Types of Stations and Installations

Seismic recording stations are not limited to just permanent primary sites. The Geophysical Network is also responsible for the installation, operation and maintenance of a secondary network: the Joint Urban Monitoring Project (JUMP). Stations that comprise JUMP are located close to population centres with 50 000 people or more. This secondary network of stations located around urban Australia are used to improve the response to Australian earthquakes in these areas through improved awareness of potential risks.

The Geophysical Network is also responsible for the operation of temporary sites for recording aftershocks and earthquake swarms following significant earthquakes. This information is used by Geoscience Australia to improve the national set of hazard maps for Australia. Temporary short-term operations have also been set up in response to natural disasters in the Australian region. One such short-term operation in Papua New Guinea was used to improve hazard maps and provide technical expertise for the Rabaul Volcanological Observatory Project.

The Geophysical Network is responsible for bringing into Geoscience Australia data from over 177 local and international stations including two seismic arrays (stations made up of several smaller stations), two infrasound arrays and a hydroacoustic station. We are principally responsible for the operation and maintenance of 61 of these stations and approximately 20 temporary stations that may be located around the country at any one time.

Map of installation locations in the Asia-Pacific, including approximately 40 stations in continental Australia, 2 in Antarctica, 2 in Papua New Guinea, 2 in the Indian Ocean Territories, and 4 on islands in the South Pacific.

Google maps image of current
network configuration

Installation

Our installations vary from small aftershock deployments - consisting of an all-in-one sensor and digitizer in a box, placed in a shallow pit and powered by a 12V battery - to km-scale arrays of permanent borehole seismometers with dedicated power and communication infrastructure. We are also responsible for providing assistance during installations of other types of sensors that measure geodetic, geomagnetic, tilt, infrasonic and hydroacoustic data.

Temporary installations

Geophysical Networks varied technical expertise has been utilised by neighbouring countries to improve their own networks or to respond to natural disasters such as earthquakes and volcanic eruptions. Aftershock Deployments are typically installed in the first couple of hours or days after a significant seismic event and are installed in less than 100km of the event's epicentre. These installations are usually less permanent and are usually removed after several weeks or once the activity has been assessed to have returned to normal levels. Data from this type of installation is recorded within the station and is analysed once the station is decommissioned.

Another type of temporary installation is conducted when searching for a new permanent location. This type of installation is used in a site survey where equipment is installed to check for hidden sources of noise that may 'mask' or 'drown' the seismic trace. These noises may come from roads, airports, railways, mining, and other significant urban developments. Smaller, more localised interference can come from electric fences, trees and power poles as well as ocean waves, running water and prevailing winds.

Permanent installations

Our more permanent installations are the Australian National Seismograph Network (ANSN) stations and the Joint Urban Monitoring Program (JUMP) stations. They are similar in technique and equipment to our temporary installations.

In the past, installations usually consisted of two green 30 litre boxes with one side containing the power (two car batteries and a charger) and the other the digitiser and communications. Power usually consisted of two solar panels on a short mast between the two boxes or came in via mains power. Communication was via an analogue landline system which, for the ANSN stations, was streamed real-time with a data delay of several minutes whilst JUMP stations were dialled into once a day and sections with possible events downloaded.

The installation of ANSN and JUMP stations starts with a site survey to determine an appropriate location. Land ownership and native title clearances are obtained before any civil works can begin.

Current best practice design principles call for the burial of a vault which is designed to reduce the effects of localised noise interference from wind as well as maintaining a thermally stable environment for the sensor. Large variances in temperature can cause the signal to sway with the large diurnal temperature changes occurring within Australia. A small sensor footing pier is constructed that stands above the bottom of the vault and is isolated from its walls to reduce the likelihood of inundation and noise interference. The other aim is to get this footing onto hard subsurface to produce good coupling with the bedrock. This increases the sensitivity of the instrument and reduces the cushioning effect caused by compactable material. The vault is then constructed using sections of concrete pipe, sealed with a water resistant coating and then backfilled with soil.

The equipment hut is constructed from prefabricated concrete walls and consists of a battery room and an equipment room. The equipment room is joined to both the battery room and the vault via conduits and provides the housing for the digitiser, field processor, communications equipment (such as modems) and power equipment (such as chargers, regulators, converters and earthing). A tropical roof and shade louvres on the outside of the building help reduce the extreme temperatures that some of these huts experience.

Power comes in through either mains power from the local grid or through solar panel arrays. Communications can be via ADSL, NextG Mobile Modems or Satellite Communications depending on location and access.