Beth L. Widmann1, Robert M. Kirkham1
Matthew L. Morgan1 and William P. Rogers1
With contributions by
Anthony J. Crone2, Stephen F. Personius2 and Keith I. Kelson3
GIS and Web design by
Karen S. Morgan1, Gerald J. Pattyn4, and Randal C. Phillips1
1Colorado Geological Survey, Denver, Colorado
2 U.S. Geological Survey, Golden, Colorado
3 William Lettis & Associates, Inc., Walnut Creek, California
4 Farragut Systems, Inc., Lafayette, Colorado
USING THE MAP SERVER
To view the internet map server, you must have:
Internet Explorer 5.0 or higher and,
The MapGuide plug-in.
Click here to download a viewer with default options for Windows (3Mb)
INTRODUCTION TO THE WEB SITE
This web site offers three ways to access Colorado late Cenozoic fault and fold information:
The Map Server displays a map of color-coded faults within Colorado. This interactive map allows quick identification of structures by displaying a pop-up information box (called a maptip) containing the name, identification, and age of the structure, when resting a cursor over any of the faults. Other layers in the map also contain maptips. For example, resting the cursor over a city area (shaded in purple) will show the city name and when resting on the background the name of the county appears (in ALL CAPS). The map legend in the leftmost web frame shows the data layers and how each feature is symbolized. Zooming in to the map displays different information layers. For instance, highways appear when the map is zoomed to 1:500,000.
The map server contains several ways to learn about a fault or fold from the Microsoft Access database. The database contains a variety of information about each structure, such as length, sense of movement, geomorphic expression, age of faulted deposits and references. To see a report from the database, simply double-click the mouse on the structure in the map frame, or click once on the structure to select it and click the "Selection Results" button in the bottom frame. You can also select a structure from the dropdown menus in the bottom frame and click the "Report" button. The report you see using any option lists all the information contained in the Access database.
Additional help with the MapGuide viewer is available at www.mapguide.com.
This database will be periodically updated as new information on Colorado's late Cenozoic faults and folds becomes available. Users of this database are encouraged to submit comments, corrections, and additions to Matt Morgan.
INTRODUCTION TO THE STUDY
The Colorado Late Cenozoic Fault and Fold Database contains information compiled from available literature about faults and folds that are known or suspected to have moved during the late Cenozoic (approximately the last 23.7 million years) i.e., that cut Miocene or younger rocks. Previous summaries of late Cenozoic structures in Colorado by Witkind (1976), Kirkham and Rogers (1981), and Colman (1985) served as an initial basis for the compilation of this database. More recent, and in many cases more detailed studies, provided updated information for many of the structures. Fault and fold traces were compiled from the references, hand transferred onto 1° x 2° (1:250,000-scale) Army Map Service base maps, and digitized. The structure traces, their identification symbols, and any trenches excavated across them as part of paleoseismic investigations are shown on the fault map.
This database and associated maps are valuable resources to anyone interested in earthquake hazards and the activity of faults and folds in Colorado. Most seismic hazard investigations generally consider only Quaternary structures, which raises the question "why include structures in the database that only have evidence of late Tertiary activity?" The current tectonic environment of Colorado apparently initiated near the beginning of the Miocene Epoch. Although the extensional stress regime probably evolved and changed since its initiation about 25 to 28 million years ago, it essentially remains the same today. Some of the structures active during the Miocene and Pliocene are also likely to have experienced movement during the Quaternary. Structures with Miocene or younger movement, which herein are classified as late Cenozoic structures, should be closely examined for evidence of Quaternary activity during seismic hazard investigations. Structures whose late Tertiary history cannot be documented due to an absence of Neogene deposits should not be ignored in seismic hazard studies. Structures with orientations favorable for slip in the modern stress environment need to be investigated, even if there is no published evidence of late Cenozoic activity. For example, a north-northwest-trending fault that cuts Precambrian rocks but is locally concealed by late Holocene deposits may still be a potential seismic source.
The Colorado Geological Survey maintains an Earthquake Reference Collection that contains more than 500 sources on faulting and earthquakes in Colorado. Many of the references cited in the database are in the collection and can be viewed by appointment. To schedule an appointment please call 303-866-2611.
This project was funded in two phases. Quaternary data collection was funded jointly by the Colorado Geological Survey, the U.S. Geological Survey National Earthquake Hazards Reduction Program, Award No. 1434-HQ-97-GR-02985, and the Colorado Office of Emergency Management. Part of the funding provided by the Colorado Geological Survey is from mineral severance taxes collected from producers of oil, gas, coal, and minerals. Pre-Quaternary data collection was funded by the Colorado Geological Survey. We thank Kathy Haller and Michael Machette, U.S. Geological Survey, for their professional support and guidance in setting up the framework for this database. Richard Dart, U.S. Geological Survey provided scripts and technical assistance in fault statistic compilation. John Ake, U.S. Bureau of Reclamation, Susan Steele Weir, Denver Water Department, Ivan Wong, Woodward-Clyde Federal Services, John Nicholl, Woodward-Clyde Consultants, and Katherine Hanson, Geomatrix Consultants, provided copies of reports prepared by their respective organizations. Gary Christiansen, Utah Geological Survey, shared knowledge and provided reports about faults along the Colorado-Utah border. Jason Wilson, Colorado Geological Survey, provided draft maps and initial data checks.
This publication should be cited as follows:
Widmann, B. L., Kirkham, R. M., Morgan, M. L., and Rogers, W. P., with contributions by Crone, A. J., Personius, S. F., and Kelson, K. I., and GIS and Web design by Morgan, K. S., Pattyn, G. R., and Phillips, R. C., 2002, Colorado Late Cenozoic Fault and Fold Database and Internet Map Server: Colorado Geological Survey Information Series 60a, http://geosurvey.state.co.us/pubs/ceno/.