The Lake Edgar Fault: an active fault in Southwestern Tasmania, Australia, with repeated displacement in the Quaternary

K. McCue, R. Van Dissen, G. Gibson, V. Jensen, B. Boreham

Abstract


The Lake Edgar Fault in Western Tasmania, Australia is marked by a prominent fault scarp and is a recently reactivated
fault initially of Cambrian age. The scarp has a northerly trend and passes through the western abutment
of the Edgar Dam, a saddle dam on Lake Pedder. The active fault segment displaces geologically young river
and glacial deposits. It is 29 ± 4 km long, and dips to the west. Movement on the fault has ruptured the ground
surface at least twice within the Quaternary and possibly the last ca. 25 000 years; the most recent rupture has
occurred since the last glaciation (within the last ca. 10000 years). This is the only known case of surface faulting
in Australia with evidence for repeated ruptures in the Late Pleistocene. Along its central portion the two
most recent surface-faulting earthquakes have resulted in about 2.5 m of vertical displacement each (western side
up). The Lake Edgar Fault is considered capable of generating earthquakes in the order of magnitude 61/2-71/4.
The Gell River Fault is another fault nearby that was apparently also active in the Late Pleistocene. It has yet to
be studied in detail but the scarp appears to be more degraded and therefore older than the most recent movement
on the Lake Edgar Fault.

Keywords


recent faults;Australia;intraplate seismicity;multiple ruptures

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References


DOI: https://doi.org/10.4401/ag-3448

Published by INGV, Istituto Nazionale di Geofisica e Vulcanologia - ISSN: 2037-416X