Jamaica: the northern Caribbeanplate boundary and earthquake risk

Prof. Simon MitchellDr. Lyndon Brown

The Earthquake UnitThe University of the West Indies

Haiti Earthquake: 12th January 2010 – Magnitude 7.0 – Depth 13 km

USGS AlaskaSeismograph

The Caribbean Plate can be defined by volcanoes

red, shallowyellow, intermediateblue, deep

and earthquakes

GPS measurements of the Caribbean Plate relative to a stationary North American Plate

We can measure movement using GPS

Caribbean Plate motion

The Gonâve MicroplateExtends from the Cayman Spreading centre (with its black smokers) eastwards into the island of Hispanola. The GonâveMicroplate 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.

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.

Restraining Bend Model – Paul Mann (various papers)NW-SE restraining bends link to E-W faults driving uplift.

Earthquake Unit ResourcesBroadband digital seismometer network (4 broadband seismographs)

Strong motion accelerometer network in key areas (12 accelerometers including: Kingston-NMIA Airport; TransJamaica Highway PortmoreToll; 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

BroadbandSeismometer

(Digital Network)

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.

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.

Seismic activity since mid-1990sNote 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 EarthquakesThe major earthquakes that affected Jamaica were the 1692 and 1907 earthquakes.

IX

VII

VIII

X

HISTORY OF MAJOR EARTHQUAKES IN JAMAICA

Date of Earthquake

Magnitude/ Intensity

Effects

1692 X Liquefaction, Tsunami‐north coast

1907 IX Tsunami –north coast, Liquefaction

1941 VII South coast of Jamaica1957 VI Western Jamaica‐

epicentre1971 VIII Kingston and Port 

Royal 1993 5.4/VII‐VIII Kingston‐major 

structural failure2005 5.1 Aenon Town –

Clarendon‐ structural  failure

LANDSLIDES

Judgement Cliff

OFFSET STREAMS

FAULTS IN ALLUVIUM (Palaeoseismic studies)

FOLDS

YOUNG UNCONFORMITIES

GEOLOGICAL MAPPING – Benbow Inlier

DoGG Geological Mapping Programme1996-2014

OBJECTIVES:

Identify faults and fault relationships

Relate seismicity to mapped fault systems

Identify rock types and thier engineering properties

GEOLOGY

Crawl River Fault Cavaliers Fault

Towards Lazaretto Inlier

Towards Lazaretto Inlier

(s)

0 1 2 3 4 50.5Kilometers

¯ #* 'Strong Motion JAD2001$' Events'POINTSMICROJAD 2001FINAL$' EventsPeriod

0.025 - 0.100.10 - 0.300.30 - 0.600.60 - 1.001.00 - 1.50

1.50 - 2.00

2.00 - 2.50

2.50 - 3.20

ELEV_M0 - 300300 - 550550 - 700700 - 12201220 - 2210#*

#*

#*#*

#*

76°42'0"W

76°42'0"W

76°48'0"W

76°48'0"W

76°54'0"W

76°54'0"W

18°0'0"N 18°0'0"N

SEISMIC MCIROZONATION-ISOPERIOD MAP OFKINGSTON METROPOLITAN AREA

White Limestone (Red Hills, Long Mountain)

Rock Types Response

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

Rock types in the Greater Kingston area and their characteristics

The Earthquake Unit – Future developmentEXPAND 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.