Unit 2: Identifying faulting styles, rates and histories through analysis of geomorphic characteristics (Lidar)
Can active faults be identified remotely, based upon their appearance in the landscape? How can the geomorphic features associated with active faults be used to classify and quantify fault movement? In this unit, students will analyze lidar data and remote sensing imagery, with the aim of discovering how different styles and timescales of faulting are recorded in the landscape. Concepts pertinent to earthquake hazard and infrastructure risk—such as average slip per event, earthquake recurrence, and fault slip rate—will be investigated.
Unit 2 Learning Outcomes
- Students will determine the most reliable geomorphic features to identify active faults and will learn how these features may be similar or different for different fault types.
- Students will identify variations in their ability to evaluate and quantify characteristic geomorphic features and changes to these features using different image types (lidar images vs. Google Earth satellite images). They also will define the accuracy of data they collect from the two types of images.
- Students will consider that the images represent a form of time series that can be used to evaluate the relationship between the earthquake cycle and landscape evolution.
Unit 2 Teaching Objectives
- Cognitive: Characterize geomorphic features that correspond to different fault types and identify specific fault types using lidar and Google Earth satellite images. Develop fault motion and surficial processes explanations for the spatial and temporal variations observed.
- Promote skills in reading and interpreting maps and topographic profiles, some of which illustrate snapshots in time and some of which illustrate changes over time (time series).
- Facilitate a synthesis of multiple types of observational tools and basis for measurements (lidar, Google Earth) to make predictions about the behavior of a natural system.
- Encourage reflection about the various local, regional, and climate-dependent interplay between fault displacements and surficial processes that may contribute to changes in a natural system and interplay and competition between these mechanisms.
- Encourage reflection about the role of uncertainty in scientists' understanding of a complex system.
Context for Use
The content in Unit 2 is appropriate for advanced geology/geoscience courses conducted at the junior and/or senior level in which geodesy data can be introduced in conjunction with traditional presentations of material on faults and faulting; this would typically be in a course on structural geology but could also be part of a course on tectonics, geomorphology, geophysics, or advanced geohazards. Units 2 and 3 activities can easily be adapted for lecture and lab settings as a series of interactive lecture activities, a lengthier in-class activity, or as part of a laboratory investigation of the use of geodesy to understand faulting and the recognition of active fault types.
In the Imaging Active Tectonics module, Unit 2 may follow a preparatory exercise that provides experience with the basic tools and also establishes a set of criteria for recognizing the geomorphic features most characteristic of different fault types. Some preparatory lecture time may be required to introduce the concept of tectonic geomorphology, such that students are aware of the relationship between the creation of topographic relief through faulting and the surficial processes that are actively modifying the landscape. Key features include fault scarps; the position, shape, and longitudinal profile of streams; and the location of stream terraces, water gaps, wind gaps, and altered stream networks (e.g. stream piracy). Since these features develop and are modified over time, application of geochronology needs to be considered as well as the potential for changes in climate that can influence sediment transport and/or deposition. Since this work is most effective when there are high-quality images to analyze, we are complementing satellite images with lidar images (primarily airborne lidar). The resolution of lidar data allows for vertical and horizontal resolution at the 20–40 cm level.
If the entire two-week module will not be utilized, we recommend pairing Unit 2 with Unit 4: The phenomenology of earthquakes from InSAR data and Unit 5: How do earthquakes affect society? to give students an opportunity to investigate the recognition of a fault, the specific characteristics of fault geometry and displacement for a specific earthquake, and assessment of the impact of an earthquake on urban and developing population centers. Unit 1: "If an earthquake happens in the desert . . .?" provides the motivation for undertaking the other exercises, but this context may be provided in lectures and other instructional modes such as a PowerPoint presentation.
Description and Teaching Materials
In Unit 2, students learn that geomorphic features of the landscape strongly reflect the type of active fault that is present, and they learn the history of fault displacement. In many if not all cases, the type of fault and history of fault movement can be determined. To that end, in the initial activity in Unit 2 (student exercise Section 2.2a), students begin by completing a brief, written exercise that requires them to identify key geomorphic features associated with active faults, which may have been described in previous lectures and assigned readings. This ideally includes example images of the three main fault types with the fault trace shown so the students can examine the images to identify specific geomorphic features associated with each type of fault. This can be done using either Internet access with prepared overlays for Google Earth or alternatively, instructors can print hard copies of the maps or project an image of the maps and complete the exercise during class time.
In Section 2.2b of the Student Exercise, students are provided access to a set of lidar images that can be evaluated separately or as an overlay displayed on a Google Earth satellite image. There are several ways to implement Unit 2; one is to follow a traditional laboratory format, where students work in small groups and individually and submit a written report at the conclusion of the lab. Alternatively, a mixture of techniques may be used including discussions in small, stationary groups or small, mobile groups in the context of a gallery walk. The lab handout provided with this exercise has been written with the assumption that the material will be covered in a traditional laboratory fashion with limited large group interaction. Small groups may be created to facilitate discussion, but individual reports would be required to provide a means of assessment of individual progress.
If a more interactive process is desired, or if this is to be undertaken as part of a lecture period, portions of the material can be handled differently. For Section 2.3 on the Wallace Creek segment of the San Andreas Fault, multiple groups can be formed and each group can work on a different portion of the fault. Students will measure small offsets in their assigned section(s) of the fault and plot the offsets as a function of position along the fault. If the errors introduced by differences in the measurement techniques used are reasonable, then the scale and repeatability of individual offsets should become apparent as shown in the plot from Zielke et al., 2010.
If you are unfamiliar with Google Earth, there are instructions for basic use of this program that can be found on the SERC website Teaching with Google Earth. Alternatively all the same data sets are available below as posters that can be printed at a variety of sizes for running the activity without computers.
Lidar data are primarily from OpenTopography data portal and acquired by National Center for Airborne Laser Mapping (NCALM).
- Student exercise
- Unit 2 student exercise (Microsoft Word 212kB Nov27 15) PDF (Acrobat (PDF) 296kB Feb17 20) - this version of the exercise assumes that students will be using Google Earth to view the lidar data. If using Google Earth is not feasible for your course, there are a couple questions related to elevation profiles, that you will need to remove and then you can do the exercise using the posters instead.
- Unit 2 supplemental student handout (Microsoft Word 2007 (.docx) 202kB Feb17 20) PDF (Acrobat (PDF) 274kB Feb17 20)
- Google Earth data - shaded relief images of study areas
- LiDAR KMZ data files - normal, reverse, strike-slip (Zip Archive 96.4MB Feb18 20)
- LiDAR KMZ Wallace Creek (San Andreas Fault) (KMZ File 15.3MB Apr6 15) - this adds to the small amount of Wallace Creek data in the main part of the exercise; in the final part of the exercise they look in more detail at the offsets in the Wallace Creek region of the San Andreas Fault.
- Poster versions
- LiDAR Poster data files - normal (Zip Archive 175.5MB Dec5 15)
- LiDAR Poster data files - reverse (Zip Archive 75.8MB Dec5 15)
- LiDAR Poster data files - strike-slip (Zip Archive 153.4MB Dec5 15)
- LiDAR Visualization Images - normal, reverse, strike-slip (Zip Archive 29.8MB Apr7 15)
Teaching Notes and Tips
Google Earth tips
- Before students undertake the lab, they should be made aware of some useful tips and resources, and ideally, have the chance to practice/investigate their use and implementation. If any of the Google Earth (KMZ) files do not appear to be rendering properly, encourage students to zoom in or out or try to view the data from directly overhead rather than obliquely. This usually clears up viewing issues.
- Another thing to check is whether "Terrain" is checked in the Layers pane. Having Terrain unchecked will be better for viewing lidar images in some heavily vegetated areas where the Google Earth image is affected by tall trees. Having Terrain checked will work better when doing elevation profiles.
- Google Earth elevation profiles always pull from the background DEM, not the lidar. They can still be useful to look at but you will need to caution students that the shaded relief is showing more detail than an elevation profile will for some sites.
- In order to make an elevation profile: Add > Path
- Make path where you want to profile > Ok
- Right-click on the path in the Places window > Show Elevation Profile
- The Google Earth and pdf map files provided in this exercise contain faults as mapped by the USGS Quaternary Fault Database. This database is very valuable for identifying potentially active faults; however you will want to caution students that many of the fault locations have not been updated since the acquisition of lidar data. Students may note that the faults are not in "the right place" based on where the fault is clearly visible in the high resolution lidar images. This is an opportunity to discuss with the students how scientific knowledge can be refined as methods improve. Using this newer data, students can "do better" than USGS scientists because they are using more recent technology.
Adding study areas
Although this unit provides a suite of case study sites, you may wish to have your students access more data sets so they know how to search and access lidar data in the future. OpenTopography provides an easily accessible data portal for lidar. A selection of the OpenTopography datasets come already available in Google Earth format. If you wish to access any data sets from OpenTopography that do not automatically come with Google Earth KMZ files (as described in #1 below), you can follow the UNAVCO instructions to generate a KMZ of any OpenTopography lidar data set. OpenTopgraphy Video Tutorials also describe this process and other data access procedures.
Unit 2 supplemental student handout (Microsoft Word 2007 (.docx) 202kB Feb17 20) - Example handout containing the information below
- Accessing lidar data through OpenTopography
The OpenTopography portal is a collection of open access lidar data. Over 150 raw data sets (i.e. point clouds) are available, and can be manipulated and processed into more useful products, such as bare earth DEMs, with specialized software (e.g. the latest version of ArcGIS; this is beyond the scope of this lab, but detailed instructions on how to do this can be found online) For around 30 of the data sets, kmz files of hillshade bare earth images are available, which are perfect for our purposes. To access these:
- Visit www.opentopography.org.
- Click on the Data tab beneath the logo at the top of the page.
- Click on the Google Earth Files link that will appear beneath the Data tab.
- A list of download links should appear below. You can filter them by location (state), if that is useful, e.g. to obtain data from the major active faults in California, which are covered by these files:
- EarthScope Southern & Eastern California Lidar Imagery (#24)
- EarthScope Northern California Lidar Imagery (#28)
- To download these two files, right-click on the links and choose "Save Link As" (or the equivalent in your browser).
- You can also view OpenTopgraphy Video Tutorials to help become familiar with this process.
If you are unfamiliar with Google Earth, there are instructions for basic use of this program that can be found on the SERC website Teaching with Google Earth. After a bit of practice, students can learn to manipulate the main imagery controls. Once students find a particularly useful or instructive view and want to save the on-screen image in Google Earth (perhaps to include in a project report), they should:
- Go under the File menu and highlight Save with the mouse pointer; from the submenu that should appear, select Save Image;
- Choose a suitable file name and place to save it and click OK;
- You now have a jpeg screenshot!
Producing annotated jpeg or png images is fairly easy when you have access to packages such as Adobe Photoshop or Illustrator or Microsoft PowerPoint. There are also some online alternatives. One we found that does a good job is Pixlr Editor (pixlr.com/editor). Here, you can upload an image to the site from your computer, add simple line and text annotations, and save it back to your computer, all with an interface reminiscent of Photoshop. Be sure to make the text of your annotations big enough to be legible when your image is imported into a word processor.
Various free methods are available online for the simple plotting of histograms. Excel is another option.
- Excel - you can use Excel's Analysis Tool Pack to make histograms
- A good overview is at https://www.excel-easy.com/examples/histogram.html
- From the drop-down menu "Select a data set" and choose "My Data."
- Click the Clear Title and Clear Data buttons.
- Enter an appropriate X-axis title under Title.
- Enter your data in the large window at the bottom, one data point per line. (It is probably best if you do this as you go along, i.e. enter data as you collect it, otherwise it gets a little tedious.) When you are done, click Update Data.
- Enter an appropriate interval (bin) size under Interval Size and click Update Interval.
- Enter an appropriate X minimum value (ideally a multiple of your interval size) and then click Set X Min.
- Once you are happy with your histogram, make a screen grab of it.
- Press Shift+Print Screen to take a screen grab and copy it to the Windows clipboard.
- Open Microsoft Paint, and paste the screen grab into the window (Control+V).
- Use the select tool to select the area of the plot.
- Click on the Crop icon to crop the image to the selection area.
- Save the image to your computer as a png or jpeg file.
Example #1: Within the context of implementation of Section 2.2a as a modified gallery walk, several informal and formal methods may be used to assess gallery walks available on the SERC website. Ultimately, students should be able to identify the three main fault types and provide the evidence they used to determine which type of fault was present. During the discussions that follow, and in each of the small-group presentations, students should be encouraged to share: concerns about the uniqueness of the methods; whether the most diagnostic features are unique to a single fault type or of there is some overlap with other faults; and whether there are features that are ambiguous or have certain length scales that must be taken into account.
Example #2: Faculty may collect student criteria lists and evidence maps at the end of the class meeting, either one set from each student or one combined set of maps from each group before and after presentations and discussions.
Example #3: Depending on the classroom setup and time constraints, faculty may choose to have group report-outs after the presentation and discussion. The faculty member could moderate the report-outs by projecting a slide of the prediction and evidence maps, asking selected groups for their predictions and rationale, populating the maps as the groups respond, and asking for alternative predictions and rationale from other groups. Alternatively, individual groups could be called to the front of the classroom to populate the maps (perhaps one group for each of the four study sites).
Example #4: For Parts 2.2b and 2.3, assessments will follow an evaluation of the student responses to the questions provided. A set of grading rubrics will include a list of criteria for student responses to each of the questions and the additional supporting graphics (concept sketches) that are requested.
References and Resources
High Resolution Data Sources (largely airborne lidar)
- OpenTopography - data portal for (mostly airborne) lidar collected by EarthScope, NCALM, and a variety of other partners
- US Interagency Elevation Inventory - shows availability of high-accuracy topographic and bathymetric data for the United States and its territories; does not provide the data but gives info on where the data may be located; as best as is known by OpenTopography
- USGS National Map - wide variety of geospatial data including lidar
- USGS Earth Explorer - wide variety of geospatial data including high resolution topographic data
- NOAA Digital Coast - lidar elevation data as well as land cover and satellite images for many of USA's coastal regions
- Oregon's DOGAMI Lidar Viewer
- Puget Sound (Washington) Lidar Consortium
- Idaho Lidar Consortium
- More state and local government and organizations are adding lidar all the time. Try searching for your region.
Additional Resources for Instructors:
- Introduction to Lidar Tutorial
- National Center for Airborne Laser Mapping (NCALM)
- Wallace Creek component of the exercise was adapted from Wallace Creek Field Trip Student Guide and Wallace Creek Virtual Field Trip. http://www.opentopography.org/index.php/resources/educators. Retrieved December 3, 2014.
- OpenTopoLidar-to-GoogleEarth tutorial This tutorial allows you to download any lidar data set in the OpenTopography archives into Google Earth kmz format, not just what has been put in the OpenLandform Catalog.
- Lidar and GIS exercise developed by the Tewksburys that includes tutorial on manipulating lidar point clouds in Arc.
Earthquake Faults Overview
Animations of Basic Earthquake Faults
- USGS Visual Glossary of Fault Types
- GEOExPro - Know Your Faults - Part I and Part II
- Faults: Introduction and Images - Leeds, UK
- Determining Earthquake Recurrence Intervals from Trench Logs: A Multi-faceted, Thought-Provoking Exercise for Students at All Levels
- World Stress Map
- UNAVCO Map Tools
- Overview of Error Analysis
- Propagation and Compounding of Errors