Salt Diapir Movements Using SAR Interferometry in the Lisan Peninsula, Dead Sea Rift Shimoni M.*a , Hanssen R. F.**b, van der Meer F.***c, Kampes B. M.**b, Ben-Dor E.****d a Geological survey division - International Institution for Aerospace Survey and Earth Sciences (ITC) and Signal and Image Centre; b Faculty of Civil Engineering and Geosiences, Department of Geodesy - Delft University of Technology; cGeological survey division International Institution for Aerospace Survey and Earth Sciences (ITC); dDepartment of Geography and Human Environment - Tel-Aviv University. ABSTRACT A several kilometres thick sequence of mostly marine salt with inter-bedded gypsum, shale and dolomite rock of Pliocene to Pleistocene age build several salt diapirs in the Dead Sea area. The Lisan Peninsula salt diapir is elongated in the N-S direction, and includes several sub-domes and a structural depression. Differential interferograms were generated for several time intervals of seven to ninety three months between 1992 and 1999 and show a large diversity of uplift and subsidence features in the peninsula. The uplift rate, which has been measured, is in correspondence to the geological rate evaluated by other geological researches. The subsidence, mainly in the south dome and the cape are much more significant. Inversion deformation in the cape between the year 1995-1996 suggested to be linked to the 22 November 1995 Nuweiba earthquake. This paper suggested a tectonic mechanism connecting the salt deformation in the Lisan Peninsula with the activity of Boqeq fault. Key Words: InSAR (IFSAR), Neotectonic, Salt diapir, Dead Sea rift. 1. INTRODUCTION In contrast to most brittle rocks in sedimentary basins, salt behaves as a viscous fluid and so can (1) deform into discordant bodies, (2) lubricate and fill in gaps between adjacent fault blocks, (3) flow at low pressure and temperature conditions, and (4) drag adjacent strata. Besides being triggered and controlled by tectonic deformation, these salt-related processes may become self-driven owing to buoyancy forces (Guglielmo et al., 1995). Consequently, initially horizontal salt layers in a sedimentary sequence can produce structures that follow complex deformation paths through time. For example, a salt layer can continuously or episodically evolve into irregular allochthonous salt sheets, salt pillows, diapirs, walls with overhangs, etc. Accurate visualization and interpretation of how these salt-related structures develop through time are complex but motivated by economical implications: salt structures are highly impermeable, so their irregular shapes can combine with sealing faults and shales to form traps for hydrocarbons The launch of the ERS-1 satellite by the European Space Agency ESA in 1991 opened a new dimension in geology and tectonic research. Deformation effects of the Earth’s surface can be measured over large areas with sub-centimetre accuracy using SAR interferometry. A demonstration of the power of the technique was given by Massonnet et al. (1993) which indicated that horizontal and vertical displacements caused by an earthquake could be measured using this technique. Comparison of the satellite measurements with numerical models showed remarkable resemblance. * [email protected]; Tel: +32 2 737 64 74; Fax: +32 2 737 64 72; RMA - Signal and Image Center, Electronic Department, Avenue De la Renaissance, 30, 1000-Brussels, Belgium. ** [email protected] and [email protected] ; Tel: + 31 15 278 25 65; Fax: + 31 15 278 2348; Faculty of Civil Engineering and Geosiences, Department of Geodesy, Delft University of Technology, Thijsseweg 11, 2629 JA Delft, Netherlands. *** [email protected] ; Tel : +31 53 48 74 353 ; Fax: +31 53 48 74 400; Geological survey division, International Institution for Aerospace Survey and Earth Sciences (ITC), Hengelosestraat 99, P.O.Box 6, 7500 AA Enschede, Netherlands. **** [email protected]; Tel: + 972 3 640 70 49 ; Fax: + 972 3 640 62 43 ; Department of Geography and Human Environment, Tel-Aviv University, P.O.Box 39040, Ramat Aviv, Tel-Aviv, 69978, Israel. Since that time, the application of differential InSAR was extended to many forms of surface deformation including: coseismic deformations (Zebker et al., 1994; Peltzer and Rosen, 1995), volcano deformation monitoring (Rosen et al., 1966), land subsidence (Amelung et al., 1999) and glacier and ice monitoring (Goldstein et al., 1993). Documented evidence of strong earthquakes along the Dead Sea rift dates to biblical times. Continuing young lateral motion on the transform fault is indicated by earthquake mechanisms and by morphological expression of young fault displacements. Coseismic displacement and global subsidence mechanism along the transform have been investigated using InSAR technique by several researchers (Dearew, 1996; Bodechtel et al., 1997; Cornet et al., 1997; Baer et al., 1999; Remi and Avouac, 1999, Baer et al., 2000). But not all the deformations along the Dead Sea rift are dramatic and some are not connected to the tectonic activity. In the Dead Sea Basin (DSB) which occupies the lowest part of the Dead Sea rift, an estuarine-lagoonal series started to overlay 5 km thick halite layer during the Early Pliocene age. This salt layer forms several diapirs, one of them is the Lisan Peninsula. The objective of this research is to measure the deformations along the Lisan diapir using InSAR technique. The results will be compared to previous geological studies and a several mechanism will be discussed. 2. GEOLOGICAL SETTING The DSB (Figure 1) is a prominent morphotectonic depression along the Dead Sea transform fault (also called rift). The basin is a young intercontinental plate boundary formed as a result of the late-Cenozoic breakup of the once continuous Arabo-African continent (Garfunkel, 1997). Since the time of the Dead Sea formation, 105 km of left-lateral horizontal movement has occurred along its length (Freund et al., 1970). The Dead Sea depression comprises two basins, each about 50-60 km long, 15-17 km wide and filled with up to 100 km of Neogene to recent sediments. Like basins in other large trans-current fault systems, the DSB basins considered to be pullapart basins formed by offset of the strike-slip faults (Quennell, 1959; Freislander and Ben-Avraham, 1989; BenAvraham et al., 1999). A B Figure 1: The Dead Sea basin, (A) Geographical setting; (B) Amplitude image of ERS-1/2 tandem pairs 03439_23112 [16-17/12/95]. The two basins of the Dead Sea are separated by a structurally complex region, part of which is occupied by the Lisan Peninsula, a salt diapir buried 100 m below surface. Its original evaporites were formed during the Pleistocene (Lisan formation) (Zak, 1967, Freund et al., 1970, Neev and Hall, 1979) and overlaid by Holocene sediments (Ze’elim Formation) (Bartov, 1999). A B Figure 2: Geological setting of the Lisan Peninsula - (A) Structural map of the upper layer (after Bartov, 1997); (B) Migrated seismic line DS-07 and interpetation (made by NRA, 1994). The main structure of the Lisan Peninsula diapir extends over 12 by 7 km (Hassouneh, 1997). Its elongated N-S dome is about 9-km by 6 km while the folds elongation are mainly NW-SE (see Figure 2A). The height differences are below 30 m. Two faults, striking N-S and SW-NE, bound the peninsula in the east and northwest, respectively. In its southern part there are two secondary domes. The southern dome is an elongated SW-NE and its length is about 3 km by 2 km. Toward the north, the dome is closed by folds and structural depression. The bedding inclinations are 3°-10° and they change orientation gradually around the dome. The East dome is an elongated SE-NW dome of about 3-km by 1.5 km. At Berkat el-Haj there is a structural depression, about 2-km wide, with inclination of 5°-10° toward its centre (Bartov, 1999). Seismic line DS-7, which crosses the Peninsula NE-SW from the centre of the south dome, is presented in Figure 2B. We can see that the Lisan is an engraved diapir with a 6.0 to 7.0 km deep salt basis (3 seconds of two way travel time, with a speed of 4000 m/second). The cross section interpretation shows a structure of three bulbs in the top layer. In both sides, the diapir creates overhang against the reflectors. Part of the layers in the N-E side bends considerably and several reflectors terminate against the diapir. This implies fault activity during the Pleistocene sediment deposition. The salt overhangs lays over pinch-out, although in the N-E side its expression is clearer. Fault structure has not been found in the cross section. Uplift rates for some of the Dead Sea diapirs were calculated using geological observations. The geological uplift rates for Mount Sedom are between 3.5 and 10 mm/year (Zak, 1967; Frumkin, 1996), whereas the calculated uplift rate of the Lisan diapir is 1-2 mm/year (Bartov, 1999). 3. DATA AND PROCESSING For the Lisan Peninsula seventeen ERS-1/2 scenes for the period between July 1992 and March 1999 were acquired by the Israeli Geological Institution. All the scenes are in descending orbit (2979/track 078) including a tandem pair suited for generating topographic information. We selected one scene to serve as Master image (03439, ERS-2) and five others scenes with a sufficiently high signal-to-noise ratio for producing five differential interferograms (Table 1). SATELLITE PAIR DATE PERPENDICULAR and TEMPORAL BASELINE ERS-2/1 03439_23112 17/12/95__16/12/95 ERS-2/1 03439_04372 17/12/95__11/06/92 ERS-2/1 03439_10744 17/12/95__05/08/93 ERS-2/2 03439_06445 17/12/95__14/07/96 ERS-2/2 03439_12958 17/12/95__12/10/97 ERS-2/2 03439_20473 17/12/95__21/03/99 B = 307 m Tandem (1 day) B = 54.85 m Bt = -42 months B = -29.6 m Bt = -28 months B = -92.6 m Bt = 7 months B = -6.6 m Bt = 22 months B = -271.2 m Bt = 51 months Table 1: Acquisition time differences and perpendicular baseline of selected ERS-1/2 SAR data. The data were processed using DORIS software for interferometric SAR processing which is free available to the scientific community (Kampes, 2001). All the slaves images are registered to one master image before generating interferograms. The ERS ground resolution is approximately 20 X 20 meters. A multilooking factor has been used in the processing, 5 in the azimuth direction and 1 in the range. The Goldstein and Werner (1998) phase filter was applied for the tandem interferogram pair. After the unwrapping of the tandem pair, topography was subtracted from the other interferograms using three-pass differential technique. Using the results of the three-pass differential interferometry, several horizontal and vertical cross sections were made along the peninsula. Because there is no Global Position System (GPS) station in the peninsula or near by on the shore, a reference area has been selected for the unwrapping process (marked in Figure 3). This reference area was identified using information from classical geological observations (Hassouneh, 1997; Bartov, 1999): an area without neotectonic evidence recorded. The following discussions are based on the hypothesis of zero vertical deformation of the reference area. This hypothesis should be confirmed by precise GPS measurements. However, the general trend deformation presented in the following results and discussions will remain correct relatively to the reference zone. The only consequence of non-probable vertical deformation of this reference would be a slight displacement of the limit between the uplift and subsidence area. The profiles were unwrapped, every fringe in the interferograms corresponds to 28 mm of range variation in the line of sight direction. However, assuming only vertical deformation, one fringe corresponds with vertical deformation of 30 mm (Hanssen, 2001). A cumulated 93 months vertical deformation map was produced using the different profiles. This map is the result of linear interpolation of the different cumulated (1992-1999) vertical deformation data generated from all the cross sections. As a last step, the vertical profiles were scaled relatively to the successive time intervals to obtain a uniform (mm per year) representation of the vertical deformation rate for the successive periods studied. 4. RESULTS Five differential interferograms of the Lisan Peninsula (for periods between 1992-1999) are presented in Figure 3. Several deformations have been distinguished in different parts of the peninsula with subsidence rates of 1.0 to 15.0 mm/year and uplift rates of 0.2 to 1.5 mm/year, within the studied period. As we can see in the cumulated deformation map (Figure 4), most of the subsidences are observed in the peninsula periphery, areas A and D. The main uplift zones are in the areas B and C. Continuing shore subsidence appears along the peninsula margins with maximum value of 44 mm/year in area A between the duration 10/1997-3/1999. Subsidence rates of 17 mm/year in D margin create a circular deformation zone, which appears in all the different interferograms. Maximum value of 40 mm/year deformations was detected in these areas in the period between 06/1992 to 08/1993. 0343904372 12/95-06/92 (-42 months) 0343910744 12/95-08/93 (-28 months) A A B B N C C D 4 KM D 2 1 3 0343912958 12/95-10/97 (22 months) 0343906445 12/95-07/96 (7 months) 0343920473 12/95-03/99 (51 months) A B A A B B E D 4 C C C D D 5 6 Figure 3: Lisan peninsula differential interferogram – 1: Amplitude image of ERS-1/2 tandem pairs 03439_23112 [1617/12/95]; 2-5: Three-pass differential interferogram representing each: (A) cape; (B) intermediate zone between the central dome and the cape; (C) Central dome; (D) South dome (E) Mor swamp. One color cycle corresponds with 30 mm of vertical deformation. White arrows represent subsidence areas, black arrows uplift areas. Uplift has been measured in C except in the period between 08/93-12/95. In this area maximum deformation of 23 mm/year measured in the duration between 06/1992-08/1993. Another local uplift rate of 18 mm that appears only in the period between 12/95 to 07/96 has been measured in E. This uplift is surrounded by subsidence area with maximum value of 31 mm. This deformation does not appear in the other pairs due to long temporal baseline, which cause a lot of decorrelations. Moreover, in wet winter most of the area is covered by water while the winter of 1995/1996 was dry and allowed good coherence. [mm] N 2 KM Figure 4: Accumulation vertical deformation map for the period between 06/92-03/99 Baer et al. (2000) found that the rates of subsidence in seven different sites in the DSB are fairly constant. The Lisan Peninsula interferograms results do not support this statement. We have found that the rate of the deformation is irregular. Figure 5 presents the results of the vertical cross-section made along the peninsula. The highest deformation measured along the peninsula is in A for the duration 12/95-7/96 with maximum value of 57 mm/year. Highest subsidence was also recorded in A with a maximum value of 43 mm/year in the period between 10/97-03/99. In C, the deformation rate is close to zero. The highest deformation rate has been measured during the period 06/92-08/93 with maximum value of 5 mm/year. Zone D seems globally to be subsidence area over the 8 years of the study (Figure 4). Most intense subsidence and uplift rates occurred between 06/92-08/93. Generally, we can state that A is a subsidence zone except during two periods. Between 12/95-7/96 there is deformation inversion of the area with maximum uplift rate values of 58 mm/year. Less intense and very localised uplift was also measured in area A between 07/96 and 03/97. 60 06/92-08/93 08/93-12/95 12/95-07/96 07/96-10/97 Vertical deformation (mm/year) 10/97-03/99 40 20 0 80 180 280 380 480 580 680 780 -20 -40 A B C D -60 Azimuth (pixel number) Figure 5: Annual rate deformation along the peninsula 5. DISCUSSION The interferometry process results and the geological evidences appear to reflect the salt active diapir that is buried about 100 m below the surface. The uplift rate which has been measured is in correspondence to the geological rate evaluated by Bartov (1999): 1 to 2 mm/year. The deformation rate measured using the differential interferogram in this study is 0.2 to 1.5 mm. However, the subsidence rates are much more significant. The deformation around zone D confirms the activity revealed by geological evidence including faults, folds and sediment displacements. It seems that in C start to uplift another sub-dome or maybe overhang which trigger the salt from the margin layer to creep and to feed its rising. By compering our results with the seismic line interpretation (Figure 2), we can suggest that the uplift in the northern part of C is due to the pinch-out in the NW side. Therefore, the uplift in the central dome causes subsidence in its periphery area (like zone A). The different deformation intensity and rates are common with salt activity including irregular shapes. The 22 November 1995 Nuweiba earthquake in the Gulf of Eilat (300 km south of the Dead Sea), probably triggered the inverse deformation in A between the duration 12/95-07/96 (and maybe also the period 07/96-10/97). When salt forms are subjected to a sudden shock such as an earthquake, it does not react in its continuing shatters pattern (Jackson, 1994). If considering that the repeat uplift of A in 95-96 to be linked to the 95 earthquake, it is interesting to remark that an inversion of deformation tendency leading to uplift is propagating from north to south (26 mm/year in the area southern to A in 07/96-10/97 ‘purple’ and +/-18 mm/year for D in 10/97-03/99 ‘black’). Many works in the last few years, including the one of Baer et al., (2000) connected the landform deformation and regional subsidence in the DSB with the continuous Dead Sea water level drop. Combination of fine and coarse-grained clastic layers with salt at shallow depth produces unstable environments. This mechanism creates sinkhols that appear in the interferogram as local deformation. However, our interferogram results show continuing uplift and subsidence patterns along the peninsula. Therefore, what is the mechanism that causes a deformation in the Lisan Peninsula salt wall? Salt domes are formed because salt is less dense than the overlying rock, and the salt “flows” upward due to buoyancy (Jackson et al, 1994). As the salt diapir begins to form a bulbe in the parent salt layer, it will deform the overlying beds into a dome shape directly above the rising salt mass. Additionally, salt from around the salt swell will migrate inwards towards the rising mass. Because of the removal of this salt, the overburden will subside around the bulbe in the salt to form a rim syncline. If the salt mass continues to rise, it may pierce the overlying rock layers, and salt from the mother layer will continue to flow laterally to feed the rising diapir (Jenyon, 1986). Such diapirism occurs only under certain conditions. Firstly, the rising material must be less dense than the overlying sediment, or the source layer must be differentially loaded. Secondly, there must be overburden pressure to initiate buoyant rising of the salt mass. Thirdly, the diapir material must have an `escape' route through the overburden. In order to initiate buoyant rising of the salt mass, there must be a lateral pressure differential so that the rising potential of the salt is concentrated into one area. Bartov (1999) found in his work that the thickness of the late sediments layer over the salt mass in the lisan peninsula are not enough to create a density inversion. Therefore, the mechanism, which responds to the deformation in the Lisan Peninsula, has to be different. Ten-Brink and Ben-Avraham (1989), proved with seismic profiles that Mt. Sedom diapir deformation is lead by Amaziahu fault, a listrict fault which is located south to the salt diapir. Little is known about the eastern margin of the DSB and whether its structure is similar to the western margin. However, it is hard to ignore the possibility that Boqeq fault, another listrict fault, located south to the Lisan Peninsula, could be the initiating cause of the diapirism deformations detected by interferometry. We can suggest that the Boqeq fault which delineate NW-SE, border the salt wall from the south while the Ein-Gedi transverse fault systems border it from the north in the same direction. Continuos stress from the south and high-density sediment mass from the east and west direction cause a salt migration upward and to the north. Because only one seismic line (Line 633) crosses the Boqeq fault (direction SSE-W), it is hard to prove this suggestion, and this suggestion will remain open in this paper. 6. SUMMARY AND CONCLUSIONS Eight continuos years of interferogram data were used to measure several uplift and subsidence deformations in the Lisan peninsula. The uplift rate which has been measured is in correspondence to the geological rate evaluated by classical geological studies while the subsidence rates are much more significant mainly in the south dome and the cape. The deformation rate and its pattern along the peninsula are irregular in space and time. The opposite deformation in the cape between the year 1995-1996 suggested to be triggered by the 22 November 1995 Nuweiba earthquake. In the peninsula, the thickness of the late sediments layer over the salt mass are not enough to create a density inversion therefore, the classical diapirism is not sufficient to justify the observed deformation. It seems also that the diapirism activity is not connected with Dead Sea water level drop. The controversy of the physical laws explaining the interaction between self-diapirism and tectonic is still not completely solved. This is because although different simple mechanism can be understood separately, it is very difficult to evaluate their proportions and interactions in such a given complex geological context. However, this paper suggested a tectonic mechanism connecting the salt deformation in the Lisan Peninsula with the activity of the Boqeq fault. Supporting geophysical and geological proofs are required for confirmation. ACKNOWLEDGMENTS We would like to thank Gidi Baer from the Israeli Geological Institution for his contribution to this research. To Salomon Kroonenberg, Zvi Ben-Avraham and Schulman Haim for fruitful discussions. And to extend our thanks to Damien Sirjacobs for his help and his reviewing. REFERENCES 1. F. Amelung, D. L. Galloway, J. W. Bell, H. A. Zebker and R. J. Laczniak, “Sensing the ups and downs of Las Vegas: InSAR reveals structural control of land subsidence and aquifer-system deformation” Geology, 27(6), pp. 483-486, 1999. 2. G. Baer, D. Sandwell, S. Williams, G. Shamir and Y. Bock, “Coseismic deformation associated with the November 1995, Mw=7.1 Nuweiba earthquake, Gulf of Elat (Aqaba), detected by synthetic aperture radar interferometry”, J. Geophys. Res. 104(B11), pp. 25221-25232, 1997. 3. G. Baer, U. Schattner, D. Wachs, D. Sandwell and S. Wdowinski, The lowest place on earth is subsiding – an InSAR prespective, Geological survey report – GSI/36/2000, 14 p., 2000. 4. Z. Ben-Avraham, T. M. Niemi, C. Heim, J. Negendank and A. Nur, “Holocene stratigraphy of the Dead Sea: correlation of high-resolution seismic reflection profiles to sediment cores”, J. Geophys. Res., 104(B), pp. 17617-17625, 1999. 5. J. Bodechtel, M. Frei, W. Tretter, T. Wever, H. Kauffman, Y. Xia and M. Beyth, “Multisensoral approach for studying the geology and tectonics of the Dead Sea rift, Israel”, Proc. IGARSS’97, Singapore, pp. 743745, 1997. 6. Y. Cornet, J. Y. Doulliez, D. Moxhet, D., Closson, A. Kourgli and A. Ozer, “Use of ERS tandem data to produce digital elevation models by interferometry and study land movements by differential interferometry in Calabria and Jordan”, 3rd ERS Symp. Interferometry, Florence, digital, 1997. 7. D. Derauw, “Preliminary results of Tandem SAR interferometry and differential interferometry over the Dead Sea area“, Proc. ESA Workshop on Applications of ERS SAR Interferometry - Switzerland, digital, 1996. 8. A. Frumkin, “Aplift rate relative to base-levels of a salt diapir (Dead Sea Basin, Isarel) as indicated by cave level”, G. I. Alsop, D. J. Blundell and I. Davidson, (eds.), Salt tectonics: Geological society special publication, 100, pp. 41-47, 1996. 9. U. Freislander and Z. Ben-Avraham, “The magnetic field over the Dead Sea and its vicinity”, Mar. Pat. Geol., 6, pp. 148-160, 1989. 10. R. Freund, Z. Garfunkel, I. Zak, M. Goldberg, B. Derin and T. Weissbord, “The shear along the Dead Sea rift”, Philos. Trans. R. Soc. London, Ser. A., 267, pp. 107-130, 1970. 11. Z. Garfunkel., (1997), “The history and formation of the Dead Sea basin”, T. M. Niemi, Z. Ben-Avraham and J. R. Gat (eds.), The Dead Sea – The lake and its setting, Oxford university press, Oxford, pp. 36-56. 12. R. M. Goldstein, H. Engelhardt, B. Kamp and R. M. Frolich, “Satellite radar interferometry for monitoring ice sheet motion: Application to an antarctic ice stream”, Science, 262, pp. 1525-1530, 1993. 13. R. M., Goldstein and C. L. Werner, “Radar interferogram filtering for geophysical applications”, Geophys. Res. Let., 25(21), pp. 4035-4038, 1998. 14. G. Jr. Guglielmo, B. C. Vendeville, D. D. Schultz-Ela and P. A. Jackson, “Animation of salt diapir”, http://www.utexas.edu/research/beg/mmedia/AGL95-MM-001/, 1995, 15. R. Hanssen, Radar interferometry – data interpretation and error analysis, p. 308, Netherlands, 2001. 16. M. Hassouneh, “Structure of the Lisan peninsula of the Dead Sea basin from gravity analysis”, p. 30, Natural resources authority, Geophysical department, Jordan. 17. M. P. A. Jackson, B. C. Vendeville, and D. D. Schultz-Ela, “Structural dynamics of salt systems”, Annual Review of Earth and Planetary Sciences, 22, pp. 93-117, 1994 18. M. K. Jenyon, Salt tectonics, p. 198, Elsevier applied science publishers, New-York, 1986. 19. Kampes, B., DORIS manual documentation, http://www.geo.tudelft.nl/doris/, p.121, 2001. 20. D. Massonnet, M. Rossi, C. Carmona, F. Adagna, G. Peltzer, K. Feigl, and T. Rabaute, “The displacement field of the Landers earthquake mapped by radar interferometry”, Nature, 364(8), pp. 138-142, 1993. 21. D. Neev and J. K. Hall, “Geophysical investigation in the Dead Sea”, Geology, 23, pp. 209-238, 1979. 22. G. Peltzer and P. Rosen, “Surface displacement of the 17 may 1993 Eureka Valley, California earthquake observed by SAR interferometry”, Science, 286(5438), pp. 272-276. 23. A. M. Quennell, “Tectonics of the Dead Sea rift”, Int. Geol. Congr., 20th, Assoc. Serv. Geol. Afr., pp. 385405, 1959. 24. M. Remi and J. Avouac, “Seismic deformation in the Dead Sea rift analysed from”, Proc. CEOS SAR Workshop - Toulouse, digital, 1999. 25. P. A. Rosen, S. Hensley, H. A. Zebker, F. H. webb and E. J. Fielding, “Surface deformation and coherence measurements of Kilauea Volcano, Hawaii, from SIR-C radar interferometry”, J. Geophys. Res., 101(E10), pp. 23109-23125. 26. G. Taylor, “Salt theory undergoes revival”, AAPG Explorer, 4, pp. 12-33, 1995. 27. U. Ten Brink and Z. Ben-Avraham, “The anatomy of a pull-apart basin: seismic reflection observations of the Dead Sea Basin”, Tectonics, 8, pp. 333-350, 1989 28. I. Zak, The geology of Mount Sedom, p. 208, PhD Thesis, Hebrew University Jerusalem, (in Hebrew), 1967. 29. H. A. Zebker, P. A. Rosen, R. M Goldstein, A. Gabriel and C. L Werner, “On the derivation of coseismic displacement fields using differential radar interferometry: The Landers earthquake”, J. Geophys. Res., 99(B10), pp. 19617-19634, 1994.