DOCSLIB.ORG

Thesisdocumentkevinchantfinal2

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Thesisdocumentkevinchantfinal2 ANALYSIS OF SHALLOW RESISTIVITY PROFILES ACROSS THE SAN JOSE FAULT ON THE CALIFORNIA STATE POLYTECHNIC UNIVERSITY, POMONA CAMPUS A Thesis Presented to the Faculty of California State Polytechnic University, Pomona In Partial Fulfillment Of the Requirements for the Degree Master of Science In Geological Sciences By Kevin J. Chantrapornlert 2016 SIGNATURE PAGE THESIS: ANALYSIS OF SHALLOW RESISTIVITY PROFILES ACROSS THE SAN JOSE FAULT ON THE CALIFORNIA STATE POLYTECHNIC UNIVERSITY, POMONA CAMPUS AUTHOR: Kevin J. Chantrapornlert DATE SUBMITTED: Winter 2016 Geological Sciences Department Dr. Jascha Polet ___________________________________________ Thesis Committee Chair Geological Sciences Dr. Jonathan Nourse ___________________________________________ Department Chair Geological Sciences Dr. Stephen Osborn ___________________________________________ Associate Professor Geological Sciences Dr. Nicholas Van Buer ___________________________________________ Assistant Professor Geological Sciences Dr. Bryan Murray ___________________________________________ Assistant Professor Geological Sciences ii ACKNOWLEDGEMENTS I would like to thank my advisor and committee chair, Dr. Jascha Polet. Without her guidance and direction, this research would not be possible. Her continued dedication and care for her students is unparalleled. Professors I would also like to thank all those who have helped me conduct my research: Homar Colin, Terry Cheiffetz, Raymond Ng, Mike Vadman, Rosa Nguyen, Julie Leiva, and Stacey Petrashek. Without the help of these friends, I would never have been able to conduct the fieldwork required for my project. iii ABSTRACT The San Jose fault extends from the San Jose hills into the Pomona Valley. The 1988 and 1990 Upland earthquakes have been attributed to this fault and large segments may rupture in a bigger future event. Sections of the fault are considered to run through the campus of California State Polytechnic University, Pomona. Resistivity surveys were conducted across several areas where the fault has been inferred to exist on the basis of boreholes, trenches, and gamma-ray spectrometer surveys by a geotechnical engineering report (GeoCon, 2001). Resistivity surveys measure how conductive the subsurface is to electrical current and therefore may be used to detect groundwater, lithologic changes, and offset due to faulting. The surveys consisted of 24 electrodes in a Wenner configuration with a spacing between 1-5 m. The data was processed using Geotomo’s RES2DINV software to obtain 2D profiles of resistivity. Surveys were performed before and after rainfall, whenever possible, to analyze its possible effect. The resulting images were interpreted to provide an enhanced understanding of the fault as it dissects the campus. Agreements as well as incongruities were found when comparing our resistivity models with the geotechnical cross-sections. Interpretations of several resistivity profiles suggest the presence of water, pounding up against the fault. Based on our results, we suggest that some fault traces may be located ~20 m south of their reported location. At the corner of Camphor Lane and University Drive, profiles with little lateral variation suggest that it is unlikely that the fault runs through this area. iv TABLE OF CONTENTS SIGNATURE PAGE ......................................................................................... ii ACKNOWLEDGEMENTS ................................................................................ iii ABSTRACT ...................................................................................................... iv LIST OF TABLES ............................................................................................. vii LIST OF FIGURES .......................................................................................... viii CHAPTER 1: Introduction ................................................................................ 1 Tectonic Overview ................................................................................. 3 The San Jose Fault ............................................................................... 6 The San Jose Fault on the Cal Poly Pomona Campus .............. 10 Research Approach ............................................................................... 16 CHAPTER 2: Surveying Methods, Equipment, and Software ......................... 19 Resistivity .............................................................................................. 19 Examples of Past Fault Studies Using Resistivity ...................... 24 Wenner Arrays ...................................................................................... 34 Equipment ............................................................................................. 36 Procedure .............................................................................................. 37 Data Processing Software ..................................................................... 46 Inversion Software ................................................................................ 48 CHAPTER 3: Inversion Results and Interpretations ........................................ 52 Site 1 .................................................................................................... 52 Site 2 ..................................................................................................... 60 v Site 3 .................................................................................................... 77 Site 4 .................................................................................................... 84 Site 5 .................................................................................................... 94 Site 6 .................................................................................................... 98 Site 7 .................................................................................................... 105 CHAPTER 4: Conclusions ............................................................................... 110 Closing Remarks ................................................................................... 112 Recommendations for Future Work ...................................................... 113 References ...................................................................................................... 116 Appendix A ...................................................................................................... 124 vi LIST OF TABLES Table 1. Resistivity values for various rocks, soils, and chemicals. .................... 20 vii LIST OF FIGURES Figure 1. The San Jose fault ................................................................................... 2 Figure 2. Map depicting the San Jose fault (red line) and the surrounding areas ....................................................................................................... 4 Figure 3. A seismicity map of the area surrounding the San Jose fault .................. 5 Figure 4. The San Jose fault acts as a barrier to flow ............................................. 7 Figure 5. The offset of the effective base of fresh water due to faulting ................. 8 Figure 6. Earthquakes in Upland California between 1981-1989 recorded by the Southern California Seismic Network ............................................... 9 Figure 7. San Jose fault location as interpreted by GeoCon (2001) .................. 12 Figure 8. Boreholes in the vicinity of Site 1 ........................................................... 14 Figure 9. A plot of the spectrometer readings used by GeoCon to help determine the location of the San Jose fault ......................................... 15 Figure 10. A plot of the spectrometer readings used by GeoCon to help determine the location of the San Jose fault ......................................... 16 Figure 11. The slip zone of the fault ...................................................................... 18 Figure 12. Current flow in a simplified homogeneous half space ......................... 21 Figure 13. Current flow between two electrodes ................................................... 23 Figure 14. An ERT image of the Los Avestruces Central High in Argentina shown above its interpreted coss-section ............................................. 27 Figure 15. An ERT image utilizing a Wenner-Schlumberger array in the Kamenička municipal in the Czech republic ......................................... 28 Figure 16. A cross section of the High Agri Valley Basin in Southern Italy ........... 29 viii Figure 17. ERT across the San Bartolo fault scarp in the Percordillera of western Argentina ................................................................................. 30 Figure 18. An ERT survey across the Tierra Blanca fault in the city of San Miguel Uspantán, Guatemala ............................................................... 31 Figure 19. An ERT profile across the Geleen fault in the Belgian Maas River valley ..................................................................................................... 32 Figure 20. An electrical resistivity tomography (ERT) profile with the corresponding interpreted geologic cross-section across the Yalguaraz fault in the Central Andes of Argentina33 Figure 21. An ERT survey utilizing a dipole-dipole array ..................................... 33 Figure 22. A Wenner electrode array with 24 electrodes. ..................................... 35 Figure 23. Survey 063005A conducted
Load more

Recommended publications
  • New Empirical Relationships Among Magnitude, Rupture Length, Rupture Width, Rupture Area, and Surface Displacement
    Bulletin of the Seismological Society of America, Vol. 84, No. 4, pp. 974-1002, August 1994 New Empirical Relationships among Magnitude, Rupture Length, Rupture Width, Rupture Area, and Surface Displacement by Donald L. Wells and Kevin J. Coppersmith Abstract Source parameters for historical earthquakes worldwide are com­ piled to develop a series of empirical relationships among moment magnitude (M), surface rupture length, subsurface rupture length, downdip rupture width, rupture area, and maximum and average displacement per event. The resulting data base is a significant update of previous compilations and includes the ad­ ditional source parameters of seismic moment, moment magnitude, subsurface rupture length, downdip rupture width, and average surface displacement. Each source parameter is classified as reliable or unreliable, based on our evaluation of the accuracy of individual values. Only the reliable source parameters are used in the final analyses. In comparing source parameters, we note the fol­ lowing trends: (1) Generally, the length of rupture at the surface is equal to 75% of the subsurface rupture length; however, the ratio of surface rupture length to subsurface rupture length increases with magnitude; (2) the average surface dis­ placement per event is about one-half the maximum surface displacement per event; and (3) the average subsurface displacement on the fault plane is less than the maximum surface displacement but more than the average surface dis­ placement. Thus, for most earthquakes in this data base, slip on the fault plane at seismogenic depths is manifested by similar displacements at the surface. Log-linear regressions between earthquake magnitude and surface rupture length, subsurface rupture length, and rupture area are especially well correlated, show­ ing standard deviations of 0.25 to 0.35 magnitude units.
    [Show full text]
  • 2017 Local Hazard Mitigation Plan
    City of Los Angeles 2017 Local Hazard Mitigation Plan Eric Garcetti, Mayor Aram Sahakian, General Manager Emergency Management Department EMERGE Ill MANAGEM August 2017 DEPART City of Los Angeles 2017 Local Hazard Mitigation Plan August 2017 PREPARED FOR PREPARED BY City of Los Angeles Emergency Management Department Tetra Tech 200 N. Spring Street 1999 Harrison Street Phone: 510.302.6300 Room 1533 Suite 500 Fax: 510.433.0830 Los Angeles, California 90012 Oakland, CA 94612 tetratech.com Tetra Tech Project # 103S4869 \\IWRS065FS1\Data\Active\0_HazMitigation\103s4869.emi_LACity_HMP\2017-08_ApprovedFinal\2017_LA_HMP_Final_2017-08-23.docx City of Los Angeles 2017 Local Hazard Mitigation Plan Contents CONTENTS Executive Summary ............................................................................................................ xxii PART 1— PLANNING PROCESS AND COMMUNITY PROFILE 1. Introduction to Hazard Mitigation Planning ................................................................... 1-1 1.1 Why Prepare This Plan? ............................................................................................................................. 1-1 1.1.1 The Big Picture ................................................................................................................................. 1-1 1.1.2 Purposes for Planning ....................................................................................................................... 1-1 1.2 Who Will Benefit From This Plan? ..........................................................................................................
    [Show full text]
  • Curriculum Vitae DON HELMBERGER Professor of Geophysics
    Curriculum Vitae DON HELMBERGER Professor of Geophysics Seismological Laboratory 252-21 California Institute of Technology Pasadena, CA 91125 Tel. (626) 395-6998; Fax (626) 564-0715 Email: [email protected] EDUCATION: B. A. (Geophysics) University of Minnesota (five year curriculum), 1962 M. S. University of California, San Diego, 1965. Ph.D. University of California, San Diego, 1967. PROFESSIONAL EXPERIENCE: Research Associate, Department of Geology and Geophysics, MIT, 1968 Assistant Professor of Geophysics, Princeton University, 1969 Assistant Professor of Geophysics, California Institute of Technology, 1970-1974 Associate Professor of Geophysics, California Institute of Technology, 1974-1979 Professor of Geophysics, California Institute of Technology, 1979 - present. Director, Seismological Laboratory, Caltech, May 1998-May 2003 RECENT HONORS AND AWARDS: First American Geophysical Union recipient of the Inge Lehmann Medal, 1997 Smits Family Professorship, California Institute of Technology, 2000-2011 Medal of the Seismological Society of America, 2002 National Academy of Sciences Member, 2004 RESEARCH INTERESTS: Seismic wave propagation and the inversion of waveforms to recover detailed information about earthquake characteristics and earth structure; particularly interested in mapping ultra-low-velocity zones and possible post-perovskite effects at the Core-Mantle Boundary. PUBLICATIONS: Helmberger, D. V. (1967). Head Waves from the Oceanic Mohorovicic Discontinuity, Ph.D. Thesis, University of California, San Diego, La Jolla, California. Helmberger, D. V. (1968). The crust-mantle transition in the Bering Sea, Seismol. Soc. Am. Bull., 58, No. 1, 179-214. Helmberger, D. V. and G. B. Morris (1969). A travel time and amplitude interpretation of a marine refraction profile, primary waves, J. Geophys. Res., 74, No. 2, 438-494.
    [Show full text]
  • City of Glendale Hazard Mitigation Plan Available to the Public by Publishing the Plan Electronically on the City’S Websites
    Local Hazard Mitigation Plan Section 1: Introduction City of Glendale, California City of Glendale Hazard Mitigati on Plan 2018 Local Hazard Mitigation Plan Table of Contents City of Glendale, California Table of Contents SECTION 1: INTRODUCTION 1-1 Introduction 1-2 Why Develop a Local Hazard Mitigation Plan? 1-3 Who is covered by the Mitigation Plan? 1-3 Natural Hazard Land Use Policy in California 1-4 Support for Hazard Mitigation 1-6 Plan Methodology 1-6 Input from the Steering Committee 1-7 Stakeholder Interviews 1-7 State and Federal Guidelines and Requirements for Mitigation Plans 1-8 Hazard Specific Research 1-9 Public Workshops 1-9 How is the Plan Used? 1-9 Volume I: Mitigation Action Plan 1-10 Volume II: Hazard Specific Information 1-11 Volume III: Resources 1-12 SECTION 2: COMMUNITY PROFILE 2-1 Why Plan for Natural and Manmade Hazards in the City of Glendale? 2-2 History of Glendale 2-2 Geography and the Environment 2-3 Major Rivers 2-5 Climate 2-6 Rocks and Soil 2-6 Other Significant Geologic Features 2-7 Population and Demographics 2-10 Land and Development 2-13 Housing and Community Development 2-14 Employment and Industry 2-16 Transportation and Commuting Patterns 2-17 Extensive Transportation Network 2-18 SECTION 3: RISK ASSESSMENT 3-1 What is a Risk Assessment? 3-2 2018 i Local Hazard Mitigation Plan Table of Contents City of Glendale, California Federal Requirements for Risk Assessment 3-7 Critical Facilities and Infrastructure 3-8 Summary 3-9 SECTION 4: MULTI-HAZARD GOALS AND ACTION ITEMS 4-1 Mission 4-2 Goals 4-2 Action
    [Show full text]
  • June 17, 2004 10:13 WSPC/124-JEE 00165 CAN SITE
    June 17, 2004 10:13 WSPC/124-JEE 00165 Journal of Earthquake Engineering, Vol. 8, Special Issue 1 (2004) 1–41 c Imperial College Press CANSITERESPONSEBEPREDICTED? DAVID M. BOORE US Geological Survey, 345 Middlefield Road, MS 977, Menlo Park, CA 94025, USA Large modifications of seismic waves are produced by variations of material properties near the Earth’s surface and by both surface and buried topography. These modifica- tions, usually referred to as “site response”, in general lead to larger motions on soil sites than on rock-like sites. Because the soil amplifications can be as large as a factor of ten, they are important in engineering applications that require the quantitative spec- ification of ground motions. This has been recognised for years by both seismologists and engineers, and it is hard to open an earthquake journal these days without finding an article on site response. What is often missing in these studies, however, are discus- sions of the uncertainty of the predicted response. A number of purely observational studies demonstrate that ground motions have large site-to-site variability for a single earthquake and large earthquake-location-dependent variability for a single site. This variability makes site-specific, earthquake-specific predictions of site response quite un- certain, even if detailed geotechnical and geological information is available near the site. Predictions of site response for average classes of sites exposed to the motions from many earthquakes can be made with much greater certainty if sufficient empirical observations are available. Keywords: Site response; amplification; transfer functions; ground motion; variability; prediction. 1.
    [Show full text]
  • Hazard Mitigation Plan
    2020 Hazard Mitigation Plan Adoption Date: mm dd, 2020 Monte Vista Water District Justin Scott-Coe, General Manager 10575 Central Avenue Montclair, California 91763 Monte Vista Water District 2020 Hazard Mitigation Plan Table of Contents Section 1 Introduction ................................................................................... 4 1.1 Purpose of the Plan ................................................................................................ 4 1.2 Authority ................................................................................................................. 4 1.3 Community Profile .................................................................................................. 4 1.3.1 Physical Setting ....................................................................................... 4 1.3.2 History ...................................................................................................... 7 1.3.3 Demographics .......................................................................................... 8 1.3.4 Existing Land Use .................................................................................... 9 1.3.5 Development Trends .............................................................................. 11 Section 2 Plan Adoption .............................................................................. 12 2.1 Adoption by Local Governing Body ....................................................................... 12 2.2 Promulgation Authority ........................................................................................
    [Show full text]
  • Source Complexity of the 1994 Northridge Earthquake and Its Relation to Aftershock Mechanisms
    Bulletin of the Seismological Society of America, Vol. 86, No. 1B, pp. $84-$92, February 1996 Source Complexity of the 1994 Northridge Earthquake and Its Relation to Aftershock Mechanisms by Hong Kie Thio* and Hiroo Kanamori Abstract We determined the source process of the 1994 Northridge earthquake in relation to the aftershock mechanisms. To study the source complexity of the mainshock, we inverted the P and SH waveforms recorded by the IRIS and IDA/IRIS networks, using the method of Kikuchi and Kanamori (1991) in which the rupture is represented by a series of discrete subevents with varying mechanisms. The wave- forms show that the rupture consisted of several subevents with about 2 sec in be- tween. Our solution consists of three subevents with essentially the same mechanism, viz., strike, dip, and slip of 130 °, 42 °, and 116 °, respectively. The first subevent occurred at a depth of about 19 kin, followed after 2 sec by the second and largest subevent at a depth of 17 km and the third subevent again 2 sec after the second at a depth of about 13 km. The total moment from the body waves of this sequence is about 1.1 × 1026 dyne • cm (Mw = 6.6) with a source duration of 7 sec. The large depths of these subevents explain the lack of any surface rupture. Fur- thermore, the upward propagation of the subevents is consistent with the depth of the hypocenter and the distribution of the aftershocks, which are shallower and more northerly than the mainshock hypocenter. The aftershocks were analyzed using data from the TERRAscope network.
    [Show full text]
  • Eight Myths About Earthquakes
    Eight Myths About Earthquakes MYTH 1 Big earthquakes always happen in the morning. Several recent damaging earthquakes HAVE happened in the early morning hours so many people assume that all big earthquakes happened then. In fact, earthquakes occur at all times during the day. The 1933 Long Beach earthquake was a 5:54 p.m. and the 1940 Imperial Valley event was at 9:36 p.m. Even recently, the 1990 Upland earthquake was at 3:43 p.m. and the 1989 Loma Prieta event was at 5:02 p.m. It is easy to notice the earthquakes that fit the pattern and forget about the ones that don't. MYTH 2 It's hot and dry - earthquake weather! Many people believe that earthquakes are more common in certain kinds of weather. In fact, no correlation with weather has been found. Earthquakes begin many kilometers below the region affected by surface weather. People tend to notice earthquakes that fit the pattern and forget the ones that don't. Also, every region of the world has a story about earthquake weather, but the type of weather is whatever they had for their most memorable earthquake. MYTH 3 Beachfront property in Arizona. The idea of California falling into the ocean has had an enduring appeal to those envious of the life in the Golden State. Of course, the ocean is not a great hole into which California can fall, but it is itself land at a somewhat lower elevation with water above it. The motion of plates will not make California sink - California is moving horizontally along the San Andreas fault and up around the Transverse Ranges.
    [Show full text]
  • City of Ontario Hazard Mitigation Plan 2011
    CITY OF ONTARIO HAZARD MITIGATION PLAN 2011 CITY OF ONTARIO HAZARD MITIGATION PLAN 2011 PAGE INTENTIONALLY LEFT BLANK REVISED: 07/23/2011 F3 PAGE i CITY OF ONTARIO HAZARD MITIGATION PLAN 2011 RESERVED FOR CITY COUNCIL RESOLUTION REVISED: 07/23/2011 F3 PAGE ii CITY OF ONTARIO HAZARD MITIGATION PLAN 2011 RESERVED FOR CITY COUNCIL RESOLUTION REVISED: 07/23/2011 F3 PAGE iii CITY OF ONTARIO HAZARD MITIGATION PLAN 2011 RECORD OF REVISIONS REV. TITLE INITIALS DATE N/A DRAFT MRG 07/23/2011 N/A Approved by CalEMA/FEMA MRG 11/23/2011 N/A Adopted by City Council MRG 12/20/2011 N/A Final Approval by FEMA MRG 01/31/2012 REVISED: 07/23/2011 F3 PAGE iv CITY OF ONTARIO HAZARD MITIGATION PLAN 2011 PAGE INTENTIONALLY LEFT BLANK REVISED: 07/23/2011 F3 PAGE v CITY OF ONTARIO HAZARD MITIGATION PLAN 2011 TABLE OF CONTENTS Executive Summary ........................................................................................................ 1 Section 1 – Introduction ................................................................................................... 2 1.1 Purpose .................................................................................................................. 2 1.2 Authority ................................................................................................................. 2 1.3 Community Profile .................................................................................................. 3 1.3.1 Physical Setting ...............................................................................................
    [Show full text]
  • 5.6 Geology and Soils
    SAN BERNARDINO COUNTYWIDE PLAN DRAFT PEIR COUNTY OF SAN BERNARDINO 5. Environmental Analysis 5.6 GEOLOGY AND SOILS This section of the draft program environmental impact report (PEIR) evaluates the potential for implementation of the San Bernardino Countywide Plan (CWP or Project) to impact geological and soil resources in the County of San Bernardino (County). The analysis in this section is based in part on the following technical report: • County of San Bernardino Safety Background Report, PlaceWorks in collaboration with Dudek, April 5, 2017. A complete copy of this study is included in the Technical Appendices to this Draft EIR (Appendix G). 5.6.1 Environmental Setting 5.6.1.1 REGULATORY BACKGROUND Federal Clean Water Act The federal Water Pollution Control Act of 1948, as amended in 1972, (33 USC § 1251 et seq.)(also known as the Clean Water Act [CWA]) is the principal statute governing water quality. The CWA establishes the basic structure for regulating discharges of pollutants into the waters of the United States and gives the US Environmental Protection Agency (EPA) the authority to implement pollution control programs, such as setting wastewater standards for industry. The statute’s goal is to end all discharges entirely and to restore, maintain, and preserve the integrity of the nation’s waters. The CWA regulates both direct and indirect discharge of pollutants into the nation’s waters. The CWA sets water quality standards for all contaminants in surface waters and makes it unlawful to discharge any pollutant from a point source into navigable waters unless a permit is obtained under its provisions.
    [Show full text]
  • TWENTY-NINE PALMS CASINO PROJECT Tribal Environmental Assessment
    TWENTY-NINE PALMS CASINO PROJECT Tribal Environmental Assessment Prepared for the January 2013 Twenty-Nine Palms Band of Mission Indians TWENTY-NINE PALMS CASINO PROJECT Tribal Environmental Assessment Prepared for the January 2013 Twenty-Nine Palms Band of Mission Indians 2600 Capitol Avenue Suite 200 Sacramento, CA 95816 916.564.4500 www.esassoc.com Los Angeles Oakland Orlando Palm Springs Petaluma Portland San Diego San Francisco Santa Cruz Seattle Tampa Woodland Hills 120307 OUR COMMITMENT TO SUSTAINABILITY | ESA helps a variety of public and private sector clients plan and prepare for climate change and emerging regulations that limit GHG emissions. ESA is a registered assessor with the California Climate Action Registry, a Climate Leader, and founding reporter for the Climate Registry. ESA is also a corporate member of the U.S. Green Building Council and the Business Council on Climate Change (BC3). Internally, ESA has adopted a Sustainability Vision and Policy Statement and a plan to reduce waste and energy within our operations. This document was produced using recycled paper. TABLE OF CONTENTS Twenty-Nine Palms Casino Project Tribal Environmental Assessment Page 1. Introduction 1-1 1.1 Introduction 1-1 1.2 Project Location 1-1 1.3 Purpose and Need 1-1 1.4 Overview of the Environmental Review Process 1-4 2. Alternatives 2-1 2.1 Proposed Project 2-1 2.2 No-Action Alternative 2-6 2.3 Alternatives Considered Previously 2-6 3. Off-Reservation Environmental Assessment 3.1-1 3.1 Aesthetics 3.1-1 3.2 Air Quality 3.2-1 3.3 Biological Resources 3.3-1 3.4 Cultural Resources 3.4-1 3.5 Geology and Soils 3.5-1 3.6 Hazards and Hazardous Materials 3.6-1 3.7 Land Use 3.7-1 3.8 Noise 3.8-1 3.9 Socioeconomic Conditions 3.9-1 3.10 Public Services 3.10-1 3.11 Transportation and Circulation 3.11-1 3.12 Utilities 3.12-1 3.13 Water Resources 3.13-1 4.
    [Show full text]
  • Basin Waves on a Seafloor Recording of the 1990 Upland, California, Earthquake: Implications for Ground Motions from a Larger Earthquake
    Bulletin of the Seismological Society of America, Vol. 89, No. 1, pp. 317-324, February 1999 Basin Waves on a Seafloor Recording of the 1990 Upland, California, Earthquake: Implications for Ground Motions from a Larger Earthquake by David M. Boore Abstract The velocity and displacement time series from a recording on the sea- floor at 74 km from the 1990 Upland earthquake (M = 5.6) are dominated by late- arriving waves with periods of 6 to 7 sec. These waves are probably surface waves traveling across the Los Angeles basin. Response spectra for the recording are in agreement with predictions from empirical regression equations and theoretical mod- els for periods less than about 1 sec but are significantly larger than those predictions for longer periods. The longer-period spectral amplitudes are controlled by the late- arriving waves, which are not included in the theoretical models and are underrepre- sented in the data used in the empirical analyses. When the motions are scaled to larger magnitude, the results are in general agreement with simulations of wave propagation in the Los Angeles basin by Graves (1998). Introduction For more than 20 years, digitally recording triggered Basin Waves on the Recording accelerometers have been installed on the seafloor near some of the oil platforms off of the southern California coast. The location of the epicenter (UP90) and recording sta- These instruments, installed by the Seafloor Earthquake tion (S3E) are shown in Figure 1. The sensor (a force-bal- Measuring System (SEMS) project, are designed to obtain ance accelerometer) is buried 1.5 m beneath the seafloor, ground shaking data on the seafloor that can be used to eval- and the water depth is 64 m.
    [Show full text]