ugrc 144 science and technology in our lives/geohazardsseismograph station (wwsss) was commissioned...
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College of Education
School of Continuing and Distance Education2014/2015 – 2016/2017
UGRC 144
Science and Technology in Our
Lives/Geohazards
Session 4 – Earthquakes in Ghana
Lecturer: Dr. Patrick Asamoah SakyiDepartment of Earth Science, UG
Contact Information: [email protected]
Session Overview
• This session introduces students to earthquake history in Ghana, including past occurrences and locations.
• Most people living in Ghana today have never experienced an earthquake, and Ghanaians may find it difficult to associate earthquake disasters with Ghana.
• However, evidence based on the history of the Gold Coast/Ghana, modern day seismograph recordings and the geology of Ghana indicates a high earthquake disaster risk for Ghana.
Dr. Patrick A. Sakyi, Dept. of Earth Science Slide 2
Session Outline
The key topics to be covered in the session are as follows:
• Topic One – History of Earthquakes in Ghana
• Topic Two – Modern Seismographs in Ghana
• Topic Three – Earthquake Risk in Ghana
• Topic Four - Earthquake Epicenters and the Regional Geological Structures of Ghana
• Topic Five – Active Faults in Ghana
• Topic Six - Earthquake Risk Map of Ghana
Dr. Patrick A. Sakyi, Dept. of Earth Science Slide 3
Reading List
• Unit 1, Section 4 of UGRC 140 II Geohazards –Institute of Continuing and Distance Education
Dr. Patrick A. Sakyi, Dept. of Earth Science Slide 4
HISTORY OF EARTHQUAKES IN GHANA
Topic One
Dr. Patrick A. Sakyi, Dept. of Earth Science Slide 5
History of Earthquakes in Ghana
• The most significant earthquakes (magnitude 6.0 and above) which caused severe damage are:
• Elmina (1615)
• Axim (1636)
• Accra (1882)
• Ho (1906)
• Accra (1939).
Dr. Patrick A. Sakyi, Dept. of Earth Science Slide 6
History of Earthquakes in Ghana
• 1939 EARTHQUAKE
• The 1939 earthquake which was located 40 km offshore to the southwest of Accra shook most of West Africa.
Dr. Patrick A. Sakyi, Dept. of Earth Science Slide 7
History of Earthquakes in Ghana
Minor Historic Earthquakes
• Notable minor tremors were also felt in:
1858 1863 1883 1907
1911 1918 1919 1923
1925 1930 1933 1935
Dr. Patrick A. Sakyi, Dept. of Earth Science Slide 8
History of Earthquakes in Ghana
Recent Significant Earthquakes
• Since 1939, no earthquake has caused any major destruction in Ghana.
• Events that have caused concern since independence have all been centered on Accra.
Dr. Patrick A. Sakyi, Dept. of Earth Science Slide 9
History of Earthquakes in Ghana
Recent Significant Earthquakes
• They were of Magnitude 4.5 or less recorded in
1964 1967 1969
1978 1985 1995
Dr. Patrick A. Sakyi, Dept. of Earth Science Slide 10
History of Earthquakes in Ghana
Recent Significant Earthquakes
• A recent notable event was a magnitude 4.4 earthquake which occurred on Independence Day
6th March1997.Dr. Patrick A. Sakyi, Dept. of Earth Science Slide 11
MODERN SEISMOGRAPHS IN GHANA
Topic Two
Dr. Patrick A. Sakyi, Dept. of Earth Science Slide 12
Modern Seismographs in Ghana
Dr. Patrick A. Sakyi, Dept. of Earth Science Slide 13
• Modern day recording of earthquakes begun in Ghana when a 6-component World Wide Standard Seismograph Station (WWSSS) was commissioned in Kukurantumi in the Eastern Region in March 1973.
• Later, many more seismographs were installed in south eastern Ghana for the monitoring of earthquakes.
• Since 1973 scores of earthquakes, some of magnitude as low as one (1) have been recorded in southern Ghana, and their epicentres determined
EARTHQUAKE RISK IN GHANATopic Three
Dr. Patrick A. Sakyi, Dept. of Earth Science Slide 14
Earthquake Risk in Ghana
• Earthquake hazard means the probability of occurrence of an earthquake of sufficient Magnitude capable of causing damage to the weakest man-made structure.
• Risk means the measure of the likelihood of harmful consequences arising from the interaction of a hazard, vulnerable community elements and the environment.
Dr. Patrick A. Sakyi, Dept. of Earth Science Slide 15
EARTHQUAKE EPICENTERS AND THE REGIONAL GEOLOGICAL STRUCTURES OF GHANA
Topic Four
Dr. Patrick A. Sakyi, Dept. of Earth Science Slide 16
Earthquake Epicenters and the Regional
Geological Structures of Ghana
Dr. Patrick A. Sakyi, Dept. of Earth Science Slide 17
2.0E+005 4.0E+005 6.0E+005 8.0E+005 1.0E+006 1.2E+006 1.4E+006 1.6E+006
EASTINGS (ft)
2.0
E+
005
4.0
E+
005
6.0
E+
00
58
.0E
+00
5
NO
RT
HIN
GS
(ft
)
0.0E+000 2.0E+005 4.0E+005 6.0E+005 8.0E+005
1.0 to 3.5
3.5 to 4.3
4.3 to 4.9
4.9 to 5.5
5.5 to 6.2
6.2 to 6.9
SEKONDI
CAPE COAST
ACCRA
KOFORIDUA
HO
Half Assini
Axim
Tarkwa
NsawamTema
Prampram
Akuse
Keta
Recent Formation
Amisian
Sekondian
Bocene
Buem Formation
Togo Series
Granite
Voltaian
Dahomeyan Mafic
Dahomeyan Felsic
Tarkwaian
Metasediments (Birimian)
Metavolcanics (Birimian)
LEGEND
FAULTS
Normal
Thrust
Downthrow
Magnitudes of Epicenters
ACTIVE FAULTS IN GHANATopic Five
Dr. Patrick A. Sakyi, Dept. of Earth Science Slide 18
Active Faults in Ghana
• All the earthquake activity in Ghana can be associated with three major tectonic zones of weakness active in Ghana.- Cote d’Ivoire Fault
- Akuapim Fault Zone
- Coastal Boundary Fault
Dr. Patrick A. Sakyi, Dept. of Earth Science Slide 19
Active Faults in Ghana
In the south-west, is the Cote d` Ivoire fault which cuts through Ghana.
Dr. Patrick A. Sakyi, Dept. of Earth Science Slide 20
2.0E+005 4.0E+005 6.0E+005 8.0E+005 1.0E+006 1.2E+006 1.4E+006 1.6E+006
EASTINGS (ft)
2.0
E+
005
4.0
E+
005
6.0
E+
00
58
.0E
+00
5
NO
RT
HIN
GS
(ft
)
0.0E+000 2.0E+005 4.0E+005 6.0E+005 8.0E+005
1.0 to 3.5
3.5 to 4.3
4.3 to 4.9
4.9 to 5.5
5.5 to 6.2
6.2 to 6.9
SEKONDI
CAPE COAST
ACCRA
KOFORIDUA
HO
Half Assini
Axim
Tarkwa
NsawamTema
Prampram
Akuse
Keta
Recent Formation
Amisian
Sekondian
Bocene
Buem Formation
Togo Series
Granite
Voltaian
Dahomeyan Mafic
Dahomeyan Felsic
Tarkwaian
Metasediments (Birimian)
Metavolcanics (Birimian)
LEGEND
FAULTS
Normal
Thrust
Downthrow
Magnitudes of Epicenters
Active Faults in Ghana
The north-east trending Akuapem fault which
intersects with the Coastal Boundary fault just to the
west of Accra
.
Dr. Patrick A. Sakyi, Dept. of Earth Science Slide 212.0E+005 4.0E+005 6.0E+005 8.0E+005 1.0E+006 1.2E+006 1.4E+006 1.6E+006
EASTINGS (ft)
2.0
E+
005
4.0
E+
005
6.0
E+
00
58
.0E
+00
5
NO
RT
HIN
GS
(ft
)
0.0E+000 2.0E+005 4.0E+005 6.0E+005 8.0E+005
1.0 to 3.5
3.5 to 4.3
4.3 to 4.9
4.9 to 5.5
5.5 to 6.2
6.2 to 6.9
SEKONDI
CAPE COAST
ACCRA
KOFORIDUA
HO
Half Assini
Axim
Tarkwa
NsawamTema
Prampram
Akuse
Keta
Recent Formation
Amisian
Sekondian
Bocene
Buem Formation
Togo Series
Granite
Voltaian
Dahomeyan Mafic
Dahomeyan Felsic
Tarkwaian
Metasediments (Birimian)
Metavolcanics (Birimian)
LEGEND
FAULTS
Normal
Thrust
Downthrow
Magnitudes of Epicenters
Active Faults in Ghana
. Near Accra is the Coastal Boundary Fault
Dr. Patrick A. Sakyi, Dept. of Earth Science Slide 22
2.0E+005 4.0E+005 6.0E+005 8.0E+005 1.0E+006 1.2E+006 1.4E+006 1.6E+006
EASTINGS (ft)
2.0
E+
005
4.0
E+
005
6.0
E+
00
58
.0E
+00
5
NO
RT
HIN
GS
(ft
)
0.0E+000 2.0E+005 4.0E+005 6.0E+005 8.0E+005
1.0 to 3.5
3.5 to 4.3
4.3 to 4.9
4.9 to 5.5
5.5 to 6.2
6.2 to 6.9
SEKONDI
CAPE COAST
ACCRA
KOFORIDUA
HO
Half Assini
Axim
Tarkwa
NsawamTema
Prampram
Akuse
Keta
Recent Formation
Amisian
Sekondian
Bocene
Buem Formation
Togo Series
Granite
Voltaian
Dahomeyan Mafic
Dahomeyan Felsic
Tarkwaian
Metasediments (Birimian)
Metavolcanics (Birimian)
LEGEND
FAULTS
Normal
Thrust
Downthrow
Magnitudes of Epicenters
Active Faults in Ghana
. Coastal Boundary Fault
• The CBF is a major fault parallel to the
coast just a few kilometers off shore and
trending east-west.
• To the east, this fault most probably
strikes inland and continues as the
faulted northern margin of the Keta Basin.
Dr. Patrick A. Sakyi, Dept. of Earth Science Slide 23
Active Faults in Ghana
. Expected Epicentre
• Anywhere along the Akwapim–Togo range (along the Akwapim fault zone)
• Out to sea along the entire coast line of Ghana (on the coastal boundary fault)
• The intersection of these two faults (near Accra in the area between Weija and Nyanyanu on the coast) would be the most likely location of the next major earthquake in Ghana.
• The date and time of such an event cannot be predicted.
Dr. Patrick A. Sakyi, Dept. of Earth Science Slide 24
EARTHQUAKE RISK MAP OF GHANATopic Six
Dr. Patrick A. Sakyi, Dept. of Earth Science Slide 25
Earthquake Risk Map of Ghana
Dr. Patrick A. Sakyi, Dept. of Earth Science Slide 26
END
Dr. Patrick A. Sakyi, Dept. of Earth Science Slide 27