Pleistocene to Quaternary strain between active faults, San Francisco Bay RegionEntry ID: SF_BAY_FOLDS_01
Abstract: The need for a better understanding of the seismic risk posed by active blind
faults is evident from recent damaging earthquakes in northern and southern
California, including the Coalinga 1983, Loma Prieta 1989, Petrolia 1992,
Northridge 1994, and Whitter Narrows 1987 events. These events are moderate
magnitude 6.5 to 7.1 and yet represent a substantial and costly hazard
(combined damage ... estimates of 30.5 billion dollars). The objective of this
project is to investigate Late Neogene and Quaternary blind thrust faulting in
the San Francisco Bay Region by developing geomorphic criteria to map,
correlate and characterize Plio-Pleistocene and Quaternary paleosurfaces using
available 30 and 90 meter digital elevation models (DEM's) and field studies.
Part of the focus is to estimate the magnitude of intra-block strain associated
with folding that is occurring between the major zones of strike-slip faulting
by using deformed surfaces as a strain markers and constructing balanced
sections in areas with good geologic control. This can provide information
about regional tilting and intrablock deformation occurring between active
faults that represents an important component of the regional long term strain
budget. It also helps to locate active large-scale structures that are buried
and which may have potential for large earthquakes. The study provides
important information about regional strain that cannot be obtained by
conventional slip studies along active faults. The study is generating
geomorphic maps of paleosurfaces and provides information to help quantify
magnitudes of strain and strain rates by constraining the age and morphology of
the surfaces. The investigation includes developing digital images of
geomorphic features, including escarpment enhancement, curvature, and slope
maps that can be used for tectonic analysis. In addition, developing grid-based
techniques for enhancing surface gradient anomalies, generating topographic
residual maps, reconstructing paleosurfaces, and rapid digital production of
stream and ridge profiles for analysis of regional tectonic flexure.
(Click for Interactive Map)
Data Set Citation
Dataset Originator/Creator: Jayko, A.S. and Lewis, S.D. compliers
Dataset Title: Pleistocene to Quaternary strain between active faults, San Francisco Bay Region
Dataset Release Date: 1996
Dataset Publisher: USGS, DOI
Issue Identification: Annual Project Summaries > Volume 37 > Northern CaliforniaOnline Resource: http://geodiscover.cgdi.ca/gdp/search?action=fullMetadata&entryId=5...
ISO Topic Category
Role: TECHNICAL CONTACT
Email: ajayko at isdmnl.wr.usgs.gov
US Geological Survey, Mail Stop 975 345 Middlefield Rd.
City: Menlo Park
Province or State: CA
Postal Code: 94025
Jayko, A. S., 1994, Geomorphic Response to Active Folding, Southwestern San
Francisco Peninsula: EOS American Geophysical Union, v. 75 , p. 682. (Special
symposium, session organizer).
Jayko, A.S., 1995, Active folding and blind thrusting associated with the San
Andreas Transform, north-central California, EOS American Geophysical Union, v.
1995, p. f559.
Jayko, A.S., and Lewis, S.D., 1996, Towards assessing the seismic risk
associated with blind thrusts: U.S.G.S. Open-file report OF-96XXX, scale
1:500,000, 137 pp (21 contributed short papers), in review.
Creation and Review Dates
DIF Creation Date: 1999-03-11
Last DIF Revision Date: 2009-03-24