In 2016, Geoscience Australia revised the magnitudes of some of Australia's historical earthquakes as part of an international project to reassess the magnitude estimates of earthquakes around the globe. Large shallow earthquakes also happen where two plates are pulling apart with the creation of new oceanic crust along mid-ocean ridges and on the transform faults that intersect them.This project aimed to revise historic earthquake measurements to more accurately reflect their true size based on modernised measuring techniques. Shallow intraplate earthquakes occur in the relatively stable interior of continents away from plate boundaries.
The underground surface along which the rock breaks and moves is called a fault plane.
Most of the 40 samples per second data are delivered within 30 seconds of being recorded at the seismometer to Geoscience Australia’s central processing facility in Canberra through various digital satellite and broadband communication systems. Most masonry structures destroyed, together with their foundations. Cement and asphalt roads and pavements badly cracked or thrown into waves. Sand and mud on beaches and flat land moved horizontally. Water from rivers, lakes, and canals thrown up on the banks. Practically all works of construction destroyed or greatly damaged. The intensity with which the earthquake is felt may also be higher on hilltops.
Seismic data are also provided by overseas Governments which have national seismic networks. Sand and mud ejected in alluviated areas, with the formation of earthquake fountains and sand craters. Some well-built wooden buildings and bridges seriously damaged. Structures designed to resist lateral forces of about 0.1g, such as those satisfying the New Zealand Model Building By-law, 1955.
The International Seismological Centre led this project which reassessed the location and magnitude of approximately 20 000 historical earthquakes worldwide as part of an effort to extend and improve their database of seismic events. Australia's largest recorded earthquake was in 1988 at Tennant Creek in the Northern Territory, with an estimated magnitude 6.6, but it occurred in a sparsely populated area.
What does this information add to our understanding of Australian seismicity? A magnitude 6.5 earthquake at Meckering in 1968 caused extensive damage to buildings and was felt over most of southern Western Australia.
Seismographs, such as the Teledyne Geotech Helicorder pictured, were used in the past to detect earthquake activity and relied on a mechanical system to record the seismic energy in the Earth onto paper.