Imaging an Active Normal Fault in Alluvium by High-Resolution Magnetic and Electromagnetic Surveys

Abstract

Research Article| March 01, 2002 Imaging an Active Normal Fault in Alluvium by High-Resolution Magnetic and Electromagnetic Surveys PETER C LA FEMINA; PETER C LA FEMINA 1Center for Nuclear Waste Regulatory Analyses, Southwest Research Institute, 6220 Culebra Road, San Antonio, TX 78238-5166 Search for other works by this author on: GSW Google Scholar CHARLES B CONNOR; CHARLES B CONNOR 1Center for Nuclear Waste Regulatory Analyses, Southwest Research Institute, 6220 Culebra Road, San Antonio, TX 78238-5166 Search for other works by this author on: GSW Google Scholar JOHN A STAMATAKOS; JOHN A STAMATAKOS 1Center for Nuclear Waste Regulatory Analyses, Southwest Research Institute, 6220 Culebra Road, San Antonio, TX 78238-5166 Search for other works by this author on: GSW Google Scholar DAVID A FARRELL DAVID A FARRELL 1Center for Nuclear Waste Regulatory Analyses, Southwest Research Institute, 6220 Culebra Road, San Antonio, TX 78238-5166 Search for other works by this author on: GSW Google Scholar Environmental and Engineering Geoscience (2002) 8 (3): 193–207. https://doi.org/10.2113/8.3.193 Article history first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation PETER C LA FEMINA, CHARLES B CONNOR, JOHN A STAMATAKOS, DAVID A FARRELL; Imaging an Active Normal Fault in Alluvium by High-Resolution Magnetic and Electromagnetic Surveys. Environmental and Engineering Geoscience 2002;; 8 (3): 193–207. doi: https://doi.org/10.2113/8.3.193 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search nav search search input Search input auto suggest search filter All ContentBy SocietyEnvironmental and Engineering Geoscience Search Advanced Search Abstract High-resolution geophysical investigations can improve paleoseismic studies and the characterization of fault zones. Here, forward modeling of detailed magnetic data indicates that 60–70 m of vertical separation occurred on the South Crater Flat fault (SCFF), Nevada, since the eruption of Pliocene basalt approximately 3.75 Ma. The average throw rate on the SCFF, therefore, is 0.017 ± 0.003 mm/year, and the average slip rate, assuming fault plane dips of 55°–65°, is 0.02 ± 0.003 mm/year during this interval. These values are approximately one order of magnitude greater than Quaternary slip rates derived from trench studies of alluvial stratigraphy across the fault and are in agreement with slip rates derived for the same period on nearby faults. In addition, these surveys reveal several synthetic and antithetic normal faults west of the SCFF and a decrease in vertical displacement on the SCFF from north to the south. A 140- to 200-m-wide, 1.5- to 2.5-milliSiemens (mS)/m electrical conductivity anomaly parallels the fault zone in the alluvial wedge of the hanging wall. This anomaly correlates with active drainageways and reflects lateral variations in allostratigraphy caused by Quaternary slip on the SCFF. These combined results indicate that displacement has been distributed across several faults and that the long-term average slip rate (Pliocene to present) is higher than Quaternary slip rates derived from trench studies alone. Thus, these geophysical methods provide an areal and temporal perspective on the fault zone that can augment traditional fault characterization techniques. You do not currently have access to this article.