The monumental tumulus Yı gma Tepe is an important part of the cityscape of the ancient city of Pergamon. The tumulus construction is estimated in the Hellenistic period, the internal structure and exact purpose have been unknown so far. Its height of 32 m and diameter of 158 m make the deep interior of the tumulus practically inaccessible for excavations. Therefore, we applied a combination of geophysical measurements and archaeological sondages to explore the structure of the Yı gma Tepe. The investigations centre on P-wave refraction soundings. They were carried out to clarify the stratigraphic structure and soil composition as a prerequisite for a better understanding of construction techniques, building history and soil deposition.Interactive seismic raytracing, traveltime tomography and visco-elastic forward modelling were applied to derive a three-dimensional seismic velocity model, which was validated by excavations and soil analysis, historical records and additional geoelectric measurements. Our results reveal that the tumulus is composed of three layers, each about 10 m thick, separated by first-order seismic discontinuities which were locally verified. These layers form a stack of conical disks, the interfaces of which define two internal plateaus. The analysis of soil samples showed that the seismic velocity increase at the interfaces is likely to be caused by anthropogenic compaction applied to soils showing increased fractions of silt and clay. By combining topographic data with results from seismic and geoelectric sounding on the tumulus, the surrounding trench and the unaltered surrounding area, we show that the tumulus was built almost completely from the surrounding soils and that 17% of its original volume was displaced by destruction and erosion. Based on this mass balance the strongly destroyed and eroded original surface of the tumulus and its surrounding trench is reconstructed.

The detection of cavities with geophysical methods is a challenging task for which a general approach has not yet been found. We show that viscoelastic SH full waveform inversion (FWI), focusing primarily on reflection events, is able to accurately locate the position of cavities, areas of decompacted sediments and, more generally, seismic low-velocity anomalies down to 30 m depth. The key for a successful FWI application is the enhancement of the reflected wavefield relative to the surface wavefield. For this purpose, we applied automatic gain control normalization in the objective function. By focusing the inversion on the reflected wavefield, we demonstrate that one can differentiate between air-filled cavities with zero shear-wave velocity and low-velocity zones. Additionally, we test the FWI approach on a field dataset, with a known collapsed tunnel system inside a 32 m high, monumental, antique grave mound. The results show that the location and extent, as well as density and S-wave velocity of the collapsed tunnel system, can be determined with sufficient accuracy by applying a 2D FWI approach to intersecting profiles, despite the 3D nature of the problem.

The Yı gma Tepe of Pergamon is one of the largest known burial mounds in the Eastern Mediterranean. Its internal structure, especially the existence and location of burials, remains unknown so far because its height of 32 m and the diameter of 158 m have restricted extensive excavations. To explore the interior of the Yı gma

Über die genaue Bauweise eisenzeitlicher Groflgrabhügel lässt sich auf der Grundlage überwiegend älterer Ausgrabungen nur wenig aussagen. Jedoch liegen mit dem Magdalenenberg bei Villingen-Schwenningen und dem sogenannten Fürstengrab von Eberdingen-Hochdorf einige gut untersuchte Befunde der jüngeren Hallstattzeit vor. Diese weisen radiale Einbauten unterschiedlicher Anordnung und Bauweise auf; ebenso sind radiale Schüttungen beobachtet worden. Ähnliche Strukturen treten auch in frü̧hlatènezeitlichen Grabhügeln Ostfrankreichs auf. Im vorliegenden Aufsatz soll auf die segmentäre Bauweise und die radialen Einbauten eingegangen sowie ihre mögliche Funktion diskutiert werden. Waren sie für die Statik relevant oder hatten sie eine Bedeutung für den Arbeitsablauf beim Bau der Grabhügel? Handelte es sich um Visierhilfen für die regelmäßige Aufschüttung oder gar um rituelle Einbauten ohne praktische Funktion?

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