Assessing the mechanical
behavior and seismic risk of the
Central Range Fault, Trinidad
John C. Weber, Professor of Geology
Grand Valley State University, Allendale, MI
6th CCCDM, P-O-S, Trinidad, GEMS session, 12/05/2011
Caribbean plate + boundary faults
Tobago
Caribbean plate motion - GPS (Weber et al. 2001)
SA
TDAD
plate
fixed
Ca
BLACK
(observed)
RED
(rigid
plate
model)
Southern plate boundary earthquake epicenters
(courtesy of FUNVISIS)
The Earthquake Cycle
Reid (1910)
coseismic
coseismic
Motion
coseismic
fault locked & accumulating
elastic strain:
no EQs
ri (ky)
EQ!
The Earthquake Cycle
Reid (1910)
fault locked & accumulating
elastic strain:
GPS; creep-, strain-meters, etc.
coseismic
coseismic
Motion
coseismic
EQ geology
ri
EQ
seismology
GPS+ geodesy
Central
Range
fault
SA fixed
1901 triang-1994 gps
1901 triang-1994 gps
1994 gps-1999 gps
Saleh et al. 2004;
Weber et al. 2010
Elastic dislocation half-space model
for locked vertical strike-slip faults
Accounts
for shallow
Vnear= Vfar tan-1 (D/d)
elastic
interseismic
effects
deep
creep
*Best Fit*
minimize
obs - mod
differences
(c2)
Elastic model fits to the GPS data
*
*
north
south
Elastic dislocation
models
creeping
fault
#69
#115
Saleh et al. 2004;
Weber et al. 2001;
Weber et al. 2010
2005, 2007 occupations
w. UWI-Surveying
(A. Rodriguez, GVSU)
Also new data from
2011 occupation:
w. UWI-SRC (ODPM)
SA fixed
New in-progress GPS results
Long-term “Cultural” creep meters
(2001)
(2001,
2002)
no creep
offsets
no creep offsets
Prentice et al. 2010
Paleoseismology: search for/study “fossil” earthquakes
EQ geology
Locked or
creeping
CRF?
Prentice et al. 2010
2002 Results (Samlalsingh, Trench 9)
Prentice et al. 2010
LAST CRF (PREHISTORIC) EVENT (EQ):
• after ~ 3,000 y.b.p.; before ~550 y.b.p.
New view from subduction zones
Slow eqs discovery: Kanamori and Kikuchi 1993
2
episodic
1
locked
3
SSEs
non-volcanic
Marone and Richardson, 2010
Locked or creeping (or both - %)
or slowly slipping CRF?
Need to build and maintain a SAF/PBOstandard Central Range Fault earthquake
(geophysical) observatory instrumented with:
• creep arrays
• creep meters
• microseismometers
• CGPS, episodic GPS
• strain meters
• strong motion instruments
+ more paleoseismology trenches
Acknowledgements
• GPS funding: NASA, NSF, PRF, BHPBilliton, Trinidad and Tobago ODPM
• Paleoseismology funding: Trinidad and
Tobago Ministry of Energy and Energy
Industries
• Logistical support: UWI - Seismic
Research Center, Department of
Surveying and Land Information; GSTT