Long-term versus short-term deformation of the meizoseismal area of the 2008 Achaia–Elia (<em>M</em><sub>W</sub> 6.4) earthquake in NW Peloponnese, Greece: Evidence from historical triangulation and morphotectonic data

The deformation of the meizoseismal area of the 2008 Achaia–Elia (M W 6.4) earthquake in NW Peloponnese, of the first significant strike slip earthquake in continental Greece, was examined in two time scales; of 102 years, based on the analysis of high-accuracy historical triangulation data describing shear, and of 105–106 years, based on the analysis of the hydrographic network of the area for signs of streams offset by faulting. Our study revealed pre-seismic accumulation of shear strain of the order of 0.2μrad/year in the study area, consistent with recent GPS evidence, but no signs of significant strike slip-induced offsets in the hydrographic network. These results confirm the hypothesis that the 2008 fault, which did not reached the surface and was not associated with significant seismic ground deformation, probably because of a surface flysch layer filtering high-strain events, was associated with an immature or a dormant, recently activated fault. This fault, about 150km long and discordant to the morphotectonic trends of the area, seems first, to contain segments which have progressively reactivated in a specific direction in the last 20years, reminiscent of the North Anatolian Fault, and second, to limit an 150km wide (recent?) shear zone in the internal part of the arc, in a region mostly dominated by thrust faulting and strong destructive earthquakes.

2008年希腊西北部伯罗奔尼撒半岛的阿哈伊亚 - 埃利亚（MW 6.4）地震是希腊大陆首次发生的重大走滑地震，对其极震区的变形在两个时间尺度上进行了研究：一个是基于对描述剪切的高精度历史三角测量数据的分析，时间跨度为102年；另一个是基于对该地区水文网络因断层错动导致河流偏移迹象的分析，时间跨度为10⁵ - 10⁶年。我们的研究揭示，研究区域内存在每年约0.2微弧度的地震前剪切应变积累，这与近期的全球定位系统（GPS）证据相符，但在水文网络中没有发现由走滑引起的显著偏移迹象。这些结果证实了这样一种假设：2008年的断层未到达地表，且未伴有显著的地震地表变形，可能是因为地表的复理石层过滤了高应变事件，该断层与一个不成熟或休眠但近期被激活的断层有关。这个长约150千米且与该地区构造地貌趋势不一致的断层，首先似乎包含在过去20年中沿特定方向逐渐重新活动的部分，这让人联想到北安纳托利亚断层；其次，它似乎界定了弧内部一个宽150千米（近期？）的剪切带，该区域主要以逆冲断层和强烈破坏性地震为主。