Mike Turnbull Whitsunday Passage 2016-08-18
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On 2016-08-18 at 04:30 UTC a magnitude ML5.8 earthquake occurred in the Whitsunday Passage, about 64 km east-north-east of the city of Bowen in Queensland (See Figure 1).
In Figure 1 the main earthquake location is shown with a yellow concentric marker. The aftershocks that occurred throughout the remaining 13 days of August are shown as smaller red markers. It should be noted that Figure 1 does not show all of the aftershocks that occurred - only those that were detected with sufficient data to obtain a location.
It can be seen that the 2016-08-18 04:30 UTC event and its associated aftershocks are occurring in a localised area. These aftershocks have been regular and ongoing up to the present time (see last update date above, also see Figure 2).
On 2020-04-15 at 07:11 UTC an ML 5.0 earthquake occurred, located to about 5 km south-west of the August 2015 event see Figure 2). This later event is considered to be another main shock, not an aftershock.
The group of yellow markers in Figure 2 are the aftershocks identified with an ML 5.7 earthquake that occurred on 2011-04-16 at 05:31 UTC
The circular arc appearance of the earthquake events shown in Figure 2 is most likely an artefact produced by the locational algorithm given that the two closest seismic monitoring stations (BW1h and BW2S) are both located in Bowen, and are only 1500 m apart: BW2S being north-west of BW1H.
The pink markers in Figure 2 indicate aftershock events that were located using only data from the two Bowen stations.
Due to the extended period of time when these "aftershocks" are being observer (almost 10 years after the initial event) and given that a major earthquake also occurred at the same place as the initial event, this sequence is considered by the author to be a reactivation sequence rather than a normal aftershock sequence. The author suggests that this pattern of earthquake events in this location may persist for many years.
As can be seen from the southern extent of the aftershocks in Figure 2, the seismic activity precipitated by the 2016 and 2020 events is extending to the south-west through the Proserpine townshop and beyond. The spatial presentation of the activity suggests a heightened risk for the Airlie Beach to Proserpine community.
The fact that the aftershock activity from the 2011-04-16 05:31 UTC event was so short-lived compared to the Whitsunday Passage events suggests that the seismic stress in the western location was relieved and transferred to the Whitsunday Passage area, where it is persisting.
A full cataloge of earthquakes that I have located since 2004 is available online.