TY - JOUR
T1 - Controls on intra-plate seismicity in southwestern Australia
AU - Dentith, Mike
AU - Featherstone, W.E.
PY - 2003
Y1 - 2003
N2 - Although the Southwest Seismic Zone (SWSZ), located about 150 km to the east of Perth in southwestern Australia, is one of the most seismically active areas in Australia, there is little understanding as to why the earthquakes are occurring.An analysis of geophysical, geological and geodetic data from the area suggests that the SWSZ coincides with a Precambrian terrane boundary. Seismic data show that the terrane boundary zone dips at a shallow angle in a northeasterly direction. Reactivation of this 'zone of weakness' in the contemporary stress field (east-west maximum horizontal stress) is interpreted to be the first-order control on seismicity in the region.Gravity data show that the terrane boundary is offset by near-orthogonal structures, which are interpreted as faults. At least one of these trends corresponds with a linear zone of epicentres. The temporal and spatial distributions of epicentres associated with the 1968 Meckering earthquake (ML 6.9) suggest that the second-order distribution of seismicity in the SWSZ can be explained by the 'intersection model', whereby stresses are amplified by space problems associated with displacements on crosscutting faults.It is speculated that a zone of high density and high seismic velocity in the lower crust may also be a second-order control on the local seismicity. However, confirmation awaits better delineation of the extent of this zone. (C) 2003 Elsevier B.V. All rights reserved.
AB - Although the Southwest Seismic Zone (SWSZ), located about 150 km to the east of Perth in southwestern Australia, is one of the most seismically active areas in Australia, there is little understanding as to why the earthquakes are occurring.An analysis of geophysical, geological and geodetic data from the area suggests that the SWSZ coincides with a Precambrian terrane boundary. Seismic data show that the terrane boundary zone dips at a shallow angle in a northeasterly direction. Reactivation of this 'zone of weakness' in the contemporary stress field (east-west maximum horizontal stress) is interpreted to be the first-order control on seismicity in the region.Gravity data show that the terrane boundary is offset by near-orthogonal structures, which are interpreted as faults. At least one of these trends corresponds with a linear zone of epicentres. The temporal and spatial distributions of epicentres associated with the 1968 Meckering earthquake (ML 6.9) suggest that the second-order distribution of seismicity in the SWSZ can be explained by the 'intersection model', whereby stresses are amplified by space problems associated with displacements on crosscutting faults.It is speculated that a zone of high density and high seismic velocity in the lower crust may also be a second-order control on the local seismicity. However, confirmation awaits better delineation of the extent of this zone. (C) 2003 Elsevier B.V. All rights reserved.
U2 - 10.1016/j.tecto.2003.10.002
DO - 10.1016/j.tecto.2003.10.002
M3 - Article
SN - 0040-1951
VL - 376
SP - 167
EP - 184
JO - Tectonophysics
JF - Tectonophysics
IS - 3-4
ER -