Download Jamaica: the northern Caribbean plate boundary and earthquake risk

Jamaica: the northern Caribbean
plate boundary and earthquake risk
Prof. Simon Mitchell
Dr. Lyndon Brown
The Earthquake Unit
The University of the West Indies
USGS Alaska
Seismograph
Haiti Earthquake: 12th January 2010 – Magnitude 7.0 – Depth 13 km
The Caribbean Plate can be defined by volcanoes
and earthquakes
red, shallow
yellow, intermediate
blue, deep
We can measure movement using GPS
GPS measurements of the Caribbean Plate relative to a stationary
North American Plate
Caribbean Plate motion
The Gonâve Microplate
Extends from the Cayman
Spreading centre (with its black
smokers) eastwards into the island
of Hispanola. The Gonâve
Microplate is moving at 11 mm/yr
relative to the North American
Plate, and 8 mm/yr relative to the
Caribbean Plate.
Black-smokers in the Cayman spreading centre.
Restraining Bend Model – Paul Mann (various papers)
NW-SE restraining bends link to E-W faults driving uplift.
Mann, P., DeMets, C. and Wiggins-Grandison, M. 2007. Toward a better understanding of the Late Neogene strike-slip
restraining bend in Jamaica: geodetic, geological, and seismic constraints. From: W.D. Cunningham and P. Mann (Eds.),
Tectonics of Strike-Slip Restraining and Releasing Bends. Geological Society, London, Special Publication, 290, 239-253.
Earthquake Unit Resources
Broadband digital seismometer network (4 broadband seismographs)
Strong motion accelerometer network in key areas (12 accelerometers
including: Kingston-NMIA Airport; TransJamaica Highway Portmore
Toll; Long Mountain; Kingston Container Terminal)
Contributes data to the upcoming Caribbean Tsunami Warning
Network in conjunction with the USGS
Acts as a Data Centre for the Comprehensive Test Ban Treaty
Organization (CTBTO).
Operates a 36-station GPS network for measuring stress accumulation
across Jamaica (in collaboration with Prof. Chuck De Mets, University
of Wisconsin).
How we record and measure earthquakes
Analog Network- Seismometers and Accelerometers
Broadband
Seismometer
(Digital Network)
Measured GPS motion within Jamaica
1. Jamaica is moving toward the WSW relative to the Caribbean Plate.
2. There is a north-south velocity gradient across Jamaica.
Mann, P., DeMets, C. and Wiggins-Grandison, M. 2007. Toward a better understanding of the Late Neogene strike-slip
restraining bend in Jamaica: geodetic, geological, and seismic constraints. From: W.D. Cunningham and P. Mann (Eds.),
Tectonics of Strike-Slip Restraining and Releasing Bends. Geological Society, London, Special Publication, 290, 239-253.
Seismic activity since mid-1990s
Note the significant cluster to the north of Kingston
(Green dots show events relocated by Margaret Grandison)
Jamaican Geology: The geology of Jamaica consists of an Eocene to
Miocene limestone succession that was uplifted and eroded in the late
Miocene-Recent to expose Cretaceous-Paleocene inliers and Paleocene to
Eocene rift-basin deposits.
Simplified geological map of Jamaica
Historical Earthquakes
The major earthquakes that affected Jamaica were the 1692 and 1907
earthquakes.
X
IX
VIII
VII
HISTORY OF MAJOR EARTHQUAKES IN JAMAICA
Date of Earthquake
Magnitude/ Intensity
Effects
1692
X
1907
IX
1941
1957
VII
VI
1971
VIII
1993
5.4/VII‐VIII
2005
5.1
Liquefaction, Tsunami‐
north coast
Tsunami –north coast, Liquefaction
South coast of Jamaica
Western Jamaica‐
epicentre
Kingston and Port Royal Kingston‐ major structural failure
Aenon Town –
Clarendon‐ structural failure
LANDSLIDES
Judgement Cliff
OFFSET STREAMS
FAULTS IN ALLUVIUM (Palaeoseismic studies)
FOLDS
YOUNG UNCONFORMITIES
GEOLOGICAL MAPPING – Benbow Inlier
OBJECTIVES:
Identify faults and fault relationships
Relate seismicity to mapped fault systems
Identify rock types and thier engineering properties
DoGG Geological
Mapping Programme
1996-2014
GEOLOGY
Crawl River Fault
Cavaliers Fault
Towards Lazaretto Inlier
Towards Lazaretto Inlier
SEISMIC MCIROZONATION-ISOPERIOD MAP OF
KINGSTON METROPOLITAN AREA
76°54'0"W
76°48'0"W
76°42'0"W
¯
* 'Strong Motion JAD2001$' Events
#
'POINTSMICROJAD 2001FINAL$' Events
Period (s)
0.025 - 0.10
0.10 - 0.30
0.30 - 0.60
0.60 - 1.00
1.00 - 1.50
1.50 - 2.00
2.00 - 2.50
*
#
*
#
18°0'0"N
2.50 - 3.20
18°0'0"N
ELEV_M
0 - 300
300 - 550
550 - 700
700 - 1220
1220 - 2210
*
#
*
#
*
#
76°54'0"W
76°48'0"W
76°42'0"W
00.51
2
3
4
5
Kilometers
Rock types in the Greater Kingston area and their
characteristics
Rock Types
Response
White Limestone
(Red Hills, Long
Mountain)
Competent rocks with relatively low
ground acceleration rates. Minimal
landslides.
Cretaceous and
Eocene clastics
(Gordon Town,
Irish Town, etc.)
Incompetent rocks, ground
acceleration likely to cause extensive
landslides particularly if waterlogged.
Alluvium
(Kingston, Spanish
Town, Portmore)
Unconsolidated rocks, amplified
ground acceleration, extensive
liquifaction and major damage.
The Earthquake Unit is establishing a netweork of accelerometers to
quantify ground acceleration rates associated with earthquakes
The Earthquake Unit – Future development
EXPAND the Broadband digital seismometer network.
EXPAND the Strong motion accelerometer network.
COMPETE the geological mapping of Jamaica and produce a new
tectonic map that can be integrated with earthquake epicentre data.
UNDERTAKE geophysical analysis of faults and palaeoseismic studies
to access fault activity.
INCREASE coverage of seismic microzonation maps.
INCREASE its outreach programme to inform Jamaicans of earthquake
risks.