Algerian Earthquake

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    Algerian Earthquake:Geological setting, source

    mechanism, and some lessons

    for earthquake hazard in otherAfrican 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: 36.964N 3.634EMagnitudes: 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 - LwandleSM @ ~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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    Lisbon1 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

    Africas 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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    Boumerdes21 May 2003

    Pieter Strobos Global Relief

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    Boumerdes21 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

    31stDecember 1932 -offshore St Lucia event

    is RSAs 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

    knownon 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