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Localization of Seismic Sources

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3D tomographic models of the earth for improvement of seismic sources localization

Tech Area / Field

  • OBS-GEO/Geology/Other Basic Sciences

Status
8 Project completed

Registration date
27.03.2001

Completion date
15.12.2006

Senior Project Manager
Malakhov Yu I

Leading Institute
Institute of Geology and Mineralogy, Russia, Novosibirsk reg., Novosibirsk

Supporting institutes

  • VNIITF, Russia, Chelyabinsk reg., Snezhinsk\nGeophysical Survey, Russia, Novosibirsk reg., Novosibirsk

Collaborators

  • GeoForschungsZentrum Potsdam, Germany, Potsdam\nPrinceton University / Department of Geosciences, USA, NJ, Princeton\nUniversité de Nice Sophia Antipolis / Geosciences Azur Laboratory, France, Valbonne

Project summary

The aim of the project is construction of high-resolution 3D tomographic models of the earth for improvement of seismic sources localization (determination of coordinates in 3D and origin time). The results of the project will be used for the nuclear explosion control, as well as for investigation of active seismic zones.

There is an important problem connected with strong mislocation of seismic sources. In most cases the error is related to roughness of standard computation methods based only on 1D earth’s models. It can be estimated that the influence of the 3D inhomogeneities in the earth on the travel time and ray path can be sufficient to cause a big localization error. That is why consideration of 3D seismic structures computed by seismic tomography can help to reduce sources mislocation.

Realization of the project implies construction of new high-resolution 3D seismic models of the earth at the global and regional scales with the use of the tomographic approaches developed by the authors. Most detailed and reliable results will be obtained in areas with high regional seismicity and dense seismological networks. However, the peculiarity of the project is that it makes possible investigation of so called “dumb” regions, where there are neither stations nor earthquakes. This is especially important for monitoring of nuclear explosions in oceans and large continental platforms. The obtained 3D seismic models will be used for correction of position and origin time of seismic events. Precise published information about strong artificial explosions will be used for verification of the obtained velocity models and algorithms developed.

One part of the project consists in construction of detailed 3D structure of the crust (down to the depth of 40-70 km) with simultaneous relocalization of seismic sources. This investigation will be based on the regional seismicity recorded by local networks (the Local Scheme). A user-orientated program will be created for investigation of crustal structure in any area with sufficient number of earthquakes and stations. It will be realized in Baikal, Altai-Sayan and Tien-Shan regions.

The main result of the project will be creation of user-orientated programs for precise localization of sources with the account of 3D structure of the earth. The algorithms of ray tracing in continuous 3D media developed by the authors of the project will be used at this step. This program will be applied both for the nuclear explosion monitoring and localization of earthquake hypocenters. The latter will greatly contribute to seismic hazard estimation and earthquake prediction.

In addition to the applied goals, the project is of important value for the fundamental science. Detailed images of the earth interior will clear many questions connected with mantle dynamics and its influence on the evolution of the crust and the lithosphere. Moreover, investigation of seismic activity zones will provide rich material about mechanisms of earthquakes origin.

The project participants have big theoretical and practical basis for creation of tomographic algorithms and their application to real data. They have developed original schemes to study the earth interior at different scales using various sorts of data. Most of the project realization will be based on the existing algorithms created and tested by the participants. There are all necessary computer facilities for realization of large calculations required in the project.

The first collaborator, Prof Steve Roecker is a recognized specialist in development and practical realization of tomographic algorithms. He has created the original schemes, which are used by different researchers for investigation of the crustal structure in different parts of the world (for instance, in Tian Shan in the ISTC KR-155 project).

Another collaborator, Prof Guust Nolet, is known as one of the world leaders in theoretical and practical tomography. His monographs serve as handbooks for the most specialists in the world dealing with seismic tomography.


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