The meckering earthquake, Western Australia, 14 october 1968

This article was downloaded by: [University of York] On: 18 October 2014, At: 08:04 Publisher: Routledge Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK Australian Geographer Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/cage20 The meckering earthquake, Western Australia, 14 october 1968 A. J. Conacher a & I. D. Murray a a University of Western Australia Published online: 24 Feb 2007. To cite this article: A. J. Conacher & I. D. Murray (1969) The meckering earthquake, Western Australia, 14 october 1968, Australian Geographer, 11:2, 179-184, DOI: 10.1080/00049186908702551 To link to this article: http://dx.doi.org/10.1080/00049186908702551 PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. 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Terms & Conditions of access and use can be found at http:// www.tandfonline.com/page/terms-and-conditions http://www.tandfonline.com/loi/cage20 http://www.tandfonline.com/action/showCitFormats?doi=10.1080/00049186908702551 http://dx.doi.org/10.1080/00049186908702551 http://www.tandfonline.com/page/terms-and-conditions http://www.tandfonline.com/page/terms-and-conditions The Australian Geographer, XI, 2(1969), pp. 179-84 THE AUSTRALIAN SCENE THE MECKERING EARTHQUAKE, WESTERN AUSTRALIA, 14 OCTOBER 1968 Australia is relatively stable in geological terms, although earth tremors are recorded from time to time, most commonly in the Spencer Gulf area of South Australia. Yet it is on the pre-Cambrian shield area in the western third of the continent that the two most severe earthquakes in Australia's recorded history have occurred: the Meeberrie earthquake of 23 April 1941; and more recently, the Meckering earthquake of 14 October 1968. l The following is a brief discussion of some of the consequences and implications of the Meckering earthquake. The magnitude of the Meckering earthquake was calculated at 6.8 on the Richter scale," only 0.05 points greater than the Meeberrie reading. Whilst the assumed epicentre of the earthquake (the Meckering locality) is situated in a recog- nized zone of weakness extending from Moora to Ongerup (Figure I ) , 3 there is no apparent relationship of this zone of weakness or of the Meckering earthquake to known faults (Figure 1) , although it has been suggested that both phen- omena may be related to a slow rise of the land east of a north-south zone through Meckering.1 Saturated as a result of prolonged rain, the soil was deformed plastically along an irregular, 17i- mile, north-south arc around Meckering (Figure 2s and Plate 1), the resulting morphology of this deformation presenting conflicting evidence con- cerning the nature of the movement or movements responsible. There is clear evidence of a rise of four to five feet on the eastern side of the arc, and of a less apparent subsidence on the western side in several portions (Section 1-4, Figure 2 ) . Lateral land movement was generally westwards, so that the soil cover now rests on the western side of the newly initiated fault with a displace- ment of up to seven feet (Sections 2, 3, 6 and 7, Figure 2 ) . However, the morphology of many sections, particularly to the north, appears to have resulted from both easterly and westerly move- ments (Sections 1-4 and vector arrows, Figure 2, and Plate 2 ) . Interpretation is made more diffi- cult through the influence of varying materials on the nature of the deformation; for example, the arc tends to be considerably subdued where it crosses unconsolidated sediments on the south side of the Mortlock river, whilst it is most clearly expressed as a 'break' in recently ploughed fields and across ridges (Section 6, Figure 2) . These and other differences may also reflect local varia- tions in soil moisture content and the character Plate 1. North-facing oblique shows the fault three miles west of Meckering across the Great Eastern Highway (for location refer Figure 2). Shadows give the impression that the predominant direction of earth movement was from the west, although the greatest fall is on the western side of the fault (see sections 2 and 3, Figure 2). Variations of the fault morphology over short distances are apparent, and field furrows clearly indicate the lack of relative lateral movement in a north-south direction. (Photo reproduced by courtesy of West Australian Newspapers Ltd.) 179 D ow nl oa de d by [ U ni ve rs ity o f Y or k] a t 0 8: 04 1 8 O ct ob er 2 01 4 180 THE AUSTRALIAN GEOGRAPHER Younger sedimentary rocks I 1 Swifts, gneiiut and other I 1 andant (pre-esmbrian) rocks — Fault* — — Zone 1 boundary Zone 2 boundary I R t f e r T e x t - — - Zone 3 boundary Figure 1. Zones of disturbance of the Meckering earthquake; location of major geological divisions, known faults, zones of seismicity and places referred to in the text. D ow nl oa de d by [ U ni ve rs ity o f Y or k] a t 0 8: 04 1 8 O ct ob er 2 01 4 THE AUSTRALIAN SCENE 181 MECKERING FAULT LINE — — Arrows indiutt tpputnt rcklivt •mount of tutirly wd urth nwiments it Wj jinn point tn tkc fwit locition of Stctitns ® Location of PliWt Ri i luj Knit crossing Fwit Stctions 1,2.3.4.6 and 7 art cnu scctimt. Sittun 5 » i Itnoitudiul ptlfik of tin Mirtlock Rivtf onirc it » crootd nally tu the fu l l . Figure 2. Location of the Meckering fault line, apparent earth movements and selected cross-sections. D ow nl oa de d by [ U ni ve rs ity o f Y or k] a t 0 8: 04 1 8 O ct ob er 2 01 4 182 THE AUSTRALIAN GEOGRAPHER Plate 2. Fault line one mile northwest of Meckering, facing north (refer Figure 2 for location). Movements from east and west have thrust up the soil cover which now overlies the ground surface on both sides of the fault, the easterly overlay being most apparent in this photograph (cf. section 7, Figure 2). (Photo by I.D.M.) of the underlying granite-gneiss lithology. In any event, the arc is not the result of simple faulting. Portions of it exhibit several features more charac- teristic of compressional folding, whilst the greater part appears to'have resulted from .low-angled overthrusting, a featureof this type of fault being that 'the scarp . . . is not straight or smooth, as in normal or reverse faults; instead it may be irregular in plan'." Further, the surface evidence shows little sign of relative lateral movement along the line of the arc (Plate 1), displacements ranging from none to a few inches in most sec- tions and reaching a foot or more in only a few places. Seismographs in many parts of the world re- corded the earthquake; and tremors were felt in Geraldton to the north of Meckering, Albany to the south, Esperance to the southeast, and east ol Kalgoorlie—an area covering at least 250,000 square miles (Zone l on Figure 1). Damage was recorded within a smaller area (Zone 2) , with two shops slightly damaged and stock shaken from shelves in Moora, power lines down in Bunbury, ceilings and walls cracked in Albany, and new cracks appearing in government buildings in Kal- goorlie. Perth reported fallen masonry, bricks and glass from some structures, and slight subsidence and lateral displacement of portions of the Kwin- ana freeway. More serious damage was caused within the area approximately delimited as Zone 3. Reports from York indicated that both hotels were badly damaged and several houses were de- clared unsafe, with 90 per cent of the buildings suffering some damage. Cunderdin, roughly in the centre of the zone, reported three houses and portions of the hotel as requiring demolition and nearly all houses damaged, whilst Doodlakine, at the eastern end of the zone, reported cracked walls and ceilings in virtually all houses. A total of only 32 people were injured within this zone, the Queen's birthday holiday almost certainly saving a death toll and a larger number of injuries. Hardest hit was the small town of Meckering (population approximately 250) and the sur- rounding locality. The earthquake caused damage estimated at over two million dollars in a wedge- shaped strip 35 miles long, with a ten miles wide base at Greenhills, due south of Meckering, and D ow nl oa de d by [ U ni ve rs ity o f Y or k] a t 0 8: 04 1 8 O ct ob er 2 01 4 THE AUSTRALIAN SCENE 183 Plate 3. The Meckering hotel after the earthquake. (Photo by I.D.M.) a one mile wide apex about seven miles north of the town.7 Farm buildings up to 15 miles from Meckering were destroyed, troughs and windmills damaged, and a number of secondary roads ren- dered impassable for several days. Parts of the Great Eastern Highway will probably have to be reconstructed, because of a five-foot upheaval three miles west of Meckering (Plate 1) and cracks in several other places. A four-foot uplift broke both the narrow and standard gauge railway lines about three miles west of the town and two nearby duplicate water pipelines serving the gold- fields and the eastern wheatbelt burst, the 30-inch diameter pipes telescoping by more than four feet. The entire business section of Meckering and more than 60 of the 80 houses were either des- troyed or rendered unsafe (Plate 3 ) : only two . houses were still habitable following the disaster, and further damage resulted from subsequent tremors. By 17 October, however, a number of shops had re-opened and public utilities were becoming fully operative; and on the following day the State government agreed in principle to rebuild the settlement a quarter of a mile from the town centre on higher ground to avoid perennial winter flooding, following geophysical investigations of the proposed site. Meckering's rural hinterland, on the other hand, should suffer few ill effects in terms of 1968 production; how- ever, the possible long-term effects are less cer- tain, particularly in relation to programmes of capital investment. On 15 October Meckering was declared a dis- aster area by the State government, which set up an emergency group to collate reports of distress and to assess the extent of the damage. The Mayor of Perth established a distress relief fund, and other Australian states and many private and public organizations offered various forms of assistance. By 1 November, 794 claims had been made from the Meckering, Cunderdin, York and Northam areas for financial assistance totalling $2,798,000. Yet on the same day the distress relief fund stood at $290,225 (including $5O,000 from the State government and a matching grant from the Federal government), the deficit stressing the need for a permanent national emergency fund, rather than relying on door to door appeals and charity concerts. Moreover, the fact that only 10 to 15 per cent of Meckering householders were covered by insurance including earthquake dam- age indicated the need for a review of insurance policies—a review which many people thought had been carried out after South Australia's 1961 earthquake. Realization that Perth escaped a major disaster by a narrow margin initiated a contro- versy over the need for a change in building design regulations to provide for the effects of earthquakes; and inevitably discussion was re- opened on the predictability of earthquakes. Geomorphologically and geophysically the earthquake is of considerable interest. Not only is it clear that at least a portion of the pre-Cambrian Australian shield is unstable, but further detailed geophysical investigations may throw light on the nature of the land movement, and hopefully its cause. These problems are almost certainly related to the confused drainage pattern of south- western Western Australia, ascribed (in different areas and by different writers) to climatic change D ow nl oa de d by [ U ni ve rs ity o f Y or k] a t 0 8: 04 1 8 O ct ob er 2 01 4 184 THE AUSTRALIAN GEOGRAPHER and to river capture following uplift.8 Long-term uplift or warping and associated stream incision would also provide a mechanism other than clim- atic change to produce a lowering of the water table, regarded as an important factor in the generally accepted explanation of 'remnant' duri- crusted or lateritized landsurfaces.9 A. J. Conacher and I. D. Murray University of Western Australia REFERENCES 1. For location of places mentioned in the text, refer to Figure 1. 2. I. B. Everingham, Chief Geophysicist at the Mun- darine Observatory, in The West Australian, 16 October 1968: based on readings from Mundaring (Western Australia), Canberra (Australian Capital Territory) and Port Moresby (New Guinea) ob- servatories. 3. Sources of Figure 1: Geological Sketch Map of Western Australia, 1:2,534,000, W.A. Dept. of Mines, 1957; Geological Sketch Map of Western Australia (no scale given), comp. by Geol. Surv., W.A., 1964; probable zones of seismicity from map prepared by B. E. Balme, Dept. Geol., Univ. of W.A., for The West Australian, 16 October 1968; earthquake disturbance zones collated from newspaper reports and field observations. 4. B. E. Balme, Senior Lecturer in Geology, University of Western Australia, in The West Australian, 16 October 1968. 5. Sources of Figure 2: Lands and Survey Dept., air photos — WA 1112 Meckering Fault Line Runs 1-10, 2, 100'; 152.92mm., 16/10/68; cross-sections drawn from authors' field surveys. 6. A. N. Strahler, Physical Geography, 2nd ed., Wiley, New York, 1960, p. 476; refer also W. D. Thorn- bury, Principles of Geomorphology, Wiley, New York, 1954, p. 272. 7. J. Gabbedy, Chairman of the Relief Advisory Com- mittee, in The West Australian, 17 October 1968. 8. J. W. Gregory, 'The lake systems of Westralia', Geog. J., Vol. 43, 1914, pp. 656-64; J. T. Jutson, The Physiography (Geomorphology) of Western Australia, W.A. Geol. Surv. Bull. No. 95, 2nd ed., 1934, pp. 167-81. 9. G. H. Dury, 'An introduction to the geomorphology of Australia', in Studies in Australian Geography, G. H. Dury and M. I. Logan (eds.), Heinemann, Melbourne 1968, pp. 16-17; W. G. Woolnough, 'The duricrust of Australia', J. Proc. Roy. Soc. N.S.W., Vol. 61, 1918, pp. 24-53. 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