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After the destructive earthquake in Petrinja measuring M6.2 occurred on 29 December 2020, which was followed by a series of foreshocks and aftershocks in the area of the rural settlements in Mečenčani and Borojevići, cover-collapse sinkholes suddenly appeared. The investigated area is located 20 km southeast of the epicentre. Some months later, more than 90 cover-collapse sinkholes appeared, jeopardising local infrastructure and residential buildings. The sinkholes appear in the area of covered karst, where there are clastic deposits 2–10 m thick on the fractured and weathered limestone bedrock. There are two geological models located in the investigated area: GM-1, where the base consists of clastic strata covering comprising Lithothamnium limestone, which in turn leads to the formation of underground cavities and cover-collapse sinkholes, and the GM-2, where the base comprises clay deposits without any cover-collapse sinkholes. These models can be effectively distinguished due to tomographic resistivity models; hence, numerous measurements were undertaken using two-dimensional electrical tomography in several phases. An estimate of the threat to infrastructural facilities was conducted, and the boundaries of the geological models were precisely determined according to which underground cavities and cover-collapse sinkholes did not develop. Tomographic measurements were also conducted over the largest cover-collapse sinkhole measuring 25 m in diameter and helped to more precisely define the entire hydrogeological model and the mechanisms involved in the formation of cover-collapse sinkholes.

Introduction. The aim of this study was to investigate the effects of replacing part of the wheat flour (WF) with brewer's barley malt flour (BMF), while reducing the sucrose in the recipe, on the quality characteristics of sponge cakes. Materials and methods. For the production of sponge cake samples, WF and three different types of brewer's BMF (Pilsen, Amber and Black) were used in different ratios with simultaneous reduction of sucrose addition. The content of reducing sugars in WF and BMF was determined, as well as the moisture content and water activity in sponge cake samples. Determination of specific volume, colour in CIEL*a*b* space, texture profile analysis (TPA) and sensory analysis using the nine-point hedonic scale were also performed. Results and discussion. The contents of reducing sugars were 0.43, 7.75, 17.05 and 61.02 g/100 g in WF, Amber, Pilsen and Black BMF, respectively. Since sucrose is known to be an excellent ingredient for lowering water activity, both moisture content and water activity in the sponge cake samples increased significantly when the addition of sucrose was reduced. The specific volume decreased from 1.99 cm3/g in the control WF sample to 1.79 cm3/g in the WF sample with reduction of sucrose content by 50.0%. Reducing the sucrose addition significantly increased the hardness and chewiness, while the resilience and cohesiveness of the cake decreased (p < 0.05). Addition of 20% BMF and reduction of sucrose to 83.3% of the original recipe mitigated these effects and there were no statistically significant differences between these samples and the control WF sample in terms of specific volume and texture parameters. The addition of BMF significantly affected all colour parameters of the sponge cake crumb (p < 0.05). Amber BMF:WF (20:80) sponge cake with reduced sucrose addition (83.3%) had the highest sensory scores for colour, appearance and overall acceptability. Pilsen BMF:WF (20:80) with reduced added sucrose (83.3%) had the best odour and the best taste was the WF control sample. Conclusion. By replacing WF with BMF in the production of sponge cakes, a very wide range of sponge cake products with different quality characteristics, improved nutritional and functional properties can be obtained. BMF has significant amounts of its own sugars, which can minimize the effect of the reduction of sucrose content in the sponge cake recipe.

Knowing the soil moisture distribution in the unsaturated zone can improve understanding the water flow through the unsaturated zone and thereby enable the calculation of aquifer recharge, which occurs through precipitation. One part of the Zagreb aquifer recharge occurs through infiltration from precipitation. In order to observe and model infiltration from precipitation through the unsaturated zone, the research polygon was constructed at the Velika Gorica well field, located in the southern part of the Zagreb aquifer, Croatia, where hourly measurements of electric conductivity (EC) and soil moisture content were carried out. EC and soil moisture data are measured by Time Domain Reflectometry (TDR) probes which are placed at different depths in the unsaturated zone. Furthermore, electrical resistivity tomography (ERT) measurements were conducted. Geophysical data, along with moisture and EC data from TDR probes, were used as input data for MoisturEC software, in order to obtain soil moisture distribution along a 2D profile. MoisturEC program offers three options for translating EC data to moisture content data which are all tested in this research. We obtained eight moisture content distributions along the observed profile and concluded that MoisturEC provides reasonable results with input data from geophysical measurements and TDR probe measurements. Soil moisture distribution in the unsaturated zone represents the initial conditions for further unsaturated flow modeling. Understanding the flow in the unsaturated zone enables the quantification of effective infiltration and can improve groundwater management., Poznavanje raspodjele vlažnosti u nesaturiranoj zoni može doprinijeti razumijevan-ju toka vode kroz nesaturiranu zonu a time i omogućiti izračun prihranjivanja vodonosnika putem oborine. Jedan dio prihranjivanja zagrebačkog vodonosnika čini oborina. U cilju promatranja i modeliranja infiltracije oborine kroz nesaturiranu zonu izgrađen je znanstveno-istraživački poligon na vodocrpilištu Velika Gorica, u južnom dijelu zagrebačkog vodonosnika, u kojem postoje satna mjerenja električne vodljivosti i sadržaja vode u tlu. Električna vodljivost i vlažnost mjere se TDR (eng. Time Domain Reflectom-etry) sondama koje su postavljene na različitim dubinama u nesaturiranoj zoni. Nadalje, provedena su i geofizička mjerenja gdje je korištena metoda električne tomografije. Podaci dobiveni geofizičkim istraživanjem te podaci o električnoj vodljivosti i vlažnosti dobiveni mjerenjima u TDR sondama korišteni su kao ulazni podaci za MoisturEC program u cilju dobivanja raspodjele vlažnosti na promatranom 2D profilu. U ovom istraživanju su testirane tri opcije MoisturEC programa za prevođenje podataka o električnim vodljivostima u podatke o sadržaju vode. Ukupno je dobiveno osam raspodjela vlažnosti po promatranom profilu te se može zaključiti da MoisturEC program daje razumne rezultate u slučaju kada su dostupni ulazni podaci o električnim vodljivostima na promatranom profilu te točkasti podaci o sadržaju vlage iz TDR sondi. Raspodjela vlažnosti u nesaturiranoj zoni može poslužiti kao početni uvjet pri modeliranju toka vode u nesaturiranoj zoni. Razumijevanje toka vode u nesaturiranoj zoni omogućava kvantifikaciju efektivne infiltracije, a time i bolje upravljanje podzemnim vodama

The area of study covers the marginal zone between the Adriatic microplate (African plate) and the Pannonian segment (Eurasian plate). We present a tomography model for this area, with special emphasis on the northwest Dinarides. A dense distribution of temporary seismic stations in the area of the Northern Dinarides along with permanent seismic stations located in the area, allowed us to construct this P-wave tomographic model. We assembled our travel-time dataset based on 26 seismic stations were used to collect the dataset. Teleseismic events were recorded for a period of 18 months and a set of 76 distant earthquakes were used to calculate the P-wave travel-time residuals. We calculated relative rather than absolute arrival-time residuals in the inversion to obtain depths of 0–400 km. We imaged a pronounced fast velocity anomaly below the NW Dinarides which directly indicates a lithosphere slab downgoing beneath the Dinarides. This fast anomaly extends towards the NW direction to at least 250 km depth, and we interpreted it as a descending lithosphere slab. The thrusting of the Adriatic microplate may be brought about by sub-lithosphere rising movement beneath the Pannonian region, along with a push from African plate. In our interpretation, the Adriatic lower lithosphere has been detached from the crust, and steeply sinks beneath the Dinarides. A lithosphere model of the contact between the Adriatic microplate and Pannonian tectonic segment was constructed based on the tomographic velocity model and results of previous crustal studies.

We present the results of Local Earthquake Tomography (LET) analysis to investigate the crust and uppermost mantle structure in the northern Dinarides and southwestern Pannonian basin. Datasets of P-wave travel times are inverted to recover a three-dimensional P-wave velocity model of the survey area. Two data subsets were used in this study: (1) data recorded on 15 temporary seismic stations, which were deployed in Croatia in the framework of ALPASS-DIPS project, and (2) travel time datasets from the Croatian Seismological Survey and ORFEUS databases. The data enabled to achieve a resolution of less than a hundred kilometres in horizontal directions and a few kilometres in vertical direction in the area with good ray coverage, as is documented by the resolution tests. Velocity variations are computed on a grid using the three-dimensional nonlinear tomographic inversion method. Our study provides the first crustal three- dimensional seismic model of the studied area, and it is correlated with previous results in the survey area allowing us to infer the main crustal structures with high confidence. The velocity model reveals crustal thickening beneath the Dinarides and significant crustal thinning beneath the Pannonian basin. The Moho surface was determined on the basis of the highest velocity gradients in the vertical cross- sections. We find relatively high velocities below the northern Dinarides at shallow depths (

A gravity model has been established at the contact of the southern part of the Pannonian basin and central Dinarides. Two-dimensional gravity modelling was carried out by means of the calibrated density set, defined at the Alp07 profile (Sumanovac, 2010), which significantly improved the resolution of the method. Gravity attraction caused by the structure in the upper mantle was analyzed in detail, which enabled construction of complete lithosphere model at the contact of the Dinarides, as a part of the Adriatic microplate, and the Pannonian basin as a segment of the Eurasian plate. Geophysical models demonstrate that overthrusting structures need to be considered in the present geological model; notably, the thrusting of the Adriatic microplate under the European plate. However, overthrusting processes cannot provide a complete explanation of the processes in the Pannonian basin. Considering that the Pannonian basin area is in fact a large geothermal anomaly, it is necessary to introduce the asthenosphere upwelling into the model. The presence of this structure is confirmed by a change in densities and seismic velocities in the uppermost mantle. This process has led to a significant thinning of the crust in the Tisia block and to the homogenization of properties as a result of the rising of the asthenosphere, and the crust can therefore be considered as a single layer. The combined effect of the push exerted by the African plate, and the rising of the asthenosphere and the thinning of the crust in the Pannonian basin caused the underthrusting of the Adriatic microplate below the Pannonian segment, thickening of the crust and steeply sinking of the Adriatic upper mantle below the Dinarides. Seismicity of the area and earthquake hypocenters enable the construction of active faults, which correlate well with the main faults at the surface and boundaries of density blocks in the crust.

The research was performed in the area of Dinarides and southwestern Pannonian basin with the aim to determine the crustal structure and Moho depths in the entire area. The Dinarides are located at the contact of the Adriatic microplate and southern part of European plate. Collision zone between them encompasses several different tectonic units. Accordingly, the crustal structure in this area is very complex. Deeper, mantle relationships are determined through recent teleseismic tomography investigations and fast velocity anomaly beneath Dinarides has been discovered which points to the Adriatic lithosphere slab steeply sinking in the asthenosphere (Šumanovac et al., 2017). But crustal structure for entire area is not resolved yet, although there are some 2D-models. The crustal characteristics are defined by different sets of geophysical data. The basic data are results of receiver functions (RF) analysis and 1D forward modelling of RF at about 40 seismic stations located in the research area. Those results are compiled with available models from active source seismic project ALP2002 along several profiles extending across this area and with gravity models (Šumanovac, 2010). The receiver functions are mainly used to map the velocity discontinuities. The Moho can be usually easy identified, but forward modelling enabled also determination of discontinuities in the crust and sedimentary basement, namely the crustal structure. The Moho depths obtained by RF method are compared with the depths from other methods and existing Moho maps which partly cover the research area. Receiver functions analysis at the stations in the Dinarides shows thickening of the crust and Moho depths are 10-15% greater than obtained by other geophysical methods (gravity and active seismic prospecting). In the Pannonian basin the Moho depths are about 25 km, which are similar to results of other data. In the transitional zone from the Dinarides to Pannonian basin which is a suture zone between Eurasia and Africa the crustal thickness is like in the pannonian part but the structure is more complex. The reason for that are ophiolite zones (Dinaridic and Sava zones). Based on different datasets high- resolution Moho depth map and model of the crustal structure in this area is constructed. The final Moho topography is average of the Moho as result of gravity modelling and active seismic data and the one obtained by receiver functions analysis. REFERENCES Šumanovac, F. 2010. Lithosphere structure at the contact of the Adriatic microplate and the Pannonian segment based on the gravity modelling. Tectonophysics 485, 94-106. Šumanovac, F., Markušić, S., Engelsfeld, T., Jurković, K., Orešković, J. 2017. Shallow and deep lithosphere slabs beneath the Dinarides from teleseismic tomography as the result of the Adriatic lithosphere downwelling. Tectonophysics 712-713, 523-541.

On the selected cases, Gotalovec in the area of Pannonian basin and Baska in the Dinaridic karst area, that are representing a common hydrogeological model in both regions of Croatia, CSAMT data together with data of other geophysical methods (electrical resistivity tomography , electrical sounding and seismic reflection) enabled the definition of a reliable prognostic geological model. The model consists of carbonate aquifer which underlies an impermeable thick package of clastic deposits. There are great variations of the dolomitic aquifer depths in the Gotalovec area due to strong tectonic activity, while in the Baska area depth changes are caused by the layer folding. The CSAMT method provides the most complete data on lithological and structural relationships in cases of hydrogeological targets deeper than 100 m. Based on the presented models we can conclude that the CSAMT method can provide greater exploration depth than electrical resistivity tomography (ERT) and can be considered as a fundamental geophysical method for exploration of buried carbonate aquifers, deeper than 100 m. But, the CSAMT research may demonstrate its advantages only in the case of very dense layout of CSAMT stations (25–50 m), due to the greater sensitivity to noise in relation to resistivity methods. Interpretation of CSAMT data is more complex in relation to resistivity methods, and a forward modelling method sometimes gives better results than an inversion due to possibility of the use of additional data acquired by other geophysical methods (ERT, electrical sounding and seismic reflection). At greater depths, the resolution of all electrical methods including the CSAMT method is significantly reduced, and seismic reflection can be very useful to resolve deeper lithological interfaces.

The study area covers the Dinarides and southwestern part of the Pannonian basin as the marginal zone between the Adriatic microplate (African plate) and the Pannonian tectonic segment (Eurasian plate). We created a three-dimensional seismic velocity model to 450 km depth using teleseismic tomography. Our travel-time dataset was collected by means of 40 seismic stations from the ORFEUS database and Croatian Seismological Survey database. A set of 90 teleseismic earthquakes were selected in the time range 2014–2015, and relative P-wave travel-time residuals were calculated. For the first time the seismic P-wave velocity model of a relatively high resolution on the entire Dinaridic mountain belt was obtained. Based on this model, a more reliable insight in the relations of the lithosphere plates has been achieved. We imaged a fast velocity anomaly extending underneath the entire Dinaridic mountain belt which indicates cold, rigid materials. The anomaly is steeply sloping towards the northeast and directly indicates the sinking of the Adriatic microplate underneath the Pannonian tectonic segment. In the Northern Dinarides the anomaly extends to the depth of 250 km, whereas in the Southern Dinarides it covers greater depths, up to 450 km. The shallow Adriatic slab extends along the External Dinarides, while the deep Adriatic slab extends beneath the Internal Dinarides and ophiolite zones in the area of central and southern Dinarides. Different slab depths are interpreted as the faster convergence of the plate in the southern Dinarides than in the northern, or the convergence of the plates had started in the southern part and systematically developed to the north.

Passive seismic experiment was carried out at the SW contact of the Dinarides and Pannonian basin to determine the crustal structure and velocity discontinuities. The aim of the experiment was to define the relationship between the Adriatic microplate and the Pannonian segment as a part of the European plate. Most of the temporary seismic stations were deployed in Croatia along the Alp07 profile—a part of the active-source ALP2002 project. About 300-km-long profile stretches from Istra peninsula to the Drava river, in a WSW–ESE direction. Teleseismic events recorded on 13 temporary seismic stations along the profile were analysed by P-receiver function method. Two types of characteristic receiver functions (RF) have been identified, belonging to Dinaridic and Pannonian crusts as defined on the Alp07 profile, while in transitional zone there are both types. Three major crustal discontinuities can be identified for the Dinaridic type: sedimentary basement, intracrustal discontinuity and Mohorovičić discontinuity, whereas the Pannonian type revealed only two discontinuities. The intracrustal discontinuity was not observed in the Pannonian type, thus pointing to a single- layered crust in the Pannonian basin. Two interpretation methods were applied: forward modelling of the receiver functions and H–κ stacking method, and the results were compared with the activesource seismic data at deep refraction profile Alp07. The receiver function modelling has given reliable results of the Moho depths that are in accordance with the seismic refraction results at the end of the Alp07 profile, that is in the area of Pannonian crust characterized by simple crustal structure and low seismic velocities (Vp between 5.9 and 6.2 km s−1). In the Dinarides and its peripheral parts, receiver function modelling regularly gives greater Moho depths, up to +15 %, due to more complex crustal structure. The depths of the Moho calculated by the H–κ stacking method vary within wide limits (±13 km), due to band limited data of short-period stations. The results at five stations have to be rejected because of huge deviations in comparison with all previous results, while at the other seven stations the Moho depths vary within ±15 % around the Moho discontinuity of the Alp07 profile.

Electrical tomography is often considered as the main geophysical method in groundwater investigations, especially in complex geological models, but in case of deep exploration it cannot achieve deeper aquifers and the electrical sounding cannot ensure complete and dense space coverage. In such a case the use of the magnetotelluric method can ensure determination of deep targets, as well as a good space sampling. The capabilities of the MT method are shown in a common hydrogeological model in Croatia which can be found in both regions, in the Pannonian basin and Dinarides. The carbonate aquifer is underlying at depths greater than 100 m below impermeable package of clastic deposits. Two filed examples of groundwater investigations are presented, Gotalovec (north-western Croatia) and Baska (karstic Adriatic island Krk) areas. A main conclusion can be drawn that the MT method provides the most complete data on lithological and structural relationships in the considered model, but it is very sensitive to surface and urban noises. The results of the other geophysical methods can improve the resolution (seismic reflection) and reduce the interpretation ambiguity (electrical tomography).

During the last two decades teleseismic studies yielded valuable information on the structure of the upper mantle below the Alpine–Mediterranean area. Subducted oceanic lithosphere forms a broad anomaly resting on but not penetrating the 670 km discontinuity. More shallow slabs imaged below the Alpine arc are interpreted as subducted continental lower lithosphere. Substantial advances in our understanding of past and active tectonic processes have been achieved due to these results. However, important issues like the polarity of subduction under the Eastern Alps and the slab geometry at the transition to the Pannonian realm are still under debate. The ALPASS teleseismic experiment was designed to address these open questions. Teleseismic waveforms from 80 earthquakes recorded at 75 temporary and 79 permanent stations were collected during 2005 and 2006. From these data, a tomographic image of the upper mantle was generated between 60 km and 500 km depth. Crustal corrections, additional station terms, and ray bending caused by the velocity perturbations were considered. A steeply to vertically dipping “shallow slab” below the Eastern Alps is clearly resolved down to a depth of ~ 250 km. It is interpreted as European lower lithosphere detached from the crust and subducted during post-collision convergence between Adria and Europe. Below the Pannonian realm low velocities or high mantle temperatures prevail down to ~ 300 km depth, consistent with the concept of a Pannonian lithospheric fragment, which underwent strike–slip deformation relative to the European plate and extension during the post-collision phase of the Alpine orogeny. Between 350 km and 400 km depth, a “deep slab” extends from below the central Eastern Alps to under the Pannonian realm. It is interpreted as subducted lithosphere of the Alpine Tethys. At greater depth, there is a continuous transition to the high velocity anomaly above the 670 km discontinuity.

In this paper, we analyse the influence of near-surface anomalies on the first arrivals of seismic waves. The traveltimes of first arrivals are calculated using the eikonal equation and are depicted in the form of the time–distance ( t – x ) graphs. We classify five simple geological models according to the shape of the t – x graphs and relate these results to more complex models one can find in the natural settings. All simple models are based on the two-layer model that is modified by a near-surface anomaly. We investigate the following cases: (i) a circular cavity impenetrable to seismic waves positioned in the upper layer, (ii) a circular object positioned in the upper layer, (iii) a part of the border between the layers is deformed into concave shape, (iv) a part of the border between the layers is deformed into convex shape, and (v) a vertical fractured zone positioned in the lower layer. The resulting t – x graphs are classified according to their shapes into three groups. The graphs in the first group are characterised by a peak point and the geological models (i) and (iii) belong to this group. The graphs in the second group are characterised by a depression in their shape and the geological models (ii) and (iv) belong to this group. The graph that corresponds to the model (v) differs from all other graphs and belongs to the third group. The seismic refraction method clearly distinguishes the models that belong to different groups, but the method cannot distinguish the models that belong to the same group because the shapes of their t – x graph are almost identical.

This paper presents a new approach to the investigation of underground cavities. Our technique is based on the refraction seismic method. We have studied a two-dimensional, two-layer geological model. In our model, the lower seismic velocity layer is situated above the higher seismic velocity layer, with a circular cavity positioned within the upper layer. We have investigated the influence exerted by the cavity on the first arrivals of seismic waves. The obtained traveltimes are solutions of the eikonal equation and are presented using the time-distance graph. All refracted waves encountering the cavity have to circumvent it, as it represents an impediment to the propagation of seismic energy. This circumvention causes delays in the first arrivals of the seismic waves at the surface as compared to traveltimes with no cavity present. These delays create a characteristic shape of the time-distance graph, characterized by the peak point in which the plot line has a discontinuous change. Using this graph and analysing the delays of the first arrivals, we have derived expressions for determining both the position and size of the circular cavity. The practical application of the derived relations has been tested on a model test site built in a natural rock setting. This simple method indicates the presence of the cavity. The accuracy of the calculated cavity parameters: the horizontal position x , the depth z and cavity radius r depends on the geophone spacing. For geophone spacing equal to or less than the cavity radius, the accuracy of the method is shown to be acceptable. The maximal estimated error is equal to a half geophone spacing. Finally, we have demonstrated that this method is also applicable in the detection of non-circular cavities.

The island of Susak differs from other Croatian islands in its geological and hydrogeological properties, because it is, for the most part, covered with fine-grained loess-type sands. At the outset of the research it was unclear whether the main aquifer lies within the superficial deposits or within the underlying carbonate rocks. This gave rise to two alternative conceptual models, depending on whether the interface between the superficial cover and the carbonates occurs above or below sea level. Hydrogeological and geophysical investigations were conducted. The primary objective of the geophysical exploration was to determine optimum positions for exploratory boreholes. The results showed that the main aquifer is contained within the carbonate rocks, and that this carbonate aquifer is overlain by a second, confined, aquifer within the superficial sandy deposits. Groundwater within the carbonate aquifer is hydraulically connected to the sea by fault zones. Measurement of electrical conductivity in boreholes established that the mixing zone of fresh and salt water is at depths from 22 to 30 m below ground level. It is necessary to ensure constant control of pumping quantities and control of the brackish water lens by monitoring of the groundwater salinity. For inclusion in public water supply, the groundwater should be treated by desalination.

In the framework of exploration of building stones electrical tomography is an essential method. It is particularly effective in three types of geological models: boundary between carbonates and clastic rocks (1), boundary between rather compact igneous rocks and clastites (2) and fault and fracture zones in hard rocks (3). These are the most common models in surveying of building stones and great potentials of electrical tomography are presented on examples of two quarry explorations. Model 1 and model 3 are shown on Vojnovec quarry where electrical tomography enabled precise definition of boundaries between carbonates and clastic rocks, as well as determination of margins of fractured zone within carbonates. Model 2 is presented by Hruskovec quarry where diabase bodies are in contact with clastites. Since high resistivities similar to the resistivity of diabase, also may be caused by dry sandstones magnetic method has been applied to distinguish between rocks of similar resistivity but different magnetic properties. In one case magnetic method was helpful in determination of the edge of diabase bodies, whereas in the second case the edge could not be determined due to changes in magnetic properties of diabases. Electrical tomography, in both cases, enabled determination of reliable two-dimensional model.

The ALP 2002 was organized as an international seismic experiment whose scientific objective is to further scientific understanding of the structure and evolution of the lithosphere in the Eastern Alps and surrounding areas. The ALP 2002 experiment included passive seismic monitoring and an active source seismic refraction experiment. Furthermore, local high-density deployments were carried out in Austria and Hungary to investigate local geologic problems. All data will be integrated with the goal of better understanding the geodynamic processes currently at work and the complex tectonic history of this region.

A water exploration in a karst area can be hardly imagined without the application of electrical and seismic methods, but karst areas are very difficult environments for any geophysical exploration due to very high surface nonhomogeneities. Dual gradient mapping (measurements performed at two depth levels), two-dimensional (2-D) resistivity imaging, refraction methods and high-resolution reflection methods have been applied on a characteristic karst case in Croatia. General overview on the subsurface resistivity distribution has been reached by using the gradient mapping measurements. This revealed low-resistivity zone points of the fractured rock filled with water. Map of relative changes of apparent resistivities with depth discovers two different zones: resistivity increases with depth in the eastern part and resistivity decreases with depth in the western part of the area. Weak reflections are seen in the stacked seismic reflection section placed with the 2-D resistivity imaging profile, but they can be followed along the entire profile. By combining refraction and reflection data, faulted and fractured zones can be determined at surface as well as at greater depths, which will enable a precise definition of their extensions. Two-dimensional inverse seismic modelling have been carried out to clarify significance of the main reflection horizon, which is probably caused by a lithologic boundary, meaning a contact of dolomites and compact limestones. The model of acoustic impedancies has been derived on the basis of refraction velocities, reflection velocities and geological data from borehole. An accurate geological model has been established on the basis of all the data. Two-dimensional resistivity surveying can be used very efficiently in karst water explorations of shallow targets, but for deeper targets the seismic methods can be very useful by reason of poor resolution of the electrical resistivity methods.

Two-dimensional gravity modelling is applied to the contact of the Dinarides and the Pannonian basin as a contribution to solving structural and tectonic relations in the area characterised by very complex relations. An interpretation procedure, which improves the resolution of gravity modelling by the use of seismic refraction data, has been developed. On the Alp07 profile, which is set up in the framework of the ALP 2002 seismic experiment and stretches in Croatia from Istra over the Dinarides to the Drava River, seismic modelling was performed in order to determine the structure of the lithosphere. A 2-D gravity modelling was also carried out on the profile to obtain calibrated rock densities using interfaces from the seismic model. Calibrated densities were applied to other profiles set up in the study area for the purpose of determining the structural relations. The structural units determined on the Alp07 profile (Pannonian crust, Transition zone and Dinaridic crust) can be easily followed on all other profiles. The Transition zone, which separates the Pannonian and the Dinaridic crusts, is very wide and characterised by lateral and vertical changes in velocities and densities. It corresponds with the ophiolite zones in more recent tectonic maps. The Tisia block can be compared with the Pannonian crust, whereas the Dinaridic crust would relate to the structural unites of the Adriatic. However, the NE boundary of the Transition zone is located much further north than the boundary of the Tisia block in published tectonic maps. Due to a marked 2-D structure, the obtained results enabled the development of a 3-D structural map of the Mohorovicic discontinuity. The main fault in the upper mantle, which was defined on the basis of geometrical relations, indicates a subduction of the Adriatic microplate beneath the Pannonian segment in the NE wing of the Dinarides.

In this paper we investigate the influence of near-surface anomalies on the first arrivals of seismic waves. The basic two-layer model is modified with the following anomalies: (1) circular cavity positioned in the upper layer, (2) buried circular object positioned in the upper layer, (3) part of the border between the layers is deformed into concave shape. All anomalies are characterized with the seismic velocities that are lower than the seismic velocity of the neighboring region. First arrivals are calculated by numerical modeling of 2D eikonal equation. Numerically obtained traveltimes are presented in the time-distance graph and are also used to construct the graph of wavefronts. In all cases, the shape of the time-distance graph is characterized by a peak point which is a consequence of slower propagation of seismic waves through the analyzed anomalies.

[1] Alp01 and Alp02 are the longest profiles recorded during ALP 2002, a large international seismic refraction and wide-angle reflection experiment undertaken in the Eastern Alps in 2002. Alp01 crosses the Alpine orogen from north to south, thus providing a cross section mainly affected by the collision between Europe and the Adriatic microplate. Alp02 extends from the Eastern Alps to the Pannonian basin, supplying evidence on the relation between Alpine crustal structure and tectonic escape to the Pannonian basin. During this experiment, 363 single-channel recorders were deployed along these profiles with an average spacing of 3.2 km. Recordings from 20 inline shots were used in this study. Two-dimensional forward modeling using interactive ray-tracing techniques produced detailed P wave velocity models that contain many features of tectonic significance. Along Alp01, the European Moho dips generally to the south and reaches a maximum depth of 47 km below the transition from the Eastern to the Southern Alps. The Adriatic Moho continues further south at a significantly shallower depth. Moho topography and a prominent south-dipping mantle reflector in the Alpine area support the idea of southward subduction of the European lithosphere below the Adriatic microplate. The most prominent tectonic feature on the Alp02 profile is a vertical step of the Moho at the transition between the Alpine and Pannonian domains, suggesting the existence of a separate Pannonian plate fragment. The development of the Pannonian fragment is interpreted to be a consequence of crustal thinning due to tectonic escape from the Alpine collision area to the Pannonian basin.

Summary Extensive explorations have been performed in the northern part of the island of Dugi Otok in the Adriatic Sea (Croatia) with the purpose of extraction of fresh and/or brackish water. The island is predominantly composed of karstified carbonate rocks of the Cretaceous age. The explorations included geological and hydrogeological mapping of the area, geophysical surveys (by means of the geoelectric tomography method, electrical resistivity sounding, and surface seismic refraction), exploratory core drilling, hydrochemical in situ and laboratory explorations, and the pumping test with the calculation of rock mass parameters. Based on the obtained results, it was concluded that it is possible to exploit the groundwater with a pumping quantity of 5 l/s without intrusion of salt water into the fresh-water lens. Choosing a pumping regime based on the parameters of the aquifer (rock mass hydraulic conductivity order of magnitude 10−4–10−6 m/s), and knowing the parameters of the well, as well as the tidal efficiency, should reduce the possibility of intrusion to the minimum. Because of the systematic quality of the performed explorations and obtained results, the island of Dugi Otok can serve as a typical example for such kinds of exploration works on other karstic islands. Hydrogeological composition behaves partly according to Ghyben–Herzberg‘s law, but because of the nature of the karstic hydrogeological system, such a statement needs to be accepted approximately because of the highly complicated relationships.

Geophysical methods play a major role in hydrogeological explorations due to the fact that they enable, through the combination with other data, the obtaining of a reliable forecasting model and the detection of new drinking water resources. However, in order to exploit water and protect the sources (wells) in an appropriate manner, it is necessary to precisely define structural and lithological relations, i.e. define an accurate model of the underground. This is particularly difficult in complex geological models, which definitely include the karst terrain characterized by carbonate sediments, limestones and dolomites (Sumanovac and Weisser, 2001), whose primary features include marked surface nonhomogeneities and sudden lateral changes at small intervals. Surface nonhomogeneities are caused by the generation of high level noise, which results in the decreased quality of measured data, and thus a reduced accuracy of interpretation. The water in karst terrains is found mostly in fault and fracture zones, which are characterized by secondary porosity. A detailed mapping of these zones is therefore the primary task of geophysical explorations. The karst area covers the largest part of Croatia, and is related to the Dinarides in the southwestern and southern parts of Croatia. The general extension of the Dinarides is northwest-southeast, where the majority of tourist industry is concentrated, with high demands for drinking water in dry summer months. Although the youngest geophysical method, electrical tomography has already secured the top position in more shallow engineering geological explorations. Considering the good results already achieved in recent years in relatively deeper hydrogeological explorations in karst terrains, it has become the dominant geophysical method in these explorations, with other methods used as supplements, or for specific purposes. Therefore, based on numerous hydrogeological explorations in karst terrains, the detection and mapping of fault zones can be best performed by applying the electrical tomography method, whose great potentials are presented on characteristic cases of karst terrains and karst springs.

We present a new technique for computing the effective permeability in heterogeneous reservoirs on a coarse scale. The method is based on the assumption that the permeability is given at a fine scale and that it is necessary to reduce the number of blocks in the reservoir model.

Electrical tomography, which gives good results even in fairly complex geological environments, has given a new lease of life to electrical methods in hydrogeological surveys. Nevertheless, a rapid decline in resolution with increasing depth remains the main problem of the electrical methods. In the Pannonian basin in Croatia, at a test area, combining both electrical tomography and seismic reflection methods provides data that better constrain the lithological and hydrogeological model of the subsurface. Electrical tomography revealed a rather thick packet of sediments with increased resistivity at depths of 40–100 m. Using the electrical forward modelling, the existence of two different hydrogeological models was shown. The first model presupposes a reasonably homogeneous packet of sandy clays or clayey sands, and the other model presupposes the alternation between layers of clays and sands. From the hydrogeological point of view, the second model is perspective, but unfortunately, the use of electrical tomography alone does not allow the ambiguity to be resolved. The separation of these two models became possible using seismic reflection. Three seismic environments were isolated from the seismic profile treated, and the strongest reflections were discovered in the first seismic environment, which covers the depths from 40 to 100 m. It was determined that the second model is more acceptable, because these reflections are caused by lithological changes, that is, the alternations of sands and clays. The interpretation is consistent with exploratory borehole data. The conclusion is that electrical tomography gives data concerning the sediment lithology up to depths of 40 m, but at greater depths combined interpretation of electrical and seismic data constrains the subsurface model better.

The problem of ambiguity in the interpretation of gravity in platform areas is analised. A theoretical example is given, presenting ambiguity in the determination of depth and position of faults, even when the form of structures is known. It has been concluded, that the best method of gravity interpretation is the construction of the map and profiles showing the depths of horizon where there is the strongest density contrast. An example is given from the Sultana area in Jordan, where the gravity map is converted into the maps of »quantitative regional« and »true residual«, by means of drilling data. Interpretation of the residual by the method of gravity modelling resulted in the construction of the map of structures and depths of the density contrast horizon, with the positions and throws of the main faults., Analiziran je problem višeznačnosti u gravimetrijskoj interpretaciji platformnih područja. Dan je teoretski primjer koji pokazuje da postoji višeznačnost u određivanju dubine i položaja rasjeda i kad je poznat oblik strukture. Zaključeno je da u interpretaciji gravimetrije najbolje rezultate daje konstrukcija karte i profila koji pokazuju dubine horizonta na kojem se javlja najjači kontrast gustoće. Dan je primjer iz područja Sultana u Jordanu, gdje je gravimetrijska karta preračunata u karte »kvantitativnog regiona-la« i »pravog reziduala«. uz korištenje podataka bušotina. Interpretacijom gravimetrijskog reziduala metodom gravimetrijskog modeliranja konstruirana je karta struktura i dubina horizonta kontrasta gustoče, s položajima i iznosima pomaka glavnih rasjeda.

Electrical methods are commonly used in groundwater investigations but in case of deeper aquifers the electrical tomography cannot achieve deeper targets and the electrical sounding cannot ensure a complete and dense space coverage. In such a case the use of the magnetotelluric method can provide for great depths of research, as well as a good space sampling. The capabilities of the MT-method are shown in two examples of deeper groundwater investigations carried out in the north-western Croatia. In the Gotalovec area the aquifers are fractured carbonates (Triassic and Miocene) underlying thick series of Neogenic clays and marls. On the basis of all results a conclusion can be drawn that the MT-method should be applied first in similar model in order to define potential aquifers and indicate the most favourable micro-locations where reflection seismics can be applied as the latter allows for a more precise mapping of aquifer depths and faults. The second geological model, investigated in the Apatovac area, is very complex consisting of clastic and magmatite bodies. The MT-method provided for a complete and clear solution to the structural relationships in the area and gave a precise definition of the deep narrow diabase body which is mineral water aquifer.