The Meckering Western Australia earthquake of October 1968
THE FAULT SCARP
INTRODUCTIONAt 10.59a.m., on 14th October, 1968, the small town of Meckering, about 130 km east of Perth, was destroyed by an earthquake. Twenty people were injured, but incredibly, no one was killed. The earthquake was felt throughout the southern half of the State and caused damage in the surrounding townships, particularly York and Northam, and in the Perth Metropolitan area. The magnitude (ML) of the Meckering Earthquake was 6.9 on the Richter Scale making it one of the largest recorded in the seismic history of Australia. Although the magnitude was moderate the focus of the earthquake was only about 7km deep and the surface intensity reached MMIX on the Modified Mercalli scale. The earthquake and its aftershocks were accompanied by surface faulting extending over an area of 200 km2 and an arcuate dextral thrust fault 37 km long was formed. Many smaller faults were generated by the earthquake, principally within the quadrant formed by the main thrust scarp, and there is some evidence to suggest that movement on at least one of these faults took place several days after the main fault formation. The Meckering Fault was the first tectonic ground breakage to be recorded in Australia. The Meckering Earthquake was located in a well-documented zone of seismic activity which is about 60 km wide and extends across the southwest corner of Western Australia. Seventeen months after the main event at Meckering, at 1.15 a.m. on 11th March 1970, a magnitude 6.0 earthquake occurred at Calingiri, 80 km northwest of Meckering. This earthquake was again shallow, with a focal depth of about 1 km, and was accompanied by surface faulting similar to that at Meckering. This location of the faulting at Meckering and Calingiri, in an otherwise stable Precambrian Shield, has shown that damaging earthquakes are a potential hazard in Western Australia, and are not confined to the margins of the major lithospheric plates. REGIONAL GEOLOGY OF THE MECKERING AREA
PHYSIOGRAPHY The Meckering area is one of relatively low topographic relief. The Meckering Line (Mulcahy, 1967) runs through the area, which marks the divide between the Swanland region(to the west) and Salinaland (to the east). The river system has been rejuvenated to the west of the Meckering Line. The Line is probably of tectonic origin and is marked by changes in topography, soil type, and in parts by granite breakaways.
In October 1968, the population of Meckering numbered about 230; a further 300 people lived on farms in the vicinity. Apart from the two-storied bank and hotel, all buildings in the town were single storied, and built of a variety of materials, ranging from unfired mud brick to reinforced concrete. There were a few modern dwellings, but otherwise the buildings were a reflection of the past, and several were unoccupied. The most substantial modern constructions were two new grain storage silos, each 11 m in diameter and 30 m high, and a horizontal storage shed 90 m long and 30 m wide. Apart from its local importance, Meckering lies astride all the main arteries connecting Perth to Kalgoorlie and the eastern states of Australia. The Great Eastern Highway, Standard and Narrow Gauge Railways, the Goldfields Water Supply pipe line and the east-west telegraph and telephone systems all pass through the town.
Eleven days before the main earthquake, at 11.03 am on 3rd October 1968, Constable Skehan, the local policeman, was walking in the main street when, he reported, "the ground seemed to turn to jelly" and he had difficulty keeping his feet. Further shaking at 11.18 am and 11.55 am confirmed the constable's opinion that a severe earth tremor had occurred. Three kilometres north of Meckering in a comparatively new house belonging to Mr. Sudholz, the shocks were strongly felt, the last being the biggest. However, the second shock did the most damage, a light fitting fell down in the kitchen, crockery and groceries fell out of cupboards and some bricks were cracked. These events were reported in Perth newspapers but raised little interest. On the 14th October, small tremors were felt by the licensee of the Railway Hotel, Mr Gordon Berryman, at 1.00 am and 7.15 am. The shaking raised considerable dust on the second storey of the hotel. Later in the day, just before l l.00 am, the publican went upstairs and was surprised to see the verandah door suddenly swing open. While moving forward to shut it he saw the unusual sight of a flock of swallows walking around the verandah in a group. As he shut the door a violent shaking commenced, accompanied by.a noise like an explosion. The easterly corner and walls of the building fell inwards, and the south, or back wall fell away as two further distinct periods of shaking occurred. Later in the day the hotel barometer was found in the rubble with the needle jammed at 28.5 inches, and the pointer at 29.7 inches where it had been set at 9.00 am in the morning. Miss Glenys Nichol was alone in the general store when it started to collapse around her. She escaped through the front door and ran across the street to the parking area. As she ran, numerous ground cracks in the parking area were opening as much as 5 cm and shutting again, and she felt a slight burning sensation on the skin and there was a slightly nauseous smell reminiscent of carbide. She experienced a similar smell following one of the major aftershocks. The local butcher, Mr. Vic Edwards, lived on the north side of the railway, about 750 m northeast of the town centre. At the time of the earthquake he was in his back yard with his family. All suddenly experienced the sensation of being thrown into the air. Mr. Edwards got to his feet but was knocked to the ground twice more and there seemed to be coincidental explosions. He saw cracks in the ground opening as much as 3.5 cm with spurts of white vapour or dust rising about 2.5 m high as the cracks shut. Most of the cracks in the ground around the ruined house settled down and were not visible a week later, but two large openings about 75 cm deep and 7.5 cm wide remained in the alluvial soil. Three distinct pulses of shaking were also felt by Mr. Owen Burges who was yarding sheep on his property 13 km south of Meckering. As he was about to enter the shearing shed, he was thrown against the east wall of the sheep race, and the sliding door of the shed opened violently eastward. He shut the door, but the same process was repeated. Thinking that a 'cockeyed bob'* had gone through his shed, he slammed the door, but was again thrown against the east wall of the sheep race as the door flew open for a third time. At the time of the earthquake, Mr. T. H. Morrell and his son were driving in the farm truck on the outskirts of Meckering, close to the cemetery. They heard a loud noise which seemed to be moving north, and the truck suddenly thumped up and down with a sensation akin to a flat-tyre. Looking to the side of the road they saw laterite pebbles jumping and bouncing as much as 50 cm from the ground. Mr. L. Solomon was sitting in his truck in Meckering at 10.59 am when the heavy vehicle seemed to be thrown into the air then dumped down. Simultaneously there was a large explosion, and immediately in front of him the front wall of the general store crashed down on an unoccupied utility van. Joined by his son he ran across the road to the parking area where, amid loud noise, two distinct groundwaves were seen to move easterly across the main street. The rolls were travelling at about 12 km/h, and the ground appeared to rise sharply and fall away slowly with about a two-second interval between the crests. Both men were brought to their knees by the ground movement. In the parking area the railway water tank was swaying alarmingly and two tie-rods parted audibly. The Solomons immediately left town, and as they drove up the main street observed the chimneys on the two-storied bank building fall northward, and on recoil, the south wall fall outward. Eight hundred metres further along the Goomalling Road mud bricks were still falling from a house as they passed by. About 2 km further along the road, when the truck was travelling at about 100 km/h, they reached the scarp of the Meckering Fault. On crossing the 1.8 m high fault scarp, the vehicle was airborne until it landed with such force that the front bumper hit the ground. Driving on, Mr. Solomon came to a second, smaller fault scarp 0.3 m high, adjacent to his ruined home. The observer closest to the Meckering Fault at the time of formation was Mr. L. A. Sheehan of Cunderdin, who was driving eastwards towards Meckering, about 6.5 km away. The trees along the roadside, already agitated by wind and rain, started to whip violently and at the same time the car rocked as if a tyre had blown out. The driver at first thought he was involved in a 'cockeyed bob*' but then immediately in front of him a 2.5 m high bump rose in the road where two seconds before none had existed. Another observer, travelling in the opposite direction along the Great Eastern Highway, felt the shaking and saw the scarp rise, and crashed into a tree at the roadside, breaking an arm. (*Cockeyed bob: a Western Australian name for a small, but violent cyclonic disturbance, particularly one which causes localised wind damage) .................... .................... Observations which might be construed as animal precognition of the earthquake are few, but two examples were reported. Mr. R. Baxter was herding sheep on his property 14 km east of the town where he noted that immediately prior to the earthquake the sheep had drawn into two circular groups with their heads inward. Mr. T. A. Liddell, of Greenhills, 32 km SSW of Meckering, was feeding his horse at the time of the earthquake. A roaring noise, like a strong wind, preceded the shock; the horse jumped in the air and then stood stock still.
Five foreshocks of magnitude 3.0 or greater were located by the Mundaring Geophysical Observatory. Three were on Oct 03 (magnitudes 3.8,3.7 and 4.2). Two events were recorded on October 14th, (magnitudes 3.3 and 3.4), approximately 4 hours and 3 hours before the main shock. Other, smaller events are also known to have occurred before the main event. On 31st August 1968, people standing in the Meckering Golf Club house felt a solid bump and saw a small whitish cloud mushroom up ... a kilometre away. About a month later, on 29th September, between 3 pm and 7 pm, three strong shocks were felt a few kilometres to the northwest of Meckering, but were not appreciable in the town. .... The main event was preceded by three shocks on 3rd October, between 11.03 am and 11.55 am ... The third tremor ... was the largest, with ML 4.2, and this was felt most strongly in the township of Meckering. On the day of the main earthquake ... some people in Meckering felt distinct tremors at 1 am and 7.15 am .... Despite the frequency of these tremors ... little damage had been caused and there appeared to be no reason why the local populace should expect a major earthquake. Several reliable observers reported the appearance of undulating waves, or slowly moving rolls on the surface of the ground. .... small surface undulations were actually seen, and in some cases felt, by many people, and, although the dimension reported may be in error and their origin doubtful, their occurrence in this and other earthquakes must be accepted as authentic. ... Mr. R. Baxter, 14 km east of Meckering observed three distinct earth waves with a north-south front moving east-northeasterly .... ... Three distinct ground waves were also seen by Mr. K. Broad on his farm 19 km south of Meckering, near the Mortlock River. ... .... At Greenhills, 32 km south-southwest of Meckering, Mr. T. A. Liddell saw eight or nine ground waves, or surface swells on the main York road. PROPERTY DAMAGE
EARTHQUAKE EFFECTS OUTSIDE THE MECKERING AREA
The Meckering Earthquake was felt for about 24 seconds in the Perth metropolitan area, although some tall buildings vibrated for as long as 3 minutes. Felt intensity was usually about MM V although there was an isolated area of MM VI reports from the city block. WHAT TO SEE TODAY
The Big Camera, a museum of Photography on the Great Eastern Highway at Meckering, also has a large collection of photographs taken in 1968. Some photographs recently taken in the Meckering area can seen by following this link Reference - The Meckering and Calingiri Earthquakes October 1968 and March 1970 Gordon, F.R. & Lewis, J. D. Geol Surv. WA Bulletin 126 (1980) |