The Hyden Fault Scarp , Western Australia : Palaeoseismic Evidence For Repeated Quaternary Displacement In An Intracratonic Setting Running title : Hyden palaeoseismic study

We present new paleoseismicity data for the 30 km long and 2.5 m high Hyden fault scarp in Western Australia, which, when combined with the results of previous research, provides the most extensive record of surface rupturing earthquakes yet assembled for an "active" Australian intracratonic fault. The data indicate that four to five surface rupturing earthquakes have occurred on the Hyden Fault during the Quaternary (E1: ca. 20 ka, E2: ca. 50-55 ka, E3: ca. 100 ka, and two events E4 and E5, >200 ka). Activity is episodic, with single seismic cycle slip rates varying from 0.03 mm/yr to less than 0.01 mm/yr. Palaeo-earthquake magnitudes are estimated to have been in the order of M 6.8. The identification of a similar fault scarp immediately northwest of the Hyden scarp, and of two air-photo lineaments to the west of the Hyden scarp, all underlain by faults imaged using high-resolution geophysical data, indicates that strain is distributed amongst a family of faults in this region. The presence of multiple faults indicates that the seismic hazard at any given location is likely to be appreciably greater than the hazard posed by a single fault considered in isolation.