Feldbiss fault.
Composite source NLCS002 mostly corresponds with the east-dipping Feldbiss fault s.s. This fault has been mapped from NE of the city of Aachen (DE) in the SE to at least the village of Born (NL) in the NW, close to the Belgian/Dutch border (Figure S3). However, we draw the source only up to the city of Sittard (NL), where it intersects the short N-S oriented fault that also defines the termination of BECS001. NW of this intersection, the fault still has a clear geomorphic expression (Michon and Van Balen, 2005) and has even been exposed in a paleoseismic trench (Houtgast et al, 2005), but the distance between the Feldbiss and Geleen faults drops below 2 km, suggesting that both faults are linked at depth. Towards the SE, the Feldbiss fault terminates near the intersection with the more or less perpendicular Variscan thrust front. However, another fault appears south of the Variscan front: the Münstergewand fault. This fault has clearly been active during the Quaternary according to the map of Knapp and Hager (1980), although its total offset seems to be reduced compared to the Feldbiss fault (Ahorner, 1962), but this has not been quantified. Because the distance between both faults is less than 2 km, we include this fault also in source NLCS002. It cannot be excluded, however, that the gap in between both sections represents a segment boundary (structural and/or behavioral).
| Fault section | Trench site | Year | Institute | Reference |
|---|---|---|---|---|
| Feldbiss fault | Hillensberg | 2001 | GDNRW | Skupin et al. (2008) |
Houtgast et al. (2002) report offsets of 25.5 m and 26.7 m for the base of the Geertruid 2 terrace (c. 1100 kyr BP) on the Feldbiss fault and 1st NE Main fault, respectively. As we assume that both faults are part of seismic source NLCS002, this corresponds to a vertical displacement rate of 0.047 mm/yr. The map of Ahorner (1962) shows offsets of up to 30 m for the base of the Upper Main Terrace Sequence (“Ältere Hauptterrassen”), which was deposited since ~2.58 Ma in the Lower Rhine Embayment. However, comparison with the more detailed map of Felder et al. (1989) indicates that this area is covered by the Noorbeek terrace, a terrace of the East Meuse that is c. 1.95 Ma old. This value would imply a vertical displacement rate of only 0.015 mm/yr, but this does not include the offset on the 1st NE Main fault, which was not mapped by Ahorner (1962). We therefore adopt a minimum deformation rate of twice this value (0.03 mm/yr), and a maximum rate of 0.05 mm/yr for source NLCS002.
| ID | Type of evidence | Offset (m) | Time period | Deformation rate (mm/yr) | Reference |
|---|---|---|---|---|---|
| 2 | Altitude-age record of Meuse River terraces on graben shoulder | Miocene – Pliocene (13 – ~3 Ma) | 0.003* | van den Berg (1994) | |
| 3 | Altitude-age record of Meuse River terraces on graben shoulder | ~3 Ma – present | 0.060* | van den Berg (1994) | |
| 36 | Displacement of base of Noorbeek terrace of East Meuse R. | 30 | Since 1.95 Ma | 0.015*** | Based on data from Ahorner (1962) and Felder et al. (1989) |
| 37 | Displacement of base of Geertruid-2 terrace | 25.5 + 26.7 | Since 1.1 Ma | 0.047 | Based on data from Houtgast et al. (2002) |
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