Slip Tendency Analysis

The occurrence of earthquakes should be avoided in the area of nuclear waste repositories. Since earthquakes preferentially occur on tectonic faults when they are reactivated under the right stress field, an estimation about the reactivation potential of the faults is important. Such an estimation is providede by the so-called slip tendency, which is calculated from the ratio of the maximum resolved shear stress to the normal stress on the fault surface. The SpannEnD-Germany model provides the stress tensor needed to calculate the shear and normal stresses.

In addition, information is required on the geometry of the tectonic faults for which the slip tendency is to be calculated. Based on various criteria, 60 faults were identified that are particularly relevant in the context of the SpannEnD project. Simple geometries were created for these faults depending on whether they are normal faults, thrust faults or strike slip faults. For a selection of the 60 faults, additional seismic sections and geological sections were researched, which were used to create more realistic geometries.


Simple geometries were created for the 60 selected faults. The faults extend to the base of the lower crust.
More complex geometries were created for a selection of the 60 faults using seismic sections and geological profiles

The stress state from the Germany model is mapped onto the created fault geometries and used for the calculation of the slip tendency of the faults. In general, the values lie between 0 and 1. The greater the calculated slip tendency, the more likely the reactivation of the fault and thus the occurrence of an earthquake.

Slip tendency has been calculated for 60 selected faults. The faults are color coded by their slip tendency. The calculation has been based on an assumed hydrostatic pore pressure.

The slip tendency can be compared with the spatial distribution of earthquakes. The map shows the slip tendency of the 60 selected faults at a depth of 8 km, where a majority of earthquakes occurs. In general, regions with increased seismicity correlate with regions of increased slip tendency.

The map shows the slip tendency of 60 selected faults in a depth of 8 km. Furthermore, earthquakes that occurred in the past (Grünthal & Wahlström, 2012) are displayed and color-coded by their moment magnitude.

Contact: Luisa Röckel

References:

Shapefiles Countries: © EuroGeographics for the administrative boundaries

Grünthal, G., and R. Wahlström (2012): The European-Mediterranean Earthquake Catalogue (EMEC) for the last millennium. J. Seismol., 16(3), 535-570, https://doi.org/10.1007/s10950-012-9302-y

Morris, Alan; Ferrill, David A.; Henderson, D. Brent (1996): Slip-tendency analysis and fault reactivation. In: Geology 24 (3), S. 275. https://doi.org/10.1130/0091-7613(1996)024%3C0275:STAAFR%3E2.3.CO;2