpg)
Motivation Some Earth Sciences problems require the imaging of large areas:
DEM generation (efficient and reliable global coverage)Deformation mapping
Carbon cycle monitoring (large basins forestry),…
So far, Wide-swath interferometry - success - applied in ground deformation monitoring: In particular, static ground deformation due to large earthquakes
Why time series processing of Wide-swath interferometry time series?
WS Time Series could:
Reduce burden for the monitoring of extended areas
Estimation of reliable long-scale smoothly variable deformation signals
![Page 4: FR01_01_GlezetalIGARSS2011.ppt](https://reader034.fdocuments.in/reader034/viewer/2022042614/55a478091a28abfe268b4778/html5/thumbnails/4.jpg)
DInSARReliable tool to measure/mapping ground deformation of the Earth’s surface Interferometric synthetic aperture radar (InSAR) combines phase information from two radar (SAR) images of the same area acquired from similar view points at different times to produce an pattern of phase interference (interferogram).
The interferogram, depicting range changes between the radar and the ground within a fraction of the wavelength precision (mm-cm) under favorable conditions.
DInSAR time seriesHowever, ground deformation and Earth surface changes are dynamic (change with time).
Time series processing (SBAS or PSI) provides with: linear velocity maps and time series of displacements.
Proved to be more precise, successful reduction of atmospheric noise.
![Page 5: FR01_01_GlezetalIGARSS2011.ppt](https://reader034.fdocuments.in/reader034/viewer/2022042614/55a478091a28abfe268b4778/html5/thumbnails/5.jpg)
SCANSAR concept Large scale coverage though
a set of radar pulses (bursts)
Covering multiple swathes (loss of azimuth resolution)
ScanSAR sensors ENVISAT ALOS TSXNumber of sub-swaths 5 3-5 4 Swath width (ground range) 400 km 250-350 km 100 km Incidence angle range 16°-44° 16°-38° 20°-45° Azimuth resolution 150 m 100 m 18.5 m Ground range resolution 20 m 100 m 1.70 - 3.49 m
400 km
400
km
Figure: DLR
![Page 6: FR01_01_GlezetalIGARSS2011.ppt](https://reader034.fdocuments.in/reader034/viewer/2022042614/55a478091a28abfe268b4778/html5/thumbnails/6.jpg)
Stack processing issues:
Synchronization of bursts is necessary for phase preservation.If no or low burst overlap, corregistration maybe be problematic, and typical single “master” stack might not be accomplished.
Coregistration of differential interferograms:
All interferograms were spectrally cross-correlated
Resampled with a 12-points cosine-raised method
Common “master” interferogram geometry (200612-200701)
100 %overlap
50 %overlap
0 %overlap
![Page 7: FR01_01_GlezetalIGARSS2011.ppt](https://reader034.fdocuments.in/reader034/viewer/2022042614/55a478091a28abfe268b4778/html5/thumbnails/7.jpg)
Our processing chain for WS time series:Our processing chain for WS time series:
1) Wide Swath or ScanSAR raw focusing.1) Wide Swath or ScanSAR raw focusing.
2) Pair-wise single SLCs coregistration.2) Pair-wise single SLCs coregistration.
3) Resampling and mosaicking.3) Resampling and mosaicking.
4) (Differential) Interferogram computation (w/o DEM and F.E.) + Coherence.4) (Differential) Interferogram computation (w/o DEM and F.E.) + Coherence.
5) Repeat 2-4 until all interferograms are computed.5) Repeat 2-4 until all interferograms are computed.
Steps computed with:Steps computed with:SARScapeSARScape
6) Corregistration of all interferograms to a single interferogram (interferograms stack).6) Corregistration of all interferograms to a single interferogram (interferograms stack).
7) Resample.7) Resample.
8) Unwrapping (SNAPHU or GAMMA)8) Unwrapping (SNAPHU or GAMMA)
9) Small Baseline time series inversion (LSQ or SVD analysis)9) Small Baseline time series inversion (LSQ or SVD analysis)
Steps computed with:Steps computed with:Home-made softwareHome-made software
![Page 8: FR01_01_GlezetalIGARSS2011.ppt](https://reader034.fdocuments.in/reader034/viewer/2022042614/55a478091a28abfe268b4778/html5/thumbnails/8.jpg)
Danakil depression (Afar) Northern most segment of the on-shore African Rift
Extensional tectonics (~normal faulting) and magmatism
Similarities with divergent mid-ocean ridges (80% volcanism)
http://www.see.leeds.ac.uk/afar/new-afar/geology-afar/structure-tech-pages/geol-afar-dep-tech.html
![Page 9: FR01_01_GlezetalIGARSS2011.ppt](https://reader034.fdocuments.in/reader034/viewer/2022042614/55a478091a28abfe268b4778/html5/thumbnails/9.jpg)
Danakil depression (Afar) Northern most segment of the on-shore African Rift
Extensional tectonics (~normal faulting) and magmatism
Similarities with divergent mid-ocean ridges (80% volcanism)
Quaternary strain localized to ~60 km long zones of
fissures, aligned eruptive centers and faults –
“magmatic segments“
http://www.see.leeds.ac.uk/afar/new-afar/geology-afar/structure-tech-pages/geol-afar-dep-tech.html
![Page 10: FR01_01_GlezetalIGARSS2011.ppt](https://reader034.fdocuments.in/reader034/viewer/2022042614/55a478091a28abfe268b4778/html5/thumbnails/10.jpg)
Recent investigations (Reilinger et al., 2010) deducted the existence of a distinguished tectonic block between Arabia, Nubia and Ethiopian plates from GPS kinematics measurements.
The Danakil block has a strong NS gradient of rapidly E-W motion w.r.t. fixed Nubia. (~0 mm/yr @ 16ºN to ~20 mm/yr @ 12ºN)
So, the diverengence (horizontal strechting) rate is about 20-30 mm/yr at the central part of the depression. This accumulated energy should release, but how?
faulting vs. magmatism.
Ideal case for analyzing
large-scale, distributed
deformation processes
![Page 11: FR01_01_GlezetalIGARSS2011.ppt](https://reader034.fdocuments.in/reader034/viewer/2022042614/55a478091a28abfe268b4778/html5/thumbnails/11.jpg)
In September 2005, a huge seismo-magmatic (163)
event alerted about a possible large intrusion event.
Wright et al., (2006) and others studied this event
using DInSAR + seismic data.
Interferograms were consistent with a megadike that release large portion of the accumulated elastic energy and correctly forecasted many more intrusions (similar to 1975-1980s Katla rifting event in Iceland)
20050611-200601072.2 km3 magma along dyke (Mt St Helens 1.2 km3).
0.5 km3 sourced from Dabbahu and Gabho volcanoes at North.Earthquakes can be responsible for < 10 % of moment release.
![Page 12: FR01_01_GlezetalIGARSS2011.ppt](https://reader034.fdocuments.in/reader034/viewer/2022042614/55a478091a28abfe268b4778/html5/thumbnails/12.jpg)
Rowland et al., (2007) reported single
Envisat Wide-ScanSAR interferograms
Full scene Envisat Wide-ScanSAR Interferogram (20050611-20060107)
![Page 13: FR01_01_GlezetalIGARSS2011.ppt](https://reader034.fdocuments.in/reader034/viewer/2022042614/55a478091a28abfe268b4778/html5/thumbnails/13.jpg)
20050611-20060107
![Page 14: FR01_01_GlezetalIGARSS2011.ppt](https://reader034.fdocuments.in/reader034/viewer/2022042614/55a478091a28abfe268b4778/html5/thumbnails/14.jpg)
Dataset and processing parameters:
ENVISAT Ascending Track 71:
Number of WSSAR (35) between 2006-2009
Here, we exclude image before 2006 (no frame overlap)
Thresholds for interferograms computation:
50% burst-overlapping (few before 2007, better onwards)
Small perpendicular baselines: < 400 m
We generate a total number of 320 interferograms
and their corresponding coherence maps
Mean coherence map shows extrem good conditions
![Page 15: FR01_01_GlezetalIGARSS2011.ppt](https://reader034.fdocuments.in/reader034/viewer/2022042614/55a478091a28abfe268b4778/html5/thumbnails/15.jpg)
Interferograms stacking
Stack (average) of differential ifgs to obtain an estimated linear velocity map
Later, processing was performed over
all pixels with average 0.3 coherence
![Page 16: FR01_01_GlezetalIGARSS2011.ppt](https://reader034.fdocuments.in/reader034/viewer/2022042614/55a478091a28abfe268b4778/html5/thumbnails/16.jpg)
Variable deformation processes:
Northern and southern segmentGrabens deepening
Unknown deflaction source:Semara volcanic centre
Post-dike inflactionDabbahu and Gabho centres
Central-segment dike intrusions + other sources:
![Page 17: FR01_01_GlezetalIGARSS2011.ppt](https://reader034.fdocuments.in/reader034/viewer/2022042614/55a478091a28abfe268b4778/html5/thumbnails/17.jpg)
Time series resultshere, we show (wrapped) as comparison between consecutive time takes.
![Page 18: FR01_01_GlezetalIGARSS2011.ppt](https://reader034.fdocuments.in/reader034/viewer/2022042614/55a478091a28abfe268b4778/html5/thumbnails/18.jpg)
Cummulative displacements (2006-2009)
Contour lines each 10 cm of line-of-sight motion
![Page 19: FR01_01_GlezetalIGARSS2011.ppt](https://reader034.fdocuments.in/reader034/viewer/2022042614/55a478091a28abfe268b4778/html5/thumbnails/19.jpg)
Modelling approach
For reduce the computational burden, a quadtree data reduction was performed to keep points representatives of sigma above the noise (phase std)
InversionInversionRegularized linearRegularized linear
Analytical models Analytical models (green functions, G)(green functions, G)
Best fitting source parameters (s):Best fitting source parameters (s):
Φ (s, k) = || G s – d ||2 + k-2 ||Δ2 s ||2 , s ≥ 0
InterpretationInterpretation
geologically sound?geologically sound?
Geodetic data (d)Geodetic data (d)
d = G s + error
![Page 20: FR01_01_GlezetalIGARSS2011.ppt](https://reader034.fdocuments.in/reader034/viewer/2022042614/55a478091a28abfe268b4778/html5/thumbnails/20.jpg)
Initial modelling with a simple rift geometry:
Essentially, dislocation geometry follows
the graben (central valley) and
simmetry of the deformation field
data
model residual
![Page 21: FR01_01_GlezetalIGARSS2011.ppt](https://reader034.fdocuments.in/reader034/viewer/2022042614/55a478091a28abfe268b4778/html5/thumbnails/21.jpg)
Improved segment geometry (extended and tortuous)
Central segment:
Deep to midcrustal magma intrusion
Shallow lateral propagation
Northern segment:
Magma chamber inflaction under Dabbahu volcano
Remainder: solution is strong dependent of the regularization parameter
data model residual
Opening distribution
![Page 22: FR01_01_GlezetalIGARSS2011.ppt](https://reader034.fdocuments.in/reader034/viewer/2022042614/55a478091a28abfe268b4778/html5/thumbnails/22.jpg)
Profiles
Northern
CentralData (blue)Model (red) Residual (black)
![Page 23: FR01_01_GlezetalIGARSS2011.ppt](https://reader034.fdocuments.in/reader034/viewer/2022042614/55a478091a28abfe268b4778/html5/thumbnails/23.jpg)
More profiles
Central
Southern
Data (blue)
Model (red)
Residual (black)
Deep deflactionary source
mainly during 2006-2007
![Page 24: FR01_01_GlezetalIGARSS2011.ppt](https://reader034.fdocuments.in/reader034/viewer/2022042614/55a478091a28abfe268b4778/html5/thumbnails/24.jpg)
Susticious long-wavelength signal:Possible relaxation of the lower crust and upper-mantle under the active segment,
it is also possible to capture partially the secular motion of the spreading plate
GPS estimates indicate significant (uplift, not shown here) and horizontal pattern following the rift events 2006-2009 (Nooner et al., 2009). Intrusions were removed.
Black arrows, secular plate motion
Red arrows, post-dike hor. velocities
![Page 25: FR01_01_GlezetalIGARSS2011.ppt](https://reader034.fdocuments.in/reader034/viewer/2022042614/55a478091a28abfe268b4778/html5/thumbnails/25.jpg)
Some remarks We show one of the first applications of wide-swath interferometric time series.
Due to burst-overlapping problems, we adopted the coregistration of interferograms, using a cross-correlation algorithm.
The Danakil depression study case shows an ideal case for long-scale deformation mapping.
Severe spatial aliasing occurred close to the central segment (Phase gradient saturation).
Potential detection in a glimpse of deformation centres. Discovery of an unknown deflactiory source farther south of the normally studied region (central segment)
Long-scale wavelength deformation signals still be challenging (orbit contributions), without tie points. Probably, ideal for deformation scales from 100 m to half-width scene.
With the addition of few sparse GPS stations, the “full” characterization and monitoring of long-scale smoothly variable deformation signals (probably, so far more reliable when combined with sparse GPS)