FENNIA wide-angle refraction and reflection profile

The FENNIA deep seismic sounding survey was carried out in the May of 1994 in Southern Finland (FENNIA Working Group 1998). The 330 km long profile is oriented from south to north and runs through the Svecofennian lithological units of the late orogenic migmatite, metasedimentary and metavolcanic belts of Southern Finland and the synorogenic Central Finland Granitoid Complex. Seismic refraction measurements were made by recording large explosions from six shot points with spacings of 60 to 80 km. 50 three-component seismic stations were deployed in three separate groupings during the experiment, equaling to 150 different station positions. Trial-and-error ray tracing method was used to obtain a two-dimensional crustal P-wave velocity model in 1998. The model shows thick crust (57 to 61 km Moho depth) in northern and central parts followed by an abrupt thinning of the crust to 48 km depth at the southern end of the profile. The seismic data was reprocessed in 2007 to address the inconsistencies in Moho depth data acquired by wide-angle, receiver function and reflection data. This yielded new two-dimensional P- and S-wave velocity models for the FENNIA profile obtained by similar ray tracing methods. The three available velocity models of the FENNIA profile were modeled by FENNIA Working Group (1998) and Janik et al. (2007). Wide-angle sections of three different seismic measurement axes are available for the FENNIA profile. FENNIA Working Group, 1998. P- and S-velocity structure of the Baltic Shield beneath the FENNIA profile in southern Finland. University of Helsinki, Institute of Seismology, Report S-38. Janik, T., E. Kozlovskaya, and J. Yliniemi, 2007. Crust-mantle boundary in the central Fennoscandian shield: Constraints from wide-angle P and S wave velocity models and new results of reflection profiling in Finland. Journal of Geophysical Research: Solid Earth 112.

FENNIA深地震勘探（FENNIA deep seismic sounding survey）于1994年5月在芬兰南部开展（FENNIA工作组1998）。该测线全长330千米，呈南北走向，横穿芬兰南部晚造山期混合岩、变沉积岩与变火山岩岩带所属的斯维科菲尼安（Svecofennian）岩石地层单元，以及同造山期芬兰中部花岗岩杂岩复合体。本次实验通过记录6个间距为60至80千米的炮点产生的大当量爆炸，开展地震折射测量。实验期间共部署50套三分量地震台站（three-component seismic stations），分为3个独立台阵，对应150个不同的台站观测位置。1998年，研究团队采用试差射线追踪法（trial-and-error ray tracing method）构建了该测线区域的二维地壳P波（P-wave）速度模型。该模型显示，测线北段与中段的地壳厚度较大，莫霍面（Moho）深度为57至61千米，随后在测线南端地壳发生突变式减薄，莫霍面深度降至48千米。2007年，研究人员对原始地震数据进行了重新处理，以解决广角地震（wide-angle seismic）、接收函数（receiver function）与反射地震数据得到的莫霍面深度结果不一致的问题。此次重新处理采用相同的射线追踪方法，得到了FENNIA测线全新的二维P波与S波（S-wave）速度模型。FENNIA测线现有3套公开可用的速度模型，分别由FENNIA工作组（1998）与Janik等人（2007）构建。FENNIA测线还包含3个不同地震测量轴的广角地震剖面数据集。

FENNIA工作组，1998。芬兰南部FENNIA测线下方波罗的海地盾的P波与S波速度结构。赫尔辛基大学地震研究所，报告编号S-38。
Janik, T., E. Kozlovskaya, 与 J. Yliniemi, 2007。芬诺斯堪的亚地盾中部的壳幔边界：来自广角P波与S波速度模型的约束及芬兰反射剖面新结果。《地球物理学研究杂志：固体地球》，112卷。