NORMAL AND STRIKE-SLIP FAULT INTERACTIONS: THREE FAULT TIPS ALONG THE QUATERNARY KANE SPRINGS WASH TRANSFER FAULT ZONE, SOUTHERN NEVADA

Fault interaction zones can foster fault propagation through linkage and relay structures or form structural boundaries hindering further fault propagation. Constraining potential fault linkage or propagation cessation is critical to seismic hazard analysis and tectonic models. In this study we document and analyze the structural distances, degrees of overlap and geometries of interaction of three ~20-65 km long Quaternary faults: the N-striking normal Coyote Spring fault (CSF); ENE-striking left-lateral Kane Springs Wash fault (KSWF); and N-striking normal Wildcat Wash fault (WWF), from N to S, respectively. The close 4-7 km spacing of the three fault tips provides an ideal example to study fault interaction models, particularly the less studied case of normal and strike-slip transfer faults that are at high angles to each other; a case that is rarely addressed by fault linkage models. Notably, these faults lie in the Southern Nevada Seismic Belt and are close enough to shake the Las Vegas metropolitan area and Alamo, NV. We used standard field mapping at 1:12,000 scale and satellite image analysis to document relative ages of Quaternary deposits, scarp locations and fault geometries, as follows. (1) The mapped area exposes Pleistocene and Holocene fans, remnant terraces and wash deposits. (2) Each fault has late Quaternary scarps. (3) Two ~N-S normal faults developed N of the KSWF. Projection of these faults along strike suggests that they represent the splaying of the CSF as it propagates toward the KSWF. The splay geometries suggest that the CSF bends SE as it approaches the KSWF. (4) The WWF branches into two strands. The eastern strand bends NE and links with the KSWF. The interaction with the western strand is accommodated by an off-fault process zone as it approaches the KSWF from the south. (5) The KSWF displacement can be traced southwestward between the CSF and WWF suggesting that the KSWF transfers strain between the CSF and WWF fault. These relations suggest that the WWF is hard linked and CSF is soft linked to the KSWF, these faults are active in the same time frame despite their different slip types, and the faults bend to accommodate the slip differences across their linkage zones. Consequently, future earthquake ruptures along these faults might pass onto another fault which increases the seismic hazard.