Velocity heterogeneities in the lithosphere of the Fennoscandian (Baltic) shield

Abstract

64 The velocity structure of the lithosphere in the Fennoscandian Shield is of great interest for two main reasons: classical problems in the study of the Earth’s deep structure and the problems in the definition of promising zones which display their mineralogenic features. To solve these problems, seismic tomography methods are commonly used to approach the inverse linearized 3D kinematic problem of seismic study. These methods have been developed since the 1960s, and they are now extensively employed for solving both the deep seismic sounding (DSS) and seismolog� ical problems. The Fennoscandian Shield has been extensively studied under international and regional seismic projects launched to better understand the structural characteristics of the Earth’s crust. Various metamor� phosed crystalline and igneous rock complexes were studied. Comparative analysis of wave fields in all the profiles is a reliable tool for selecting a general model of the Earth’s crust and using it as the basis for reveal� ing the general pattern of variations in the physical parameters of the crystalline crust of the study area. Such a model is an approximation of the real velocity structure of the crust; the sections of all profiles can be presented in a uniform fashion and a 3D velocity model can be constructed, based on this model [1–4].