# Lithosphere Structure of the Southern Dinarides and Continuity of the Adriatic Lithosphere Slab Beneath the Northern Dinarides Unravelled by Seismic Modelling

## Abstract

**:**

## 1. Introduction

## 2. Area of Study including the Regional and Geological Setting

**Figure 1.**Topographic and position map with tectonics of the Pannonian–Dinaridic including the border area of the Alcapa (Alpine–Carpathian tectonic unit). Permanent seismic stations in the survey area are shown as blue diamonds and the seismic profiles P-6 and P-7 as black lines [8]. The main tectonic units and faults are superimposed on the topographic map (PAF—Periadriatic fault, CF—Ćićarija fault, SMF—South marginal fault of the Pannonian Basin). The borders of the suture zone after [15].

## 3. An Overview of Adriatic Subduction

## 4. Seismic Network and Resolution

## 5. Forward and Inverse Problems of the Teleseismic Tomography

_{i}) and mean residual (a

_{av}) for the selected earthquake:

_{i}= a

_{i}− a

_{av}.

_{i}) and predicted travel times (a

_{ip}):

_{i}= t

_{i}− a

_{ip},

## 6. Seismic Modelling

## 7. Discussion

## 8. Conclusions

## Funding

## Data Availability Statement

## Acknowledgments

## Conflicts of Interest

## Appendix A

**Figure A1.**Resolution test—spike test. Positive and negative velocity anomalies (dV = ±0.4 km/s) were superimposed in a regular pattern on the ak135 model and recovered by an inversion with the parameters used for the solution model. A synthetic model is shown together with the inversion slices at 110 km and 350 km (upper part), and at the west–east profile (44.0 N) and south–north profile (17.0 E; lower part). Better resolution is achieved at greater depths. Inversion model shows that applied geometry can resolve the structure of the Dinarides.

## References

- Ustaszewski, K.; Schmid, S.M.; Fügenschuh, B.; Tischler, M.; Kissling, E.; Spakman, W. A map-view restoration of the Alpine-Carpathian-Dinaridic system for the Early Miocene. Swiss J. Geosci.
**2008**, 101 (Suppl. 1), 273–294. [Google Scholar] [CrossRef] [Green Version] - Mitterbauer, U.; Behm, M.; Brückl, E.; Lippitsch, R.; Guterch, A.; Keller, G.R.; Koslovskaya, E.; Rumpfhuber, E.M.; Šumanovac, F. Shape and origin of the East-Alpine slab constrained by the ALPASS teleseismic model. Tectonophysics
**2011**, 510, 195–206. [Google Scholar] [CrossRef] - Handy, M.R.; Ustaszewski, K.; Kissling, E. Reconstructing the Alps-Carpathians-Dinarides as a key to understanding switches in subduction polarity, slab gaps and surface motion. Int. J. Earth Sci.
**2015**, 104, 1–26. [Google Scholar] [CrossRef] [Green Version] - Ustaszewski, K.; Kounov, A.; Schmid, S.M.; Schaltegger, U.; Krenn, E.; Frank, W.; Fügenschuh, B. Evolution of the Adria-Europe plate boundary in the northern Dinarides: From continent-continent collision to back-arc extension. Tectonics
**2010**, 29, TC6017. [Google Scholar] [CrossRef] - Bijwaard, H.; Spakman, W. Non-linear global P-wave tomography by iterated linearized inversion. Geophys. J. Int.
**2000**, 141, 71–82. [Google Scholar] [CrossRef] [Green Version] - Piromallo, C.; Morelli, A. P wave tomography of the mantle under the Alpine-Mediterranean area. J. Geophys. Res.
**2003**, 108, 2065. [Google Scholar] [CrossRef] - Koulakov, I.; Kaban, M.K.; Tesauro, M. P- and S-velocity anomalies in the upper mantle beneath Europe from tomographic inversion of ISC data. Geophys. J. Int.
**2009**, 179, 345–366. [Google Scholar] [CrossRef] [Green Version] - Šumanovac, F.; Markušić, S.; Engelsfeld, T.; Jurković, K.; Orešković, J. Shallow and deep lithosphere slabs beneath the Dinarides from teleseismic tomography as the result of the Adriatic lithosphere downwelling. Tectonophy
**2017**, 712–713, 523–541. [Google Scholar] [CrossRef] - Hua, Y.; Zhao, D.; Xu, Y. P wave anisotropic tomography of the Alps. J. Geophys. Res. Solid Earth
**2017**, 122, 4509–4528. [Google Scholar] [CrossRef] - Sun, W.; Zhao, L.; Malusà, M.G.; Guillot, S.; Fu, L.Y. 3-D Pn tomography reveals continental subduction at the boundaries of the Adriatic microplate in the absence of a precursor oceanic slab. Earth Plan. Sci. Lett.
**2019**, 510, 131–141. [Google Scholar] [CrossRef] - Pamić, J. North Dinaridic late Cretaceous-Paleogene subduction-related tectonostratigraphic units of southern Tisia, Croatia. Geol. Carp.
**1998**, 49, 341–350. [Google Scholar] - Pamić, J.; Tomljenović, B.; Balen, D. Geodynamic and petrogenetic evolution of Alpine ophiolites from the central and NW Dinarides: An overview. Lithos
**2002**, 65, 113–142. [Google Scholar] [CrossRef] - Schmid, S.M.; Bernoulli, D.; Fügenschuh, B.; Matenco, L.; Schefer, S.; Schuster, R.; Tischler, M.; Ustaszewski, K. The Alpine-Carpathian-Dinaridic orogenic system: Correlation and evolution of tectonic units. Swiss J. Geosci.
**2008**, 101, 139–183. [Google Scholar] [CrossRef] [Green Version] - Šumanovac, F.; Orešković, J.; Grad, M.; ALP2002 Working Group. Crustal structure at the contact of the Dinarides and Pannonian Basin based on 2-D seismic and gravity interpretation of the Alp07 profile in the ALP2002 experiment. Geophys. J. Int.
**2009**, 179, 615–633. [Google Scholar] [CrossRef] [Green Version] - Šumanovac, F. Lithosphere structure at the contact of the Adriatic microplate and the Pannonian segment based on the gravity modelling. Tectonophy
**2010**, 485, 94–106. [Google Scholar] [CrossRef] - Posgay, K.; Bodoky, T.; Hegedüs, E.; Kovácsvölgyi, S.; Lenkey, L.; Szafián, P.; Takács, E.; Tímár, Z.; Varga, G. Asthenospheric structure beneath a Neogene Basin in southeast Hungary. Tectonophy
**1995**, 252, 467–484. [Google Scholar] [CrossRef] - Herak, M. A new concept of geotectonics of the Dinarides. Acta Geol. Zagreb
**1986**, 16, 1–24. [Google Scholar] - Moretti, I.; Royden, L. Deflection, gravity anomalies and tectonics of doubly subducted continental lithosphere: Adriatic and Ionian Sea. Tectonics
**1988**, 7, 875–893. [Google Scholar] [CrossRef] - Markušić, S.; Gülerce, Z.; Kuka, N.; Duni, L.; Ivančić, I.; Radovanović, S.; Glavatović, B.; Milutinović, Z.; Akkar, S.; Kovačević, S.; et al. An updated and unified earthquake catalogue for the Western Balkan region. Bull. Earthq. Eng.
**2016**, 14, 321–343. [Google Scholar] [CrossRef] - Tari, V.; Pamić, J. Geodynamic evolution of the northern Dinarides and the southern part of the Pannonian Basin. Tectonophy
**1998**, 197, 269–281. [Google Scholar] [CrossRef] - Brückl, E.; Bleibinhaus, F.; Gosar, A.; Grad, M.; Guterch, A.; Hrubcová, P.; Keller, G.R.; Šumanovac, F.; Tiira, T.; Yliniemi, J.; et al. Crustal structure due to collisional and escape tectonics in the Eastern Alps region based on profiles Alp01 and Alp02 from the ALP 2002 seismic experiment. J. Geophys. Res.
**2007**, 112, B06308. [Google Scholar] [CrossRef] [Green Version] - Skoko, D.; Prelogović, E.; Aljinović, B. Geological structure of the Earth’s crust above the Moho discontinuity in Yugoslavia. Geophys. J. Roy. Astr. Soc.
**1987**, 89, 379–382. [Google Scholar] [CrossRef] - Šumanovac, F. Lithosphere model of the Pannonian-Adriatic overthrusting. Tectonophy
**2015**, 665, 79–91. [Google Scholar] [CrossRef] - Orešković, J.; Šumanovac, F.; Hegedűs, E. Crustal structure beneath Istra peninsula based on receiver function analysis. Geofizika
**2011**, 28, 247–263. [Google Scholar] - Stipčević, J.; Herak, M.; Molinari, I.; Dasović, I.; Tkalčić, H.; Gosar, A. Crustal Thickness Beneath the Dinarides and Surrounding Areas from Receiver Functions. Tectonics
**2020**, 12, 2633–2669. [Google Scholar] [CrossRef] - Belinić, T.; Kolinsky, P.; Stipčević, J.; AlpArray Working Group. Shear-wave velocity structure beneath the Dinarides from the inversion of Rayleigh-wave dispersion. Earth Plan. Sci. Lett.
**2020**, 555, 116686. [Google Scholar] [CrossRef] - Šumanovac, F. Gravity map of Yugoslavia. In Gravimetrijska Karta SFR Jugoslavije—Bouguerove Anomalije, 1:500.000; Federal Geological Institute: Beograd, Serbia, 1972. [Google Scholar]
- Mohorovičić, A. Potres od 8. X 1909. In Godišnje Izvješće Zagrebačkog Meteorološkog Opservatorija za Godinu; English translation in 1992, Earthquake of 8 October 1909. Geofizika 9:3-55; WorldCat Publisher: Dublin, OH, USA, 1909; Volume 9, pp. 1–56. (In Croatian) [Google Scholar]
- Dragašević, T.; Andrić, B. Deep seismic sounding of the Earth’s crust in the area of the Dinarides and the Adriatic Sea. Geophys. Pros.
**1968**, 6, 54–76. [Google Scholar] [CrossRef] - Belinić, T.; Stipčević, J.; Živčić, M.; Alp Array Working Group. Lithospheric thickness under the Dinarides. Earth Plan. Sci. Lett.
**2018**, 484, 229–240. [Google Scholar] [CrossRef] - Balling, P.; Grützner, C.; Tomljenović, B.; Spakman, W.; Ustaszewski, K. Post-collisional mantle delamination in the Dinarides implied from staircases of Oligo-Miocene uplifted marine terraces. Sci. Rep.
**2022**, 11, 2685. [Google Scholar] [CrossRef] - Šumanovac, F.; Dudjak, D. Descending lithosphere slab beneath the Northwest Dinarides from teleseismic tomography. J. Geod.
**2016**, 102, 171–184. [Google Scholar] [CrossRef] - Zhao, L.; Paul, A.; Malusa, M.G.; Xu, X.; Zheng, T.; Solarino, S.G.; Guillot, S.; Schwartz, S.; Dumont, T.; Salimbeni, S.; et al. Continuity of the Alpine slab unraveled by high-resolution P wave tomography. J. Geophys. Res. Sol. Earth
**2016**, 121, 8720–8737. [Google Scholar] [CrossRef] - Rappisi, F.; VanderBeek, B.P.; Faccenda, M.; Morelli, A.; Molinari, I. Slab Geometry and Upper Mantle Flow Patterns in the Central Mediterranean from 3D Anisotropic P-Wave Tomography. J. Geophys. Res. Sol. Earth
**2022**, 127, e2021JB023488. [Google Scholar] [CrossRef] [PubMed] - Malusà, M.G.; Guillot, S.; Zhao, L.; Paul, A.; Solarino, S.; Dumont, T.; Schwartz, S.; Aubert, C.; Baccheschi, P.; Eva, E.; et al. The deep structure of the Alps based on the CIFALPS seismic experiment: A synthesis. Geochem. Geophys. Geosyst.
**2021**, 22, e2020GC009466. [Google Scholar] [CrossRef] - Šumanovac, F.; Hegedűs, E.; Orešković, J.; Kolar, S.; Kovács, A.C.; Dudjak, D.; Kovács, I.J. Passive seismic experiment and receiver functions analysis to determine crustal structure at the contact of the northern Dinarides and southwestern Pannonian Basin. Geophys. J. Int.
**2016**, 205, 1420–1436. [Google Scholar] [CrossRef] [Green Version] - Bezada, M.J.; Faccenda, M.; Toomey, D.R. Representing anisotropic subduction zones with isotropic velocity models: A characterization of the problem and some steps on a possible path forward. Geochem. Geophys. Geosyst.
**2016**, 17, 3164–3189. [Google Scholar] [CrossRef] [Green Version] - Jansson, B.; Husebye, E.S. Application of array data techniques to a network of ordinary seismograph stations. Pure Appl. Geophys.
**1966**, 63, 83–104. [Google Scholar] [CrossRef] - Gangi, A.F.; Fairborn, J.W. Accurate determination of seismic array steering delays by an adaptive computer programme. Suppl. Al Nuovo Cim. Ser.
**1968**, 1, 105–115. [Google Scholar] - Rawlinson, N.; Kennett, B.L.N. Rapid estimation of relative and absolute delay times across a network by adaptive stacking. Geophys. J. Int.
**2004**, 157, 332–340. [Google Scholar] [CrossRef] - Rawlinson, N.; Reading, A.M.; Kennett, B.L.N. Lithospheric structure of Tasmania from a novel form of teleseismic tomography. J. Geophys. Res.
**2006**, 111, B023101. [Google Scholar] [CrossRef] - Kennett, B.L.N.; Engdahl, E.R.; Buland, R. Constraints on seismic velocities in the Earth from travel times. Geophys. J. Int.
**1995**, 122, 108–124. [Google Scholar] [CrossRef] [Green Version] - Kennett, B.L.N.; Sambridge, M.S.; Williamson, P.R. Subspace methods for large scale inverse problems involving multiple parameter classes. Geophys. J. Int.
**1988**, 94, 237–247. [Google Scholar] [CrossRef] [Green Version] - Graeber, F.M.; Houseman, G.A.; Greenhalgh, S.A. Teleseismic tomography of the Lachlan Fold Belt and the Newer Volcanic Province, Southeast Australia. Geophys. J. Int.
**2002**, 149, 249–266. [Google Scholar] [CrossRef] [Green Version] - Dando, B.D.E.; Stuart, G.W.; Houseman, G.A.; Hegedues, E.; Brückl, E.; Radovanovic, S. Teleseismic tomography of the mantle in the Carpathian-Pannonian region of central Europe. Geophys. J. Int.
**2011**, 186, 11–31. [Google Scholar] [CrossRef] [Green Version] - Kapuralić, J.; Šumanovac, F.; Markušić, S. Crustal structure of the northern Dinarides and southwestern part of the Pannonian Basin inferred from local earthquake tomography. Swiss J. Geosci.
**2019**, 112, 181–198. [Google Scholar] [CrossRef] - Kästle, E.D.; Rosenberg, C.; Boschi, L.; Bellachsen, N.; Meier, T.; El-Sharkawy, A. Slab break-offs in the Alpine subduction zone. Sol. Earth
**2020**, 109, 587–603. [Google Scholar] [CrossRef] [Green Version] - Handy, M.R.; Schmid, S.M.; Paffrath, M.; Friederich, W.; AlpArray Working Group. Orogenic lithosphere and slabs in the greater Alpine area—Interpretations based on teleseismic P-wave tomography. Sol. Earth
**2021**, 12, 2633–2669. [Google Scholar] [CrossRef] - Ren, Y.; Stuart, G.W.; Houseman, G.A.; Dando, B.; Ionescu, C.; Hegedüs, E.; Radovanović, S.; Shen, Y. Upper mantle structures beneath the Carpathian-Pannonian region, Implications for the geodynamics of continental collision. Earth Plan. Sci. Lett.
**2012**, 349–350, 139–152. [Google Scholar] [CrossRef]

**Figure 2.**A simple resolution test showing excellent horizontal but poor vertical resolution. The structure, a high velocity block (dV = +0.4 km/s), is shown by the depth slice of 100 km and the vertical cross section of 45.5° N (left side). The inverse model recovered from synthetic travel-time residuals is shown on the right side [32]. Black squares and triangles represent permanent and temporary seismic stations used to collect the observed data.

**Figure 4.**Depth slice at 100 km using the three-dimensional velocity SU-model [8]. Pronounced fast anomaly can be followed in the entire Dinaridic mountain belt. Diagonal cross-sections placed in the Northern and Southern Dinarides (P-6 and P-7) point out the steep fast anomaly beneath the Dinarides probably caused by the descent Adriatic lithospheric slab. Damping of the fast anomaly in the Northern Dinarides is seen on the depth slice.

**Figure 5.**First model. Three-dimensional velocity models showing two depth slices (150 km and 350 km, upper part) and two cross sections (46° N and 17.5° E, lower part). A high-velocity vertical slab in the synthetic model is assumed (left side), where it is shallow in the Northern and deep in the Southern Dinarides. The inverse model recovered from synthetic travel-time residuals is shown in the middle part, and the inverse model of observed travel-time residuals in the SU-model [8] is shown on the right side. Additional low-velocity block is assumed in the Pannonian Basin.

**Figure 6.**Second model. Three-dimensional velocity models showing two depth slices (150 km and 350 km, upper part) and two cross sections (46° N and 17.5° E, lower part). A shallow high-velocity vertical slab in the synthetic model is assumed in the Northern Dinarides, while deep slab in the Southern Dinarides is divided in two parts, and the deeper part of the slab is shifted towards the northeast (left side). The inverse model recovered from synthetic travel-time residuals is shown in the middle part, and the inverse model of observed travel-time residuals in the SU-model [8] is shown in the right side. Better correlation between the shapes of the anomalies of the inverse models for the synthetic and the observed data than for the first model (Figure 5) can be noticed.

**Figure 7.**Third model. Three-dimensional velocity models showing two depth slices (150 km and 350 km, upper part) and two cross sections (46° N and 17.5° E, lower part). A shallow high-velocity vertical slab in the synthetic model is assumed in the Northern Dinarides, while deep slab in the Southern Dinarides is divided into two separate blocks, the shallow one and the deep one (left side). The inverse model recovered from synthetic travel-time residuals is shown in the middle part, and the inverse model of observed travel-time residuals in the SU-model [8] is shown in the right side. The correlation between the shapes of the anomalies of the inverse and the observed models is similar (profile 17.5° E) to the second model (Figure 6). Discontinuity in the slab along its depth is difficult to determine due to poor vertical resolution of the method, and deep fast anomaly in the Southern Dinarides cannot be unambiguously interpreted.

**Figure 8.**Fourth model. Three-dimensional velocity models showing two depth slices (150 km and 350 km, upper part) and two cross sections (46° N and 17.5° E, lower part). A narrow lateral discontinuity between the Northern and Central Dinarides and two separated blocks in the Southern Dinarides in the deep slab are assumed (left side). The inverse model recovered from synthetic travel-time residuals is shown in the middle part, and the inverse model of observed travel-time residuals in the SU-model [8] is shown on the right side. The shapes of the anomalies of the inverse model for synthetic data have a poor correlation with the shape of the anomalies of the inverse model for observed data, especially seen at depth slices. The slab breakage is pronounced as a discontinuation of the fast anomaly. Therefore, lateral discontinuities in the slab can be very efficiently determined due to good horizontal resolution. Damping of the fast anomaly in the observed model in the Northern Dinarides is the result of the slab geometry and applied seismic network, rather than slab breakage.

**Figure 9.**Two possible structural models of the lithosphere in the Southern Dinarides can be devised using forward seismic modelling. The first model (on the left) assumes a steeply dipping continuous Adriatic lithospheric slab [8]. The second model (on the right) presumes that the Adriatic slab consists of two separate blocks, with the deeper block resulting from delamination of the Adriatic lithosphere in a previous subduction. The position of profile P-7 is shown in Figure 1 and Figure 4.

**Figure 10.**Depth slice at 600 km sketched from the 3D velocity model after [45] showing a donut-shaped fast velocity anomaly underneath the Pannonian Basin. Connection of the East Alpine fast anomaly with this deep fast Pannonian anomaly (slag graveyard) is noticeable on profile F sketch (upper part). The deep fast anomaly in the Southern Dinarides from profile P-7 [8] is situated over profile E sketch after [45] in the lower part. A connection between the Dinaridic fast anomaly and deep Pannonian fast anomaly can be seen.

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**MDPI and ACS Style**

Šumanovac, F.
Lithosphere Structure of the Southern Dinarides and Continuity of the Adriatic Lithosphere Slab Beneath the Northern Dinarides Unravelled by Seismic Modelling. *Geosciences* **2022**, *12*, 439.
https://doi.org/10.3390/geosciences12120439

**AMA Style**

Šumanovac F.
Lithosphere Structure of the Southern Dinarides and Continuity of the Adriatic Lithosphere Slab Beneath the Northern Dinarides Unravelled by Seismic Modelling. *Geosciences*. 2022; 12(12):439.
https://doi.org/10.3390/geosciences12120439

**Chicago/Turabian Style**

Šumanovac, Franjo.
2022. "Lithosphere Structure of the Southern Dinarides and Continuity of the Adriatic Lithosphere Slab Beneath the Northern Dinarides Unravelled by Seismic Modelling" *Geosciences* 12, no. 12: 439.
https://doi.org/10.3390/geosciences12120439