Abstract
We digitize surface rupture maps and compile observational data from 67 publications on ten of eleven historical, surface-rupturing earthquakes in Australia in order to analyze the prevailing characteristics of surface ruptures and other environmental effects in this crystalline basement-dominated intraplate environment. The studied earthquakes occurred between 1968 and 2018, and range in moment magnitude (Mw) from 4.7 to 6.6. All earthquakes involved co-seismic reverse faulting (with varying amounts of strike-slip) on single or multiple (1–6) discrete faults of ≥ 1 km length that are distinguished by orientation and kinematic criteria. Nine of ten earthquakes have surface-rupturing fault orientations that align with prevailing linear anomalies in geophysical (gravity and magnetic) data and bedrock structure (foliations and/or quartz veins and/or intrusive boundaries and/or pre-existing faults), indicating strong control of inherited crustal structure on contemporary faulting. Rupture kinematics are consistent with horizontal shortening driven by regional trajectories of horizontal compressive stress. The lack of precision in seismological data prohibits the assessment of whether surface ruptures project to hypocentral locations via contiguous, planar principal slip zones or whether rupture segmentation occurs between seismogenic depths and the surface. Rupture centroids of 1–4 km in depth indicate predominantly shallow seismic moment release. No studied earthquakes have unambiguous geological evidence for preceding surface-rupturing earthquakes on the same faults and five earthquakes contain evidence of absence of preceding ruptures since the late Pleistocene, collectively highlighting the challenge of using mapped active faults to predict future seismic hazards. Estimated maximum fault slip rates are 0.2–9.1 m Myr-1 with at least one order of uncertainty. New estimates for rupture length, fault dip, and coseismic net slip can be used to improve future iterations of earthquake magnitude—source size—displacement scaling equations. Observed environmental effects include primary surface rupture, secondary fracture/cracks, fissures, rock falls, ground-water anomalies, vegetation damage, sand-blows / liquefaction, displaced rock fragments, and holes from collapsible soil failure, at maximum estimated epicentral distances ranging from 0 to ~250 km. ESI-07 intensity-scale estimates range by ± 3 classes in each earthquake, depending on the effect considered. Comparing Mw-ESI relationships across geologically diverse environments is a fruitful avenue for future research.
Highlights
In the 50 years between 1968 and 2018 Australia experienced eleven known surface rupturing earthquakes (Table 1, Figure 1)
Creek ruptures are contained within a single report) with key data presented in Tables Tables 3–9 and Figures 3–10, and provided as Supplementary Data
The Meckering, Calingiri, Cadoux, and Katanning events occurred in the Archean Yilgarn Craton within ~25 km of significant terrane boundaries (Figure 1)
Summary
In the 50 years between 1968 and 2018 Australia experienced eleven known surface rupturing earthquakes (Table 1, Figure 1). Studies of Australian surface rupturing earthquakes have contributed. Geosciences 2019, 9, 408; doi:10.3390/geosciences9100408 www.mdpi.com/journal/geosciences to improvements in our collective understanding of intraplate earthquake behavior, including rupture recurrence, in stable continental regions (SCR) [1,2,3,4,5]. In the 50 years between 1968 and 2018 Australia experienced eleven known surface rupturing for reverse earthquakes [6,7,8,9]. This paper available published literaturehave on contributed historic surface earthquakes Australian surface rupturing earthquakes ruptures (Tables and 2)
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