The epicentre of a small earthquake was recorded just south of Picton, near the northern edge of Lake Nepean around 10:36pm.

It had a strength of 2.8 magnitude, a depth of 10 kilometres with so far 304 felt reports as of 8:25am Tuesday - with residents from Unanderra and Farmborough Heights noting on social media they too felt the earth move.

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Jonathan Bathgate, Senior Seismologist with Geoscience Australia, said our country typically records about 100 small tremors around magnitude 3 each year and "many many more in magnitude 2".

"In this area in particular, it is not uncommon to have earthquakes around this size," he said, referring to just inland of the Illawarra.

"Last year we recorded three magnitude 2's within 50 kilometres of this one and the year before something similar."

Dr Bathgate said the area has also had its share of larger events with a 4.8 magnitude earthquake in 1999, another at 5.5 in 1973, plus one near Bowral in 1961 measuring 5.8.

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"We're on a tectonic plate that's moving north at about seven centimetres every year and we're colliding with tectonic plates to our north," he said of the cause behind the tremor.

"The stresses from those collisions transfer back to within the plate, and those stresses build up across local fault lines. It then releases that stress through - generally small - earthquakes on a regular basis."

Monday's seismic activity follows two other earthquakes in the Southern Tablelands last week near Taralga (west of Wombeyan caves).

One of 2.6 magnitude felt last Tuesday night with a depth of 10 kilometres and another on Wednesday with a 2.0 magnitude and depth of 3 kilometres.

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