Posted by: ctbtonewsroom | November 13, 2015

Interview | Detecting Nuclear Explosions through Seismology – A geo-software used by the United Nations

The Comprehensive Nuclear-Test-Ban Treaty (CTBT) aims to ban all nuclear explosions, whether for military or peaceful purposes. The organisation mandated by the UN with verifying treaty compliance, the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO), uses the software SeisComP3, developed by the GFZ German Research Centre for Geosciences in Potsdam. This software was originally programmed for tsunami warning systems as part of the GFZ project German-Indonesian Tsunami Early Warning System (GITEWS1). Winfried Hanka, GFZ scientist and former head of the GITEWS earthquake monitoring subproject, explains the software’s performance and why it is suitable for CTBT verification.

GFZ: How did the SeisComP3 software come to the attention of the UN, and why did they decide to use it for CTBT verification?

Winfred Hanka: Since it was developed for the Indonesian tsunami warning system, SeisComP3 has become a worldwide standard seismic software package. It is used not only for tsunami warning or earthquake monitoring, but increasingly also for more local monitoring of the underground, for example at oil, gas or geothermal fields. In the context of CTBT verification, many National Data Centres (NDCs) are already using SeisComP3 in their role as national earthquake services. The NDCs must have argued for using SeisComP3 also for CTBT verification so as to avoid having to work with different software packages.

GFZ: What are the functions of SeisComP3 and why is it suitable for the CTBT verification?

Hanka: SeisComP3 registers and archives data in real time and streams it directly to users. The software then screens the data for seismic events, rapidly localising and quantifying them. Comparable to tsunami warning, the first main task for CTBT verification is general seismic event monitoring. While tsunami centres focus further on large events under the sea floor, the CTBTO and NDCs are more interested in known nuclear test sites or regions not known for seismic activity.

GFZ: Underground nuclear explosions are the challenging ones for CTBT verification.  What are distinctive seismic features of underground nuclear explosions and to what extent can they be distinguished from the seismic patterns of earthquakes?

Hanka: The seismic source of an underground nuclear explosion is very shallow, energy radiation is radial symmetric, and the energy spectrum isvery high frequency. The seismic signals are therefore usually simple, high-frequent, attenuate relatively fast and hardly show any dependency on direction.

Seismic  signals  of  strong  earthquakes  and  underground  nuclear  explosions  can  be distinguished relatively easily through waveform, spectral characteristics and seismic centre parameters. It becomes more difficult with smaller events near the detection threshold. The main problem here is to detect the event in the first place. Therefore, the CTBTO’s seismic network does not consist of individual stations but almost exclusively of particularly sensitive seismic arrays. Arrays consist of many interconnected individual stations within two to three kilometres distance. This setup requires special software modules for data analysis.

For very small signals, for example nuclear tests in the low single-digit kiloton range or even below one kiloton, the standard discrimination procedures may eventually not work2. Then it may become necessary to carry out on-site inspections, as envisaged by the CTBT for suspicious cases.

GFZ: SeisComP3 was mainly developed by the GFZ spin-off gempa. How and why has this company been established and what are its other fields of activity?

Hanka: During the GITEWS-Project, it became clear how complex a tsunami warning system’s seismological componentis, and how much effort it takes to maintain and further develop it. So the idea came up to establish a company which would exercise these functions for Indonesia, the GFZ and other users. This idea was implemented in 2008 by the SeisComP3 developers Bernd Weber and Jan Becker, who were both involved in GITEWS. They founded the gempa GbR (later GmbH). Apart from providing services and upgrading SeisComP3 and other tsunami-warning related software, gempa also offers software installation and training worldwide. Also construction surveillance in earthquake prone areas is becoming a business area.

GFZ: How do GFZ scientists and gempa cooperate on SeisComP3?

Hanka: New software modules are developed jointly, with GFZ’s focus more on methods andgempa’s on implementation. Gempa also services GFZ’s IT infrastructure for servicing the SeisComP3 software, supports the user community and assists GFZ in operating the GEOFON3 datacentre and seismological centre.

GFZ: What are the next steps in the development of the software used by the CTBTO as “Extended NDC-in-the-box”?

Hanka: GFZ is not directly involved in that project so we are not aware of all details. Generally, it seems that specialized software already used at the CTBTO or at NDCs is integrated into or connected to SeisComP3.

Interview by Ariane Kujau

Notes:

  1. The German-Indonesian Tsunami Early Warning System GITEWS is a German Federal Government project, coordinated by the GFZ, for the establishment of a tsunami early warning system for the Indian Ocean region. Germany cooperated with Indonesia, one of the most endangered regions in the Indian Ocean due to its proximity to the seismically active Sunda Arc.
  2. [Comment CTBTO]: Even the smallest of the three announced nuclear tests by the Democratic People’s Republic of Korea in 2006 (4.1 magnitude) was confidently detected by 22 CTBTO seismic stations. At the time, the network was still far from completion.
  3. GEOFON contributes to basic seismological research as well as to earthquake and tsunami risk mitigation. It is a part of GFZ’s the Modular Earth Science Infrastructure (MESI) and offers a variety of services in the field of global networks, data storage, allocation and communication. It offers a seismological infrastructure for research on thecomplex system Earth and thus contributes to earthquake and tsunami hazard mitigation.

This interview was originally published in German on the website of the GFZ German Research Centre for Geosciences, Potsdam, Germany


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