Seismicity in Southeast Australia
The intraplate seismicity in SE Australia is extensive with a number of earthquakes with magnitude greater than 5.0. The instrumental coverage of the region has improved with the deployment of RSES, ANU local network in 1958. The major events in the area and the current seismic stations are presented in Figure 1.
Figure 1.
This network has recorded and located more than 7600 events. Their distribution in time together with the number of stations through out the years are displayed in Figure 2.
Figure 2
The cumulative energy release is usually an indication of the elastic stress state in a given area. This graphic for SE Australia is shown in Figure 3.
Figure 3
A magnitude regression has been carried out for all reported events and is displayed in figure 5. For magnitudes greater than 2 the catalogue appears to be well defined and can be summarised by the logarithmic relation between the number of earthquakes N and the magnitude M:
log N = a - bM
where a = 5.66 and b = 0.99. Graphical distribution of this regression is presented in Figure 4.
Figure 4
We have divided the region into 1 by 1 geographical degrees cells and have examined the number of earthquakes and the total energy release in the period 1958-1995 in relation to physiographic features and the pattern of mapped faults. From the number of events and energy release three different types of cell have been separated as indicated in figure 5.
Figure 5.
A) The first class occupies the largest territory and represents cells with a relatively small number of earthquakes and low amount of released energy. Nearly half of all the cells lie in class A (26 cells from a total of 56) and so the seismological characteristic of this zone should be close to that for the whole of SE Australia.
B) The second group of cells is characterised by a large number of seismic events and relatively high release of elastic energy. This is likely to be the area with the highest stress content and where the most of this stress is released. It is worth mentioning that the orientation of the zone is parallel to the Australian plate boundary several hundred kilometres to the east.
C) The third group of 3 cells is distinguished by a relatively large number of earthquakes, but a low amount of elastic energy release (indicating a lack of strong seismic events) and suggests the presence of a distinct seismogenic zone. Such a type of seismic behaviour is common for regions with induced seismicity, and/or very high crustal fracturing.
There is a group of cells in the north-western corner and in the south-eastern of the region where no significant earthquakes have been registered. These regions lie well outside the network so that small events are likely to be missed, but could represent a separate seismogenic zone, without enough empirical data to be characterised.
You can find more about the earthquakes in Australia from ASC 
Database in AGSO.
You are
visitor of this page since 20 June 1996!
The local seismicity site is:
Local Earthquakes:
Report Earthquakes at:
Incident
Last modified:28 February 2008