Mecca Hills field trip

Introduction

Study of the active fault trace with high resolution topography and imagery

Balloon photography

OpenTopography for high resolution DEM data

Rectifying and mapping

Assignment--Due Thursday April 2, 2009

1. Compute DEMs on the http://www.opentopography.org site for the research location. Experiment with the grid computation settings for both local binning and the spline method.
2. Rectify a subset of the balloon photography that covers the study location with the best combination of quality and coverage.
3. Rectify your field mapping and note locations
4. Produce a digital map of the fault traces, major geomorphic features (channels, ridges, surfaces), and identify the major offset channels
5. Measure and quality rate as many of the offsets as possible. Quality rating should be poor, fair, good, excellent and indicate the quality of the reconstruction. The measurement should include a +/- uncertainty.
6. Turn in:
   • A few demonstrative DEM and imagery graphics
   • The map
   • Tabulation of offsets, uncertainty, and quality rating
   • Short writeup including methods; description of the fault zone structure, geomorphology, offsets; and interpretation of what you think the slip in the last few earthquakes may have been and what assumptions go into that interpretation (incision timing relative to earthquake offset timing)

Study of the structure of the fault zone

GIS data

GIS tasks

• strike dip type unit/feature operator
• vocabulary for the type:
• bedding
• fault
• contact
• foliation
• fold_axis_anticline
• fold_axis_syncline

Analysis of structures

Folding analysis

• Figure out file format
• Compute poles to bedding planes
• Fit great circle to poles
• Pole to that plane is the fold axis

Field Photos

Assignment--Due Thursday April 9, 2009

1. Build GIS, rectify the field mapping
2. Compile strike and dips for bedding, faults, foliation and point features for fold axes and deliver shapefile to group with format as indicated above to Ramón on Tuesday March 31
3. Compile polylines and polygons representing the faults, macroscopic fold axes, contacts, etc. Use agreed upon colors/symbology. Share above with group by deadline
4. Analyze folds and compare fold orientations with other structural orientations such as faults
5. Geologic cross section through the mapping area (include linework in the air, maintain stratigraphic thickness where plausible, use geologic intuition and field observations to help draw features, calculate apparent dip in the plane of cross section if the structural bearing is less than 65 degrees, see also slide 31 in Introductory powerpoint). Use either Kink or Busk method, depending on which you think is better for this case. See also: Fold analysis and cross sections
6. Turn in (avoid literature review):
   • The geologic map
   • The geologic cross-section
   • Analysis of structures with illustrations
   • Short writeup including methods; brief description of the main geologic units; description of the fault zone structure including faults and folds based on both map and the cross-section; and interpretation of the shear zone: if the main faults are all strike-slip, how do the folds relate and how did they develop (can be more than one way)?

Group photo