Fracture systems in granite pavements of the eastern Pilbara Craton, Western Australia: Indicators of neotectonic activity?  

Authors / CoAuthors

Clark, D.J. | Bodorkos, S.

Abstract

Continental Australia is characterised overall by relatively high levels of seismic activity in comparison with intracratonic areas worldwide. However, the link between earthquake events and earthquake-related geomorphology in Australia remains poorly understood for all except the largest events, because landscape impact unambiguously attributable to seismic activity is typically difficult to recognise. In this context, we describe several unusual fracture systems of possible tectonic origin that transect granite pavements in the Archaean eastern Pilbara Craton of Western Australia. Occurring at four localities (Gallery Hill, North Shaw, Mulgandinnah Hill and Muccan) separated by up to 150 km, the fracture systems typically range up to 100 m in length and 20 m in width, locally offset pavement surfaces by up to 15 cm vertically, and expose uniformly fresh-looking rock. At one locality (Muccan), the fractures directly crosscut two generations of aboriginal petroglyphs etched into the pavement surface, which suggests that fracture formation occurred relatively recently, and probably quite rapidly. All four localities are characterised by extensional structures (tension fractures and dilated joints) striking 020?040?, and three preserve compressional structures (steeply-dipping reverse faults at Gallery Hill and North Shaw, A-tent crestal fractures at Mulgandinnah Hill) trending 100?135?. These strongly correlated alignments militate against an origin controlled purely by weathering-related phenomena, and the observed pattern is compatible with the formation of all documented fracture systems within a single East Pilbara-wide stress field, dominated by pure shear and characterised by NE?SW to NNE?SSW directed maximum horizontal compression. This orientation is consistent with that derived via spatial averaging of the stress orientation data available from northwestern Australia. The results are preliminary, but have exciting implications for: (1) inexpensive field-based determination of regional stress orientation, and (2) probabilistic seismic hazard assessment and the identification of earthquake-prone regions using granitic landforms.

Product Type

nonGeographicDataset

eCat Id

61165

Contact for the resource

Keywords

• External PublicationScientific Journal Paper

( Theme )

• geomorphology

( Theme )

• earthquakes

( Theme )

• geohazards

• AU-WA

Australian and New Zealand Standard Research Classification (ANZSRC)

• Earth Sciences

• Published_Internal

Publication Date

2004-01-01T00:00:00

Creation Date

Security Constraints

Australian Government Security ClassificationSystem    

Classification - unclassified

Legal Constraints

Creative Commons Attribution 4.0 International Licence    

Access - restricted

Use - license

Status

Purpose

Maintenance Information

unknown

Topic Category

geoscientificInformation

Series Information

Lineage

Unknown

Parent Information

Extents

[-22.0, -20.0, 118.0, 121.0]

Reference System

Spatial Resolution

Service Information

Associations

Downloads and Links

Source Information

Source data not available.