High-resolution, Digital Mapping of the Seismic Hazard within the Gulf of Evia Rift, Central Greece Using Normal Fault Segments as Line Sources

Seismic hazard within juvenile rift systems ismodelled by a semi-statistical procedure based onfault segmentation theory. Fault segmentationprovides the physical basis for strong earthquakerecurrence in regions undergoing extension, andtherefore, it may control the position and size of rupture areas for future events. The computercode FRISK (McGuire, 1978) is applied to calculateprobabilistic estimates of ground motion parameters. Six normal fault segments, on average 25 km long, aremodelled as the earthquake sources within the Gulf ofEvia Rift, Central Greece. The position and length ofsegments have been determined from image processing ofremotely-sensed data and field work. FRISK output isdirected to a Geographical Information System (GIS)and a series of high-resolution (0.1 by 0.1 of adegree) digital maps are produced. The results for100 year acceleration (63% not to be exceeded) showa 50% increase in the seismic hazard from previouslyestimated magnitudes. Areas of maximum hazard (over0.4 g) are located on the south coast of the Gulf ofEvia between the towns of Kammena Vourla and Arkitsa. The obtained shape of Peak Ground Acceleration (PGA)contours is slightly elliptical with the long axis ofthe ellipse trending E-W, and symmetric, with respectto the rift axis.