Nickolas Zouros

Seismic fault geometry and kinematics of the 13 May 1995 Western Macedonia (Greece) earthquake

Abstract During the devastating earthquake of 13 May 1995, in the Kozani-Grevena area (Western Macedonia, Greece), many surface ruptures formed in the epicentral area. Most of these fractures were due to faulting, but some were secondary ground ruptures and landslides. Geological field work in the area has shown that the Aliakmon river neotectonic fault consists of several (three or more) fault strands: the Servia, the Rymnio and the Paleochori-Sarakina strands. Using geological criteria, all of these fault strands were judged to be active faults affecting recent (Holocene) deposits and scree. The main new surface fractures caused by the earthquake, and particularly those clearly of tectonic origin, follow systematically the traces of the last two neotectonic fault strands, forming a new fracture line. This tectonic line, trending ENE-WSW (N 70 °), coincides with the focal mechanism solution and the satelite image major lineament. Both the geological and instrumental seismological data suggest that the seismogenic fault is a segment of the Aliakmon river neotectonic fault zone situated among the villages of Rymnio, Paleochori, Sarakina, Kentro and Nisi. The total length of the reactivated fault segment is about 30km long overall and is separated from the non-activated Servia fault segment by a geometrical seismic segment barrier near the village of Goules. The seismic fault is a normal fault trending ENE-WSW and dipping to NNW, with high angle at the surface and low angle at depth. The majority of the epicentres of the seismic sequence were distributed on the hangingwall of this reactivated fault segment. Additionaly a series of subparallel antithetic surface fractures, mainly striking E-W or ENE-WSW and dipping to the South, following previous neotectonic strike-slip faults, were reactivated during the earthquake with the geometry of normal faults antithetic to the main seismic fault. The most important of these are the Chromio-Varis-Myrsina fracture line (length 15km), along the Vourinos corridor dextral strike-slip structure and the Felli fracture line (length 6 km) along the Felli sinistral strike-slip fault. An interpretation of the geometry and kinematics of the reactivated faults is shown in the proposed geological model with simplified cross sections.

Paleoseismicity of the Souli Fault, Epirus, Western Greece

Abstract The E-W trending left-lateral Souli Fault, an old Alpine structure in Epirus, northwestern Greece, affecting Lias-Eocene carbonate and siliceous rocks and Oligocene-Burdigalian flysch exhibits geological evidence of past individual coseismic events. Along some sectors of the fault, or in associated structures, young morphotectonic features have been recognised thereby emphasising the recency of tectonic activity. In a natural paleoseismological section, at least three distinct seismic events pre- and post-dating wedge layers of 20,000 to 26,000 yr (C14) lignite type sediments, have been recognised.

The Petrified Forest of Lesvos A Unique Natural Monument

The Petrified Forest of Lesvos covers an area of 15,000 ha and has been declared a Protected Natural Monument. Fossil sites with standing and lying petrified tree trunks are found in many localities on the western part of Lesvos Island. The Petrified Forest was developed during Late Oligocene to Lower-Middle Miocene, due to intense volcanic activity in the area. In order to protect the Petrified Forest and ensure its proper management, serious efforts have been made during the last decades, including the foundation of the Natural History Museum of Lesvos Petrified Forest, scientific research, geoconservation, site protection measures etc. All these elements comprise the main parameters for the operation of the Western Lesvos Geopark, a body whose aims are the protection of the geological heritage and sustainable local development.

High-resolution magnetic gradient and electrical resistivity tomography survey at the Plaka Petrified Forest Park in Lesvos Island, Greece

Lesvos Island, in the North Aegean area of Greece, exposes large accumulations of fossilized tree trunks. They are collectively known as the Petrified Forest of Lesvos, a designated protected natural monument. The paper describes the results of a geophysical study that has been carried out in the area of Plaka on the western part of Lesvos in order to investigate the near-surface geology and detect buried fossilized tree trunks. In situ and laboratory measurements of magnetic and electrical properties of the trunks have been conducted. Considering the magnetic susceptibility distribution and the contrast between the trunks and the surrounding material, magnetic gradient anomalies of negative signature were expected to reflect the existence of trunks. Electrical resistivity tomography has also been conducted in order to detect buried trunks, based on their resistivity contrast with the pyroclastic surrounding material. Flow paths of the pyroclastic material that can be related to the tectonic features at the time have been detected. In general, petrified trunks have been detected as high resistive bodies. In one case, where the trunk was buried very close to the surface, the resistivity was lower than the surrounding material. 2D and 3D subsurface resistivity models of the surveyed area have been constructed, pointing out probable locations of buried petrified trunks. Excavations that followed the geophysical survey revealed petrified trunks in most of the cases although some of the excavated resistive targets proved to be surface fracture systems filled with resistive oxides.