TY - JOUR

T1 - 3-D geometry and displacement variation of thrust faults

AU - Hathaway, Tanya

AU - Gayer, R.A.

N1 - Conference code: 8

PY - 1995

Y1 - 1995

N2 - Mine extraction data from the South Wales Variscan Coal Basin have been used to study 3-D geometries, displacement gradients and strain variation in the thrust volume. 164 parallel sections from 3 adjacent opencast coal mines were analysed using the Fault Analysis Projection System. All sections are parallel to the thrust transport direction and have a spacing range from 16 to 25m. On-site observations were taken from two further coal mines and from limestone quarries in the South Wales Basis. Contoured plots of displacement show nearly elliptical patterns with displacement variation maxima at the fault centre decreasing to zero at the tip-lines. With a given level of contractional strain the dip of the fault place is the primary control on displacement. High displacements are associated with ramps. Displacement gradients in thrust faults can be much higher than those for normal faults and range from 0.09, in the case of flats, to >0.5 in ramps. Contoured heave plots show similar pattens of displacement whereas throw plots show considerable dissimilarities with plots of displacement and heave.Thrust ramps develop either as isolate structures, or as systems linked by a decollement. Isolated thrust ramps, where displacement decreased both up- and down-dip, develop within an ellipsoidal volume with the major axis parallel to thrust strike. Strain diminishes radially outwards, forming four zones of alternating compression and extension, accommodated by either sub-horizontal or sub-vertical tension cracks and changes in bed volume. Strains at the leading and trailing tip-lines of isolated thrusts and in the immediate hanging wall and football generate asymmetric folds. Thrusts exhibit predictable geometries and show similar geometries and strain accommodation features within differing lithologies of the basin.

AB - Mine extraction data from the South Wales Variscan Coal Basin have been used to study 3-D geometries, displacement gradients and strain variation in the thrust volume. 164 parallel sections from 3 adjacent opencast coal mines were analysed using the Fault Analysis Projection System. All sections are parallel to the thrust transport direction and have a spacing range from 16 to 25m. On-site observations were taken from two further coal mines and from limestone quarries in the South Wales Basis. Contoured plots of displacement show nearly elliptical patterns with displacement variation maxima at the fault centre decreasing to zero at the tip-lines. With a given level of contractional strain the dip of the fault place is the primary control on displacement. High displacements are associated with ramps. Displacement gradients in thrust faults can be much higher than those for normal faults and range from 0.09, in the case of flats, to >0.5 in ramps. Contoured heave plots show similar pattens of displacement whereas throw plots show considerable dissimilarities with plots of displacement and heave.Thrust ramps develop either as isolate structures, or as systems linked by a decollement. Isolated thrust ramps, where displacement decreased both up- and down-dip, develop within an ellipsoidal volume with the major axis parallel to thrust strike. Strain diminishes radially outwards, forming four zones of alternating compression and extension, accommodated by either sub-horizontal or sub-vertical tension cracks and changes in bed volume. Strains at the leading and trailing tip-lines of isolated thrusts and in the immediate hanging wall and football generate asymmetric folds. Thrusts exhibit predictable geometries and show similar geometries and strain accommodation features within differing lithologies of the basin.

M3 - Meeting Abstract

VL - 7

SP - 273

JO - Terra nova

JF - Terra nova

SN - 0954-4879

IS - 1

T2 - European Union of Geosciences 8

Y2 - 9 April 1995 through 13 April 1995

ER -