Shear-wave splitting is associated to different sources in the upper crust. Preferentially oriented minerals, stress-aligned microcracks and tectonic structures have all been identified as causes of seismic anisotropy in the upper crust. However, distinguishing between them and discovering the actual origin of the splitting effect has important implications; changes in the anisotropic properties of the medium related to the behavior of fluid-filled microcracks could have potential connections to the occurrence of an impending significant earthquake. The recent 2020 Samos M_w = 6.9 event and its associated sequence was a great opportunity to study shear-wave splitting in the area. The spatial constrains in such studies, i.e., the requirement of events located very close to the receivers, did not permit exploring local anisotropy in the past, due to a severe lack of suitable data. To establish a background of splitting, we searched for any appropriate earthquake in a five-year period preceding the mainshock. We performed an automatic analysis on over 200 event-station pairs and obtained 164 high-quality splitting observations between January 2015 and November 2020. Results indicated a strong connection to local structures; S_fast polarization axes seem to align with faults in the area. However, we also observed a period of increasing and decreasing time-delays, associated with an M_w = 6.3 earthquake that occurred on June 2017 near Lesvos Island. The latter behavior implies the possibility of stress-induced anisotropy in the area. Thus, the Samos Island could be represented by two different sources of splitting; structures to the NW and microcracks to the SE.

剪切波分裂与上地壳的不同震源有关。优先定向的矿物，应力取向的微裂纹和构造结构都被认为是上地壳地震各向异性的原因。但是，区分它们并发现分裂效应的实际来源具有重要意义。与充满流体的微裂纹行为有关的介质各向异性特性的变化可能与即将发生的重大地震有关。最近的2020 Samos M _w = 6.9事件及其相关序列是研究该地区剪切波分裂的绝佳机会。由于严重缺乏合适的数据，此类研究中的空间限制（即，非常靠近接收器的事件要求）过去不允许探索局部各向异性。为了确定分裂的背景，我们在主震发生前的五年内搜寻了适当的地震。在2015年1月至2020年11月之间，我们对200多个事件站对进行了自动分析，获得了164个高质量的分裂观测结果。小号_快极化轴似乎与该区域的断层对齐。然而，我们也观察一段时间增加和减少时间延迟的，具有相关的中号_W¯¯  ，关于2017年6月莱斯沃斯岛附近发生洲= 6.3级地震。后一种行为暗示了该地区应力诱发各向异性的可能性。因此，萨摩斯岛可以用两种不同的分裂来源来表示。NW的结构和SE的微裂纹。