Isoseismal maps

The Meeberrie earthquake was one of the largest to have occurred in Australia. Its magnitude was ML 7.2 and it was felt over a wide area of Western Australia. The isoseismal map shown here, by Clarke & others (1955), is based on intensities on the Rossi-Forel scale at about 25 points and is significantly different from that compiled in BMR from about 50 observations. The Meeberrie homestead's report of the effects there is reproduced by Everingham (1968). Intensity / distance results given by Everingham & Parkes (1971) include those of Clarke & others (1955) and should be revised.

REFERENCES

CLARKE, E. DE C., PRIDER, R. T., & TEICHERT, C., 1955- ELEMENTS OF GEOLOGY FOR WESTERN AUSTRALIAN STUDENTS, 3rd Edition. University of Western Australia Press, Perth.

EVERINGHAM, I. B., 1968-Seismicity of Western Australia. Bureau of Mineral Resources, Australia, Report 132,38-39.

EVERINGHAM, I. B., & PARKES, A. A., 1971-Intensity data for earthquakes at Landor ( 17 June 1969) and Calingiri ( 10 March 1970) and their relationship to previous Western Australian earthquakes. Bureau of Mineral Resources, Australia, Record 1971/80 ( unpublished) .

ISOSEISMAL MAP OF THE MECKERING EARTHQUAKE, WESTERN AUSTRALIA, 14 OCTOBER 1968

Text extracted from the Isoseismal Atlas -

'In the region with intensity VII or greater most old brick or stone buildings were unsafe after the earthquake. Car passengers in this region at the time of the earthquake reported feeling that the tyres were flat and that wind was unusually strong. Ground waves were reported to have been seen by several people in the open during the earthquake. Railway- lines, pipe-lines and roads were all fractured at the fault zone, and extensive cracking of the ground occurred in its immediate vicinity. Old brick houses within 100 metres of the fault were flattened but timber framed sheds and open or closed verandahs remained upright. Away from the fault, cracks due to slumping were common, particularly along river banks, around salt lakes, and where roads run along embankments.'

'In Meckering a bank, hotel, shire hall, three churches and sixty of about seventy-five houses were wrecked. Few of the remaining buildings were habitable, fibro and galvanised iron clad timber-framed structures being outstanding because of the comparative lack of damage to them.' 'The region of intensity MM VI was characterised by notable cracking of oldest brick and masonry buildings, and alarm caused to many residents. Changes of water flow in wells and springs were noted at several localities.' 'It is of interest to examine an independent assessment of an intensity level made by the W .A. Government Relief Advisory Committee when examining damage claims. ..the areas' of proven damage (which were drawn by the Committee without reference to the authors) generally coincide with the area where the intensity rated was MM VI or more and confirm the shape of the MM V -VI isoseismal. Their results show that notable damage would not be expected where the intensity was less than MM VI.' (Everingham & Gregson, 1970). Damage is estimated to have cost approximately 2.2 million dollars (1968 prices).

REFERENCE

EVERINGHAM, I. B., & GREGSON, P. I., 1970 -Meckering earthquake intensities and notes on earthquake risk in Western Australia. Bureau of Mineral Resources, Australia, Record 1970/97 (unpublished}

CADOUX EARTHQUAKE, WESTERN AUSTRALIA- 2 JUNE 1979

At 17:48 local time on 2 June 1979 an earthquake with magnitude ML 6.2 occurred in the proximity of the small township of Cadoux (population 36) in a farming area 180 km northwest of the State capital, Perth. Cadoux was wrecked but only one person was injured.

The earthquake damaged or wrecked buildings and structures in an area of approximately 4000 km 2 centred on Cadoux. Roads, pipes, and power and railway lines were damaged by movements on a complex pattern of surface faulting caused by the earthquake in a zone extending 7 km to the north and to the south of Cadoux.

An isoseismal survey (700 questionnaires) was initiated immediately after the earthquake, and damage in the Cadoux area was inspected. About 500 questionnaires were answered. Results showed that the earthquake was felt clearly over a radius of 500 km. The maximum Modified Mercalli intensity of MM IX was observed adjacent to the earthquake fracture, and intensities MM VII or greater occurred up to 5 km from the surface fracture. Intensities in Perth ranged between MM IV and MM V.

Information from insurance and Government Works Department sources indicate that damage costs amounted to around $3.8 million (1979 prices).

Four accelerographs in the Meckering area, 90 km from Cadoux, recorded maximum accelerations of approximately 0.1 m.s-2. At Mundaring Weir, 120 km from Cadoux, the accelerograph recorded maximum east, vertical, and north component accelerations of 0.4, 0.2, and 0.1 m.s-2 respectively (Gregson, 1980b).

REFERENCE

GREGSON, P. J., 1980b-Mundaring Geophysical Observatory Annual Report, 1979. Bureau of Mineral Resources, Australia, Record 1980/51 (unpublished).

NEWCASTLE, DECEMBER 1989

ISOSEISMAL MAP OF THE ADELAIDE EARTHQUAKE, SOUTH AUSTRALIA- 28 FEBRUARY 1954

'In the early hours of 1st March 1954 (local time), most of the inhabitants of the city of Adelaide were awakened by a loud rumbling noise followed by a shaking severe enough to crack the walls and loosen plaster from many houses. For most persons in Adelaide, this was their first experience of an earthquake, and it is the first record in almost a hundred years of any movements in the earth's crust in the vicinity of the city. Although a relatively minor one by the standards of countries prone to earthquakes, it was sufficiently severe to cause material damage to many buildings, as the possibility of earthquake damage had never been taken into consideration in their construction. There were no injuries as a result of the earthquake.
'In the absence of any instrumental records from distances under 400 miles from the epicentre, numerous reports available of the effects of the earthquake and the experiences of persons who felt it were investigated by the geophysical staff of the Department of Mines. An abundance of information was naturally available from the Adelaide metropolitan area, but data from more remote country areas is sparse as few people were awake at the time of the earthquake. From these reports it has been possible to draw isoseismal lines and establish the approximate position of the epicentre ...
The maximum intensity of the earthquake has been established as Intensity 8 on the Modified Mercalli scale. A second or minor epicentre with Intensity 7 appears to occur in the vicinty of Beaumont' (Kerr-Grant, 1956). 'On the 1st March 1954 (LT) ...the southern suburbs of Adelaide experienced the strongest ground shaking in their short history. Widespread damage occurred, mainly to old domestic dwellings (30,000 insurance claims were filed....) and whilst the average claim was only one hundred pounds, the estimated total loss was about four million pounds' (McCue, 1975).

REFERENCES

KERR-GRANT, C., 1956-The Adelaide earthquake of 1st March
1954. Transactions of the Royal Society of South Australia, 59,
177-185.
McCuE, K. F., 1975 -Seismicity and seismic risk in South Australia. University of Adelaide Report, ADP 137.