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

Abstract

On June 8, 2008 a Mw = 6.4 earthquake occurred in NW Peloponnese, western Greece. This event is the largest strike-slip earthquake to occur in western Greece during the past 25 years. 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 hypocentrer was determined at 18 km depth beneath village Mihoi in SW Achaia. The 24-hr aftershock region extends approximately 30 km in length, and the width of the surface projection of the aftershocks ranges between 5–10 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 epicenter 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 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) – Eurasia convergence.