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Tectonophysics 41

Introduction

TRANSALP—A transect through a young collisional

orogen: Introduction

1. Introduction

TRANSALP is a multidisciplinary and international

research programme for investigating the deep structure

and evolution of the Eastern Alps (Fig. 1) as a

paradigmatic example for mountain building by conti-

nent–continent collision.

The Alps as the youngest and highest mountain

range in Europe have always been a challenge for

geoscientists, and have played a key role in the

development of new concepts and theories of mountain

building (e.g. Termier, 1904; Ampferer, 1906; Argand,

1924; Dal Piaz, 1934; Dewey and Bird, 1970;

Laubscher, 1970; Oxburgh, 1972). While our former

understanding was mainly based on geology and low

resolution geophysical methods such as gravimetry and

deep seismic soundings (DSS) with wide-angle and

refraction seismics, more recently remarkable progress

has been gained in the Western and Central Alps by

applying the high-resolution technology of deep seis-

mic reflection profiling (Roure et al., 1990; Pfiffner et

al., 1997), adapted from exploration techniques used in

oil and gas industry.

The combination of the seismic reflectivity image

with depth extrapolation from surface geology led to a

new concept, the key structure of which is a wedge-

shaped indenter of Adriatic lower crust and upper

mantle splitting up the European crust, peeling and

folding its upper part, and overriding and pushing its

lower part down into the mantle. This model has been

eagerly taken up and adapted to the Eastern Alps,

although conspicuous west–east differences like the

existence of the Austroalpine mega-nappe and the

northward offset of the Periadriatic Lineament suggest

the necessity of modifications or even basically

different concepts in the east. In any case, it became

0040-1951/$ - see front matter D 2005 Elsevier B.V. All rights reserved.

doi:10.1016/j.tecto.2005.10.030

obvious that, for validation, extension or improvement

of the model deep seismic reflection profiling is an

indispensable prerequisite also in the Eastern Alps.

This insight has given new impetus to the many

years standing plan of connecting the deep seismic

reflection networks of DEKORP (Deutsches Kontinen-

tales Reflexionsseismik Programm) in Germany and

CROP (Crosta Profonda) in Italy by a transect through

the Eastern Alps, and at the same time motivated the

formation of the OECORP group in Austria. Repre-

sentatives from Austria, Germany and Italy initiated the

bEast-Alpine Reflection Seismic TraverseQ as a joint

priority programme, later shortly termed TRANSALP.

Its primary objectives can be outlined by the following

questions:

– What are the effects of super-indentation by the

Adriatic microplate to the structure of the Eastern

Alps, which is different from the Western Alps?

– Where is the boundary between the European and

the Adriatic/African plates at depth?

– Is there a unilateral subduction of one plate beneath

the other (the European beneath the Adriatic micro-

plate, as seen in the Western/Central Alps, or vice

versa)?

– Or is there a more symmetric sub-vertical subduction

of both lithospheric plates?

– Or created continental collision a complex imbrica-

tion and wedging pattern at lithospheric scale?

– Are there basic differences in the deep structure of

the Western and Eastern Alps?

– Is the timing of the orogen structural accretion

similar in the Western–Central Alps and Eastern

Alps?

– Which is the youngest compression belt in the

structure of the Eastern Alps?

4 (2006) 1–7

Fig. 1. Location map showing the TRANSALP transect in the Eastern Alps. Previously completed seismic profiling in the Western Alps by the

national programmes NFP20 (Switzerland), ECORS (France) and CROP (Italy) are shown for comparison on the left-hand side. Tectonic map is

simplified from European Geotraverse EGT (Blundell et al., 1992). 1=Helvetic units, 2=Penninic units including Tauern Window, 3=Austroalpine

units including Northern Calcareous Alps, 4=Southern Alps including Dolomite Mountains, 5=Periadriatic intrusions (Paleogene).

Introduction2

More specific targets related to these questions

concern (a) the geometry and reflectivity of the Moho

and lower crust of both plates; (b) the depth of the

crystalline basement beneath the Northern and Southern

Calcareous Alps; (c) the possibility and extent of over-

thrusting younger, potentially hydrocarbon bearing

sediments beneath the Northern Calcareous Alps; (d)

the deep structure of the Tauern Window (TW), a

metamorphic core complex; (e) the geometry of

Penninic structure of the TW in comparison to the

large flat fold nappes of the Western–Central Alps; (f)

the dip direction and significance of the Periadriatic

Lineament; and (g) possible relationships between

seismic structure and seismicity of the Eastern Alps.

These challenging problems and possibilities to their

solution have been discussed at various international

meetings and workshops from May 1994 to February

1998. The final research programme was worked out by

the Steering and Technical Committees, both compris-

ing members from the CROP, OECORP and DEKORP

groups, in close contact with colleagues from the Swiss

NFP20 project. The TRANSALP programme focuses

on a 300 km long and 40 km wide north–south transect,

approximately between Munich and Venice, acquired

across the whole structural edifice of the Alps. The

transect has been located at the meridian where the

north–south width of the Alps is maximum and where

the indentation of the Adriatic into the European plate,

marked by the Periadriatic Lineament, reaches furthest

to the north, indication of a maximum north–south

compression. In the organising phase, TRANSALP was

subdivided in two main parts: (1) seismic and seismo-

logical projects, and (2) complementary geophysical,

geologic and petrologic projects. This special issue of

Tectonophysics contains a selection of key papers

presented at the Final TRANSALP Conference, held

at Trieste on 10–12 February 2003, which closed the

series of congresses and workshops, held at Vienna

(TRANSALP Colloquium on April 26th, 1999),

Munich (International TRANSALP Colloquium, 13–

14 February, 1998 and 8–9 October, 2000), Obergurgl

(TRANSALP sessions of the Alpine Workshop, 18–20

September, 2001) and Salzburg (Pangeo Austria Con-

gress, 28–30 June, 2002).

The final meeting at Trieste was organised into two

major sections: (1) the TRANSALP core project

Introduction 3

(seismic and seismological studies) and complementary

geophysical and geological project, including 17 oral

papers and 11 posters, and (2) geology of the Eastern

Alps and interpretation and modelling of the seismic

sections, including 28 oral papers and 19 posters.

Invited speakers provided comparisons with other

orogens of similar age: Carlo Doglioni (Four subduc-

tions in NE-Italy), Alfred Hirn (Pyrenees and Hima-

layas), Onno Oncken (The Andes mountain belt),

Rinaldo Nicolich (CROP profiles in the Central Alps),

Adrian Pfiffner (Swiss Alps), Stefan Schmid (Western–

Eastern Alps transition) and Cestmir Tomek (Car-

pathian arc).

2. Contributions to the special issue

Here we summarize the selected 17 papers, which

are ordered in a similar way, starting with seismic–

seismological papers, turning over to complementary

geophysical and geological papers and concluding with

papers, which focus on interpretation of seismic data

from depth extrapolations of surface geology and retro-

deformation. Finally, in order to provide the reader with

a wider context, we will outline main results of some

TRANSALP-related key papers published elsewhere.

The reader is also referred to summarising papers

published by the TRANSALP group earlier (TRANS-

ALP Working Group, 2001, 2002; Castellarin et al.,

2003; Luschen et al., 2004).

Luschen et al. present in the first paper the seismic

database of the TRANSALP traverse and its technical

details. A 300 km long Vibroseis near-vertical reflec-

tion section is shown at its complete length, together

with selected sectors emphasizing specific targets. The

simultaneously acquired explosive seismic reflection

section focuses better on deep crustal features, the

reflective lower crust and its bottom, presumably the

crust–mantle boundary (Moho). Dominant features of

the presented sections are the foreland Molasse basins

and the frontal thrust zones in the North and in the

South, the giant bi-vergent structure at crustal scale in

the centre of the profile and crustal thrust ramps (sub-

Tauern ramp, sub-Dolomites ramp). A thin reflective

lower crust, beneath a relatively transparent upper crust,

dips smoothly with its bottom from 30 km beneath the

Bavarian Molasse basin in the North to about 55 km

depth significantly south of the main Alpine crest.

There, leaving a gap of 20–30 km length, the lower

crustal signature changes dramatically. Its thickness

appears to be twice of the northern one and subdivided

into two distinct, northward dipping patterns with

maximum depth at about 45 km. It might be argued

that this is due to a lower crustal tectonic erosion of the

Adriatic plate and subsequent stacking, while the

European crust and Penninic domains subducted

beneath the Adriatic crust.

Millahn et al. provide data of E–W oriented cross-

lines, distributed at regular distances along the TRANS-

ALP transect, which recorded passively the Vibroseis

and explosive sources of the main N–S line. These

cross-lines enabled three-dimensional control of deep

structures by pre-stack depth migration, as originally

designed for, but also provided unexpectedly important

by-products: seismic anisotropy indicating E–W orient-

ed paleostrain in the Tauern Window and, when

processed on N–S running bin lines, closure of gaps

in the main line because of better recording conditions

on the cross-lines. Thus, it has been shown that

simultaneously recorded cross-lines can be regarded

as a very helpful and economic way to complement a

two-dimensional transect.

Bleibinhaus and Gebrande report on a new seismic

velocity model derived from tomographic inversion of

refraction and wide-angle reflected signals, which were

recorded from Vibroseis and explosive sources by a

stationary seismic network distributed all along the

transect. Their model shows remarkable details in the

upper and middle crust, correlated with geological

surface structures, such as the high-velocity rocks of

the Northern Calcareous Alps in the North and the

Dolomites Mountains in the South. Mantle-refracted

waves (Pn) could not be observed because of non-

sufficient observation distance; however, the crust–

mantle boundary is illuminated by wide-angle reflec-

tions. These show a gently dipping European Moho, in

accordance with the bottom of the near-vertical reflective

lower crust and, leaving a gap of about 50 km length, a

relatively flat Adriatic Moho at about 40 km depth. Here,

particularly closer to the Alpine roots, the near-vertical

reflectivity and the wide-angle derived Moho seem to

image different structures. Other main features of the

velocity model are the differences in the middle and

lower crust between the European and the Adriatic

domains, showing higher velocities on the Adriatic side.

Bleibinhaus et al. present preliminary data from the

crustal-scale seismic refraction project ALP2002, ac-

quired in 2002. A network of profiles covering the

easternmost Alps and surrounding areas is expected to

provide a three-dimensional image of the crustal

thickness and Moho geometry in the next future.

Seismographs were deployed again on the TRANSALP

transect and recording signals from shotpoints located

in the East. First interpretations generally confirm the

velocity model derived by Bleibinhaus and Gebrande

Introduction4

(see above). Large-scale features seem to be continuous

towards the east, with a slight eastward dip component

of the Adriatic Moho. From final models in the future,

the two-dimensional character of the TRANSALP

project may be extended into the third dimension.

Cassinis re-assesses seismic velocity models from

DSS in the 1970s. Five sections are presented, oriented

perpendicular to the main Alpine strike direction. One

of these sections has been produced along the

TRANSALP transect by interpolation of adjacent older

sections. This section shows remarkable similarities in

the large-scale crustal architecture with the modern

TRANSALP section. Although the resolution capabil-

ities were far beyond the modern characteristics, the

author concludes that the reliability of the old refraction

seismic data and their interpretative models has

improved.

Thomas et al. show results from reprocessing of

industrial seismic profiles gathered until the 1980s and,

from processing of short, shallow high-resolution

reflection data, both with the aim of studying the

southern Bavarian Molasse and the contact between the

autochthonous Foreland Molasse and the allochthonous

Folded Molasse. The sections show steep normal faults

and southward thickening of Molasse sediments.

Southward dipping tectonic contacts between Foreland

and Folded Molasse could be imaged very close to the

surface by the high-resolution seismics, using one mini-

vibrator as source. This technique, therefore, provides a

closer link between surface geology and deep seismic

reflection profiling, which often shows inherent data

gaps at near surface.

Ullemeyer et al. describe laboratory measurements

on a suite of deformed, metamorphic rocks from the

Tauern Window and surrounding belts with respect to

elastic properties, seismic anisotropy and whole-rock

texture. They find P-wave anisotropies that are mainly

controlled by microcrack fabric in gneisses and schists,

and by crystallographic preferred orientations in mar-

bles and amphibolites. Effects of fluids are decreasing

P-wave velocity and increasing anisotropy of immersed

samples. The authors conclude that marble-gneiss and

metabasite-gneiss contacts, as well as boundaries

between dry and wet series, are the favourite candidates

to provide seismic reflectivity in the crust.

Kummerow et al. analysed teleseismic SKS and

SKKS phases from a temporary short-period and broad-

band station network along the TRANSALP traverse.

This is a popular technique to investigate seismic

anisotropy in the mantle by calculating the delay time

between the fast and the slow shear-wave and the fast

axis direction. The delay times appear to increase

slightly from north to south and the fast-axis directions

prove to be rather uniform along the profile, coinciding

well with the trend of the Eastern Alps, thus suggesting

orogen-parallel flow in the upper mantle.

Zanolla et al. compiled all existing gravity data in

Germany, Austria and Italy of a wide area, covering

275 by 445 km in size and centred on the TRANSALP

transect, together with newly acquired data in the

Southalpine area. Gravity corrections and calculations

of anomaly maps were done consistently over the area.

The authors present new Free-Air, Bouguer and

Isostatic gravity maps, and discuss their main features.

The Bouguer anomaly shows a pronounced minimum

beneath the main Alpine crest. A pronounced maximum

in the South is attributed to the Venetian Tertiary

Volcanic Province. Here, the modelling requires high-

density magmatic rocks, but also a relatively shallow

crust–mantle boundary. Results of density modelling

are shown in the context of seismic near-vertical

reflectivity, seismic velocity modelling and seismolog-

ical receiver-function analysis. The density modelling

confirms higher-density rocks in the middle and lower

crust on the Adriatic side, as compared to the European,

in accordance with higher-velocity rocks.

Ebbing et al. investigate the three-dimensional

lithospheric density structure of the Eastern Alps by

integrating results from near-vertical reflection profiling,

receiver-function analysis and lithospheric tomography.

Inhomogeneities at the lithosphere–asthenosphere

boundary have some effects; however, they are over-

printed by the density contrast at the crust–mantle

boundary and by intra-crustal inhomogeneities. The

authors conclude that full isostatic equilibrium is not

achieved. Calculations of the isostatic lithospheric

thickness show two areas of lithospheric thickening with

a transition zone beneath the location of the TRANSALP

profile. This appears to be in agreement with a

tomographic study featuring a change in subduction

direction.

Vosteen et al. simulate the effects of transient thermal

signals, Pleistocene surface temperatures and exhuma-

tion of great rock volumes, on the current thermal

regime of the Eastern Alps. They find that the change of

surface temperatures in the past and exhumation,

particularly in the Tauern Window, affects mainly the

uppermost part of the crust. Moho heat flow appears to

be not critically disturbed by exhumation. The com-

bined effect of changing temperatures at the surface and

exhumation is compared with steady-state temperatures

at 1 km and 8 km depth and at the Alpine roots.

Thony et al. present new paleomagnetic data from

the Northern Calcareous Alps and the Central Alps of

Introduction 5

Austria and reinterpret data from previous paleomag-

netic studies. Their results suggest large-scale vertical

axis rotation jointly of the Northern Calcareous Alps,

the Central Alps and the Southern Alps. A first

clockwise rotation occurred during the Early Oligocene

and a second counterclockwise rotation in the Late

Oligocene to Middle Miocene, the latter contempora-

neously with counterclockwise rotation in the Apen-

nines and opening of the Balearic basin.

Zattin et al. reconstruct the thermal evolution of the

crust in the Dolomites by means of vitrinite reflectance

and fission track (FT) investigations. The results

indicate that no significant uplifting, respectively,

exhumation/denudation event occurred for more than

100 Ma until Middle–Late Miocene times. FT data

obtained on the basement rocks of the Valsugana thrust

(Agordo zone) testifies an important exhumation event

as old as about 10 Ma. The consequent erosion

processes have been studied by the combined use of

the arenite petrography and FT analysis on samples of

the Venetian foredeep succession (VittorioVeneto).

Basic palaeogeographic changes occurred during Ser-

ravallian when most of the Dolomites and related

covers became the main source of sediments for the

Venetian foredeep.

Castellarin et al. discuss a new tectonic scenario

for the Giudicarie lineament, a major structural

element between Western and Eastern Alps. The

Pre-Adamello structural belt is present only in the

internal Lombardy zone, located west of the Adamello

massif and is unknown in the areas east of the

Giudicarie lineament. Upper Cretaceous–Early Eocene

thick syntectonic Flysch deposits of Lombardy and

Giudicarie are well preserved along the southern and

eastern border of the Pre-Adamello belt. To the east,

in the northeast sector of the Dolomites, equivalent

remnants of Flysch deposits, Aptian–Albian and

Senonian in age, are present. Very probably, they

were formerly in connection with those of Lombardy

along the N-Giudicarie corridor. The different location

of the western and eastern opposite blocks (the pre-

Adamello belt versus the northern belt of the

Dolomites) can be related to the Upper Cretaceous–

Lower Eocene N-Giudicarie strike-slip fault, part of a

former wider transfer zone, which produced their

sinistral lateral displacement for about 50 km. The

former setting of the structure was variously rear-

ranged by further Neogene deformations.

Based on surface geology, TRANSALP section and

well data, Behrmann and Tanner performed a three-

dimensional reconstruction of the N-directed nappe

structure in central sectors of the Northern Calcareous

Alps. The 3D volume allowed the recognition of a floor

detachment system that diverges upwards into four

thrust surfaces. Detailed balancing indicates laterally

heterogeneous internal N–S shortening of 50% to 67%.

As the TRANSALP section shows, the nappe complex

of the Northern Calcareous Alps was transported ca. 55

km over the underlying Rhenodanubian Flysch and

Molasse units. The 3D reconstruction also gave

evidence for significant thickness variations of Middle

Triassic carbonates of the Northern Calcareous Alps,

which resulted from N-trending growth faults.

Ortner et al. describe the structure of the northern

central sectors of the TRANSALP profile at the

transition between the thin-skinned Northern Calcare-

ous Alps thrust belt to the thick-skinned Central

Austroalpine basement complex. The special emphasis

is on the Inn valley shear zone, which is interpreted as a

late-stage, Miocene out-of-sequence thrust with a

significant transpressional component. This thrust is

considered to root in the sub-Tauern ramp beneath the

Tauern window. Consequently, the thrust also contrib-

uted to the aerial surface uplift of the Tauern window

and adjacent units. A further topic is the correlation of

transpressional effects with eastward located thrusts

found in industrial wells.

Castellarin et al. analyse the seismic images mostly

across the southern sector of the TRANSALP profile

remarking that pre-collision and early-collision struc-

tures of the Alps are not easily recognizable. Converse-

ly, good records of the Neo-Alpine to present

architecture were provided by the seismic sections.

Two general interpretation models (bCrocodileQ and

bExtrusionQ) have been sketched by the TRANSALP

Working Group. Both illustrate the strong mechanical

interaction of the facing European and African margins,

as documented by giant lithosphere wedging processes.

Arguments consistent with the bExtrusionQ model and

with the indentation of Adriatic (Southalpine) litho-

sphere underneath the Tauern Window are clearly

indicated in the paper. Moreover, the tectonic accretion,

which affected, during the Messinian and the Plio-

Pleistocene, only the S-vergent structures of the Eastern

Alps (Montello-Friuli thrust belt) is considered a further

element consistent with the deep under-thrusting and

wedge indentation of the Adriatic lithosphere under-

neath the southern sector of the orogen.

3. Other selected key publications in the context of

the presented TRANSALP papers

Lippitsch et al. (2003) presented a new three-

dimensional P-wave velocity model of the Upper

Introduction6

Mantle beneath the Alpine orogen and surrounding

areas, obtained from teleseismic arrival times. They

used a three-dimensional crustal model from controlled

source seismology for corrections. The tomographic

images illuminate the uppermost mantle down to about

400 km depth. Along strike of the Alpine orogen, the

images show a SE-dipping high-velocity slab in the

Western and Central Alps and a NE-dipping slab in the

Eastern Alps. The authors interpret their images with a

southeastward subducted European continental litho-

sphere in the West and with a northeastward subducted

continental Adriatic lower lithosphere beneath the

European plate in the East.

Ebbing et al. (2001) and Ebbing (2004) performed

three-dimensional density modelling in order to derive

constraints for the crustal architecture and for local and

regional isostatic conditions. The Bouguer gravity

anomaly is mostly explained by the uppermost geolog-

ical features, by the geometry of the crust–mantle

boundary and by lower crustal densities (in accordance

with lower crustal seismic velocities). The Eastern Alps

seem to be locally not isostatically compensated and

residuals correlate strongly with exposed geological

formations. Subsurface loading at the crust–mantle

boundary has been calculated from contrasting 3D

models to investigate regional isostasy. Generally, small

rigidity values are determined for the Eastern Alpine

lithosphere. However, in the model of a 40 km thick

Adriatic crust, high flexural rigidities are inferred for

the Adriatic plate.

Kummerow et al. (2004) analysed teleseismic

dreceiver functionsT, P-to-S-wave converted signals

illuminating the Alpine crust from below and compared

their images with those of the of the near-vertical

reflection profiling. The European crust–mantle transi-

tion appears as a clear P-to-S converter, dips gently

from 35 km beneath the northern foreland to a

maximum depth of 55 km at the Alpine root, in

accordance with the bottom of the reflective lower

crust, and shows a vertical step to the 40 km thick

Adriatic crust–mantle boundary. Additionally, the sig-

nificance of receiver functions for intra-crustal struc-

tures is discussed and compared with the distribution of

earthquake epicentres. Upper mantle features exhibit

slightly uplifted d410 kmT and d660 kmT discontinuities.

Acknowledgements

The Bundesministerium fur Bildung und Forschung

(BMBF, Bonn), the Bundesministerium fur Wis-

senschaft und Verkehr (BMWV, Vienna), the Consiglio

Nationale delle Ricerche (CNR, Roma) and the

company ENI-AGIP (Milan) jointly financed the

TRANSALP programme. The Deutsche Forschungsge-

meinschaft (DFG, Bonn), the Wissenschaftsfond (FWF,

Vienna), the Consiglio Nazionale delle Ricerche (CNR,

Roma) and the Swiss National Science Foundation

have funded in parts accompanying projects.

We thank our contractors THOR (Kiel/Germany),

DMT (Essen/Germany), Joanneum Research (Leoben/

Austria), GEOITALIA (Milano/Italy), GEOTEC (Cam-

pobasso/Italy), OGS (Trieste/Italy) and TERRACOT-

TEM (Bolzano/Italy) for their excellent work.

Administrative services of the GFZ (Potsdam/Ger-

many) are gratefully acknowledged. Seismological

equipment was provided by the instrument pool of

the GFZ, by ETH-Zurich and by the University of

Genova.

The project benefited in an unprecedented way from

contributions of the oil and gas industry. First of all, the

company ENI-AGIP not only financed major parts of

the project, but contributed also by providing seismic

and gravimetric data sets from its own database.

Scientists of ENI-AGIP played a major role in

processing and interpretation of the TRANSALP data.

The company OMV (Vienna) provided insight into its

database of seismic sections within the Northern

Calcareous Alps. The companies RAG (Vienna) and

ForestOil (Denver) acquired parts of the TRANSALP

seismic section in the Bavarian Molasse for their own

specific processing purposes and contributed with their

interpretation. The German consortium of oil compa-

nies, which explored the Bavarian Molasse until the

1980s, provided their original seismic data for repro-

cessing purposes. Brenner Basistunnel (BBT) ex-

changed gravity data with TRANSALP in the

Southern Alps. All these companies are gratefully

thanked for their enthusiastic participation.

Last, but not least, all reviewers are thanked for their

contributions: Jorg Ansorge, ETH Zurich; Luigi Bur-

lini, ETH Zurich; Giovanni B. Carulli, University of

Trieste; Vladimir Cermak, Czech Academy of Sciences;

Bernhard Grasemann, University of Vienna; Frank

Horvath, University of Budapest; Thomas Jahr, Uni-

versity of Jena; Gianreto Manatschal, Universite Louis

Pasteur, Strasbourg; Emo Marton, University of Buda-

pest; Bruno Meurers, University of Vienna; Manfred

Muller, Schongau; Rinaldo Nicolich, University of

Trieste; Vincenzo Picotti, University of Bologna; Gian

A. Pini, University of Bologna; Till Popp, Institut fur

Gebirgsmechanik GmbH, Leipzig; Lothar Ratschba-

cher, University of Freiberg; Martha Savage, Victoria

University, Wellington; Randell Stephenson, Vrije

University of Amsterdam; Gabriel Strykowski, National

Introduction 7

Survey and Cadastre, Denmark; Jenny Tait, University

of Munich; Cestmir Tomek, University of Salzburg;

Gian B. Vai, University of Bologna; Bruno Della

Vedova, University of Trieste; Michael Wagreich,

University of Vienna; and six anonymous reviewers.

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Helmut Gebrande

University of Munich, Department fur Geo-und

Umweltwissenschaften, Theresienstrasse 41,

D-80333 Munchen, Germany

E-mail address:

gebrande@geophysik.uni-muenchen.de.

Tel.: +49 89 2180 4235.

Alberto Castellarin

University of Bologna, Dipartimento de Scienze della

Terra and Geologico Ambientali, Via Zamboni 67,

I-40127 Bologna, Italy

E-mail address: castello@geomin.unibo.it.

Tel.: +39 051 2094554.

Ewald Luschen

University of Munich, Department fur Geo-und

Umweltwissenschaften, Theresienstrasse 41,

D-80333 Munchen, Germany

Present address: Huntloser Strasse 13,

D-27801 Dotlingen, Germany

E-mail address:

lueschen@geophysik.uni-muenchen.de.

Tel.: +49 171 3647569.

Karl Millahn

Montanuniversity Leoben, Institut fur Geophysik,

Franz-Josef Strasse 18, A-8700 Leoben, Austria

E-mail address: karl.millahn@unileoben.ac.at.

Tel.: +43 3842 402 360.

Franz Neubauer

University of Salzburg, Fachbereich Geographie,

Geologie und Mineralogie, Hellbrunnerstrasse 34,

A-5020 Salzburg, Austria

E-mail address: franz.neubauer@sbg.ac.at.

Corresponding author. Tel.: +43 662 8044 5401.

Rinaldo Nicolich

University of Trieste, Dipartimento di Ingegneria

Civile, Via Valerio 10, I-34127 Trieste, Italy

E-mail address: r.nicolich@units.it.

Tel.: +39 040 5583478.