Aeromagnetic Mapping Of Hydrologically Important Faults, Albuquerque Basin, New Mexico

Data from high-resolution aeromagnetic surveys over the Albuquerque basin show expressions<br>of numerous hydrologically important faults that offset basin fill or volcanic rocks, many of which were<br>previously unknown. The faults generally strike northerly and are commonly sinuous and linearly<br>extensive, up to 50 km in length.<br>Aeromagnetic profiles across the faults reveal a range of signatures, from symmetric curves with<br>one inflection point to asymmetric curves with multiple inflection points. All the fault signatures can be<br>explained by the juxtaposition of lithologic layers having different magnetic properties. The asymmetric<br>signatures are distinctive and indicate a thin magnetic layer on the upthrown side and a thick magnetic<br>layer on the downthrown side of the fault, called the "thin-thick layers" model. The thicker,<br>downthrown layer may have resulted from sedimentation related to growth faulting. The model may<br>indicate a concentration of possibly high-permeability, coarse-grained material on the downthrown side<br>of the fault. This is corroborated by a comparison of water-level data to aeromagnetic signatures over<br>two splays of the hydrologically important Hubbell Springs fault system. Therefore, aeromagnetic data<br>have potential for providing information on the causes of subtle changes in water level that are important<br>for siting individual water wells.