SEISMIC ACTIVITY IN THE SNOWY MOUNTAINS REGION AND ITS RELATIONSHIP TO GEOLOGICAL STRUCTURES
The first solution, a high-angle reverse fault parallel to the Crackenback is therefore tentatively selected as more likely to be the correct one.
It is then necessary to consider that the Crackenback fault and also the Wollondibby-Little Thredbo and Mowamba faults die out on the western side of the Jindabyne valley. This valley is a graben between a north-south trending warped zone to the west, and the well-defined scarp of the Jindabyne fault to the east. One exposure of the Jindabyne fault shows it dipping very steeply west. The scarp dies out to the north, but faulting on about the same line of strike continues.
It is suggested that the mobile block whose movement caused the Berridale tremor lies to the west of the steep Jindabyne fault, thus being in the form of a wedge facing south-east. The focus of the tremor would be on the Crackenback fault plane close to where it terminates on the Jindabyne fault. Movement of this wedge to the south-east dragging on the Jindabyne fault plane strained the country to the east of it. The succeeding swarm of tremors in this region may represent relief of strain by transcurrent movements. It is noteworthy that AA´ is close to the Jindabyne fault and parallel to it, and that BB´ is parallel to a number of lineaments in its immediate neighbourhood.
Tremors Nos. 14, 22, 24, 25, 43 and 45 may indicate movements along the Western side of the block.
ACKNOWLEDGMENTS
This project of locating near earthquakes to the highest possible accuracy was initiated by Professor ]. C. Jaeger who has maintained a keen interest in it throughout. In the early stages he was assisted by Dr. E. A. Flinn. We are grateful to many officers of the Snowy Mountains Authority, notably Mr. K. Hogan, Dr. K. E. Timmel and Messrs. D. Norris, L. Alexander and P. Illes, who at various times have been responsible for installing and supervising the stations, also to the station observers, Messrs. A. Kelso, D. Collman and H. Butler. Mrs. B. Fry and Miss H. Halpin were responsible for preliminary scanning of the records. The paper is presented by permission of the Snowy Mountains Authority, but the views expressed are not necessarily those of the Authority.
