Some features of the subsurface geoelectric structure in the sinkhole occurance sites along the dead sea shore line.

Direct‐current (DC) resistivity tomography has been applied to different mountain permafrost regions. Despite problems with the very high resistivities of the frozen material, plausible results were obtained. Inversions with synthetic data revealed that an appropriate choice of regularization constraints was important, and that a joint analysis of several tomograms computed with different constraints was required to judge the reliability of individual features. The theoretical results were verified with three field experiments conducted in the Swiss and the Italian Alps. At the first site, near Zermatt, Switzerland, the location and the approximate lateral and vertical extent of an ice core within a moraine could be delineated. On the Murtel rock glacier, eastern Swiss Alps, a steeply dipping boundary at its frontal part was observed, and extremely high resistivities of several MΩ indicated a high ice content. The base of the rock glacier remained unresolved by the DC resistivity measurements, but it could be constrained with transient EM soundings. On another rock glacier near the Stelvio Pass, eastern Italian Alps, DC resistivity tomography allowed delineation of the rock glacier base, and the only moderately high resistivities within the rock glacier body indicated that the ice content must be lower compared with the Murtel rock glacier.

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“…As shown for the Murtel example (Fig. 9), DC measurements can also be complemented with TEM data (see also Hauck et al . 2001).…”

Section: Discussionmentioning

confidence: 85%

Using DC resistivity tomography to detect and characterize mountain permafrost

Hauck

Mühll

Maurer

2003

Geophysical Prospecting

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“…CVES and GPR results have been described in a several reports (Bruner et al ; Ezersky ,). In this paper, we present CVES resistivity and GPR sections only along the seismic line MF‐2.…”

Section: Geophysical Surveysmentioning

confidence: 78%

“…) predicted a density deficiency of 0.10 mGal at the site where, three years later, settling S3 appeared at the surface. The seismic identification of the occurrence of a salt layer was first performed by Shtivelman et al () using the seismic refraction method and it was verified by drilling (Yechieli et al ). Ezersky (, 2005) suggested the criterion for salt identification and the technique for mapping the salt edge.…”

Section: Discussion Of Resultsmentioning

confidence: 99%

“…The present assumption is that void formation at depth of tens of metres causes changes in the soil structure and properties (conductivity, density, velocity, etc.). These changes occur in the subsurface above the cavity extending to the surface, as well as encompassing gradual long‐term subsurface soil decompaction, subsidence and/or collapse (Bruner et al ; Ezersky ,). In the present study, this assumption is corroborated by a methodology that uses a combination of high‐resolution seismic reflection and diffraction, seismic refraction, СVES and GPR methods.…”

Section: Introductionmentioning

confidence: 99%

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Integrated study of the sinkhole development site on the Western shores of the Dead Sea using geophysical methods

Ezersky

Bruner

Keydar

et al. 2006

Near Surface Geophysics

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This paper presents a combination of high‐resolution seismic diffraction, reflection, refraction, continuous vertical electric sounding (CVES), ground‐penetrating radar (GPR) and microgravity methods to study the structure and properties of the shallow subsurface at the sinkhole development site in the Nahal Hever southern area (on the shore of the Dead Sea) in Israel. These methods have different resolutions and penetration depths. The methods are complementary to each other and reveal useful information about the subsurface. Each one investigates certain characteristics, but when combined they provide us with new information about the subsurface. The seismic refraction method is utilized to map salt layers and to detect dissolved zones. The analysis of all of the seismic refraction data obtained at the Dead Sea area, verified by the information gained from a borehole, has shown that the P‐wave velocity of the salt layer varies from 2900 to 4250 m/s. The velocity of 2900 m/s was used as the minimum velocity criterion for salt‐layer identification at this site. A low‐velocity zone (VP < 2800 m/s) revealed within a high‐velocity area (VP=2900−4250 m/s) is interpreted as a dissolved salt or non‐saline unit. The site is characterized by two significant geological features. The first feature is a water‐filled cave, detected recently by a borehole in the depth interval 23–28.5 m, and the second feature is a depression at the surface. Geophysical results show that the depression site is presently characterized as a heavily perturbed zone in both lateral and vertical directions. Soil decompaction in the subsurface is clearly identified by the CVES method as a high‐resistivity anomaly. This decompaction is assumed to be associated with the voids and fractures occurring down to a depth of 100–120 m (by diffraction data) and in the uppermost subsurface (by GPR data). The zone containing the cave is characterized by a lateral (funnel) and vertical (faults) distortion of the subsurface structure (by seismic reflection data) and has a faint diffraction anomaly in the shallow subsurface. A slightly increased resistivity anomaly appears in the depth interval 6–12 m (from CVES data). Drilling data reveal this interval as a decompaction zone. No GPR anomalies were detected at the buried cave site. The microgravity survey at the buried void site in 1999 detected an anomaly that is very similar to the funnel‐shaped one.

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“…Lanz et al 1997, Hauck et al 2000. Electromagnetic induction methods show good results, in particular the EM-31 for determining the permafrost distribution and the PROTEM for assessing the overall permafrost thickness (cf.…”

Section: Geophysical Mappingmentioning

confidence: 98%