Dr. Jeff Marshall’s Research
Tectonics & Earthquakes
Nicoya Peninsula, Costa Rica
Research Experience for Undergraduates Megathrust
earthquakes and morphotectonic segmentation of the Nicoya Peninsula seismic
gap
Funding from the National Science Foundation MARGINS
Program - Seismogenic Zone Experiment (SEIZE) Project Vignette (from Key
Concepts in Geomorphology) |
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Digital elevation model
of southern Central America, showing NASA-SRTM topography for Nicaragua and
Costa Rica linked to offshore IFM-GEOMAR multi-beam bathymetry (courtesy of
C. Ranero, ICM-CSIC, Barcelona). This image reveals the relationship between
the morphology of the subducting Cocos Plate and the morphotectonic structure
of the overriding fore arc and volcnic arc of the Caribbean Plate and Panama
block. |
Upper Image: Digital elevation model
of the Nicoya Peninsula (NASA-SRTM) showing areas of uplifted marine and
fluvial terraces within the Pleistocene Iguanazul, Carrillo-Camaronal,
Cobano, and La Mansión geomorphic surfaces (red areas); and the Holocene
Garza and Cabuya surfaces (yellow areas). Rectangles outline three coastal
study areas. Lower Image: Summary diagram showing
coastal terrace elevations, age data, and uplift rates. Numbers in circles
indicate specofic terrace study sites. Terrace ages based on sea level curve
correlations and isotopic dates (OSL and 14C, as indicated). Differences in
uplift rates for each study area reflect variations in the subducting
seafloor and seismogenic zone structure across the EPR, CNS-1, and CNS-2
segment boundaries. |
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Project Overview: The Nicoya
Peninsula, Costa Rica is an ideal setting for the study of megathrust
earthquakes and the growth and decay of coastal topography along the Middle America
convergent margin. Located only 60-70 km inboard of the Middle America
Trench, this outer fore arc peninsula sits directly above the seismogenic
zone within a high potential seismic gap. The last major earthquake centered
beneath the Nicoya peninsula occurred on October 5, 1950 with a magnitude of
Mw=7.7. This event produced widespread damage, and generated 1.0-1.5 m of
sudden coseismic uplift along the peninsula's central coast, followed by
several decades of gradual interseismic subsidence (Marshall and Anderson,
1995). The net deformation pattern associated with the seismic cycle is
recorded by emergent late Quaternary marine terraces along the coast and
uplifted alluvial fill terraces within interior valleys (e.g., Hare and
Gardner, 1985; Marshall and Anderson, 1995; Gardner et al., 2001; Marshall et
al., 2001). The goal of this
research is to determine the lateral extent and elevations of uplifted
Quaternary marine and fluvial terraces along the length of the Nicoya seismic
gap, and to use this information to constrain variations in uplift rates
along this transect. At present, Pleistocene marine terraces and Holocene
paleo-shorelines have been mapped along three segments of the Nicoya
Peninsula’s coastline: 1) the peninsula’s northern coast (“Iguanazul
surface”), 2) central coast (“Carrillo-Camaronal Surface”), and 3) the
peninsula’s southern tip (“Cobano surface”). In addition, alluvial fill
terraces have been mapped within interior valleys of the central peninsula
(“La Mansión surface”). The results of this investigation will allow us to
assess the relationship between Quaternary deformation patterns, upper plate
faulting, characteristics of the subducting seafloor, and the geometry of the
interplate seismogenic zone. Images: Project
photos and illustrations Student
Researchers: Amber Butcher Evelyn Mejía Liliana Nuñez Brent Ritzinger Kacie Wellington Research Abstracts: 2009 GSA
Annual Meeting Abstract (1): Geological Society of America Annual
Meeting, Portland, Oregon, 2009 2009 GSA
Annual Meeting Abstract (2): Geological Society of America Annual
Meeting, Portland, Oregon, 2009 2008 GSA
Annual Meeting Abstract: Geological Society of America Annual Meeting,
Houston, Texas, 2008 2008 NSF
MARGINS SEIZE Workshop Abstract: NSF MARGINS SEIZE Workshop, Mt. Hood, Oregon, 2008 2008
Central American Geologic Congress Abstract: IX Congreso Geológico de América
Central, San José, Costa Rica, 2008 2007 AGU Fall
Meeting Abstract: American Geophysical Union Fall Meeting, San Francisco,
California, 2007 2007 NSF
MARGINS Meeting Abstract: NSF MARGINS Central America Focus Site Meeting,
Heredia, Costa Rica, 2007 2006
GSA Cordilleran Meeting Abstract (1): Geological Society of America
Cordilleran Section Meeting, Anchorage, Alaska, 2006 2006
GSA Cordilleran Meeting Abstract (2): Geological Society of America
Cordilleran Section Meeting, Anchorage, Alaska, 2006 2005 GSA
Annual Meeting Abstract: Geological Society of America Annual Meeting,
Salt Lake City, Utah, 2005 2004 AGU Fall
Meeting Abstract: American Geophysical Union Fall Meeting, San Francisco,
California, 2004 2004 GSA
Cordilleran Meeting Abstract: Geological Society of America Cordilleran
Section Meeting, Boise, Idaho, 2004 2003 GSA
Annual Meeting Abstract: Geological Society of America Annual Meeting,
Seattle, Washington, 2003 Related Publications: Marshall,
J.S., Gardner, T.W., Protti, M., and
Nourse, J.A., 2009, International geosciences field research with
undergraduate students: Three models for experiential learning projects
investigating active tectonics of the Nicoya Peninsula, Costa Rica, in
Whitmeyer, S.J., Mogk, D.W., and Pyle, E.J., eds., Field Geology Education:
Historical Perspectives and Modern Approaches: Geological Society of America
Special Paper 461, p. 77-98, doi: 10.1130/2009.2461(08). Marshall,
J.S., 2008, Megathrust earthquakes,
coastal uplift, and emergent marine terraces of Costa Rica’s Nicoya
Peninsula, in Bierman, P. and Montgomery, D., eds., Key Concepts in Geomorphology -
Vignettes, [online supplement]: On the
Cutting Edge Program, Science Education Resource Center (SERC), Carleton
College, Northfield, Minnesota. [ http://serc.carleton.edu/vignettes/collection/25559.html
] Marshall, J.S., Gardner, T.W.,
Fisher, D.M., Sak, P.B., and Protti, M., 2001, Quaternary neotectonics of the
Costa Rican coastal fore arc: Field Guide for the National Science Foundation
MARGINS Program Workshop on Central American Tectonics (SEIZE and SubFac
Initiatives), Heredia, Costa Rica, July 2001, 62 p. Gardner, T.W., Marshall,
J.S.,
Merritts, D.J., Protti, M., Bee, B., Burgette, R., Burton, E., Cooke, J.,
Kehrwald, N., Fisher, D., and Sak, P., 2001, Holocene fore arc block rotation
in response to seamount subduction, southeastern Península de Nicoya, Costa
Rica: Geology, v. 29, p. 151-154. Marshall,
J.S., and Anderson, R.S., 1995,
Quaternary uplift and seismic cycle deformation, Península de Nicoya, Costa
Rica: Geological Society of America Bulletin, v. 107, p. 463-473. Images: Project
photos and illustrations Back to: |
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