Welcome!

This page is a construction zone that will soon evolve into a collection of resources related to one of the Richard H. Jahns Lectures for 2022-23. Please revisit this site as its content evolves.

How can an engineering geologist find an active fault?

Description

This talk will summarize techniques my students and I use to find the ground-surface trace of seismogenic/active faults. It will emphasize the ideas of geoscience to benefit society, the primacy principle of protecting human life/safety, the comingling of basic fieldwork with analysis of geophysical data (relocated earthquake hypocenter data, earthquake focal mechanisms, GPS geodesy, LiDAR-based geomorphic analysis), and the virtue of continuing education throughout a geoscientist's career.

Some Resources

• Topographic maps
  • Access to USGS topographic maps in digital form via TopoView: https://ngmdb.usgs.gov/topoview/viewer/
  • Another source of GeoPDF files of USGS topographic maps: viewer.nationalmap.gov/basic/?basemap=b1&category=ustopo&title=US Topo Download
  • US National Map interactive viewer: https://apps.nationalmap.gov/viewer/
• Geologic maps and maps of active faults
  • National Geologic Map Database: https://ngmdb.usgs.gov/ngmdb/ngmdb_home.html
  • Quaternary Fault and Fold Database of the United States (QFFDBUS): https://www.usgs.gov/natural-hazards/earthquake-hazards/faults
    QFFDBUS interactive map: https://usgs.maps.arcgis.com/apps/webappviewer/index.html?id=5a6038b3a1684561a9b0aadf88412fcf
• LiDAR-based digital elevation models
  • OpenTopography.org (it is suggested that you use either Firefox, Chrome, "or another WebGL2 browser" so that you will have full access to the results): https://opentopography.org
    — Video made in support of Cronin's "Intro to Structural Geology" lab, showing an example of acquiring a DEM from OpenTopography: https://youtu.be/hcRqC2bYS14
    • Download the compressed DEM Results (a file called "rasters_sdem.tar.gz")
    • Decompress the file, resulting in a folder named something like "rasters_sdem" and open that folder to see three files with names something like the following: output_hh.asc, output_hh.asc.aux.xml, and output_hh.prj.
    • You can open the file with the .asc tag using a common text editor like TextEdit or BBEdit to examine its contents. You will see six header rows that specify various important information about the datafile (number of columns, number of rows, the UTM coordinates of the lower left corner of the dataset, the horizontal spacing between nodes in the square grid, and the value used to indicate a missing value in the dataset), followed by hundreds or thousands of rows and columns of data. Each datum in that sea of numbers is an elevation above sea level. It is this dataset of elevations that allows us to write computer code to analyze or visualize the ground surface in this area.
    • Close the file, and change the file name to something meaningful to you, and replace the .asc tag of this file with a .dat tag so we can use it in Mathematica codes such as MakeHillshade.nb or the SLAM code SLAMcode20210103.nb.
  • "The Impact of Open Access Lidar Topography" by Emily Zawacki in Lidar Magazine (July 26, 2022), accessible via https://lidarmag.com/2022/07/26/the-impact-of-open-access-lidar-topography/
  • UNAVCO video about LiDAR: https://youtu.be/chSywRqgIGY?list=PLzmugeDoplFM5pPI80wwi3qmtZH99Ism2
  • NEON video about LiDAR: https://www.youtube.com/watch?v=EYbhNSUnIdU&feature=youtu.be
• Recorded modern earthquakes
  • Initial location of hypocenters
    • Bulletin of the International Seismological Centre (ISC): http://www.isc.ac.uk/iscbulletin/
    • NationalEarthquake Information Center (NEIC) earthquake catalog: https://earthquake.usgs.gov/earthquakes/search/
    • Northern California Earthquake Data Center (NCEDC): https://ncedc.org/web-services-home.html
    • Southern California Earthquake Data Center (SCEDC): https://scedc.caltech.edu
      SCEDC earthquake catalogs: https://scedc.caltech.edu/data/eq-catalogs.html
  • Relocation of hypocenters
    • Felix Waldhauser's home page at Lamont: https://www.ldeo.columbia.edu/~felixw/
    • Real-time double-difference earthquake locations for northern California: http://ddrt.ldeo.columbia.edu/DDRT/index.html
    • Double-difference earthquake catalog for Northern California (1984-2011): https://www.ldeo.columbia.edu/~felixw/NCAeqDD/
    • Hauksson et al (2011) Waveform Relocated Earthquake Catalog for Southern California (1981-2022): https://scedc.caltech.edu/data/alt-2011-dd-hauksson-yang-shearer.html
  • Focal mechanisms
    • Focal mechanism primer (Cronin, 2010): https://croninprojects.org/Vince/Course/IntroStructGeol/Focal_mechanism_primer_v4.pdf
      For a more technical treatment, see Jost and Herrmann (1989) or a seismology textbook, e.g., Stein and Wysession (2003), Shearer (1999), Kasahara (1981), Lay and Wallace (1995).
    • Some FM and Moment Tensor data sources
      • USGS National Earthquake Information Center (NEIC):https://neic.usgs.gov/neis/FM/
      • Searchable NEIC databases: https://neic.usgs.gov/neis/sopar/
      • Berkeley Moment Tensor Catalog, accessed via http://seismo.berkeley.edu/mt/
      • SCSN Moment Tensor Catalog: https://service.scedc.caltech.edu/eq-catalogs/CMTsearch.php
        SCSN Focal Mechanism Catalog: https://service.scedc.caltech.edu/eq-catalogs/FMsearch.php
      • Cheng et al (2022), Refined focal mechanism catalog for southern California: https://scedc.caltech.edu/data/alt-2022-cheng.html
      • Global CMT Project: https://www.globalcmt.org/ and https://www.globalcmt.org/CMTsearch.html
      • Bulletin of the International Seismological Centre (ISC): http://www.isc.ac.uk/iscbulletin/
      • National Earthquake Information Center (NEIC) earthquake catalog: https://earthquake.usgs.gov/earthquakes/search/
• Seismo-lineament analysis: https://croninprojects.org/Vince/SLAM/
• GNSS/GPS
  • Site velocity data
    GAGE facility network portal: https://www.unavco.org/instrumentation/networks/networks.html
    Nevada Geodetic Laboratory GPS networks map: http://geodesy.unr.edu/NGLStationPages/gpsnetmap/GPSNetMap.html
  • Estimating current crustal strain from GNSS/GPS velocity data
    • GETSI module "GPS, Strain, and Earthquakes" resources: https://serc.carleton.edu/getsi/teaching_materials/gps_strain/index.html
    • Triangle-strain explanations
      • Primer on infinitesimal strain analysis in 1, 2, and 3-D (revised December 2021): https://croninprojects.org/Vince/Geodesy/GPS_Strain_Primer.pdf (.pdf, 1.3 MB)
      • Algorithm for triangle-strain analysis (revised December 2021): https://croninprojects.org/Vince/Geodesy/TriangleStrainAlgorithm.docx (.pdf, 769 KB)
    • Triangle strain calculators
      • Microsoft Excel version: https://CroninProjects.org/Vince/Geodesy/Calculators/GPS-strain-calculator-20220821.xlsx (Excel 31 kb)
        Video "How to use the Excel spreadsheet that computes crustal strain in a triangle between 3 GPS stations": https://youtu.be/nJJudaorc4w
      • Wolfram Mathematica notebook version that reads input data from a CSV file: https://CroninProjects.org/Vince/Geodesy/Calculators/GPS-strain-calculator-InputCSV-20220822.nb
        — PDF file showing the Mathematica code after a sample run: https://CroninProjects.org/Vince/Geodesy/Calculators/GPS-strain-calculator-InputCSV-20220822.pdf
        — Sample input CSV data file for Truckee-area analysis, NAM14 reference frame: https://CroninProjects.org/Vince/Geodesy/TruckeeAreaGPS-velocities-20220821.csv
      • MatLab version (zip file): https://d32ogoqmya1dw8.cloudfront.net/files/getsi/teaching_materials/gps_strain/gps_strain_calculator_matlab.zip
  • Focal mechanisms as crustal-strain indicators

References

(Not yet compiled. Please check later.)

If you have any questions or comments about this site or its contents, drop an email to Vince Cronin.