Rock Properties and Structure Within the San Andreas Fault Observatory
Total Page:16
File Type:pdf, Size:1020Kb

Load more
Recommended publications
-
Introduction San Andreas Fault: an Overview
Introduction This volume is a general geology field guide to the San Andreas Fault in the San Francisco Bay Area. The first section provides a brief overview of the San Andreas Fault in context to regional California geology, the Bay Area, and earthquake history with emphasis of the section of the fault that ruptured in the Great San Francisco Earthquake of 1906. This first section also contains information useful for discussion and making field observations associated with fault- related landforms, landslides and mass-wasting features, and the plant ecology in the study region. The second section contains field trips and recommended hikes on public lands in the Santa Cruz Mountains, along the San Mateo Coast, and at Point Reyes National Seashore. These trips provide access to the San Andreas Fault and associated faults, and to significant rock exposures and landforms in the vicinity. Note that more stops are provided in each of the sections than might be possible to visit in a day. The extra material is intended to provide optional choices to visit in a region with a wealth of natural resources, and to support discussions and provide information about additional field exploration in the Santa Cruz Mountains region. An early version of the guidebook was used in conjunction with the Pacific SEPM 2004 Fall Field Trip. Selected references provide a more technical and exhaustive overview of the fault system and geology in this field area; for instance, see USGS Professional Paper 1550-E (Wells, 2004). San Andreas Fault: An Overview The catastrophe caused by the 1906 earthquake in the San Francisco region started the study of earthquakes and California geology in earnest. -
Fault Rocks and Fault Mechanisms
Fault rocks and fault mechanisms R. H. SIBSON SUMMARY Physical factors likely to affect the genesis of the with the production of mylonite series rocks various fault rocks--frictional properties, tem- possessing strong tectonite fabrics. In some cases, perature, effective stress normal to the fault and fault rocks developed by transient seismic fault- differential stress--are examined in relation to ing can be distinguished from those generated the energy budget of fault zones, the main by slow aseismic shear. Random-fabric fault velocity modes of faulting and the type of fault- rocks may form as a result of seismic faulting ing, whether thrust, wrench, or normal. In a within the ductile shear zones from time to conceptual model of a major fault zone cutting time, but tend to be obliterated by continued crystalline quartzo-feldspathic crust, a zone of shearing. Resistance to shear within the fault elastico-frictional (EF) behaviour generating zone reaches a peak value (greatest for thrusts random-fabric fault rocks (gouge--breccia-- and least for normal faults) around the EF/OP cataclasite series--pseudotachylyte) overlies a transition level, which for normal geothermal region where quasi-plastic (QP) processes of gradients and an adequate supply of water, rock deformation operate in ductile shear zones occurs at depths of lO-15 km. SINCE LAPWORTH'$ (I885) description of the type mylonite from the Moine Thrust in NW Scotland, there have been many petrographic descriptions and classifications of the texturally distinctive rocks found associated with fault zones (e.g. Waters & Campbell 1935, Hsu 1955, Christie 196o , 1963, Reed 1964, Spry I969, Higgins 1971 ). -
Lithology and Internal Structure of the San Andreas Fault at Depth Based
1 1 Lithology and Internal Structure of the San Andreas Fault at depth based on 2 characterization of Phase 3 whole-rock core in the San Andreas Fault Observatory at 3 Depth (SAFOD) Borehole 4 By Kelly K. Bradbury1, James P. Evans1, Judith S. Chester2, Frederick M. Chester2, and David L. Kirschner3 5 1Geology Department, Utah State University, Logan, UT 84321-4505 6 2Center for Tectonophysics and Department of Geology and Geophysics, Texas A&M University, College Station, 7 Texas 77843 8 3Department of Earth and Atmospheric Sciences, St. Louis University, St. Louis, Missouri 63108 9 10 Abstract 11 We characterize the lithology and structure of the spot core obtained in 2007 during 12 Phase 3 drilling of the San Andreas Fault Observatory at Depth (SAFOD) in order to determine 13 the composition, structure, and deformation processes of the fault zone at 3 km depth where 14 creep and microseismicity occur. A total of approximately 41 m of spot core was taken from 15 three separate sections of the borehole; the core samples consist of fractured arkosic sandstones 16 and shale west of the SAF zone (Pacific Plate) and sheared fine-grained sedimentary rocks, 17 ultrafine black fault-related rocks, and phyllosilicate-rich fault gouge within the fault zone 18 (North American Plate). The fault zone at SAFOD consists of a broad zone of variably damaged 19 rock containing localized zones of highly concentrated shear that often juxtapose distinct 20 protoliths. Two zones of serpentinite-bearing clay gouge, each meters-thick, occur at the two 21 locations of aseismic creep identified in the borehole on the basis of casing deformation. -
Western States Seismic Policy Council Policy Recommendation 18-3
WESTERN STATES SEISMIC POLICY COUNCIL POLICY RECOMMENDATION 18-3 Definitions of Recency of Surface Faulting for the Basin and Range Province Policy Recommendation 18-3 WSSPC recommends that each state in the Basin and Range physiographic province (BRP), through consultation with state and federal geological surveys and other earthquake-hazard experts, define scientifically and societally relevant categories for recency of surface faulting (generally earthquake magnitude ≥M 6.5). WSSPC further recommends that in the absence of information to the contrary, all Quaternary faults be considered to have the recency of activity documented in the USGS Quaternary fault and fold database until more adequate data can be developed. Executive Summary Fault recency definitions are limited to the Quaternary because this period of geologic time is considered by the scientific community to be most relevant to paleoseismic studies of earthquake faults (Machette and others, 2004). The recency class of a fault is the youngest class based on the demonstrated age of most recent surface faulting. Latest Pleistocene-Holocene faults are included within the definition of late Quaternary faults, and both latest Pleistocene-Holocene and late Quaternary faults are included in Quaternary faults. Establishment/definition of surface-faulting recency categories are based on the ways that faults are portrayed on geologic maps and on the availability of geologic data in the BRP. Policy makers (owners, regulators, governmental agencies) should consult with state and federal geological surveys and other earthquake-hazard experts in using these recency categories and additional geologic data in developing definitions of hazardous faults to be considered in planning for development or infrastructure projects. -
Late Quaternary Faulting in the Kaikoura Region, Southeastern Marlborough, New Zealand
AN ABSTRACT OF THE THESIS OF Russell J. Van Dissen for the degree of Master of Science in Geology presented on February 15, 1989. Title: Late Quaternary Faulting in the Kaikoura Region, Southeastern Marlborough, New Zealand Redacted for privacy Abstract approved: Dr. Robert 8.0eats Active faults in the Kaikoura region include the Hope, Kekerengu, and Fidget Faults, and the newly discovered Jordan Thrust, Fyffe, and Kowhai Faults. Ages of faulted alluvial terraces along the Hope Fault and the Jordan Thrust were estimated using radiocarbon-calibrated weathering-rind measurements on graywacke clasts. Within the study area, the Hope Fault is divided, from west to east, into the Kahutara, Mt. Fyffe, and Seaward segments. The Kahutara segment has a relatively constant Holocene right-lateral slip rate of 20-32 mm/yr, and an earthquake recurrence interval of 86 to 600 yrs: based on single-event displacements of 3 to 12 m. The western portion of the Mt. Fyffe segment has a minimum Holocene lateral slip rate of 16 + 5 mm/yr .(southeast side up); the eastern portion has horizontal and vertical slip rates of 4.8+ 2.7 mm/yr and 1.7 + 0.2 mm/yr, respectively (northwest side up). There is no dated evidence for late Quaternary movementon the Seaward segment, and its topographic expression is much more subdued than that of the two western segments. The Jordan Thrust extends northeast from the Hope Fault, west of the Seaward segment. The thrust has horizontal and vertical slip rates of 2.2 + 1.3 mm/yr and 2.1 + 0.5 mm/yr, respectively (northwest side up), and a maximum recurrence interval of 1200 yrs: based on 3 events within the last 3.5 ka. -
Present Day Plate Boundary Deformation in the Caribbean and Crustal Deformation on Southern Haiti Steeve Symithe Purdue University
Purdue University Purdue e-Pubs Open Access Dissertations Theses and Dissertations 4-2016 Present day plate boundary deformation in the Caribbean and crustal deformation on southern Haiti Steeve Symithe Purdue University Follow this and additional works at: https://docs.lib.purdue.edu/open_access_dissertations Part of the Caribbean Languages and Societies Commons, Geology Commons, and the Geophysics and Seismology Commons Recommended Citation Symithe, Steeve, "Present day plate boundary deformation in the Caribbean and crustal deformation on southern Haiti" (2016). Open Access Dissertations. 715. https://docs.lib.purdue.edu/open_access_dissertations/715 This document has been made available through Purdue e-Pubs, a service of the Purdue University Libraries. Please contact [email protected] for additional information. Graduate School Form 30 Updated ¡ ¢¡£ ¢¡¤ ¥ PURDUE UNIVERSITY GRADUATE SCHOOL Thesis/Dissertation Acceptance This is to certify that the thesis/dissertation prepared By Steeve Symithe Entitled Present Day Plate Boundary Deformation in The Caribbean and Crustal Deformation On Southern Haiti. For the degree of Doctor of Philosophy Is approved by the final examining committee: Christopher L. Andronicos Chair Andrew M. Freed Julie L. Elliott Ayhan Irfanoglu To the best of my knowledge and as understood by the student in the Thesis/Dissertation Agreement, Publication Delay, and Certification Disclaimer (Graduate School Form 32), this thesis/dissertation adheres to the provisions of Purdue University’s “Policy of Integrity in Research” and the use of copyright material. Andrew M. Freed Approved by Major Professor(s): Indrajeet Chaubey 04/21/2016 Approved by: Head of the Departmental Graduate Program Date PRESENT DAY PLATE BOUNDARY DEFORMATION IN THE CARIBBEAN AND CRUSTAL DEFORMATION ON SOUTHERN HAITI A Dissertation Submitted to the Faculty of Purdue University by Steeve J. -
Composition, Alteration, and Texture of Fault-Related Rocks from Safod Core and Surface Outcrop Analogs
Pure Appl. Geophys. Ó 2014 Springer Basel DOI 10.1007/s00024-014-0896-6 Pure and Applied Geophysics Composition, Alteration, and Texture of Fault-Related Rocks from Safod Core and Surface Outcrop Analogs: Evidence for Deformation Processes and Fluid-Rock Interactions 1 1 1 1 1 KELLY K. BRADBURY, COLTER R. DAVIS, JOHN W. SHERVAIS, SUSANNE U. JANECKE, and JAMES P. EVANS Abstract—We examine the fine-scale variations in mineralogi- 1. Introduction cal composition, geochemical alteration, and texture of the fault- related rocks from the Phase 3 whole-rock core sampled between 3,187.4 and 3,301.4 m measured depth within the San Andreas Fault Well-constrained geological, geochemical, and Observatory at Depth (SAFOD) borehole near Parkfield, California. geophysical models of active fault zones are needed if This work provides insight into the physical and chemical properties, we are to understand fault zone behavior and earth- structural architecture, and fluid-rock interactions associated with the actively deforming traces of the San Andreas Fault zone at depth. quake deformation, constraining the factors that affect Exhumed outcrops within the SAF system comprised of serpentinite- the distribution of earthquakes, and the nature of slip bearing protolith are examined for comparison at San Simeon, Goat in the shallow crust by developing realistic models of Rock State Park, and Nelson Creek, California. In the Phase 3 SAFOD drillcore samples, the fault-related rocks consist of multiple subsurface fault zone structure and ground motion juxtaposed lenses of sheared, foliated siltstone and shale with block- predictions. Earthquakes nucleate in rocks at depth in-matrix fabric, black cataclasite to ultracataclasite, and sheared (e.g., FAGERENG and TOY 2011;SIBSON 1977; 2003), serpentinite-bearing, finely foliated fault gouge. -
A GPS and Modelling Study of Deformation in Northern Central America
Geophys. J. Int. (2009) 178, 1733–1754 doi: 10.1111/j.1365-246X.2009.04251.x A GPS and modelling study of deformation in northern Central America M. Rodriguez,1 C. DeMets,1 R. Rogers,2 C. Tenorio3 and D. Hernandez4 1Geology and Geophysics, University of Wisconsin-Madison, Madison, WI 53706 USA. E-mail: [email protected] 2Department of Geology, California State University Stanislaus, Turlock, CA 95382,USA 3School of Physics, Faculty of Sciences, Universidad Nacional Autonoma de Honduras, Tegucigalpa, Honduras 4Servicio Nacional de Estudios Territoriales, Ministerio de Medio Ambiente y Recursos Naturales, Km. 5 1/2 carretera a Santa Tecla, Colonia y Calle Las Mercedes, Plantel ISTA, San Salvador, El Salvador Accepted 2009 May 9. Received 2009 May 8; in original form 2008 August 15 SUMMARY We use GPS measurements at 37 stations in Honduras and El Salvador to describe active deformation of the western end of the Caribbean Plate between the Motagua fault and Central American volcanic arc. All GPS sites located in eastern Honduras move with the Caribbean Plate, in accord with geologic evidence for an absence of neotectonic deformation in this region. Relative to the Caribbean Plate, the other stations in the study area move west to west–northwest at rates that increase gradually from 3.3 ± 0.6 mm yr−1 in central Honduras to 4.1 ± 0.6 mm yr−1 in western Honduras to as high as 11–12 mm yr−1 in southern Guatemala. The site motions are consistent with slow westward extension that has been inferred by previous authors from the north-striking grabens and earthquake focal mechanisms in this region. -
Active and Potentially Active Faults in Or Near the Alaska Highway Corridor, Dot Lake to Tetlin Junction, Alaska
Division of Geological & Geophysical Surveys PRELIMINARY INTERPRETIVE REPORT 2010-1 ACTIVE AND POTENTIALLY ACTIVE FAULTS IN OR NEAR THE ALASKA HIGHWAY CORRIDOR, DOT LAKE TO TETLIN JUNCTION, ALASKA by Gary A. Carver, Sean P. Bemis, Diana N. Solie, Sammy R. Castonguay, and Kyle E. Obermiller September 2010 THIS REPORT HAS NOT BEEN REVIEWED FOR TECHNICAL CONTENT (EXCEPT AS NOTED IN TEXT) OR FOR CONFORMITY TO THE EDITORIAL STANDARDS OF DGGS. Released by STATE OF ALASKA DEPARTMENT OF NATURAL RESOURCES Division of Geological & Geophysical Surveys 3354 College Rd. Fairbanks, Alaska 99709-3707 $4.00 CONTENTS Abstract ............................................................................................................................................................ 1 Introduction ....................................................................................................................................................... 1 Seismotectonic setting of the Tanana River valley region of Alaska ................................................................ 3 2008 fi eld studies .............................................................................................................................................. 5 Field and analytical methods ............................................................................................................................ 5 Dot “T” Johnson fault ....................................................................................................................................... 7 Robertson -
Rnic~Ess T~Ese
GEOPHYSICAL RESEARCH LETTERS, VOL. 18, NO.5, PAGES 979-982, MAY 1991 HYDROGEOLOGY OF THRUST FAULTS AND CRYSTALLINE THRUST SHEETS: RESULTS OF COMBINED FIELD AND MODELING STUDIES Craig B. Forster Department of Geology & Geophysics, University of Utah James P. Evans Department of Geology, Utah State University Abstract. Field,. laboratory, and.modeling studies of faulted obtained for systems that span a wide range of spatial scales, rock yield insight 1Oto the hydraulic character of thrust faults. aid in establishing appropriate scales of observation. Although Late-stage fau lts comprise foliated and su?par~lel faults, ~ith our numerical models cannot provide a unique answer that clay-rich gouge and fracture zones, that YIeld mterpenetratmg applies directly to a given field situation, the numerical results layers of low-permeability gou~e and higher-permeab~l~ty do provide insight into this class of groundwater flow system. damage zones. Laboratory testmg suggests a permeabIlity contrast of two orders of magnitude between gouge and damage zones. Layers of differing permeability lead to overall Fault Zone Hydrogeology permeability anisotropy with maximum permeability within the plane of the fault and minimum permeability perpendicular to the fault plane. Numerical modeling of regional-scale fluid Precambrian granites and gneisses found in our field area flow and heat transport illustrates the impact of fault zone (northwest Wyoming) were thrusted over adjacent sedimentary hydrogeology on fluid flux, fluid pore pressure, and rocks along moderately-dipping thrust faults. About 150 m of temperature in the vicinity of a crystalline thrust sheet. exposed fault were examined through large-scale field mapping and detailed sampling both across and along strike. -
Region of the San Andreas Fault, Western Transverse Ranges, California
Thrust-Induced Collapse of Mountains— An Example from the “Big Bend” Region of the San Andreas Fault, Western Transverse Ranges, California By Karl S. Kellogg Scientific Investigations Report 2004–5206 U.S. Department of the Interior U.S. Geological Survey U.S. Department of the Interior Gale A. Norton, Secretary U.S. Geological Survey Charles G. Groat, Director U.S. Geological Survey, Reston, Virginia: 2004 For sale by U.S. Geological Survey, Information Services Box 25286, Denver Federal Center Denver, CO 80225 For more information about the USGS and its products: Telephone: 1-888-ASK-USGS World Wide Web: http://www.usgs.gov/ Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this report is in the public domain, permission must be secured from the individual copyright owners to reproduce any copyrighted materials contained within this report. iii Contents Abstract ……………………………………………………………………………………… 1 Introduction …………………………………………………………………………………… 1 Geology of the Mount Pinos and Frazier Mountain Region …………………………………… 3 Fracturing of Crystalline Rocks in the Hanging Wall of Thrusts ……………………………… 5 Worldwide Examples of Gravitational Collapse ……………………………………………… 6 A Spreading Model for Mount Pinos and Frazier Mountain ………………………………… 6 Conclusions …………………………………………………………………………………… 8 Acknowledgments …………………………………………………………………………… 8 References …………………………………………………………………………………… 8 Illustrations 1. Regional geologic map of the western Transverse Ranges of southern California …………………………………………………………………………… 2 2. Simplified geologic map of the Mount Pinos-Frazier Mountain region …………… 2 3. View looking southeast across the San Andreas rift valley toward Frazier Mountain …………………………………………………………………… 3 4. View to the northwest of Mount Pinos, the rift valley (Cuddy Valley) of the San Andreas fault, and the trace of the Lockwood Valley fault ……………… 3 5. -
Strength of Chrysotile-Serpentinite Gouge Under Hydrothermal Conditions: Can It Explain a Weak San Andreas Fault?
Strength of chrysotile-serpentinite gouge under hydrothermal conditions: Can it explain a weak San Andreas fault? D. E. Moore D. A. Lockner U.S. Geological Survey, Menlo Park, California 94025 R. Summers Ma Shengli Institute of Geology, State Seismological Bureau, Beijing, China J. D. Byerlee U.S. Geological Survey, Menlo Park, California 94025 ABSTRACT more, it has been suggested that at higher temperatures (Reinen et Chrysotile-bearing serpentinite is a constituent of the San An- al., 1993) and/or lower strain rates (Reinen and Tullis, 1995) the dreas fault zone in central and northern California. At room tem- frictional strength of chrysotile may be reduced to Յ 0.1. As a test perature, chrysotile gouge has a very low coefficient of friction ( of this hypothesis, we report here on the strength of a pure chrysotile Ϸ 0.2), raising the possibility that under hydrothermal conditions gouge at elevated temperatures and a wide range of velocities, in- might be reduced sufficiently (to <0.1) to explain the apparent tended to more closely represent conditions at depth in the fault. weakness of the fault. To test this hypothesis, we measured the Our results suggest that chrysotile alone is not a likely explanation frictional strength of a pure chrysotile gouge at temperatures to for a weak San Andreas fault. ؇C and axial-shortening velocities as low as 0.001 m/s. As 290 temperature increases to Ϸ100 ؇C, the strength of the chrysotile EXPERIMENTAL PROCEDURES gouge decreases slightly at low velocities, but at temperatures The chrysotile gouge used in this study was prepared from a ؇C, it is substantially stronger and essentially independent of soft, layered, light to medium grayish-green rock from the New Idria 200< velocity at the lowest velocities tested.