Dr. Jeff Marshall
Research with Undergraduate Students
Nicoya Peninsula, Costa Rica
Research Projects: Geomorphology and
geochronology of uplifted marine terraces and shore deposits Coastal tectonics,
paleo-geodesy, and paleo-seismology of the Nicoya seismic gap Megathrust seismic hazards and effects of the M7.7 1950 Nicoya Peninsula
earthquake
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On the Cutting Edge Program – Tectonic Geomorphology of Nicoya
Peninsula: Megathrust
earthquakes, coastal uplift, and emergent marine terraces of Costa Rica’s
Nicoya Peninsula
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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 provides an optimal setting for the study of upper
plate deformation 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 5
October 1950 with a magnitude of Mw=7.7. This event produced widespread
damage and generated 1.0-1.5 m of coseismic uplift along the peninsula's
central coast (Marshall and Anderson, 1995). The net pattern of upper plate
deformation related to large subduction earthquakes is recorded by emergent
Quaternary marine terraces along the peninsula’s 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. Research Abstracts: 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 Students
working on these projects: Images: Project
photos and illustrations Prior Related Publications: 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. 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.,
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. Back to: |
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