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Studies in Surveying and Mapping Science (SSMS) Volume 1 Issue 1, March 2013
TABLE 1 DIFFERENTAL INTERFERO GRAMS WITH TEMPORAL AND SPATIAL PERPENDICULAR BASELINES.
Stacking Results A stack rate of interferograms can be calculated for each pixel through the following equation: (4) where
is the average deformation velocity
measured in rad/yr and is the phase of th interferogram (radians) calculated over a time period (years). We tried to reduce another error sources in DInSAR processes. Therefore, we can assume
~
(Samsonov, 2010). We applied 6 differential unwrapped interferograms from descending path frame 2830 to generate stacked map over Tabriz area. TABLE 1 shows detail of used interferograms. Stacking is an effective method to reduce residual noises and errors of interferograms providing average rate of displacements (Wright et al., 2001; Walters et al., 2011). For revealing land subsidence and fault rates, we create three profiles along TP and NTF. FIG. 6 shows stack map and A, B and C transects. We considered a weighted value for pixels and fitted curves for better assessment.
No
Master
Slave
T.Baseline (D)
P.Baseline (m)
1
2003.11.28
2004.04.16
140
184
2
2003.11.28
2004.05.21
175
222
3
2004.05.21
2006.12.22
945
51
4
2004.06.25
2008.04.25
1400
93
5
2006.02.10
2007.01.26
350
23
6
2007.05.11
2008.04.25
330
-108
FIG. 6 shows general land subsidence in the research area whose rate is about 20mm/yr. Also, fitted curves indicate about 7 mm/yr slip rate between south and north part of NTF. This rate is consistent with the results of the similar research in which GPS measurement was used for slip rate partitioning (Rastbood and Voosoghi 2011). FIG. 7 shows InSAR image frame and GPS network of NW Iran. Further analysis is required to obtain independent slip rates from InSAR dataset. As an alternative, we will utilize time series analysis methods such as persistent scatterer InSAR (PSI), Small Baselines Interferometry (SBAS) or Stanford Method for Persistent Scatterers (StaMPS) (Motagh et al., 2007; Lanari et al., 2007; Hooper et al., 2010).
FIG. 6 LEFT IS THE STACK MAP OF INTERFEROGRAMS WHICH MENTIONED IN TABLE 1. RIGHT IS WEIGHTED PIXELS OF A, B AND C TRANSECTS AND SHOWS YEARLY DISPLACEMENTS IN TABRIZ REGION RESPECT TO NTF. A AND B TRANSECTS SHOW LAND SUBSIDENCE PHENOMENA IN SOUTH PART OF NTF. CURVES ARE ILLUSTRATED WITH CONFIDENT OF 95%. YELLOW STAR SHOWS THE LOCATION OF VANYAR DAM. RED AND GREEN POINTS ARE OUTLIER DATA AND THEY HAVE NOT BEEN USED...
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