The Search For Ancient Helike: A Gpr Case Study

Abstract

In 373 BC, the Classical city of Helike, on the Gulf of Corinth in Greece, was destroyed by a catastrophic earthquake and mass-movement of the deltaic sediments upon which it was built. Due to subsequent burial by sedimentation, and tectonic uplift of the northern Peloponnesos, the ruined site is now believed to be on land. Since 1988, the search for Helike has been conducted using sonar, bore hole drilling, geophysical survey (including magnetometry and GPR), and excavation. In June 1996 we used GPR in seven areas near the presumed site of Helike. Data collected using GSSI’s SIR-2 and monostatic 400 MHz antemra achieved a maximum penetration of 3 m using filters and a running weighted average stack. Despite limited resolution and penetration, we observed several hyperbolic targets. One of these was a tile floor dating from the Roman Era. GSSI’s multi-low-frequency bistatic antenna, used in the 80 MHz configuration, achieved depths of approximately 5 to 6 meters in some areas. INTRODUCTION In 373 BC, the Classical city of Helike, on the southern shore of the Gulf of Corinth in Greece, was destroyed by a catastrophic earthquake and tsunami. From references in Pausanias, and other ancient writers, the site is believed to be a few kilometers southeast of Aigion, in the area of the coalesced deltas of the Selinous, Kerynites, and Vouraikos Rivers (Figure 1). This Gilbert-type fan delta constitutes the hanging wall of the Helike Fault, which is one of several subparallel faults bounding the southern margin of the Gulf of Corinth. The Helike Fault marks the sharp contact between the delta and the mountains. This is a high energy environment, subjected to violent flooding, shifting of the three rivers and their anastomosing distributaries, tectonic uplift, and the mass-movement of deltaic sediments. Stratigraphically, the delta is extremely heterogeneous, with an interfingering of terrestrial flood plain deposits, lacustrine-lagoonal silt and clay, and beach and delta front marine sediments. At least part of Helike was apparently submerged by the earthquake. However, due to subsequent sedimentation and tectonic uplift, the main site is now believed to be on land. Since 1988, the Helike Project has been directed by Dora Katsonopoulou and Steven Soter, under the auspices of the American School of Classical Studies in Athens. They have employed sidescan and subbottom sonar, bore hole drilling, geophysical survey (including magnetometry and GPR), and excavation. Using bore hole drilling they have located ceramic bearing occupation horizons from near 1. Radar Solutions International, 72 Orange Street, Suite 2, Waltham, MA 02154