OROGENESIS AND DEEP CRUSTAL STRUCTURE—ADDITIONAL EVIDENCE FROM SEISMOLOGY1

Abstract

Research Article| May 01, 1954 OROGENESIS AND DEEP CRUSTAL STRUCTURE—ADDITIONAL EVIDENCE FROM SEISMOLOGY1 HUGO BENIOFF HUGO BENIOFF CALIFORNIA INSTITUTE OF TECHNOLOGY, PASADENA, CALIFORNIA Search for other works by this author on: GSW Google Scholar Author and Article Information HUGO BENIOFF CALIFORNIA INSTITUTE OF TECHNOLOGY, PASADENA, CALIFORNIA Publisher: Geological Society of America Received: 09 Feb 1953 First Online: 02 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Copyright © 1954, The Geological Society of America, Inc. Copyright is not claimed on any material prepared by U.S. government employees within the scope of their employment. GSA Bulletin (1954) 65 (5): 385–400. https://doi.org/10.1130/0016-7606(1954)65[385:OADCSE]2.0.CO;2 Article history Received: 09 Feb 1953 First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation HUGO BENIOFF; OROGENESIS AND DEEP CRUSTAL STRUCTURE—ADDITIONAL EVIDENCE FROM SEISMOLOGY. GSA Bulletin 1954;; 65 (5): 385–400. doi: https://doi.org/10.1130/0016-7606(1954)65[385:OADCSE]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 Seismic evidence indicates that the principal orogenic structure responsible for each of the great linear and curvilinear mountain ranges and oceanic trenches is a complex reverse fault. A study of eight regions in which orogenic activity is in progress reveals that these great faults occur in two basic types, here designated oceanic and marginal. Oceanic faults, situated within the oceanic domain, extend from the surface to depths of 550 to 700 km. They exhibit an average dip of 61°. Their elastic strain-rebound characteristics show that these faults are composed of two separate mechanical units—a shallow component extending from the ocean bottom to a depth of roughly 60 km, and a deeper component extending to the 700km crustal boundary. The marginal faults situated along the continental margins occur in dual and triple forms. The dual faults comprise a shallow member extending from the surface to a depth of approximately 60 km and an intermediate member extending to a depth of 200 to 300 km. The average dip is 33°. The marginal triple form is similar to the dual down to the 300 km level. At this depth the dip changes abruptly to 60° to form a third component extending down to the 650± km crustal boundary. The elastic strain-rebound characteristics of the marginal faults indicate that the components of these structures also move as separate units, although in South America the two lower elements exhibit some evidence for mechanical coupling. In the continental domain the 300 km level thus represents a tectonic discontinuity not as yet revealed by seismic wave-propagation studies but which is apparently the lower boundary of the continents. Since the oceanic faults and the deep components of the marginal faults have the same average dip (61°) it may be assumed that both are fractures in a single, continuous mechanical structure subject to a single stress system. The different average dip (33°) of the marginal intermediate fault components suggests that they occur in a structure mechanically distinct from the deep oceanic and continental layer and that they are activated by a different stress system. A hypothesis offered for the origin of the volcanoes associated with the faults assumes that the source of volcanic energy is heat produced in the fault rocks by the inelastic components of the repeated to-and-fro strains involved in the generation of the sequences of earthquakes and aftershocks. 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.