Methods

The database for the modelling are the seismicity, deformation, strain and stress data existing already and being gathered in future in the measuring efforts of the proposers to this research project. A long historical record of earthquakes larger than 6 is available for events since 1700 and instrumental data are available from 1926 on. Starting 1990, data from the SIL seismic network complete down to magnitude 0 within the test site can be used. Furthermore, the model calculations will make use of data on crustal deformation, especially on distance changes measured by geodimeters and GPS techniques. Moreover strain changes are recorded by volumetric borehole strainmeters. In general, it is based on the current state of knowledge of seismotectonics of Iceland and the interpretations of crustal strain and movements in the region.

The objectives of these investigations are:

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A better understanding of the distribution of seismicity in space and time, its clustering and migration in Iceland.

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To seek a detailed explanation for the relation between the left-lateral strike direction of the SISZ and the fact that after historical earthquakes new cracks were often created following the complementary N-S right-lateral strike direction.

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To make a contribution to the intermediate-term earthquake prediction in this populated and economically important region of Iceland.

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To provide models for the joint interpretation of the data gathered in the common research programme proposed here.

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To compare models of stress fields at SIL to those for stress fields in other regions, e.g. the North Anatolian fault zone.

On a wider scope, more insight in the relation of seismic and volcanic activity is envisaged as well as into the possibilities of earthquake prediction. The situation on Iceland is very favourable for both, as there are volcanos and longer faults. Concerning scale, the SIL area fills a gap between small experiments in the laboratory and investigations in mines on one hand and the research on large areas as the North Anatolian fault or the San Andreas fault, on the other. Thus, the transfer of results from one scale to another might get easier.

The forward modelling of stress fields will be done by applying static dislocation theory to geodetic data and data obtained through seismic moments from seismograms. It allows to calculate displacements, strain and stresses due to double-couple and extensional sources in layered elastic and inelastic earth structures. Besides the change in displacement during the event, the changes caused by the movement of plates can be included.