Complex Tectonic Structure Research Articles

Efficiency analysis of the application of thermal methods at the Pirallahi and Darwin bank fields

The efficiency of oil and gas field development is associated with the correct choice of appropriate measures to be implemented. This research considers the Pirallahi and Darwin Bank fields with hard-to-recover oil reserves. The Pirallahi field is located in the eastern part of the Absheron Peninsula. The initial balance reserve for the facility is 4 million tons, and the level of reserve utilization is 19%. Among the notable features, the Pirallahi deposit represents the southern fold of the PK (Pre-Kirma- ki) horizon. Across the horizon, the initial balance reserve is approximately one million tons, and the utilization rate is 17%. In other groups, the level of utilization exceeds 20%. Accordingly, the volume of initial balance reserves ranges between 8-35 million tons. Industrially important objects here are KSv (Kirmaki suite, fifth horizon), KSn (Kirmaki suite, n horizon), and PKS (Post-Kirmaki suite). To develop oil reserves, more than 1000 production wells were drilled at different stages of the development process. The southern fold consists of a brachyanticline extending from northwest to southeast. The main tectonic element of the southern fold is its thrust nature and its very complex tectonic structure. The fold is heavily watered. Therefore, to increase the efficiency of developing these fields, it is necessary to use appropriate methods of influencing the formations. To enhance the efficiency of the development process in the northern part, the in-situ combustion method was applied. The Darwin Bank field belongs to the Absheron archipelago and has a tectonic brachyanticlinal structure. The structure is complicated by numerous longitudinal and transverse faults. It is divided into six tectonic zones by several transverse and one longitudinal fault passing through the crest. Darwin Bank oils are heavy oils with low sulfur content. In addition, low paraffin and high resin content are observed in the composition of field oil. For both fields, the recovery rate of geological reserves fluctuates around 30%. The article, primarily, examines the selection of objects and the use of enhanced oil recovery methods in these fields. The in-situ combustion method was used in the northern part of the Pirallahi field and Darwin Bank.

Assessment of geomechanical properties of Sakhalin shelf reservoirs based on modeling results

Background. Due to the complex tectonic structure of the Sea of Okhotsk shelf and intense geodynamic activity in this area, specialized technologies are required to study reservoir properties. In this work, we implement the technology of secondary permeability estimation using the Kirinskoye and Ayashskoye license blocks as an example. The research objects included structural and lithologic traps of different complexes. It was found that the Prisakhalin shelf, including the Kirinsky and Ayashsky license areas, is subject to the modern shear stress field with the sublatitude-oriented axis of maximum compression. This initiates the formation of a local stress field, launches changes in the degree of fracture openness, and determines the secondary porosity and permeability of rocks. 3D modeling allowed us to calculate predicted permeability for each stratigraphic horizon. A significant difference of secondary permeability in the upper and lower stratigraphic horizons is noted.Aim. To evaluate secondary filtration and capacitance properties of reservoirs by geomechanical modeling.Materials and methods. Geomechanical modeling to assess the filtration and capacitance properties of Sakhalin shelf reservoirs was carried out using the ROXAR software package.Results. This work allowed not only the filtration efficiency to be predicted, but also the processes occurring in the geological section of the shelf of the Sea of Okhotsk to be elucidated.

Advanced 3D seismic hazard analysis for active compression in the Adriatic Thrust Zone, Italy

The probabilistic seismic hazard assessment contains two ingredients: (1) the seismic source model with earthquake rates and rupture parameters for specification of the statistical distribution of earthquakes in time and space and (2) the ground motion model, for estimation of ground shaking level at a site for each earthquake rupture. The selection of these models significantly impacts the resulting hazard maps, and it can be challenging, particularly in seismotectonic regions where overlapping structures, sited at different depths, coexist. Eastern Central Italy is a well-known active compressional environment of the central Mediterranean with a complex tectonic structure with a lithospheric double shear zone. In this study, we propose a seismic hazard assessment to analyze the contribution of these two shear zones as overlapping multi-depth seismogenic volumes to ground motion at a given hazard level. We specifically focus on selecting relevant and applicable parameters for earthquake rate modeling, emphasizing the importance of defining rate computation and rupture-depth parametrization in hazard analysis. To achieve this, we utilized a seismotectonic- and catalog-based 3D adaptive smoothed seismicity approach following the methodology given by (Pandolfi et al. in Seismol Res Lett 95: 1–11, 2023). Finally, we demonstrated how this innovative 3D approach can identify with high resolution the individual sources' contribution with particular attention to the depth location of structures that strongly influence the ground motion. Moreover, combining seismotectonic data with seismicity avoids the challenges associated with structures with scarce geologic, geodetic, or paleoseismological data. Our result provides detailed insights into the seismic hazard within the Adriatic Thrust Zone.

Assessment of Sakhalin shelf reservoirs by geomechanical modeling

Background. The complex tectonic structure of the Sea of Okhotsk shelf, its high geodynamic activity and the presence of non-anticlinal traps in plays requires special technologies for studying the secondary filtration-volumetric parameters of reservoirs. The prediction of the location and direction of open fractures is complicated by their small size. Such fractures are frequently too small to be detected by such conventional logging or seismic instruments. The detection of fracturing by seismic methods is impossible in principle; however, some high-resolution logging tools are capable of detecting fractures under favorable circumstances. In cases where neither logging nor seismic exploration can detect fractures, geomechanical modeling can be used. Geomechanical modeling makes it possible to predict the effective porosity and permeability in the сrosshole space.Aim. To assess the geomechanical properties and secondary permeability parameters of the Sakhalin shelf reservoirs.Materials and methods. The ROXAR reservoir modeling software was used to assess the secondary filtration-volumetric parameters of the Sakhalin shelf reservoirs.Results. The modern shear stress field was revealed. The permeability of each stratigraphic horizon was calculated. The filtration capacity of local structures was established.

ANN-based ground motion model for Turkey using stochastic simulation of earthquakes

SUMMARY Turkey is characterized by a high level of seismic activity attributed to its complex tectonic structure. The country has a dense network to record earthquake ground motions; however, to study previous earthquakes and to account for potential future ones, ground motion simulations are required. Ground motion simulation techniques offer an alternative means of generating region-specific time-series data for locations with limited seismic networks or regions with seismic data gaps, facilitating the study of potential catastrophic earthquakes. In this research, a local ground motion model (GMM) for Turkey is developed using region-specific simulated records, thus constructing a homogeneous data set. The simulations employ the stochastic finite-fault approach and utilize validated input-model parameters in distinct regions, namely Afyon, Erzincan, Duzce, Istanbul and Van. To overcome the limitations of linear regression-based models, artificial neural network is used to establish the form of equations and coefficients. The predictive input parameters encompass fault mechanism (FM), focal depth (FD), moment magnitude (Mw), Joyner and Boore distance (RJB) and average shear wave velocity in the top 30 m (Vs30). The data set comprises 7359 records with Mw ranging between 5.0 and 7.5 and RJB ranging from 0 to 272 km. The results are presented in terms of spectral ordinates within the period range of 0.03–2.0 s, as well as peak ground acceleration and peak ground velocity. The quantification of the GMM uncertainty is achieved through the analysis of residuals, enabling insights into inter- and intra-event uncertainties. The simulation results and the effectiveness of the model are verified by comparing the predicted values of ground motion parameters with the observed values recorded during previous events in the region. The results demonstrate the efficacy of the proposed model in simulating physical phenomena.

Traces of paleogeodynamic processes in the zone junctions of the Middle and Lower Kura depressions

The territory of Azerbaijan covers the southeastern part of the Greater Caucasus meganticlinorium, the northeastern parts of the mountain systems of the Lesser Caucasus and Talysh, i.e., basins of the Lower and Middle Kura, as well as the southwestern and western zones of the Middle and South Caspian depressions, respectively. The combination of these large structural elements determines the very complex tectonic structure of the territory of Azerbaijan, including the Middle and Lower Kura basins.
 The article presents the results of a study conducted to study the paleotectonic processes that took place in the Cenozoic in the junction zone of the Middle and Lower Kura depressions, according to modern (2017—2018) seismic survey data using the common depth point method. The geological structure of the constituent parts of these depressions is considered, and paleotectonic processes are described that played an important role in their formation and led to the divergence of the geological sections of these depressions in the interval from the end of the Cretaceous to the end of the Lower Pliocene. When comparing the seismic wave pattern representing the geological sections of the Middle and Lower Kura depressions, it becomes clear that the compensation of the volumes of sedimentary material is carried out by Pliocene terrigenous deposits in the Lower Kura and Paleogene sediments in the Middle Kura depressions. At the same time, here, the hypsometry of the Miocene-Maikop interval of the section differs by 1300—1500 m.
 The article presents the author’s positions on the post-Cretaceous tectonic processes of the evolutionary development of the geological structure of these basins in the zone of their junction, where the Mingacheir-Saatli-Talysh transverse Mesozoic uplift (Saatly-Geokchay zone of Mesozoic uplifts) occupies an important place.

Mapping of the Structural Lineaments and Sedimentary Basement Relief Using Gravity Data to Guide Mineral Exploration in the Denizli Basin

The Aegean Graben System is a complex tectonic structure in Western Anatolia and the Denizli Graben is a member of this system that hosts many geothermal springs, ore deposits, and travertine areas. In this study, the gravity data were analyzed to determine the subsurface geological structures and the depth model of the basin. The Bouguer gravity anomaly has a NW–SE pattern that is consistent with the general trend of the Denizli Basin. The pre-Neogene basement depths range from 0.1 km to 2.3 km. The Denizli Basin is composed of the Çürüksu Basin and the Laodikia sub-basin. The basins have undulated structures with many depressions; the deepest depression region is in the northern part of the Çürüksu Basin, which is close to the Pamukkale Fault Zone. In addition, the new gravity lineament map was obtained by using new-generation edge detection techniques: the tilt angle of the horizontal gradient amplitude (TAHG), and fast sigmoid-edge detection (FSED) of gravity data. The new proposed lineament map shows that the Denizli Basin has complex structures consisting of NW–SE, E–W, and NE–SE trending lineaments, and the major NW–SE trending faults and NE–SW trending lineaments control the main structural configuration. The uplifts and depressions in the basin deposit and the intersection area of lineaments are promising prospective areas for mineral deposits and have energy resource potential.

Recognition of the flysch substrate using the electrical resistivity tomography (ERT) method to assess the effectiveness of the injection process

During the construction of a section of the S-7 Lubień – Rabka-Zdrój dual expressway, located in the area of the Carpathian flysch (Carpathian Flysch Belt, South Poland), damage to the embankment was observed, as well as cracks and depressions in the new pavement. An analysis of the geological and engineering conditions in the area of the road section under construction showed the existence of a complex tectonic structure of the flysch formations, a shallow groundwater table, and numerous landslides. In order to stabilize the road substrate, it was decided to carry out injections, and the locations of these injections were initially geotechnically tested. However, due to the high variability of the geological structure, the target method employed was electrical resistivity tomography (ERT), which performed the survey in two stages. In Stage I, the geoelectrical/geochemical structure of the near-surface zone was identified, and the probable causes of road damage were indicated. This stage was completed by performing the stabilization and sealing process of the ground with an injection mixture. In Stage II, studies were carried out to evaluate the effectiveness of the injection process. The ERT method effectively identified the shallow geological structure and, in particular, delineated the zone of strong fractures in the flysch and areas associated with faults. Using the electrical resistivity tomography method, it was also possible to determine the injection mixture’s approximate penetration depth and the loosening zone’s degree of filling.

Comprehensive use of the Gutenberg–Richter law and geotomography for improving seismic hazard evaluation in hard coal mines

Mining-induced seismicity occurs in numerous underground mines worldwide where extraction is conducted at great depths or in areas characterised by complex tectonic structure. It is accompanied by rock bursts, which result in the loss of working functionality and the possibility of accidents among personnel. The issue of a constant and reliable seismic hazard evaluation is of key significance for both the safety of miners and the stability of production. Research on its improvement is directed at developing new interpretive solutions and methods. The nature of the presented solution is the complex interpretation of seismological data that characterise rock mass seismicity and of underground measurement results in the form of a map presenting the longitudinal wave propagation velocity distribution in the rock surrounding the mined coal seam. The solution was tested in hard coal mines located in the Upper Silesian Coal Basin. The mines are equipped with a modern seismological system enabling the constant monitoring of seismicity together with hazard level evaluation as well as with seismic apparatus for conducting periodic measurements of the seismic wave propagation velocity before the mining face. Comprehensive seismic hazard evaluation criteria were determined based on the obtained results, involving the anomaly of the Gutenberg–Richter law “b” value and the maximum longitudinal seismic wave propagation velocity in the roof rock. The obtained experience and the result validation of this new comprehensive hazard evaluation method confirm its practical usefulness and indicate the directions of improvement for the solution in question.

Refinement of the Structure of the Pirallahi-south Area and the Prospects for Oil and Gas Potential of the Qala Suite

Despite the fact that the area is in a long-term development, its prospects are closely related to the refinement of the geological structure and the study of the section of productive deposits. The complex tectonic structure of the structures located in the northwest of the Absheron archipelago does not allow for an accurate determination of the boundaries of the distribution of deposits, including the Qala suite. For this article, new structural maps were compiled based on a comparison of numerous geological and geophysical profiles and well logs. The areas of distribution of sedimentary deposits of QaS have been clarified, and drilling of an appraisal (exploratory) well 1202 has been proposed in order to clarify the tectonic structure of the area. Keywords: Reservoir; Sediment; Fault; Well; Block; Overthrust; Correlation.

APPLICATION OF MORPHOMETRIC ANALYSIS FOR SMALL RIVER BASINS OF THE BAIKAL RIFT ZONE BASINS

The article discusses the use of morphometric analysis to study the features of formation and development of small river basins in the western branch of the Baikal rift zone basins (by example of the Ihe-Uhgun river basin). The author has prepared a hydrologically correct digital elevation model based on satellite data ALOS Digital Surface Model (DSM). A comprehensive assessment of the earth's surface was carried out, including for the purposes of geomorphological and hydrological analysis, as well as an automated calculation and mapping of standard morphometric indicators based on DEM data. The work is based on general physiographic research methods, the method of morphometric analysis of the relief using GIS, the method of geoinformation mapping. Statistical data of morphometric and hydrological indicators were collected using SAGA GIS, patterns of their distribution over the basin area were revealed, which, as a result, made it possible to draw conclusions about the factors and patterns of the river network development and determine the set of presented exogenous processes of relief formation in the Ihe-Uhgun river basin territory. The main factors in the small river basins development are: high base levels, complex tectonic structure of the territory, steep slopes and southern orientation of the slope exposure, etc. It was revealed that the geometry of the basin relief determines the direction and volume of surface runoff, as well as the intensity of exogenous geomorphological processes.

Rationale for the Use Of Radonometry to Identify the Areas of Tectonic Faults During the Passage of Subway Tunnels in Dnipro

Purpose. The article is aimed to substantiate the choice of the most effective method of geophysical research within the metropolis for more accurate mapping of fault zones in erupted rocks for the purposes of 2nd stage subway construction in the city of Dnipro. Methodology. Practical and organizational measures for radonometry for seismotectonics during the 2nd stage construction of the city subway were developed in detail, which in case of continued mining operations in the ravine-beam system contributes to further safe operation of the facility. Findings. Based on the analysis and evaluation of all profile studies conducted in the city in different years, one of the emanation methods was chosen – radonometry, and the method for its implementation was proposed, which provides dense urban development and complex tectonic structure of the region (fault zones) to obtain the necessary quality characteristics of soil incision. Originality. This paper for the first time provides a rationale for radonometry to identify fault zones in erupted rocks and assess their activity within the city. Practical value. The given technique is recommended for ensuring seismically safe conditions of drilling and blasting works during the passage of mine workings, which will ensure the maximum construction speed. In the future, these studies may be required when creating a ventilation system for underground structures of the 2nd stage of the city subway. Also, the radonometry results can be taken into account when placing elements of geotechnical (deformation) monitoring systems, both in tunnels and other deep-seated subway structures, and in buildings and structures. Clarification of the position of fault zones with the assessment of their activity can directly affect the choice of certain methods of measuring the deformation parameters of the observed objects, facilitate the choice of means of tunnel processing, highlight their qualitative or quantitative parameters.

The Spatio-temporal Analysis of b-value in the Banda Arc, Indonesia

Banda arc is a complex tectonic structure manifests by high seismicity due to the collision of a continent and an intra-oceanic island arc. Using the relocated earthquakes data from ISC-EHB and BMKG catalogues from the time period of 1960 to 2018, we have conducted a spatial and temporal variation of b-value using the Guttenberg-Richter formula in the area. Our results show that the spatial distribution of low b-values located in the south of Ambon Island and southeast of Buru Island. On the other hand, the temporal variation of b-value shows a decrease in the northern part of the Banda sea probably high potential to produce large earthquakes in the future. Therefore, further mitigation is needed to minimize the impact of earthquakes in the area.

Timan–Pechora Composite Tectono-Sedimentary Element, Northwestern Russia

Abstract The Timan–Pechora Composite Tectono-Sedimentary Element (CTSE) represents a significant part of the Timan–Pechora petroleum province, which is the second largest in the Circum-Arctic. It contains as much as up to 10 km of Paleozoic and Mesozoic strata hosting the excellent hydrocarbon source rock, the Domanik Formation, and a variety of hydrocarbon plays prolific for both oil and natural gas. The complex tectonic structure of the CTSE formed as result of several tectonic phases: two extensional events, post-rift thermal sag in a passive-margin setting, and a series of late Paleozoic and early Mesozoic compressional events. The latter modified the extensional fabric, and led to the formation of a number of inverted swells and smaller anticlinal structures providing the major trapping capacities. The deposition of source and reservoir facies occurred during the extensional tectonic phases, while the main reservoir-prone sedimentary units were deposited during late Paleozoic and early Mesozoic orogenic phases.

Estimation of the High-Frequency Attenuation Parameter Kappa for the Zagreb (Croatia) Seismic Stations

The city of Zagreb (Croatian capital) is situated in the contact area of three major regional tectonic units: the SE Alps, NW Dinarides, and Tisza Unit in the southwestern margin of the Pannonian Basin. The Zagreb seismic zone encompasses the Medvednica Mountains and the city of Zagreb with its surrounding areas, which was struck by the strongest instrumentally recorded earthquake (M5.5) on 22 March 2020. The objective of this contribution is the estimation of the high-frequency attenuation spectral parameter kappa (κ) and its local site-specific component for the Zagreb (Croatia) seismic stations to which we were particularly encouraged after the scale of the damage after the Zagreb 2020 earthquake. We tested linear dependence of κ with epicentral distance using traditional linear least square regression, linear regression for data with errors, and constrained model at close distances to estimate near-site attenuation (κ0). Regression-estimated site kappa values at zero-distance are within the range of the uncertainty (±1 standard deviation) with constrained κ0 value as well within the range of existing global κ0 and VS30 (shear wave velocity in the top 30 m) values. Spatial distribution of κ within the Zagreb seismic zone shows that κ is not isotropic and high-frequency attenuation anisotropy is probably affected by local and regional geological variability, regional active faults and a complex tectonic structure in each direction.

Features of the Structure and Development of the Southeastern Part of the East European Platform and the Caspian Basin in the Late Precambrian‒Early Paleozoic

The geological and sedimentological interpretation of several time and deep seismic profiles within junction zone of the Volga‒Ural area of the East European Platform, Pre-Caspian Depression, Ural Foredeep, Bashkir Anticlinorium, and northern margin of the Scythian Platform allowed us to identify a number of previously unknown structural features of Later Precambrian and Early Paleozoic formation. On this basis, structural-facies maps were compiled for the Riphean and Vendian stages of development. It was shown that as a result of the collision of the southeastern passive margin of the continent Baltica with Scythia in the Early Vendian and with the Timanides of the Urals in the Later Vendian, a complex tectonic structure of the Orenburg tectonic node was formed, which forms the foundation of the Caspian oil and gas province. The results obtained substantially clarify the structure of the sedimentary cover of the East European Platform and the Pre-Caspian Basin, the stages of the formation and evolution of their structure, and the degree of influence on the sedimentation of structural changes in the adjacent territories of the folded Urals and the Scythian Platform.

Differences Between Recent Heat Flow Maps of Poland and Deep Thermo-Seismic and Tectonic Age Constraints

Poland is situated in a place of contacts between three continental scale geologic structural units: the Precambrian East European Craton (EEC) to the northeast, the Variscan West European Platform (WEP) terranes to the southwest, and the younger Carpathian Alpine arc in the south. The Trans-European suture zone (TESZ) between the EEC and WEP is a deep-seated discontinuity zone reaching down to a depth of about 200 km. The conjunction of all these continental scale geologic units is reflected in the complex tectonic structure of this area. Apart from the complex seismic structure, this area is also associated with pronounced gravity, magnetic and heat flow anomalies. Significant differences exist between heat flow maps of Poland published in recent works, with values reaching 20 to 30 mWm-2. Examples are differences in heat flow based on models that use well log interpreted mineral and porosity content and assigned world averages of rock and fluid thermal conductivities versus ones based on averaging thermal conductivity values measured using borehole cores only. These differences in heat flow between the methods are discussed in the context of their relationship with tectonic age. Also considered are depth differences between lithosphere – asthenosphere boundary (LAB) derived from thermal model vs those that obey seismological constraints. Higher heat flow estimates reaching up to or more than 100 mWm-2, based on conductivity values derived from well-logs, are found to be quite improbable. This likely reason for overestimate of heat flow is discussed.

GEODYNAMIC FEATURES OF DOBROGEA FORMATION

The formation of Dobrogea as a modern geographical unit dates back to the late Neogene. The complex tectonic structure indicates multiphase changes in this key area that are buried under sediment or reflected in outcrops. Separate outcrops to Mesozoic sedimentary rocks and Precambrian-Paleozoic crystalline basement have been identified, while the main part of the region is characterized by Paleogene-Neogene outcrops. According to the peculiarities of the tectonic structure of Dobrogea, it is divided into the Southern, Central and Northern parts, which are separated by faults of the north-western extension and the Pre-Dobrogea depression. The main part of Dobrogea is located in Romania, within Ukraine there is the Prut ledge of the Northern Dobrogea and the Pre-Dobrogea depression, and part of the Southern Dobrogea goes within the borders of Bulgaria - the southern slope of the Dobrogea massif.The geodynamics of the joint zone determined the stages of formation, which were accompanied by platform transformations and tectonic-magmatic processes, as well as the formation of sedimentary complexes with coal, coal seams and oil and gas reservoirs. Based on the factor of destruction of Cretaceous and, possibly, Jurassic and Triassic deposits and their transformation into younger, Paleocene and Maikop deposits, it can be said that large accumulations of gas on structures in Paleogene traps are unlikely.Modern gas migration is characteristic of both the sedimentary strata of the Pre- Dobrogea Depression, ie the northern part of the study region, and the south-eastern part of Southern Dobrogea in carbonate deposits.

A New Model of the Ninety East Ridge Formation, Indian Ocean

The comprehensive analysis of geological, geophysical, and geochemical data makes it possible to obtain the most complete picture of the geological structure of the central part of the Ninety East Ridge (NER), the Osborn Plateau, and the adjacent part of the Central Basin. This region has been established to be a complex tectonic structure. In respect of the revealed structural features of the major near-NS faults of Indrani, Indira, and Lanka, they are not transform faults. Based on the generalization of all available data on the northern and southern parts of the NER, supplemented by the studies of the NER’s central part, it is found out that the NER was constructed on the continental crust of an ancient continent, likely Lemuria. According to a new formation model, the NER is a relict fragment of this continent, preserved in the form of a block or an escarp, as an extended horst structure. This paper involves the primary data obtained by different Russian scientific and production organizations in the course of expeditions in the Central Basin during the 1980–1990s, as well as other data, including those obtained from foreign sources.

Evolution of a structural basin: Numerical modelling applied to the Dehdasht Basin, Central Zagros, Iran

The Dehdasht Basin, a small structural basin located in the southeast of the Dezful Embayment in the Zagros fold-and-thrust belt, has a complex tectonic structure characterized by both compressional and halokinetic features. 2D numerical models are used to test how geometrical and rheological parameters affected the Miocene-Pliocene evolution of this deep basin. The analysed parameters include rates of syntectonic sedimentation and erosion, thickness and viscosity of the lower detachment (Hormuz salt) and of the upper detachment (Gachsaran evaporites) developing diapiric salt walls, salt extrusions and minibasins-growth synclines that characterize the internal structure of the Dehdasht Basin. Assuming reasonable dimensions and rheologies (0.5 km Hormuz basal detachment with moderate viscosity of 1019 Pa·s, and Gachsaran upper detachment with a minimum original thickness of 1.5 km and viscosity between 5 · 1018 and 1019 Pa·s), our models reveals that an almost intermediate ratio between the rates of surface processes and deformation well approximate the geological and geophysical observations. A local decrease in the thickness of the Hormuz salt below the Dehdasht Basin with respect to surrounding regions was of great importance for its structural evolution. We suggest that the large volume of Gachsaran evaporites presently filling the basin was partly due to their gravitational flow from the emerging surrounding anticlines into the basin. The numerical experiments also demonstrate that in a compressional setting, shortening is the main factor for the rapid initial growth of the diapirs, although, with increasing syntectonic sedimentation the effect of shortening diminishes.