Earthquake
Page last updated:2 May 2025
What is an earthquake?
Earthquakes occur when rocks deep within the earth suddenly break and slip past one another. What we feel as earthquake vibrations and shaking (seismic waves) is the energy that propagates through the earth when the rocks break. The rocks break along pre-existing fractures, or zones of weakness known as a fault, or a fault plane.
The focus, or hypocentre, of an earthquake is the point where it originated within the Earth. The point on the Earth's surface directly above the hypocentre is called the earthquake epicentre.
The size or magnitude of earthquakes is a measure of the energy released by the earthquake and is determined by measuring the amplitude of the seismic waves recorded on a seismometer, together with the distance of that seismometer from the earthquake. These parameters are used in a formula which converts them to a magnitude. For every one unit increase in magnitude, there is roughly a thirty-fold increase in the energy released. For instance, a magnitude 6.0 earthquake releases approximately 30 times more energy than a magnitude 5.0 earthquake, while a magnitude 7.0 earthquake releases approximately 900 times (30×30) more energy than a magnitude 5.0.
Earthquake magnitude was traditionally measured on the Richter scale. It is often now reported as moment magnitude, which is calculated from seismic moment. The seismic moment of an earthquake is calculated using the area of the fault that ruptured, the strength of the rocks that slipped (the shear modulus), and the amount of slip along the fault during the earthquake.
Where do earthquakes occur?
No part of Earth's surface is immune from earthquakes, but some regions experience them more frequently than others. They are most frequent and largest at tectonic plate boundaries. They particularly occur around the margins of the Pacific Plate; for example in New Zealand, Vanuatu, the Solomon Islands, Papua New Guinea, Japan and the Americas, and also along the Indonesian islands arc, where the Australian Plate collides with the Eurasian Plate. Earthquake hypocentre depths in these collision zones can range from the surface to 700 km in depth.
Away from plate boundaries in intraplate regions, earthquakes are less frequent and do not follow easily recognisable patterns. Intraplate areas can be defined as either active intraplate closer to plate boundaries, or stable continental regions far from plate boundaries. Australia is considered a stable continental region, though the offshore of northern Western Australia is considered active intraplate as it is closer to the Indonesia – Australia plate collision zone.
Intraplate earthquakes generally originate at shallow depths (i.e. less than 20 km), but can still be of large magnitude. In 1811-1812 four earthquakes of estimated magnitude >7 occurred in the New Madrid region of the eastern United States (a stable continental region). More recently, the magnitude 7.7 2001 Bhuj earthquake in intraplate India killed more than 20,000 people (and active intraplate region).
Why do we get earthquakes in Australia?
The Australian plate is the fastest moving continental land mass on Earth and is colliding into the Pacific plate to Australia's north and east, and the Eurasian Plate to the northwest. This generates mainly compressive stress in the interior of the Australian continent, which is slowly building up across the plate as it moves northeast about 7 cm per year. Australia's earthquakes are caused by the sudden release of this stress when rocks deep underground break and move along a fault line. While some parts of the country are more likely to experience earthquakes than others, large earthquakes can occur anywhere across the continent, and without warning.
On average 100 earthquakes of magnitude 3 or more are recorded in Australia each year. Earthquakes above magnitude 5.0, such as the destructive 1989 Newcastle earthquake, occur on average every one-to-two years. 女女视频 every ten years Australia experiences a potentially damaging earthquake of magnitude 6.0 or more.
Australia's largest recorded earthquake was in 1988 at Tennant Creek in the Northern Territory, with an estimated moment magnitude of 6.6. It occurred in a sparsely populated area and resulted in damage to a major gas pipeline. A magnitude 6.5 earthquake at Meckering in 1968 caused extensive damage to buildings and was felt over most of southern Western Australia. These earthquakes are two of the eleven Australian earthquakes that created surface ruptures or fault scarps. These occur when the earthquake ruptures along a fault from depth all the way to the ground surface.
Over 400 fault scarps are mapped across Australia, these are termed . Most faults mapped by geologists in Australia are very old and non-active. However, neotectonic features are those with landscape evidence for large, often repeating, earthquakes over the last 5 to 10 million years and might therefore host large earthquakes into the future.
Field photograph of part of the fault scarp produced by the 14th October 1968 MW6.5 Meckering earthquake (photo credit Ian Everingham)
What is Geoscience Australia's role in reducing risk to Australians from earthquakes?
We provide earthquake data and scientific information to help Australians understand the consequences of earthquakes, which contributes to more resilient communities now and in the future. Our capability spans the earthquake value chain from maintenance of a national-scale monitoring network, to 24-hour monitoring and alerting, to national earthquake hazard and risk assessments.
We collaborate with a range of stakeholders in Australia and through Australia’s overseas aid program to apply this value chain to develop actionable earthquake risk information to support evidence-based decisions for disaster risk reduction.
We do this by:
- developing nationally consistent data, information and advice to enable informed decisions on preparedness and response to the impact of earthquakes
- advancing our understanding of Australia’s earthquake hazard through data collection and scientific research
- advancing our understanding of the earthquake vulnerability of Australia’s built environment to support mitigation and reduce the cost of disasters
- providing ongoing real-time monitoring, analysis and advice on significant earthquakes and potentially tsunamigenic earthquakes to help safeguard Australian and Indian Ocean communities.
To learn more about our work, access our latest data or hazard assessment tools, visit the Community Safety page.
How do we record earthquakes?
We monitor, analyse and report on significant earthquakes to alert the Australian Government, State and Territory Governments and the public about earthquakes in Australia and overseas.
Earthquakes are detected by scientific instruments called seismometers. The word seismo originates from the Greek word seismos which means to shake or move violently and was later applied to the science and equipment associated with earthquakes. Old paper seismometers relied on a mechanical system to record the seismic energy in the Earth onto rotating paper drums. In contrast, modern seismometers detect and convert any small movement in the Earth into an electrical signal for use in computer systems, as shown in the digital seismogram image of seven seismic sensors which detected the magnitude 7.2 earthquake in the Banda Sea, north of Australia on 24th June 2019.
Digital seismogram image of seven seismic sensors which detected the magnitude 4.5 earthquake near Hawker in the Flinders Ranges of South Australia on 11th January 2025. The tremors from this earthquake were felt in Adelaide.
Determining the location of an earthquake
The arrival times of the seismic waves at the seismometers, together with the locations of the seismometers and the speed at which the seismic waves travel to the seismometers are all used to “triangulate” the location of the earthquake. The location relies on models that estimate the speed at which seismic waves generated by earthquakes travel through the Earth. This location is also known as its focus or hypocentre which is represented by the latitude, longitude and depth below the surface.
How does 女女视频monitor earthquakes?
We monitor seismic data from more than 150 locations in Australia and in excess of 500 stations worldwide in near real-time, 24 hours a day, seven days a week. Data are delivered within 30 seconds of being recorded at the seismometer to our central processing facility in Canberra through various digital satellite and broadband communication systems.
Seismic data are also provided by overseas Governments which have national seismic networks. We use data provided by the Governments of New Zealand, Indonesia, Malaysia, Singapore and China and have access to data from global seismic networks provided by the USA, Japan, Germany and France. These networks, together with the International Monitoring System, also provide seismic data for tsunami warning purposes.
The seismic data are collected and analysed automatically and immediately reviewed by our Duty Seismologists.
As part of the Joint Australian Tsunami Warning Centre (JATWC), Duty Seismologists are also responsible for analysing and reporting within 10 minutes of the origin time of significant Australian earthquakes, or earthquakes which have the potential to generate a tsunami. An earthquake alert is then sent to our partner in the JATWC, the Australian Bureau of Meteorology, to determine tsunami advice and publish tsunami bulletins.
The parameters of all other earthquakes with a magnitude greater than 3.5 are generally computed within 20 minutes. The analysis includes an earthquake’s magnitude, origin time and date of the earthquake and the location of its hypocentre. Smaller earthquakes that are not detected by many seismometers are difficult to locate in real-time and, consequently, are located by Seismic Analysts during normal business hours.
Geoscience Australia's National Earthquake Alerts Centre
What are the impacts of earthquakes?
The size and intensity of the shaking caused by an earthquake depends on many factors, such as the magnitude, distance from the epicentre, depth, topography, and the local ground conditions.
In Australia, earthquakes with magnitudes of less than 3.5 seldom cause damage, and the smallest magnitude earthquake known to have caused fatalities is the magnitude Mw 5.4 (ML5.6) Newcastle earthquake in 1989. However, magnitude 4.0 earthquakes occasionally topple chimneys or result in other damage which could potentially cause injuries or fatalities.
Apart from causing shaking, earthquakes of magnitude 4.0 or greater can also trigger landslides, which can impact communities and infrastructure. The larger the magnitude of the earthquake, the bigger the area over which landslides may occur.
In areas underlain by water-saturated loosely packed sediments, large earthquakes, usually magnitude 6.0 or greater, may cause liquefaction. The strong ground shaking causes the sediment to lose its strength and stiffness. Subsidence from liquefaction can affect the foundations of structures and cause buildings to topple, allow sub-surface infrastructure to become buoyant and float to the surface, and the sediment might erupt at the surface from craters and fountains.
Undersea earthquakes can cause a tsunami, or a series of waves which can cross an ocean and cause extensive damage to coastal regions.
The destruction from strong earthquake shaking can be worsened in some parts of the world by fires caused by downed power lines and ruptured gas mains.
Large earthquakes are often followed by aftershocks, which can themselves be large enough to cause damage. The size and number of aftershocks generally decreases quickly with time after an earthquake, though in Australia aftershocks can continue for days, years, or even decades.
Some earthquakes, such as the 1968 Meckering earthquake in Western Australia, rupture along a fault from depth to the ground surface. This can cause significant damage, particularly to linear infrastructure which may cross the rupturing fault such as roads, pipes, power lines, trainlines, and large infrastructure such as dams, powerplants, and mines.
Earthquake effects, based on human observation, are rated using the Modified Mercalli (MM) intensity scale, which ranges from I (imperceptible) up to XII (total destruction) (see table below).
The Modified Mercalli Intensity (MMI) scale
| Intensity | Shaking | Description/Damage |
|---|---|---|
| I | Not felt | Not felt except by a very few under especially favorable conditions. |
| II | Weak | Felt only by a few persons at rest,especially on upper floors of buildings. |
| III | Weak | Felt quite noticeably by persons indoors, especially on upper floors of buildings. Many people do not recognize it as an earthquake. Standing motor cars may rock slightly. Vibrations similar to the passing of a truck. Duration estimated. |
| IV | Light | Felt indoors by many, outdoors by few during the day. At night, some awakened. Dishes, windows, doors disturbed; walls make cracking sound. Sensation like heavy truck striking building. Standing motor cars rocked noticeably. |
| V | Moderate | Felt by nearly everyone; many awakened. Some dishes, windows broken. Unstable objects overturned. Pendulum clocks may stop. |
| VI | Strong | Felt by all, many frightened. Some heavy furniture moved; a few instances of fallen plaster. Damage slight. |
| VII | Very strong | Damage negligible in buildings of good design and construction; slight to moderate in well-built ordinary structures; considerable damage in poorly built or badly designed structures; some chimneys broken. |
| VIII | Severe | Damage slight in specially designed structures; considerable damage in ordinary substantial buildings with partial collapse. Damage great in poorly built structures. Fall of chimneys, factory stacks, columns, monuments, walls. Heavy furniture overturned. |
| IX | Violent | Damage considerable in specially designed structures; well-designed frame structures thrown out of plumb. Damage great in substantial buildings, with partial collapse. Buildings shifted off foundations. |
| X | Extreme | Some well-built wooden structures destroyed; most masonry and frame structures destroyed with foundations. Rails bent. |
Source: Replicated from the
Magnitude vs Intensity
- Earthquake magnitude is related to the energy released over its ruptured fault area
- The intensity of an earthquake refers to the level of ground-shaking at a given location
- Earthquake intensity typically decreases with increasing distance away from an earthquake
- The Modified Mercalli Intensity (MMI) scale is commonly used to describe the damage and felt effects of an earthquake at a given location
- MMI is a qualitative assessment of earthquake effects on structures and people
- Earthquake magnitude is a quantitative measure based on physical recordings made on seismometers
Australia's largest historical earthquakes
The Australian continent has experienced many large earthquakes in the historical past. The 10 largest recorded earthquakes are listed in the table below. However, evidence preserved in the Australian landscape demonstrates that the continent has experienced much larger earthquakes in its pre-historical past. Some of these earthquakes are even represented in First Nations Dreaming stories (link to: https://www.abc.net.au/news/2021-09-25/ancient-earthquakes-cadell-fault-diverted-murray-river/100489426).
| Magnitude post-2016 revisions | Magnitude pre-2016 revisions | Location | Date |
|---|---|---|---|
| 6.6 | 6.7 | Tennant Creek, NT | 1988 |
| 6.5 | 6.9 | Meckering, WA | 1968 |
| 6.4 | 5.6 | Simpson Desert, NT | 1941 |
| 6.3 | 6.4 | Tennant Creek, NT | 1988 |
| 6.3 | 7.2 | Meeberrie, WA | 1941 |
| 6.2 | 6.3 | Collier Bay, WA. | 1997 |
| 6.2 | 6.3 | Tennant Creek, NT | 1988 |
| 6.1 | 6.2 | Cadoux, WA | 1979 |
| 6.1 | N/A | Petermann Ranges, NT | 2016 |
| 6.0 | 6.0 | West of Lake Mackay, WA | 1970 |
* The earthquakes listed above have epicentres on the Australian mainland or adjacent to the Australian coast.
To learn more about our work, access our latest data or hazard assessment tools, visit the Community Safety page.