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.
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How can an engineering geologist find an active fault?
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.
- Topographic maps
- Geologic maps and maps of active faults
- 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
- Relocation of hypocenters
- Focal mechanisms
- Seismo-lineament analysis: https://croninprojects.org/Vince/SLAM/
(Not yet compiled. Please check later.)
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