MIKE Sandiford grew up on the Mornington Peninsula and experienced mild earthquakes probably generated by the Selwyn Fault, but never dreamed he'd become one of the world's foremost earthquake experts.
Professor Sandiford is the Australian Research Council professor at the school of earth sciences at University of Melbourne and has studied earthquakes around the world including in Indonesia, Timor, China and Australia.
He says that in the past 55 years, the region around Melbourne has experienced more than 70 earthquakes, all below magnitude 5 ML (Local Magnitude or Richter scale) and most barely perceptible.
One of the strongest quakes to hit southern Victoria occurred in September 1932 when the peninsula was rocked by a 6.0 quake with its epicentre at Mornington. Many buildings were damaged but no lives lost.
The earthquake was probably on the Selwyn Fault, a major fault that has thrust Mornington Peninsula up and Port Phillip down. It has been active for millions of years, and has a total accumulated vertical displacement of almost one kilometre.
Professor Sandiford says Melbourne people live in a relatively stable geological area. "For example, Sumatra, where the earthquake and tsunami of Boxing Day 2004 caused major destruction and loss of life, is 120 times more active than greater Melbourne."
Nevertheless, Selwyn Fault rattles the region with a 7.0 quake every 1800 years and no one knows when this last occurred. "A magnitude 7 can do lots of damage, especially if it is shallow [less than 10 kilometres below the surface]," Prof Sandiford said.
He says very big quakes can only occur on tectonic plate boundaries like the one near Sumatra. "The magnitude 9 quake in Sumatra was caused by a 1000-kilometre long faultline slipping about 10 metres. Selwyn is about 100 kilometres long, stretching from Bass Strait south of Cape Schanck to Dandenong South."
It is the most significant fault in the region but a faultline map shows 14 between the western side of Port Phillip and Western Gippsland including 11 criss
crossing the peninsula and Western Port.
The best place to see evidence of Selwyn Fault is on the coast at the end of Gulls Way in Frankston South, near the border of Frankston and Mornington Peninsula Shire. The area is a well-known landslip zone.
"My research is about trying to understand more of the framework of earthquakes," Professor Sandiford said. "Firstly by studying the dynamics of the plate, what sort of forces are applied to it to keep it moving, and how those forces result in the stress distribution we can infer from known earthquakes."
He says the second approach is to look at the landscape to try to understand geological history. "Many Australians think the continent is old and has little geological activity, but this is false."
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