Algerian Earthquake
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Transcript of Algerian Earthquake
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Algerian Earthquake:Geological setting, source
mechanism, and some lessons
for earthquake hazard in other African coastal cities(Cape Town included)
C.J.H. Hartnady
Cape Disaster Debrief 2004
DMISA Western Cape Branch, 2004 Feb 04
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Algerian Earthquake :2003 May 21 18h 44m 20.1s
Statistics
Epicentre: 36.964ºN 3.634ºEMagnitudes: Mw 6.7; MS 6.9; mb 6.5 (USGS)
Death toll: 2266+
Injured: 10261
Homeless: 150000>1234 buildings damaged or destroyed
Cost: US$100 million(2 m tsunami damaged boats on Balearic Islands)
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Geotectonic Background
Global Plate Tectonics
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NB-EU-NA Plate Motions
NB
EU
NA
nk lg
goug
suth
hrao
mas1
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African Plate Neotectonics
NB = Nubia
SM = SomaliaUN = Ukerewe
Nyanza
RV = Rovuma
TG = Transgariep
LW - Lwandle<0.5 mm/yr
TG->SM @ ~3 mm/yr
NB->AR
@ ~7 mm/yr
NB->EU
@ ~6 mm/yr
Stable NB
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Hartebeesthoek (HRAO) Motion
GPS velocity of
HRAO
relative to
ITRF2000
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NB-EU Plate Kinematics
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Seismotectonic Framework
L
Am
Ba
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GSHAP: Ibero-Maghreb region
Global
Seismic
HazardAssessment
Program1755
Agadir1960
1365
Historic
earthquake
disasters
El Asnam
1980
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Lisbon – 1 November 1755
Estimated
Magnitude
~ Mw 9
St AlexiusDeath toll > 50000
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Mechanism & Tectonic Setting
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Landsat-7 image of affected area
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Model of slip in fault plane
from Y. Yagi [email protected]
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Impact on buildings
Agadir, Morocco 1960
Africa’s worst earthquake disaster:
Before and after views ofa tourist hotel
Shallow moderate-strong(M5.9) event on 1960 Feb 29
caused 10000-15000 deaths
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Boumerdes – 21 May 2003
Pieter Strobos – Global Relief
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Boumerdes – 21 May 2003
Pieter Strobos – Global Relief
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Major Earthquake:
consequences for coastal city Large loss of life and property, due to building
collapse, consequent fires, landslides on
unstable slopes Large-scale disruption of “lifeline” infrastructure;
e.g., sudden breach or failure of dam walls,water mains, disruption of road, rail, or fuel
pipeline links Tsunami inundation of harbours, resorts due to
massive failure on steep continental slope
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Lesotho-KZN Seismic Hazard
Potentialearthquake
risk to:
BloemfonteinMaseruKatse-Mohale
DurbanPietermaritzburgPort ShepstoneRichards Bay
Durban
1860
Pt Shepstone
1942
Zastron
1957
Fauresmith
1912
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SE African Earthquakes
31st December 1932 -offshore St Lucia event
is RSA’s largest (M6.5)earthquake
Beware recurrence of
similar or larger eventscloser to Beira, Maputo,Richards Bay, Durban
1932
1915
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Prehistoric Great Quake:
Bilila-Mtakataka Faulting (M8+)Site A ( S of Lake Malawi):“If the scarp were produced in
a single event, with an averageslip of ~10 m over 100 kmlength, it would be the biggestnormal faulting earthquake
known on the continents” (Jackson & Blenkinsop, 1997, p. 148)
Rukwa 1910
B, C, D = sites of other ~100 km-long,geologically young, surface-breakingfault scarps (major-great palaeoseisms)
MoDs
Be
Mp
PeCt
Db
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Finis