A second earthquake with magnitude larger than 5 occurred today (November 9, 2018) near Lake Muir in southwestern Western Australia, and Geoscience Australia assigned it a magnitude of 5.4. This earthquake, shown by
A second earthquake with magnitude larger than 5 occurred today (November 9, 2018) near Lake Muir in southwestern Western Australia, and Geoscience Australia assigned it a magnitude of 5.4. This earthquake, shown by the large red dot in Figure 1, occurred about 10 km southeast of the magnitude 5.7 earthquake that occurred on 17 September 2018. The aftershocks of today’s earthquake, shown by small red dots in Figure 1, are located at the southern end of the aftershock zone of the September 17 event, shown by the yellow dots. Today’s earthquake was preceded by a series of foreshocks that occurred overnight, and was felt between Albany and Perth. The shaking intensities of the two earthquakes are shown in Figures 2 and 3.
The orientation of the fault plane on which the 17 September earthquake occurred is shown on a Wulf net projection in Figure 4. This shows that the earthquake had a thrust mechanism on a fault plane striking east-northeast. The InSAR (interferometric Synthetic Aperture Radar) map in Figure 5 shows that the west side moved up and the east side moved down on a plane dipping down to the west-northwest. The change in elevation along this dip direction is shown at the upper left of Figure 5.
The two earthquakes are shown by the yellow stars on a map of historical earthquake epicentres in the Southwest Western Australia Seismic Zone (SWWASZ) in Figure 6. The contours show annual probability of events of magnitude 5 and 