Differential compaction mechanism for earth fissures near Casa Grande, Arizona

Abstract

Research Article| October 01, 1982 Differential compaction mechanism for earth fissures near Casa Grande, Arizona ROBERT C. JACHENS; ROBERT C. JACHENS 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 Author and Article Information ROBERT C. JACHENS 1U.S. Geological Survey, 345 Middlefield Road, Menlo Park, California 94025 THOMAS L. HOLZER 1U.S. Geological Survey, 345 Middlefield Road, Menlo Park, California 94025 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1982) 93 (10): 998–1012. https://doi.org/10.1130/0016-7606(1982)93<998:DCMFEF>2.0.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 ROBERT C. JACHENS, THOMAS L. HOLZER; Differential compaction mechanism for earth fissures near Casa Grande, Arizona. GSA Bulletin 1982;; 93 (10): 998–1012. doi: https://doi.org/10.1130/0016-7606(1982)93<998:DCMFEF>2.0.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 Precise gravity measurements indicate that earth fissures or tension cracks caused by ground-water withdrawal within a 10-km2 area southeast of Casa Grande, Arizona, are associated with relief on the buried interface between the alluvial aquifer and underlying bedrock. All of the fissure zones; which have a cumulative length of >8.7 km, occur above either ridges or steps in the bedrock surface. Intersecting fissure zones overlie intersecting bedrock features, and the angle of intersection of the zones accurately reflects the angle between the bedrock features. These relations suggest that the fissures are forming in response to localized differential compaction caused by localized variations of aquifer-system thickness. Topographic profiles across fissures on undisturbed desert floor confirm differential compaction proportional to the variations in aquifer thickness. The occurrence of the fissures at points of maximum convex-upward curvature in profiles of both the topographic and buried bedrock surfaces indicates that the fissures result from tensile strains caused by bending of the strata above the buried bedrock features in response to the differential compaction. Tensile strains at failure are estimated to range from ∼ 0.02% to 0.2% on the basis of modeling of the bending process. 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.