Task 2: To map seismically active minifaults of the seismic fault systems

Start: March 1996 (month 1)
End: February 1998 (month 24)
Responsible partner: IMOR.DG
Cooperative partners: UUPP.DGEO, NVI

Provided the time accuracy of the seismic data of the SIL system, close to 1 millisecond, active faults can be mapped with accuracy of the order of 10 meters. Fault plane solutions based on spectral amplitudes of P- and S-waves are then used as a part of the mapping to reveal the sense of the fault motion. Several special fault mapping efforts have been carried out related to ongoing earthquake sequences in other parts of the country, so gradually information on fault arrangement in different parts along the plate boundary is being collected [].

Very significant results have been obtained in using seismological data for mapping active earthquake faults in the Tjörnes fracture zone at the north coast of Iceland (Figure 3).

  

Figure: Mapped faults within the Tjörnes fracture zone off the north coast of Iceland. Black lines indicate faults mapped with conventional reflection seismic methods or by direct observations on-land. Red lines are 60 active fault segments mapped using accurate relative locations of microearthquakes recorded by the SIL network. Seismic stations are denoted by triangles. Grey patches are fissure swarms in the Eastern volcanic zone. The depth contour interval is 100 m.

The method used is a multievent method based on cross-correlating similar signals at the same seismic station [,].

Similar research has been carried out for the Hengill triple junction in SW-Iceland. Fault plane solutions of more than 20.000 earthquakes have been studied in the area and faults have been mapped by multievent location procedure (Figure 4) [].