Imaging of the Hellenic subduction zone with S-P converted phases

到目前为止，用P波接收功能得到的希腊俯冲带的地震图像在克里特海和爱琴海中部有很大的空白。利用近震和远震的S-P转换波均可探测P波接收函数未覆盖地区的地壳结构。结果表明，S-P转换波的转换点位于距台站70-80公里的地方，转换深度为25公里，这是因为在地震边界上转换的震相偏离垂直方向折射。与部署海底地震仪以研究在地震边界的同一点上急剧传播的P-S震相相比，这提供了一个利用附近陆地台站的数据以低成本对海域地震边界进行采样的机会。我们将利用现有的中深度本地地震和浅层远距离地震的台站数据，对出现在S和SKS前兆的S-P转换相进行全面研究，这些转换相为推断克里特海和爱琴海中部地区地震边界的深度和速度对比提供了一种替代方法。这将补充我们的P-S希腊俯冲带接收功能图像，并在区域范围内为所讨论的克里特岛中部钻探地点提供完整的结构框架。

The seismological images of the Hellenic subduction zone derived so far with P-wave receiver functions have large gaps in the Sea of Crete and the central Aegean. The crustal structure in areas not covered by P-wave receiver functions can be probed with S-P converted waves from both nearby local earthquakes and distant earthquakes. It can be shown that the conversion points of S-P converted waves lie up to 70-80 km off the stations for conversion depths of 25 km because the upgoing converted phases are refracted away from the vertical at seismic boundaries. This offers an opportunity to sample seismic boundaries in sea areas with data from nearby land stations at low costs as compared to the deployment of ocean-bottom seismographs for the study of steeply propagating P-S phases that are converted at the same point of a seismic boundary. We will use existing station data from intermediate-depth local and shallow distant earthquakes for a comprehensive study of S-P converted phases that appear as precursors to S and SKS and that offer an alternative method to infer depths to, and velocity contrasts across seismic boundaries in the area of the Sea of Crete and the central Aegean. This will complement our P-S receiver function images of the Hellenic subduction zone and provide, on a regional scale, a complete structural frame for the discussed drilling site in central Crete.