Fieldwork was conducted in Finnmark, nort
hern Norway, wit
h t
he purpose of detecting and measuring stress-relief features, induced by quarrying and road works, and to derive from t
hem valuable information on t
he s
hallow-crustal stress orientations and magnitudes. Two kinds of stress-relief features were considered in t
his study. T
he first consists of drill
hole offsets t
hat were found along blasted road-cuts and w
hic
h were triggered by t
he sudden rock unloading following t
he actual blasting. Vertical axial fractures found in t
he concave remains of bore
holes represent t
he second kind of stress-relief feature. T
he axial fractures are tension fractures produced by gas overpressure inside t
he drill
hole w
hen t
he blast occurs. As suc
h, t
heir strike reflects t
he orientation of t
he ambient maximum
horizontal stress axis. T
he bore
hole offsets s
how mostly reverse-slip displacements to t
he E–SE and t
he axial fractures trend NW–SE on average, in agreement wit
h NW–SE compression induced by Nort
h Atlantic ridge-pus
h forces. Mec
hanical considerations of t
he slip planes offsetting some of t
he drill
holes lead to t
he conclusion t
hat t
he magnitude of t
he maximum
horizontal stress at t
he surface is in t
he range
![]()
http://www.sciencedirect.com/scidirimg/entities/223c.gif"" alt=""not, vert, similar"" border=0>0.1–
![]()
http://www.sciencedirect.com/scidirimg/entities/223c.gif"" alt=""not, vert, similar"" border=0>1 MPa. T
his range of magnitudes is 1–2 orders less t
han t
he
horizontal stress magnitudes measured at t
he surface in ot
her post-glacial environments (e.g. Canada). It is suggested t
hat t
his difference is related to t
he marked decline in stress t
hat followed t
he tremendous post-glacial burst of eart
hquake activity t
hat affected Fennoscandia but apparently not t
he Canadian S
hield.