SEISMIC ACTIVITY IN THE SNOWY MOUNTAINS REGION AND ITS RELATIONSHIP TO GEOLOGICAL STRUCTURES
Firstly, it is clear that the fault plane cannot correspond in strike and dip to that of Berridale, because of the dilatation at Melbourne. On the hypothesis that both movements have been produced by a stress field acting uniformly throughout the area, it seems likely that the direction of movement would be approximately the same in both cases, the directions of the fault planes being influenced by the presence of local weaknesses in the crust. In view of the evidence from isoseismals that the fault plane may strike in a meridional direction and that it dips to the west, the possibility exists that it may correspond to an extension of the Murrumbidgee Fault. The corresponding fault plane solution does in fact satisfy the data (Fig. 5). In this case both the fault and auxiliary planes intersect the Pn cone, and thus there are four azimuthal lines on the figure.
The trace of the Berridale fault plane is shown in Fig. 1. It can be seen that AA´ and BB´ are both nearly at right angles to this line. A possible explanation is that the sequence of minor shocks in the area occurred as a result of shear strains produced in this direction by the original movement (i.e., along the side of the faulted block). It seems reasonable therefore to suggest that AA´ and BB´ represent transcurrent faults striking approximately in a direction of secondary shear strain, the first series of movements along AA´ causing a transference of strain to BB´.
| No. | Wambrook | Jindabyne | Geehi | Cabramurra |
|---|---|---|---|---|
| 7 | C | C | R | |
| 8 | C | C | (C) | |
| 9 | C | C | C | R |
| 10 | C | R | R | |
| 12 | R | C | (R) | R |
| 13 | R | C | (R) | R |
| 15 | C | R | ||
| 16 | C | |||
| 17 | C | C | C | R |
| 19 | C | |||
| 20 | R | C | C | |
| 28 | C | (C) | ||
| 31 | C | (C) |
