Crestone Science Center, Inc.
600 East Galena Avenue
P.O. Box 837
Crestone, Colorado 81131
USA
2001 RESULTS: FIELD METHODS IN NEOTECTONICS AND PALEOSEISMOLOGY
(June 7-20, 2001)
DIGITAL TRENCH LOGGING, RETRODEFORMATION OF THE LOG
The 2001 trench was
excavated across a rather small scarp of the Villa Grove fault zone. Vertical
surface offset was 2.5 meters, so this is the minimum vertical displacement we
expect to find on the underlying fault.
The 2001 trench was logged
manually via a string line grid, and then scanned and heads-up digitized.
The trench
log was then retrodeformed by successively removing deposits and restoring
fault displacements, going back through time from the present. During this
procedure we use several “rules of thumb” for estimating the pre-erosion
geometry of eroded units.
The
final stage of interpretation was a speculative reconstruction of fault
geometry. The reconstruction was felt necessary because the main fault exposed in
the trench actually has a reverse-fault geometry, even though the VGFZ is a
normal fault zone.
For
more information, contact Crestone Science Center at the
address below:
600
East Galena Ave.
P.O. Box 837
Crestone, CO 81131
Phone: (719) 256-5227Fax: (719) 256-5228E-mail: mccalpin@geohaz.comJames P. McCalpin(mccalpin@geohaz.com)