The use of Network code for Arrivals at the ISC and in ISCLoc
The ISC has implemented the use of the IASPEI station coding standard ADSL (Agency.Deployment.Station.Location.Channel) from data year 2021.
This allows the use of many additional stations and complements the increasing usage of reporting formats, such as QuakeML, where more extensive station information is a requirement. As of 2024, 27 agencies report data to the ISC, in a format that includes a network code (this is the equivalent of deployment in ADSL standard). Currently we use stations that are included in the FDSN registry https://www.fdsn.org/ in addition to the International Station Registry (IR) which is hosted by the ISC, both are the equivalent of Agency in ADSL. Any agencies established in the future will be able to fit within this framework as required. To ensure users can utilise all station information contained within the ISC Bulletin, station coordinates and agency/network codes are included in ISF 2.1. It also allows for greater attribution of the data reported in the ISC Bulletin.
The map below shows the location of FDSN registered stations (1848) that are not in or very near to an IR registered station. These are counted in a similar way to the IR, that is, the new stations are positions that are at least 2 km from any other station. The number would be much higher if multiple networks and channels were included in the count.
The below plot shows a step change in secondary azimuthal gaps of the ISC hypocentres from 2021 onwards, this improvement is a direct result of the switch to ADSL.
All the progams used by the ISC, the locator ISCLoc, database and public search tools have all had to be changed to deal with network codes. A new public version of the locator will be released in 2024.
Details of all stations used in the ISC Bulletin can be found here stations
