Studies in Surveying and Mapping Science (SSMS) Volume 1 Issue 1, March 2013 www.as-se.org/ssms

1

Using Advanced Space-borne Radar Technology for Detection and Measurement of Land Subsidence and Interseismic Slip Rates, the Case Study: NW Iran Sadra Karimzadeh1, Farshid Farnood Ahmadi *2 1 Faculty of Environmental Design, Kanazawa University, Japan 2 Department of Geomatics Engineering, University of Tabriz, Iran 1 sadrakarimzadeh@yahoo.com; *2

farshid_farnood@yahoo.com

Abstract

We used synthetic aperture radar interferometry (InSAR) to measure land subsidence in Tabriz Plain (TP) and strain accumulation along North Tabriz Fault (NTF). Thermal power plant of Tabriz city locats in the area called Tabriz Plain which supplies electric energy for NW Iran. Its facilities need to be constantly cool, so there are more than twenty water pumping stations in some parts of TP. Moreover, the power plant, petrochemical, refinery and Vanyar dam are located near at a hazardous tectonic structure called North Tabriz Fault. InSAR is one of satellite radar observation methods which is used in space geodesy. In this paper, we have applied twenty ASAR SLC images of Envisat satellite from descending orbits during May 2003 to July 2010. InSAR analysis shows about 20mm/yr land subsidence and about 7mm/yr slip rate for NTF.

Keywords

ASAR; InSAR; Fault; Slip Rate; Subsidence; Tabriz

Introduction

InSAR is a radar remote sensing technique used in space geodesy (Motagh et al., 2007 and Biggs et al., 2009). This geodetic method uses at least two or more synthetic aperture radar (SAR) images to generate Digital Elevation Model (DEM) or topographic maps using phase information within interferograms (Zebker et al., 1994b). Differential SAR Interferometry (DInSAR) technique enables the measurement of surface deformation with an accuracy of a few millimeters to centimeters for wide spatial coverage. Interferograms are generated by differentiating the phase values of two co-registered SAR images acquired at different times over the same area.

Differential interferograms have significant amount of useful data, such as surface deformations due to seismic events (Massonnet et al., 1993; Jacobs et al., 2002). It has applications for geophysical monitoring of natural hazards, for example earthquakes, volcanoes, landslides, land subsidence and also faults (Liu et al., 2004; Pathier et al., 2003; Rosen et al., 1996; Motagh et al., 2006; Lanari et al., 2007; Cakir et al., 2007). In the recent years, other methods such as use of historical Qanat (traditional water tunnel) canals displacement for calculation of annual rate of NTF, have been used (Hessami et al., 2003). But wide spatial coverage of InSAR data and its semi continuous observations hold more advantages than the same land techniques such as conventional leveling, displacement of historical Qanats or even GPS (Motagh et al., 2006 and Anderssohn et al., 2008). North west and south east directions of NTF are good orientations for using InSAR. It can help us to detect Earth deformations caused by fault movements and land subsidence. This paper is the first attempt to detect land subsidence of Tabriz Plane.

In the field of tracking fault movements and land subsidence, various researches have been done using InSAR. Some of them include investigations on North Anatolian Fault, Turkey (Wright et al., 2001, Cakir et al., 2005, Motagh et al., 2007; Walters et al., 2011), San Andreas Fault, U.S (Lyons and Sandwell 2003), Altyn Tagh Fault, Tibet (Elliott et al., 2008), the subsidence of Mexico City (Osmanoğlu et al., 2011), the subsidence of Mashhad Plain, Iran, (Motagh et al., 2006; Dehghani et al., 2009) and etc.

www.as-se.org/ssms Studies in Surveying and Mapping Science (SSMS) Volume 1 Issue 1, March 2013

2

Background

In this section, we will present geological and techni-cal characteristics of Tabriz region and Differential Synthetic Aperture Radar Interferometry (DInSAR) respectively.

Geological Background of Tabriz Region

Tabriz is the fourth largest city in Iran which is located in northwest of the country in East-Azerbaijan province and situated in the valley between Eynali and Sahand mountains.

The valley opens out into a Tabriz Plain (TP) that slopes slowly down to the northern end of Urmieh Lake and the North Tabriz Fault (NFT) is a major feature of Iran tectonics in the surrounding of Tabriz. NFT is one of the most active faults in NW Iran that has a clear surface expression. Geodetic data is not enough along most of its length especially. So wide spatial coverage of InSAR technique and north west - south east direction of NTF are good orientations for using InSAR.

1) Subsidence Phenomena at Tabriz Plain Land subsidence is the motion of a surface part as it moves downward relative to a datum. It may occur for different reasons such as: earthquake; over capacity extraction of oil, natural gas and groundwater; some mining and urban activities such as: coal extraction, metro and tunnel constructions and etc. It has been recognized as a serious environmental problem in many areas (Motagh et al., 2006; Dehghani et al., 2009 and Osmanoğlu et al., 2011). Some vital structures are located in the vicinity of TP such as: thermal power plant, petrochemical and refinery center. This paper is the first attempt to detect land subsidence of TP.

Iran's climate is arid and semiarid, therefore rain rate of this country and natural recharge are lesser than global average (Sedighi et al., 2010). Thus groundwater resources are needed for expansion of cities, agriculture and industrial uses, (Dehghani et al., 2009). Also, the thermal power plant which supplies electrical energy for NWof Iran needs to be constantly cool. So, there are more than twenty deep or semi deep wells in some parts of TP. The amount of water taken from the wells is about 5 million cubic meters per year, while allowable amount is 3 million cubic meters for each year (Razzaghmanesh et al., 2006). FIG. 1 shows some of water pumping stations in the study area.

FIG. 1 OUTLINE OF TABRIZ PLAIN. SOME WATER PUMPING

STATIONS ARE SHOWN BY TRIANGULARS

2) Strain Accumulation on North Tabriz Fault

As shown in FIG. 2 the fault has an average strike of NW-SE over a length of about 150 km (Hessami et al., 2003) and which extends from Misho mountain in the west to Bostanabad city in the east (Vafaie et al., 2008). It is located within 5km of Vanyar dam (Mozaffari et al.,).

“NW Iran is a region with intense deformation and seismicity situated between two thrust belts, the Caucasus to the north and the Zagros mountains to the south (Hessami et al., 2003). The NTF is one of the most active faults in NW of Iran which has a clear surface expression. FIG. 1 shows its trace. The NTF did not generate large earthquakes during the last 200 years. The recurrence interval of the NTF is calculated for 300 years approximately based on the historical movements such as surface displacements of old Qanat lines (Hessami et al., 2003). Right-lateral movement along this fault has been suggested from aerial photographs (Berberian and Arshadi, 1976; Berberian et al., 1999). This can be clearly confirmed observing the field (Karakhanian et al., 2004). Through wide cover InSAR observations, we can quantify NTF trends. The seismic risk for the built environment and the population is estimated to be high and alerting which has gradually gained significant scientific and public interest. One major factor affecting the level of high risk is that the area is expanding rapidly with vulnerable infrastructure develop-ment and constructions. As an example, the petro-chemical plant or the Tabriz-Miandoab water distribution project are exposed directly to the potential NTF earthquakes. Furthermore, Vanyar dam can induce stress changes and intensify the movement (Moghaddam and Saghafi, 2006).

Studies in Surveying and Mapping Science (SSMS) Volume 1 Issue 1, March 2013 www.as-se.org/ssms

3

FIG. 2 A) SATELLITE IMAGE AROUND NTF FROM MISHO MOUNTAIN IN THE WEST TO BOSTANABAD CITY IN THE EAST. B) THE

IMAGE SHOWS WATERWAYS OFFSET CAUSED BY NTF CREEP ON ONE HILL BETWEEN SOFIAN AND TABRIZ CITY. C AND D, TWO IMAGES ARE TAKEN FROM ROSHDIYE TOWN IN NORTH OF TABRIZ (JULY 2010) THAT SHOW THE FAULT IS ACTIVE

Technical Background

Synthetic Aperture Radar Interferometry is a technique which measures the phase difference between two radar images taken from two slightly different positions. The formation of an interferogram can be expressed as:

(1)

where denotes interferogram, are the

across and along-track image coordinates, and

are the complex master and slave images, denotes

the complex conjugate operator, and is the pixel wise multiplication operator. The interferometric

phases reflect the range changes in the radar line of sight (LOS) direction between the two SAR passes (Zebker et al., 1994a,b). Different types of errors are presented in the interferograms that need to be estimated and, if possible, corrected. Often ionospheric error is presented, which also manifests itself as a linear trend such as ramp of colors from red to blue across interferograms. However, ionospheric phase contributions become more evident with L- and P-band (3 GHz-300 MHz) SAR systems. The ionospheric effects for C-band (5.4 GHz) Envisat data are negligible (Lyons and Sandwell 2003; Takada et al., 2009). Equation 2 presents the several important components of an interferogram for each pixel.

(2)

is related to the deformation of the surface

between the two acquisitions, is related to the

difference of atmospheric conditions, is

related to errors in the topographic model, represents the errors in orbital information,

represents phase changes caused by

temporal decorrelation, and relates to the phase changes due to thermal noise (Zebker et al., 1992, 1997; Gatelli et al., 1994).

Nine interferograms exhibiting lower level of noises were selected among fifty interferograms produced from a pool of twenty SAR complex images acquired from May 2003 to July 2010. Analyzing the interferograms which are near the faults indicates traceable phase difference patterns.

Analysis & Results

Interferograms are generated by differentiating the phase value of two coregistered radar images acquired from different times over the same area. Some of these interferograms were select to contribute to making a rate map of displacements by stacking approach (Wright et al., 2001, Motagh et al., 2006; Walters et al., 2011).

DInSAR Results

DInSAR technique allows monitoring inter-seismic motion in order to better assess the seismic risk of

www.as-se.org/ssms Studies in Surveying and Mapping Science (SSMS) Volume 1 Issue 1, March 2013

4

regions. We chose the so-called two-pass technique to generate nine interferograms obtained from twenty C-band (5.6cm) Envisat ASAR descending images track 49 acquired from May 2003 to July 2010. FIG. 3 displays the location of the SAR scenes.

In order to avoid snow cover and temporal variability, we selected data pairs within the same season. Images taken at 2 May 2003 and 9 July 2010 were removed due to large baseline, undesired Doppler centroid and excessive noise. Interferograms with temporal baselines of up to 5 years were generated to detect and measure the amount of seismic slip. The fault creep in interferograms appears as a shift in phase at the surface trace of the fault. In other words, fault-creep gives rise as a discontinuity in phase across the fault if it reaches to the surface. Therefore, the amount of phase shift defines the creep rate (Cakir et al., 2005). The images were processed using the DORIS software on ADORE console (Kampes et al., 2007; Osmanoğlu 2010). Precise orbits were used to estimate the exact position of the satellite during the image acquisition (Otten et al., 2010). Shuttle Radar Topography Mission (SRTM http://dds.cr.usgs.gov/srtm) and Digital Elevation Model (with resulotion of 90m) data were

used to remove the topographic phase. An error of

in DEM can propagate into the deformation phase measurement. The topographic phase error is:

(3)

where is the slant range from the sensor to the

ground, is the local radar incidence angle and is the length of the perpendicular baseline. It is clear that

approaches to zero when approaches to zero. Therefore short perpendicular baselines were used to obtain higher accuracy.

In top and bottom areas of most of the interferograms shown in FIG. 4, phase variation is observed. For the top part of the images, the phase variation is caused by dense and tall vegetation. Envisat uses C-band (5.6 cm wavelength) that exhibits lower penetration into vegetation in comparison with other sensors like L-band (15-30 cm wavelength). In the bottom part of the above mentioned images, no vegetation is observed. The resulted dominate phase signature on the bottom of the images may be related to the land subsidence of TP and movements of NTF. White arrows indicate the location of subsidence area which is observed on TP. FIG. 5 shows ground subsidence around some of the water pumping stations.

FIG. 3 A) OVERVIEW OF ACQUIRED SAR DATA FRAME. B) THE FOOTPRINT OF THE ACQUIRED ASAR DATA OVER TABRIZ VIA

BLACK BOX. C) TECTONIC MAP OF IRAN. IT SHOWS NW OF IRAN AFFECTED BY COLLISION OF ARABIA AND EURASIA PLATES. BLACK RECTANGULAR SHOWS INSET B. YELLOW STAR SHOWS LOCATION OF VANYAR DAM. CS = CASPIAN SEA, TP = TABRIZ

PLAIN, NTF = NORTH TABRIZ FAULT

Studies in Surveying and Mapping Science (SSMS) Volume 1 Issue 1, March 2013 www.as-se.org/ssms

5

FIG. 4 SOME DIFFERENTIAL INTERFEROGRAMS (WRAPPED) WITH TEMPORAL AND SPATIAL BASELINE FOR TABRIZ REGION. THE INTERFEROGRAMS ARE CORRECTED ACCORDIN TO THE TOPOGRAPHY. WHITE ARROWS ILLUSTRATE SUBSIDENCE AREA. EACH

COLOR CYCLE REPRESENTS ABOUT 28MM FOR THE ENVISAT RADAR SENSOR

FIG. 5 GROUND SUBSIDENCE AROUND SOME OF THE WATER PUMPING STATIONS IS EVIDENT (SEPTEMBER OF 2011)

www.as-se.org/ssms Studies in Surveying and Mapping Science (SSMS) Volume 1 Issue 1, March 2013

6

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.

TABLE 1 DIFFERENTAL INTERFERO GRAMS WITH TEMPORAL AND SPATIAL PERPENDICULAR BASELINES.

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...

Studies in Surveying and Mapping Science (SSMS) Volume 1 Issue 1, March 2013 www.as-se.org/ssms

7

FIG. 7 INSAR IMAGE FRAME AND GPS NETWORK OF NW IRAN

(MASSON ET AL.,2006). UL = URMIEH LAKE

Conclusions

This paper is a feasibility study in the field of detecting hydrogeological and seismological phenomenon such as land subsidence and interseismic slip rates detection using InSAR technique in Tabriz Plain and North Tabriz Fault. The results of the research show that stacking is an effective method to reduce residual noises and errors of interferograms providing average rate of displacements. This method illustrates that the rate of general land subsidence in the research area is 20mm/yr. Meanwhile, fitted curves indicate about 7 mm/yr slip rate between south and north part of NTF.

Increasing density of GPS stations near NTF, precise leveling process around TP, taking more SAR images which cover wide domain of the study area and combination of ascending and descending data for extracting 3D velocity rate of NW Iran by InSAR, are recommended for future studies.

In the last months of 2012, several earthquakes occurred around Tabriz fault. The earthquakes with high intensity and frequency show that this area is very active from geodynamical point of view. The rate of land slip and land subsidence measured in this research using space-borne radar technology, confirm this activity. So, the methodology of this investigation can help researchers for earthquake prediction.

REFERENCES

Anderssohn J., Wetzel H-U., Walter T.R., Motagh M.,

Djamour Y., Kaufmann H., 2008, Land subsidence

pattern controlled by old alpine basement faults in the

Kashmar Valley, northeast Iran: results from InSAR and

levelling. Geophysical Journal International.

Berberian M., Arshadi S., 1976, On the evidence of the

youngest activity of the North Tabriz Fault and the

seismicity of Tabriz city, Geol. Surv. Iran., 39, 397-418.

Berberian M., Yeats R.S., Patterns of historical earthquake

rupture in the Iranian Plateau, 1999, Bulletin of the

Seismological Society of America, 89, 120–139.

Biggs J., Burgmann R., Freymueller J.T., Lu Z., Parsons B.,

Ryder I., Schmalzle G., Wright T., 2009, The postseismic

response to the 2002M 7.9 Denali Fault earthquake:

constraints from InSAR 2003–2005. Geophysical Journal

International. 353–367.

Cakir Z., Akoglu A.M., Belabbes S., Ergintav S., Meghraoui

M., 2005, Creeping along the Ismetpasa section of the

North Anatolian fault (Western Turkey): Rate and extent

from InSAR . Earth and Planetary Science Letters 238,

225– 234.

Dehghani M., Valadan Zoej M.J., Entezam I., Mansourian A.,

Saatchi S., 2009, InSAR monitoring of progressive land

subsidence in Neyshabour, northeast Iran. Geophysical

Journal International. 178, 47–56.

Elliott J. R., Biggs J., Parsons B., and Wright T. J., 2008, InSAR

slip rate determination on the Altyn Tagh Fault, northern

Tibet, in the presence of topographically correlated

atmospheric delays. Geophysical Research Letters, VOL.

35, L12309, doi:10.1029/2008GL033659.

Gatelli F., Guarnieri M.A., Parizzi F., Pasquali P., Prati C.,

Rocca F., 1994, The wavenumber shift in SAR

interferometry. IEEE Transactions on Geoscience and

Remote Sensing, 32(2), 855-865.

Hessami K., Pantosi D., Tabassi H., Shabanian E., Abbassi M.,

Feghhi K., Sholaymani S., 2003, Paleoearthquakes and

slip rates of the North Tabriz Fault,NWIran: preliminary

results, Annals of Geophysics, 46, 903–915.

Jacobs A., Sandwell D., Fialko Y., Sichoix L., 2002, The 1997

(Mw= 7.1) Hector Mine, California, earthquake: Near

field postseismic deformation from ERS interferometry.

BSSA Special Issue on Hector Mine Earthquake 92

(4),1433–1442.

Kampes B.M., Hanssen R.F., Perski Z., 2007, RADAR

Interferometry with public domain tools.

www.as-se.org/ssms Studies in Surveying and Mapping Science (SSMS) Volume 1 Issue 1, March 2013

8

Karakhanian A., Jrbashyan R., Trifonov V., Philip H.,

Avagyan A., Hessami K., Jamali F., Bayraktutan M.,

Bagdassarian H., Arakelian S., Davtyan V., Adilkhanyan

A., 2004, Active faulting and natural hazards in Armenia,

eastern Turkey and Northern Iran, Tectonophysics, 380,

189–219.

Lanari F., Casu F., Manzo M., Lundgren P., 2007,

Application of the SBAS-DInSAR technique to fault creep:

A case study of the Hayward fault, California, Remote

Sensing of Environment 109, 20-28.

Liu G.X., Dinga X.L., Lia Z.L., Lia Z.W., Chena Y.Q., Yub S.B.,

2004, Pre- and co-seismic ground deformations of the

1999 Chi-Chi, Taiwan earthquake, measured with SAR

interferometry, Computers & Geosciences, 30, 333–343.

Lyons S., Sandwell D., 2003, Fault creep along the southern

San Andreas from interferometric synthetic aperture

radar, permanent scatterers, and stacking. Journal of

Geophysical Research, VOL. 108.

Massonnet D., Rossi M., Carmona C., Adragna F., Peltzer G.,

Feigl K., 1993, The displacement field of the Landers

earthquake mapped by radar interferometry. Nature 364,

138–142.

Masson F., Djamour Y., Van Gorp S., Chéry J., Tatar M.,

Tavakoli F., Nankali H., Vernant P., 2006, Extension in

NW Iran driven by the motion of the South Caspian

Basin. Earth and Planetary Science Letters, 252, 180–188.

Moghaddam M.H.R., Saghafi M., 2006, Geomorphologic

hazards for Vanyar Dam with emphasis on the

reactivation of Tabriz fault, northwest Iran. The

Geological Society of London, Paper number 339.

Motagh M., Djamour Y., Walter T.R., Wetzel H-U., Zschau J.,

Arabi S., 2006, Land subsidence in Mashhad Valley,

northeast Iran: results from InSAR, levelling and GPS.

Geophysical Journal International, 1-9.

Motagh M., Hoffmann J., Kampes B., Baes M., Zschau J.,

2007, Strain accumulation across the Gazikoy–Saros

segment of the North Anatolian Fault inferred from

Persistent Scatterer Interferometry and GPS

measurements, Earth and Planetary Science Letters, 255,

432–444.

Mozaffari P., Nourbakhsh M., Mozaffari N., Alizadeh H.,

Seismotectonics and seismicity of Vanyar dam by

installing a temporary network. The geophysical institute

of seismology, University of Tehran.

Osmanoğlu B., 2010, Tutorial: Processing Envisat SAR

Interferograms with ADORE.

Osmanoğlu B., Dixon T.H., Wdowinski S., Canob E.C.,

Jianga Y., 2011, Mexico City subsidence observed with

persistent scatterer InSAR. International Journal of

Applied Earth Observation and Geoinformation, 13, 1–12.

Otten M., Flohrer C., Springer T., Dow J., 2010, DORIS

processing at the European Space Operations Centre.

Advances in Space Research, 46, 606-1613.

Pathier E., Fruneau B., Deffontaines B., Angelier J., Chang C-

P., Yu S-B., Lee. C-T., 2003, Coseismic displacements of

the footwall of the Chelungpu fault caused by the 1999,

Taiwan, Chi Chi earthquake from InSAR and GPS data.

Earth and Planetary Science Letters, 212, 73-88.

Razzaghmanesh M., Salemi T., Seraj M., 2006, Groundwater

quality and quantity of Tabriz plain. National

Conference on Irrigation and Drainage Network

Management (In Persian).

Rosen P.A., Hensley S., Zebker H.A., Webb F.H., Fielding

E.J., 1996, Surface deformation and coherence

measurements of Kilauea Volcano, Hawaii, from SIR-C

radar interferometry, 23,109–23,126.

Rastbood A., Voosoghi B., 2011, Extension and slip rate

partitioning in NW Iran constrained by GPS

measurements. Journal of Geodetic Science 1(4), 286-304.

Samsonov S., 2010, Topographic Correction for ALOS

PALSAR Interferometry. IEEE Transactions on

Geoscience and Remote Sensing.

Sedighi M., Nankali H.R., Arabi S., Tavakoli F., 2010,

Subsidence Detection in Salmas Area Using InSAR and

Geodetic Techniques. Geospatial Engineering Journal,

Vol. 1, No. 4.

Takada Y., Kobayashi T., Furuya M., Murakami M., 2009,

Coseismic displacement due to the 2008 Iwate-Miyagi

Nairiku earthquake detected by ALOS/PALSAR:

preliminary results. Earth Planets Space, 61, e9–e12.

Vafaie J., Taghikhany T., Tehranizade M., 2008, Near field

Uniform Seismic Hazard Spectra of Tabriz Zone. The

14th World Conference on Earthquake Engineering,

Beijing, China.

Studies in Surveying and Mapping Science (SSMS) Volume 1 Issue 1, March 2013 www.as-se.org/ssms

9

Walters R.J., Holley R.J., Parsons B., Wright T.J., 2011,

Interseismic strain accumulation across the North

Anatolian Fault from Envisat InSAR measurements.

Geophysical Research Letters, VOL. 38, L05303.

doi:10.1029/2010GL046443.

Wright T., Parsons B., Fielding E., 2001, Measurement of

interseismic strain accumulation across the North

Anatolian Fault by satellite radar interferometry

Geophysical Research Letters, 28, NO. 10, 2117-2120.

Zebker H.A., Rosen P.A., Goldstein R.M., Gabriel A., Werner

C.L., 1994a, On the derivation of coseismic displacement

fields using differential radar interferometry: the Landers

earthquake. Journal of Geophysical Research 99(1),

19617–19634.

Zebker H.A., Rosen P.A., Hensley S., 1997, Atmospheric

effects in interferometric synthetic aperture radar surface

deformation and topographic maps. Journal of

Geophysical Reasearch, 102(2), 7547-7563.