Modern ground failure in the Garlock fault zone, Fremont Valley, California

Abstract

Research Article| May 01, 1988 Modern ground failure in the Garlock fault zone, Fremont Valley, California EARL H. PAMPEYAN; EARL H. PAMPEYAN 1U.S. Geological Survey, 345 Middlefield Road Menlo Park, California 94025 Search for other works by this author on: GSW Google Scholar THOMAS L. HOLZER; THOMAS L. HOLZER 1U.S. Geological Survey, 345 Middlefield Road Menlo Park, California 94025 Search for other works by this author on: GSW Google Scholar MALCOLM M. CLARK MALCOLM M. CLARK 1U.S. Geological Survey, 345 Middlefield Road Menlo Park, California 94025 Search for other works by this author on: GSW Google Scholar GSA Bulletin (1988) 100 (5): 677–691. https://doi.org/10.1130/0016-7606(1988)100<0677:MGFITG>2.3.CO;2 Article history first online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation EARL H. PAMPEYAN, THOMAS L. HOLZER, MALCOLM M. CLARK; Modern ground failure in the Garlock fault zone, Fremont Valley, California. GSA Bulletin 1988;; 100 (5): 677–691. doi: https://doi.org/10.1130/0016-7606(1988)100<0677:MGFITG>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Modern ground failures, ranging from renewed displacement on 2.5-km-long fault scarps to 1-km-long tension cracks, occur in Fremont Valley, California. Most of the failures formed along pre-existing Holocene fault scarps that are part of the tectonically active Garlock fault system. The failures began to form in the 1960s and currently affect an area of ∼17 km2 that is coincident with ground-water-level decline induced by pumping for crop irrigation. Several observations indicate that these failures were caused by water-level decline rather than natural tectonism. First, modern ground failure began after water level started to decline and was restricted to the area affected by decline. Land subsidence was associated with this decline and appears to be caused by aquifer compaction. Second, geodetic monitoring from 1977 to 1982 of faults near the center of the cone of depression demonstrated that fault creep occurred during periods of seasonal water-level decline and stopped during periods of seasonal water-level recovery. By contrast, faults near the margin of the cone of depression, where water levels declined at a constant rate, moved at a steady rate. Third, surface strain fields near failures suggest that subsurface fault-associated deformation was restricted to aquifer-level depths. And fourth, seasonal rebound of the land surface across one fault was caused by elastic expansion of the aquifer system that was induced by large seasonal water-level recovery. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.