Abstract. The Dinaric Fault System in western Slovenia, consisting of NW-SE trending, right-lateral strike-slip faults, accommodates the northward motion of Adria with respect to Eurasia. These active faults show a clear imprint in the morphology and some of them hosted moderate instrumental earthquakes. However, it is largely unknown if the faults also had strong earthquakes in the Late Quaternary. This hampers our understanding of the regional tectonics and the seismic hazard. Geological evidence of co-seismic surface ruptures only exists for one historical event, the 1511 Idrija Earthquake with a magnitude of ~M6.8, but the causative fault is still disputed. Here we use geomorphological data, near-surface geophysical surveys, and paleoseismological trenching to show that two of these faults, the Predjama Fault and the Idrija Fault ruptured in strong earthquakes in the Holocene. In a paleoseismological trench across the Predjama Fault we found at least one earthquake with a minimum magnitude of M_W6.1 that occurred between 13–0.7 ka, very likely not earlier than 8.4 ka. At the Idrija Fault, a surface-rupturing earthquake with a magnitude of at least M_W6.1 happened in the last ~2.1 ka. This event could correspond to the 1511 Idrija earthquake. Our results show that the faults rupture in rare, but strong earthquakes, which dominate the seismic moment release. We show that instrumental and historical seismicity data do not capture the strongest events in this area. The fact that many of the NW-SE trending, parallel faults are active implies that the deformation in western Slovenia is distributed, rather than focussed on one major structure.

中文翻译：

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斯洛文尼亚西部Dinaric断层系统的全新世地表破裂地震

摘要。斯洛文尼亚西部的Dinaric断层系统由NW-SE趋势，右侧走滑断层组成，适应了Adria向欧亚大陆的北移。这些活动断层在形态上显示出清晰的印记，其中一些还发生了中度仪器地震。但是，断层在第四纪晚期是否也发生了强烈地震，这在很大程度上是未知的。这阻碍了我们对区域构造和地震灾害的理解。同震表面破裂的地质证据仅存在于一个历史事件中，即1511年Idrija地震，震级约为M6.8，但因果断层仍存在争议。在这里，我们使用地貌数据，近地表地球物理勘测和古地震学开挖来显示其中两个断层，Predjama断层和Idrija断层在全新世强烈地震中破裂。在横跨Predjama断层的古地震沟中，我们发现至少一场地震，其最小震级为M_W 6.1发生在13–0.7 ka之间，很可能不早于8.4 ka。在Idrija断层，最后一个〜2.1 ka发生了至少M _W 6.1的表面破裂地震。此事件可能对应于1511年Idrija地震。我们的结果表明，断层在罕见但强烈的地震中破裂，这些地震主导了地震矩的释放。我们表明仪器和历史地震活动性数据未捕获该地区最强烈的事件。NW-SE的许多趋势，平行断层活跃的事实表明，斯洛文尼亚西部的变形是分布的，而不是集中在一个主要结构上。