1 INTRODUCTION
ALP2002 is a large-scale refraction seismic experiment for the study of the lithosphere in the Eastern Alps. It consists of a network of 13 passive lines of several hundred of kms length recording up to 40 shots. Its westernmost receiver line coincides with the TRANSALP profile and the results from that project will therefore provide valuable constraints for the analysis of the ALP2002 data.

2 TECTONIC SETTING OF THE INVESTGATION AREA
Fig.1: Major structures of the investigation area
Although earlier tectonic processes left their imprints in the Alps, we can choose the existence of Pangea in the Permian and Triassic eras as the beginning of the generation of the Alps. In the Jurassic, contemporaneous with the opening of the Atlantic Ocean, there was a sinistral strike-slip motion of Africa with respect to Europe. In the Cretaceous, this movement changed to a rotation of Africa relative to Europe, contracting the Tethys Ocean and introducing the convergence phase. The continent-continent collision between the European plate and the Apulian (Adriatic) micro-plate took place in the Oligocene. Continued convergence throughout the Tertiary led to the present orogenic pattern. However, the continent-continent collision is not the only imprinting tectonic process in the area of the ALP2002 investigation. In the late Oligocene and Miocene, escape took place from the compressed Central Alps to the unconstrained margin in form of the Pannonian Basin. The significant eastward thinning of the crust corresponds to the extrusion and tensional processes (Ratschbacher et al., 1991). The present day seismicity in the area of our investigation follows a pattern compatible with the escape tectonic model (Aric et al., 1987).
While the characteristic features of a continent-continent collision may be well described by a cross-section (2-D), the extrusion and escape processes require considerations in 3-D.

3 EXISTING SEISMIC INFORMATION OF THE LITHOSPHERE IN THE ALP2002 AREA
The exploration of the lithosphere of the Eastern Alps by seismic refraction and wide-angle reflection experiments started with refraction lines around the Eschenlohe quarry 40 years ago. Seismic lines spread out from this shot point over the Alps to the shot points Lago Lagorai and Trieste (Giese et al., 1976). The projects ALP 75, ALP 77 and ALP 78 supplied further refraction and wide-angle reflection lines. First results were published swiftly after the field experiments, and more elaborate interpretations followed later (Scarascia et al., 1997). The NE region of the ALP2002 study area was explored in parts by CELEBRATION 2000, a refraction and wide-angle reflection seismic experiment of a new generation covering a large portion of Central Europe (Guterch et al., 2001). Shots were recorded not only in a traditional in-line fashion but also in cross-line geometries. Therefore, the shooting and recording scheme offers improved possibilities for a 3-D interpretation, which will contribute substantial seismic information to ALP2002.
Deep reflection seismic profiling started in former Czechoslovakia in 1980. Most interesting for the ALP2002 experiment are the profiles 3T and 8HR (Tomek, 1993). The Pannonian Basin in Hungary was explored by deep reflection seismic profiling during the occasion of the Pannonian Geotraverse (Posgay et al., 1996). In Austria, deep reflection seismic profiling was carried out in the area of the Rechnitz Penninic window in NE Styria (Weber et al., 1995; Graßl, 1999). The most important deep reflection line for ALP2002 is TRANSALP.

4 ALP2002 FIELD EXPERIMENT
The ALP2002 field experiment was designed to meet the following criteria:
Realization of a 3-D geometry and coverage of the whole area of investigation,
Application of the CELEBRATION 2000 data acquisition technique,
Connection to CELEBRATION 2000, 3rd deployment, for later merging of both data sets,
Connection to the TRANSALP profile,
Positioning of shots in areas favouring good transmission of seismic energy,
Implementation of a pilot study for passive seismic monitoring.

During the explosion seismic experiment we employed a total of 32 “strong” shots (Fig. 2) with the following standard shooting scheme: 5-6 boreholes, depth 40-50 m, 300 kg explosives. Additionally 8 shots with charges < 100 kg where shot in Hungary.

A total number of 926 TEXAN seismic instruments (RefTek) equipped with 4.5 Hz geophones were deployed along the lines ALP01 - ALP13 (Fig. 3). Line ALP04 overlaps and extends the CELEBRATION 2000 line CEL10. Line ALP12 follows the TRANSALP reflection line. The total length of the lines is 4300 km. The sample rate was 100 Hz and the recording time 300 s, starting 60 s before shooting.
Additionally a reflection recording spread was deployed in Austria (shotpoints 801 and 504) and a dense local 3-D-deployment was deployed in Hungary. Furthermore, 70 stations for passive seismic monitoring were deployed along lines ALP04 and ALP12=TRANSALP.

Fig.2: Shot locations           Fig.3: Receiver lines

The temporal sequence of the field activities was as follows:
10 June: Start of passive monitoring on line ALP04 = CEL10
28 June: Start of passive monitoring on line ALP12 = TRANSALP
01-02 July: Deployment of seismic recorders for active experiment
02-05 July: Shooting during the night
05-06 July: Retrieval of seismic recorders
12 July: Retrieval of passive monitoring stations completed.

5 DATA
The raw data of all shots were converted to SEGY, completed by the addition of information on recording geometry and saved on CDROM. They are ready for downloading from a server by all members of the ALP2002 working group. Samples of recordings, demonstrating the quality of the data are shown in Fig. 4-8.

Fig.4: Shot 110 on ALP01      Fig.5: Shot 110 on ALP02       Fig.6: Shot 205 on ALP02

Fig.7: Shot 208 on ALP02       Fig.8: Shot 201 on ALP12 = TRANSALP

6 INTERPRETATION
The ALP2002 experiment was designed to mesh perfectly with the CELEBRATION 2000 experiment. Therefore the ALP2002 data were merged with the data from CELEBRATION 2000 -3rd deployment.
An important task of the ALP2002 experiment is its connection to TRANSALP. As TRANSALP represents the (western) boundary of the ALP2002 investigation area we cannot expect detailed information about the crust along that profile from the ALP2002 data. Therefore the implementation of the TRANSALP velocity model into the ALP2002 3D-velocity solution is a demand. On the other hand, the 3D-solution for the Moho delay times and depths along ALP12=TRANSALP will supply additional information for the TRANSALP project. Also, a ray tracing solution for the deep structures along ALP12=TRANSALP should be constructed.
The work on the 3D-solution for the Moho delay times and the interactive ray tracing interpretation of shot 201 along ALP12=TRANSALP implementing the TRANSALP velocity model is in progress. Results of the latest state of interpretation will be presented.

ACKNOWLEDGEMENTS
Major Sponsors of the ALP2002 project are Österreichische Akademie der Wissenschaften, FWF - Der Wissenschaftsfonds, Bundesministerium für Bildung, Wissenschaft und Kultur, Landesregierung Kärnten and Steiermark, Austria, National Science Foundation, Texas Higher Education Coordinating Board, USA and several national sponsors from Croatia, Czech Republic, Hungary and Slovenia. We thank all participants of the ALP2002 experiment not mentioned in the working group for their enthusiastic cooperation.

ALP2002 WORKING GROUP
AUSTRIA: E. Brueckl (Coordinator), M. Behm - Institute of Geodesy and Geophysics, Vienna University of Technology, K. Aric - Institute of Meteorology and Geophysics, University of Vienna, V. Hoeck, C. Tomek - Institute of Geology and Paleontology, University of Salzburg, R. Schmöller, S. Hock - Institute of Geophysics, University of Leoben, Chr. Schmid. H. Grassl - Institute of Applied Geophysics, Joanneum Research, Leoben
CANADA: Z. Hajnal - Department of Geological Sciences, University of Saskatchewan
CROATIA: F. Sumanovac - Faculty of Mining, Geology and Petr. Eng., University of Zagreb
CZECH REPUBLIC: A. Spicak, P. Hrubcova - Geophysical Institute, Academy of Sciences of the Czech Republic
DENMARK: H. Thybo - Geological Institute, University of Copenhagen
FINLAND: J. Yliniemi - Sodankylä Geophysical Observatory, University of Oulu, T. Tiira - Institute of Seismology, University of Helsinki
GERMANY: H. Gebrande, F. Bleibinhaus - Department of Earth and Environmental Sciences, University of Munich
HUNGARY: E. Hegedues - Eötvös Loránd Geophysical Institute, Budapest
POLAND: A. Guterch - Institute of Geophysics, Polish Academy of Sciences Warsaw, M. Grad - Institute of Geophysics, University of Warsaw
SLOVENIA: A. Gosar - Ministry for Environment and Spatial Planning, Environmental Agency of the Republic
USA: G.R. Keller, K.C. Miller, S.H. Harder - Department of Geological Sciences, University of Texas at El Paso, C.M. Snelson - University of Nevada at Las Vegas, Department of Geoscience.

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