EFFECTS OF THREE-DIMENSIONAL BEDROCK TOPOGRAPHY ON EARTHQUAKE MOTIONS IN SEDIMENTARY BASINS

Work being done at the U.S. Geological Survey on 3-D simulations of earthquake ground motions in sedimentary basins is described. The ultimate goal of this research is to predict strong ground motions in sedimentary basins for expected large earthquakes. Throughout this paper, the inadequacy of using flat-layered models for synthesizing ground motions in sedimentary basins is emphasized. It has been demonstrated with 2-D and 3-D simulations how the slope of the alluvium-bedrock interface can trap S-waves in the basins, producing prolonged trains of surface waves. These surface waves are not generated in flat-layered models, which underestimate the duration and peak amplitude of shaking. It is necessary to account for the increased duration and amplitude of surface waves in sedimentary basins when designing man-made structures with natural periods of 1 sec and greater. Results are presented for 3-D simulations of earthquakes on the San Andreas fault in the San Bernardino and Santa Clara valleys in California. These simulations show the importance of S-wave-to-surface-wave conversions at the edges of the valleys. A contour map of maximum ground velocity in the San Bernardino Valley is produced from the simulation of a magnitude 6.5 earthquake on the San Andreas fault. Areas of especially large ground motions occur where surface waves reflected from the edges of the basin constructively interfere with trapped waves behind the direct S-wave.

• Record URL:
  http://onlinepubs.trb.org/Onlinepubs/trr/1993/1411/1411-001.pdf
• Record URL:
  https://scholar.google.com/scholar_lookup?title=EFFECTS+OF+THREE-DIMENSIONAL+BEDROCK+TOPOGRAPHY+ON+EARTHQUAKE+MOTIONS+IN+SEDIMENTARY+BASINS&author=A.+Frankel&publication_year=1993
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• Supplemental Notes:
  • This paper appears in Transportation Research Record No. 1411, Earthquake-Induced Ground Failure Hazards. Distribution, posting, or copying of this PDF is strictly prohibited without written permission of the Transportation Research Board of the National Academy of Sciences. Unless otherwise indicated, all materials in this PDF are copyrighted by the National Academy of Sciences. Copyright © National Academy of Sciences. All rights reserved
• Authors:
  • Frankel, Arthur
• Publication Date: 1993

Language

• English

Media Info

• Features: Figures; References;
• Pagination: p. 1-8
• Monograph Title: Earthquake-induced ground failure hazards
• Serial:
  • Transportation Research Record
  • Issue Number: 1411
  • Publisher: Transportation Research Board
  • ISSN: 0361-1981

Subject/Index Terms

• TRT Terms: Alluvium; Amplitude (Physics); Bedrock; Earthquakes; Forecasting; Interfaces; Mathematical models; Rayleigh waves; Seismicity; Simulation; Slopes; Time duration; Topography
• Uncontrolled Terms: Duration
• Geographic Terms: San Andreas Fault
• Old TRIS Terms: Sedimentary basins
• Subject Areas: Geotechnology; Highways; I42: Soil Mechanics; I43: Rock Mechanics;

Filing Info

• Accession Number: 00641447
• Record Type: Publication
• ISBN: 030905558X
• Files: TRIS, TRB
• Created Date: Jan 27 1994 12:00AM