Top Of Wall Research Articles

Active methane venting observed at giant pockmarks along the U.S. mid-Atlantic shelf break

Detailed near-bottom investigation of a series of giant, kilometer scale, elongate pockmarks along the edge of the mid-Atlantic continental shelf confirms that methane is actively venting at the site. Dissolved methane concentrations, which were measured with a commercially available methane sensor (METS) designed by Franatech GmbH mounted on an Autonomous Underwater Vehicle (AUV), are as high as 100 nM. These values are well above expected background levels (1–4 nM) for the open ocean. Sediment pore water geochemistry gives further evidence of methane advection through the seafloor. Isotopically light carbon in the dissolved methane samples indicates a primarily biogenic source. The spatial distribution of the near-bottom methane anomalies (concentrations above open ocean background), combined with water column salinity and temperature vertical profiles, indicate that methane-rich water is not present across the entire width of the pockmarks, but is laterally restricted to their edges. We suggest that venting is primarily along the top of the pockmark walls with some advection and dispersion due to local currents. The highest methane concentrations observed with the METS sensor occur at a small, circular pockmark at the southern end of the study area. This observation is compatible with a scenario where the larger, elongate pockmarks evolve through coalescing smaller pockmarks.

Performance of Counterfort Walls with Reinforced Granular and Fly Ash Backfills: Experimental Investigation

Experimental investigations on model counterfort retaining walls have been carried out to study the lateral movement of the walls and the nature of the failure modes. Mild steel plates of size 1,000 × 900 × 8 mm were used as model retaining walls and were placed in a tank of size 900 × 900 × 670 mm. Ennore sand, obtained from Madras India, and Fly ash, obtained from Panki Thermal Power Plant, India were used as backfill material. Tests were carried out both with and without reinforced backfill. Two types of loading conditions were applied: (i) line load and (ii) uniform surcharge. The shape and size of the failure wedge was studied by observing displacement of bands of colored through a Perspex plate fixed on one side of the tank. Plots of overturning moment against the rotation of a wall top show that with the increase in rotation of wall, the overturning moment decreases. The minimum value of overturning moment is taken as the limiting value. The failure surfaces obtained in different cases are linear and parabolic in shape.

Nonlinear Behavior of Precast Concrete Coupling Beams under Lateral Loads

This paper presents an analytical investigation of the nonlinear behavior of precast concrete coupling beams under monotonic lateral loading. In contrast to conventional monolithic concrete coupling beams, coupling of reinforced concrete wall piers in the proposed system is achieved by posttensioning the beams and the walls together at the floor and roof levels. Under lateral loads, the nonlinear deformations of the coupling beams occur primarily due to the opening of gaps at the beam-to-wall interfaces. The new system offers several advantages over monolithic systems, such as simpler detailing for the beams and the wall piers (no need for diagonal reinforcement crossing the beam-to-wall joints), reduced damage to the structure, and an ability to self-center, thus reducing the residual lateral displacements of the building after a large earthquake. Steel top and seat angles are used at the beam ends to yield and provide energy dissipation during the earthquake. The paper investigates the effects of design parameters, such as the amount of posttensioning, beam and wall properties, and top and seat angle properties, on the lateral strength and displacement characteristics of floor-level coupling beam subassemblies. The results are used to determine how the system behavior can be controlled by design. A procedure to estimate the nonlinear lateral load-deformation relationship of the subassemblies is developed.

Optimum design of cantilever sheet pile walls in sandy soils using inverse reliability approach

In this paper an approach for obtaining depth and section modulus of the cantilever sheet pile wall using inverse reliability method is described. The proposed procedure employs inverse first order reliability method to obtain the design penetration depth and section modulus of the steel sheet pile wall in order that the reliability of the wall against failure modes must meet a desired level of safety. Sensitivity analysis is conducted to assess the effect of uncertainties in design parameters on the reliability of cantilever sheet pile walls. The analysis is performed by treating back fill soil properties, depth of the water table from the top of the sheet pile wall, yield strength of steel and section modulus of steel pile as random variables. Two limit states, viz., rotational and flexural failure of sheet pile wall are considered. The results using this approach are used to develop a set of reliability based design charts for different coefficients of variation of friction angle of the backfill (5%, 10% and 15%). System reliability considerations in terms of series and parallel systems are also studied.

Practical Limitations to Carrier Layer Formation on Inclined Planes

Abstract Two important instabilities associated with carrier layer formation on the inclined plane of slide-fed coating processes are explored, with a two liquid layer prototype configuration employed to mimic the slide-bead process as used by industry. The work relates to both slide-bead and curtain coating methods. Experiments first reveal how broad diffuse bands, that destroy the quality of the final coating, are formed as the carrier layer flow rate is reduced. The bands are found to be exacerbated by either decreasing the viscosity or flow rate of the carrier layer or by increasing the viscosity of the upper layer. As the flow rate of the carrier layer is reduced further, the upper layer begins to invade the carrier layer delivery slot. Flow visualisations reveal that a parallel sided delivery slot is superior to a chamfered one in terms of robustness against invasion of the interface and that reducing the slot width increases robustness further. Experiments and complementary numerical simulations confirm the existence of a recirculating eddy near the top of the downstream wall as the carrier layer flow rate is reduced and this insight is used to propose an instability mechanism for the onset of the bands. Further experiments expose the mechanism for the formation of cross bars. These can develop downstream of the carrier layer delivery slot and arise because the merging of the layers there becomes increasingly influenced by the flow, demonstrating that the sensitivity of cross bars to pump induced disturbances grows rapidly as the critical carrier layer flow rate for instability is approached and then collapses as the flow rate is reduced to a value where the layer is no longer effective in lubricating the flow of adjacent layers.

Divisions of Manet

Throughout Foucault's work references to Manet surface and resurface, sometimes more or less obscure, but always the context of the dawn of modernity, that point history which the objects and discourses that we are today so familiar with first came into existence. Unfortunately, the book that Foucault had planned, Le noir et la couleur, dealing strictly with Manet never came to fruition, and we are left with Foucault's lecture transcripts from presentations given between 1967 and 1971 Milan, Tokyo, Florence, and finally Tunisia. These lectures, published by Seuil and edited by Maryvonne Saison, were effectively given by Foucault under the heading La Peinture de Manet on May 20, 1971 at the Tahar Haddad Club Tunisia.1 Foucault begins the lecture with a series of apologies for his fatigued state, for his inexpertise on both painting and Manet, and his general lack of preparation saying that he will be speaking in profane on the subject. However, this colloquial tone, at times bordering on insouciance (he mistakes the names of several paintings), that Foucault maintains throughout the conference is stark contrast to the content of that which he attributes to Manet's painting. For Manet's work we witness the first stages of a mutation, a fracturing that would entail a reorganization of the spectacle, the spectator, visibility, and invisibility. By associating Manet with the emergence of a new, semi-modern object, which he calls the tableau-objet, Foucault will use Manet's work to illustrate the advent of a new force painting: the force of objecthood that would alter the order of vision. As we shall see, this transformation the functioning of vision is fact a malfunctioning, a temporary moment of blindness, as the canvas transitions from the site of the represented spectacle to its modern role which the picture plane exists as nonrepresentational object, revealing something that cannot be represented. Traditional Representation versus Modern Objecthood To begin, Foucault charts the history of the relationship between paint and canvas as well as the techniques of traditional representational painting since the Renaissance. Through the use of certain lines, lighting, and color, tactics were developed that work to hide the material components of the canvas, that is, its rectangularity, its flatness, and its underlying support structure. These are well-documented artistic techniques including the use of strong oblique lines a painting to create the illusion of depth, drawing the spectator's gaze away from the edges of the picture plane towards the middle where a spectacle is presented. Additionally, the spectacle is lit so as to complement this fictional space, which is to say a lighting that comes from inside the painting, either from above as most Renaissance art or from the side as is popular later Baroque and Rococo works. This has the effect of illuminating a space that is ulterior to our world as it is lit by an ideal source, and although this ideal lighting may flow out into our space, our light of day never penetrates the picture plane. We can see for example Velazquez's Las Meninas all of these techniques at work. In that painting the strongest, boldest line is without doubt the top of the right-hand wall of the salon-a robust line that moves diagonally, cutting across the vertical and horizontal axes of the two-dimensional canvas. It is primarily on the strength of this line that all the depth of the room is opened up to us, and consequently, by creating this deep space which the spectacle of the Infanta will be situated, the flat surface of the picture plane is necessarily masked. In fact, even placing the back stretcher of a canvas the scene and thus representing the supporting architecture of the canvas the picture plane, Velazquez only does so a way that furthers the creation of an ideal space existing independently of the rectangular two-dimensional support structure. …

腰壁・垂れ壁が中心接合されるRC柱のせん断耐力

In previous work, the authors presented that the joint between spandrel walls and column was observed to reduce significantly the shear capacity of column at a experimental test data. The reduction is defined as the reduction ratio in shear strength to them of columns of which the column heigth is equal to the opening height from lower spandel wall top to upper bunging wall bottom. This paper clarifies the reductions in shear strength of column, based on other research data found in the literature and authors' additional experimental test data. The reduction ratio in shear strength is approximately 70% to 90%. A formula to predict the reduction ratio is suggested herein.

Integrated geophysical and geological investigation of a heterogeneous fluvial aquifer in Columbus Mississippi

A heterogeneous fluvial aquifer system exposed in a sand and gravel quarry outcrop in northeastern Mississippi was examined to quantify the relationship between geophysical attributes and lithostratigraphic properties. Two dimensional seismic reflection, ground penetrating radar, and DC resistivity profiles collected along the top of the quarry wall were compared with outcrop descriptions, photographs, and laboratory resistivity measurements and grain-size analysis conducted on a core collected near the center of the geophysical profiles. The aquifer is composed of an upper laterally continuous sandy-clay meandering fluvial system and a lower cross-bedded gravelly-sand braided fluvial system separated by a terrace. Seismic reflection data image the terrace, but depositional structures within the aquifer are below seismic resolution. These structures, including meter-scale channels and decimeter-scale channel-fill facies are imaged with ground penetrating radar , which correlates well with the outcrop and with the DC resistivity profile. The meandering fluvial facies is characterized by relatively low resistivity values (500–1250 Ω-m) and laterally continuous high-amplitude radar reflections. Lateral reflection terminations in the radar data indicate onlap at channel boundaries, which are filled with silty clay and clayey silt with very low resistivity values (50–400 Ω-m). The braided fluvial facies is characterized by higher resistivity values (1600–2600 Ω-m) and low-amplitude short bidirectional dipping radar reflections. Laboratory measurements of resistivity from a core collected along the quarry wall show a linear correlation to clay + silt content in all units within the meandering facies that have greater than 2% clay fraction, allowing surface DC resistivity data to be used as a predictor of clay + silt content in this facies. This is confirmed by comparison of predictions of clay + silt fraction based on the resistivity data to outcrop lithology. The combination of all three geophysical datasets is essential to fully characterize compartmentalization within this heterogeneous aquifer system.

Advance of allochthonous salt sheets in passive margins and orogens

Allochthonous salt sheets advance in four ways: (1) extrusive advance, (2) open-toed advance, (3) thrust advance, and (4) salt-wing intrusion. These mechanisms are determined primarily by the geometry and thickness of the roof that overlies the advancing sheet. An extrusive sheet spreads without a roof or with a roof of negligible mechanical strength. An open-toed sheet is partially covered by a mechanically significant roof but has an extrusive toe. An overthrusting sheet advances along a thrust fault at its leading edge, carrying its roof with it. A salt wing intrudes from the flank of a diapir into a shallower salt layer.Extrusive, open-toed, and overthrusting salt sheets are found in both passive margins and orogens. A sheet typically evolves through two or more of these mechanisms. Three lineages, or evolutionary paths, are common. Plug-fed extrusions emanate from the top of a salt dome or salt wall. Plug-fed thrusts form the base of the hanging wall of thrust faults that are rooted in the tops of salt domes or salt walls. Finally, source-fed thrusts initiate as thrust faults rooted in the autochthonous salt layer. Source-fed thrusts form the largest individual salt sheets, some covering thousands of square kilometers. Salt-wing intrusions form only under special circumstances, so they are not part of the three major lineages. These intrusions are restricted to compressionally inverted basins containing multiple salt layers and are known only in the Zechstein salt basin.

Transient flow and heat transfer leading to periodic state in a cavity with inlet and outlet ports due to incoming flow oscillation

A finite-volume-based computational study of transient laminar flow and heat transfer (neglecting natural convection) leading to periodic state within a square cavity with inlet and outlet ports due to an oscillating velocity at the inlet port is presented. The inlet port is placed at the top of the left wall and the outlet port is positioned at the bottom of the right wall of the cavity. The inlet velocity varies sinusoidally with time for a range of dimensionless frequencies ( St = 0.1, 0.5, 1, 2 and 10). The instantaneous Reynolds number also varies sinusoidally between 100 and 500 and Pr = 5. It takes more cycles for the temperature field to reach its periodic state in comparison to the corresponding flow field. For cases with higher Strouhal numbers, it takes more cycles to reach a periodic state. The throughflow stream undergoes cyclic growth and decay. The throughflow is in constant contact with the clockwise rotating primary vortex, which in turn interacts with two rotating vortices on the left wall. A counterclockwise rotating vortex at the top right corner also experiences periodic growth and decay. Minimal heat transfer is consistently observed on the left wall. In contrast, certain segments of the other three walls and the boundary of the throughflow are zones of active heat exchange. For St = 0.1, the mean Nusselt numbers on the four walls clearly exhibit large amplitudes of oscillation and periodicity. With St = 10, the amplitudes of oscillation on various walls are generally degraded. These behaviors are directly linked to the relation between the period of oscillation and the convection time scale. Regardless of the Strouhal number, heat transfer enhancement in comparison to the steady state case is consistently observed. The best heat transfer rate is realized when the Strouhal number is close to unity. This is the case when the period of the incoming stream resonates with the convection time scale.

Hydrothermal waves in differentially heated shallow annular pools of silicone oil

The characteristics of thermocapillary flow and hydrothermal waves (HTWs) in a shallow pool ( r i = 20 mm , r o = 40 mm and depth d = 1.0 mm ) of silicone oil (0.65 cSt, Pr = 6.7 ), heated from the outer wall and cooled at the inner wall, are investigated by numerical simulations. The critical Marangoni number ( Ma c) for the incipience of HTWs is determined, using a very fine mesh system (202×603×16), to be M a c = 3.36 × 1 0 5 ( Δ T c = 5.03 K ) under a microgravity condition and M a c = 3.94 × 1 0 5 ( Δ T c = 5.895 K ) for normal gravity. These critical values are smaller than those determined by 2D simulations by a factor of 0.926 for 0 G, and 0.912 for 1 G. The wave number and angular velocity of HTWs vary with Ma. Under small Ma’s, a single group of HTWs propagating in the azimuthal direction become dominant after a long calculation time. Numerical simulations with larger values of Ma show the coexistence of several groups of HTWs with different wave numbers and propagation directions. Analysis of motions of fluid elements indicates that the fluid elements exhibit small azimuthal displacements, although the HTW patterns are constantly traveling in the azimuthal direction. However, interference between different HTW groups causes a large displacement in the azimuthal direction. Numerical simulations reveal the mechanism of the large bending of the curved arms of HTW near the hot wall. Large values of Nusselt number appear at the top of the inner wall. Tempospatial variation of the Nusselt number appears on both walls corresponding to the propagation of HTW patterns.

Influences of Cannula Exit Shape on Blood Flow in Aortic Arch

The liquid flow perfused from the four types of cannula into an aortic arch glass model was visualized by using the PIV method. In the case of end-hole and Dispersion cannulae, the liquid jet from a cannula impinges on the inner wall of an aorta near a first bood vessel branch and flows toward a descending aorta along the outer wall of curvature of the aortic arch. The rms value of the velocity and the magnitude of the strain rate tensor have their large values on the outer wall of curvature. In the case of Soft-Flow cannula, the liquid jet from the cannula impinges on the top of the inner wall of curvature of the aortic arch, and flows toward the third branch. The rms value shows its large values in the whole area of the aortic arch. The magnitude shows its large values on the outer wall of curvature near third branch and the top of the inner wall of curvature. In the case of the SELECT 3D cannula, the liquid flow from a cannula impinges on the top of the inner wall of curvature, and then flows toward the descending aorta along the inner wall of curvature. The rms value and the magnitude have their large values on the descending aorta side of the inner wall of curvature.

Moment/Rotation Effects on Laterally Loaded Drilled Shaft Group Response

Drilled shaft groups are often designed to resist lateral loads for transportation structures. The shaft group capacity usually corresponds to a load being applied at the shaft cap level. However, in abutment wall applications, the lateral load is, in fact, applied well above the cap elevation. Thus, the load is transferred to the cap with an additional moment, causing the cap to deflect and rotate more than if this added moment were absent. As a result, the lateral capacity for a given allowable deflection of the group should be reduced because of this effect. Design engineers usually select or approve the allowable deflection at the top of the abutment wall. However, deflection at the cap level is needed to design the group capacity. The main objective of this paper is to report the results from a series of finite-element analyses on abutment wall cap configurations to study the effect of moment on the capacity of the shaft group under lateral load. A scaling factor is defined as the ratio between the group capacity for load applied at a given height above the cap and the group capacity for load applied at the bottom of the cap, and it was found to be dependent on the wall height, the spacing between shafts, and the cap deflection level, and more or less independent of the soil type, the cap thickness, and the shaft diameter. The ratio between the deflection at the top of the abutment wall and the deflection at the cap was found to be dependent on the wall stiffness (wall thickness to wall height ratio).

The itinerant Natterer: physical and thermal characteristics of summer roosts of Myotis nattereri (Mammalia: Chiroptera)

Natterer's bat Myotis nattereri is one of the least known European bats, using roosts inaccessible to humans and shifting to alternative roosts every few days. The characteristics of day and night roosts used by maternity colonies during summer was assessed. Roosts were located by radio-tracking. Roost sites (which may contain more than one roost) were concentrated mainly in core areas of up to 2 km2, within which roost site density ranged from 7 to 15 per km2. Day roosts included tree cavities, apices of attics, mortises in attics and in barns, soffit boxes at eaves, tops of gable walls, crevices in stone walls and a modern cavity wall. Trees comprised 67% of roost sites. Two maternity colonies each used between 21 and 31 roosts distributed across 15 to 25 roost sites. During late summer, the temperature of roosts adjacent to a roof covering averaged 22.5 °C during the day and were significantly warmer than roosts in trees, which averaged 17.3 °C. Attic mortise roosts were intermediate at 20.0 °C. The maximum ambient roost temperature in which bats remained was 32 °C and the maximum body surface temperature recorded while roosting was 37.6 °C. Thus, bats seem to require access to a large number of roosts with a range of temperatures that they can use depending on their reproductive state and energy requirements. The study colonies also exhibited high inter-annual fidelity to roosts. Attic maternity roosts used during late gestation and early lactation were reused for the same function in successive years, as were heavily timbered barns during late lactation and post-lactation. This continuing dependence upon established roosts indicates that these types of maternity roost should be given high conservation priority. Field boundaries should also be managed to maintain mature trees with cavities for potential day roosts and hedges suitable as night perches.

Successful treatment of recurrent vesicourethral stricture after radical prostatectomy with holmium laser: Report of three cases

We report three cases with severe anastomotic strictures, which recurred several times after radical prostatectomy despite repeated treatments of urethral dilation, internal urethrotomy and/or transurethral resection. All three cases were finally treated with holmium laser successfully without any intraoperative or postoperative complications after repeated failures of each treatment. There were two specific characteristics in these three cases: the early onset of the stricture and the pinhole opening located on the top (12-o'clock) of the stricture wall.

Doping of Electrochemically Etched Pore Arrays in n-Type Silicon: Processing and Electrical Characterization

Silicon p-n diodes formed in the walls of deep pores have been electrically characterized. The pores were electrochemically etched in low-doped n-type silicon substrates, and the entire pore array was doped by boron diffusion at . Two different process flows were investigated to disconnect the layers from one pore to another. The first consists of removing a few micrometers of silicon at the top of the sample using reactive ion etching after diffusion while the second enables the prevention of doping at the top of the pore walls with an oxide, acting as a barrier during diffusion. Current-voltage and capacitance-voltage characteristics of p-n junctions are presented and related parameters, such as the serial resistance and the ideality factor are discussed. The results show good rectifying behavior of the diodes with a reverse current about four to five decades smaller than the forward current. Measurements with two pores connected in a transistor-like configuration , were also performed. Device simulations were used to examine the device behavior. Finally, our results demonstrate that pores could work as individual detector pixels for moderate reverse voltages, suitable for radiation imaging applications.

壁式プレキャスト鉄筋コンクリート系低層住宅の構造性能に及ぼす直交壁の効果

An experimental study on real scaled one-bay-one-story frames with transverse walls in precast reinforced concrete housing of low-rise wall-building system was carried out to examine the effect of the transverse walls on the structural performance of the housing. An outline of the testing is described and the shear resistant mechanisms of the transverse walls are examined based on the test results in this paper. The conclusions obtained are; (1) The transverse wall effect is effectively developed in the frame. (2) Strength induced by the transverse wall effect can be estimated as the minimum value among the followings: a) direct shear of the floor rib at the top of wall panel, b) punching shear of the floor rib at the top of the transverse walls, and c) tension of joint bolts at the top of the transverse walls. (3) Relationship between the horizontal displacement of the frame and the transverse wall effect can be evaluated by bi-linear skeleton curves.

Analysis of liquid film formation in a horizontal annular flow by DNS

The role of the disturbance waves for transferring liquid toward the top of a horizontal tube wall to cope with the drainage due to gravity is investigated by the direct numerical simulation (DNS) which is based on the continuity equation and the Navier–Stokes equations in three-dimensional cylindrical coordinate system. The level set method is used for capturing the interface between gas–liquid two fluids. Developing flow from a separated to an annular flow is simulated by using this numerical technique, and the liquid film formation is reproduced. It is demonstrated by this calculation result that liquid is transferred in the circumferential direction as the liquid film by the pumping action of disturbance waves which has been proposed by one of the present authors. That is, the pressure gradient formed within a disturbance wave in the circumferential direction plays an important role for the liquid film formation in a horizontal annular flow.

MIXED CONVECTIVE COOLING OF A RECTANGULAR CAVITY WITH INLET AND EXIT OPENINGS ON DIFFERENTIALLY HEATED SIDE WALLS

A numerical study is conducted to investigate mixed convective cooling of a two-dimensional rectangular cavity with differentially heated side walls. The horizontal walls are assumed to be adiabatic. Cold fluid is blown into the cavity from an inlet in the side wall of the cavity and is exited through an outlet in the opposite side wall. This configuration of mixed convective heat transfer has application in building energy systems, cooling of electronic circuit boards, and solar collectors, among others. The objective of the research is to optimize the relative locations of inlet and outlet in order to have most effective cooling in the core of the cavity by maximizing the heat-removal rate and reducing the overall temperature in the cavity. Various placement configurations of the inlet and outlet are examined for a range of Reynolds number and Richardson number. For a given Reynolds number, the Richardson number is varied from 0, which represents pure forced convection, to 10, which implies a dominant buoyancy effect. Injection of air at the top and bottom of hot and cold walls is compared and the results are presented in the form of isotherms, streamlines, cooling efficiency, average temperature, and local and average Nusselt number at the hot wall. It is observed that maximum cooling effectiveness is achieved if the inlet is kept near the bottom of the cold wall while the outlet is placed near the top of the hot wall.

Origin of the salt valleys in the Canyonlands section of the Colorado Plateau: Evaporite-dissolution collapse versus tectonic subsidence

The salt valleys over the axis of the salt-cored anticlines in the Paradox fold and fault belt (Canyonlands, Utah and Colorado) are created by subsidence of the anticline crests. Traditionally, the collapse of the anticlinal crests was attributed to dissolution of the salt walls (diapirs) forming the anticline cores. Recent studies based on scaled physical models and field observations propose that the salt valleys are a result of regional extension and that salt dissolution had only a minor influence in the development of the axial depressions. This paper presents several arguments and lines of evidence that refute the tectonic model and support the salt dissolution subsidence interpretation. The development of contractional structures in salt dissolution experiments led the advocates of the tectonic interpretation to reject the dissolution-induced subsidence explanation. However, these salt dissolution models do not reproduce the karstification of salt walls in a realistic way, since their analog involves removal of salt from the base of the diapirs during the experiments. Additionally, numerous field examples and laboratory models conducted by other authors indicate that brittle subsidence in karst settings is commonly controlled by subvertical gravity faults. Field evidence against the regional extension model includes (1) a thick cap rock at the top of the salt walls, (2) the concentration of subsidence deformation structures along the crest of the anticlines (salt walls), (3) deformational structures not consistent with the proposed NNE extension, like crestal synforms and NE–SW grabens, (4) dissolution-induced subsidence structures controlled by ring faulting, revealing deep-seated dissolution, (5) large blocks foundered several hundred meters into the salt wall, (6) evidence of recent and active dissolution subsidence, and (7) the aseismic nature of the recently active collapse faults. Although underground salt dissolution seems to be the main cause for the generation of the salt valleys, this phenomenon may have been favored by regional extension tectonics that enhance the circulation of groundwater and salt dissolution.