On the Mw 6.4 SW-Achaia (western Greece) earthquake sequence of 8 June 2008: Seismological, field, GPS observations and stress modeling

Abstract

On 8 June 2008 an Mw(NOA)=6.4 earthquake occurred in NW Peloponnesus, western Greece. This event is the largest strike-slip earthquake to occur in western Greece during the past 25 years. The hypocentre was determined at 18 km depth beneath village Mihoi in SW Achaia. No surface rupture was observed. Many rock falls, slides and liquefaction features have been found as is typical for an earthquake of this size. Double-difference relocations of 370 aftershocks show a linear pattern of events and define a clear NE-SW striking mainshock fault plane. The aftershock region extends approximately 30 km in length, and the width of the surface projection of the aftershocks is as large as 10 km. The depth of the aftershocks rarely exceeds 22 km. Analysis of high-rate GPS data showed that station RLS (Riolos) which is located 12.8 km N5°W of the epicentre was displaced co-seismically 7 mm to the North in agreement with right-lateral kinematics of the rupture. Static (Coulomb) stress transfer analysis indicates loading of faults near the towns of Patras (north) and Amaliada (south), respectively. The earthquake put more emphasis on the role of strike-slip fault in the deformation of western Greece also indicating that seismic strain is partitioned between strike-slip and normal-slip events due to obliquity of the Nubia (Africa) subduction and the N-S extension of the overriding Aegean upper plate