TSUNAMIThe Underrated HazardEdward Bryant

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SecondEdition

Contents

Preface xi

Acknowledgements xv

List of figures xxi

List of tables xxvii

List of symbols xxix

List of abbreviations and acronyms xxxüi

PART I Tsunami as a known hazard l

1 Introduction 3Introduction 3Five stories 4

1 An Aboriginal legend 42 The Kwenaitchechat Legend, Pacific Northwest 53 Krakatau. August 27, 1883 64 Burin Península, Newfoundland. November 18, 1929 75 Papua New Guinea, July 17, 1998 9

Scientific fací or Icgcnds? 10Causes of tsunami 12Distribution and fatalities 14

Meditcrranean Sea 15Caribbcan Sea 15

vi Contente

Pacific Ocean Región (including Indonesia) 16New Zealund and Australia 22Bays, fjords, inland seas, and lakcs 23

Meteorológica! phenomena, freak wavcs, and slorm surges 24

Tsunami dy na mies 27Introduction 27Tsunami characteristics , 27Tsunami wave thcory 31

Rcsonance 36Shallow-water, long-wavc theory 37

Run-up and inundation 40Run-up 40Inland penctration 45Depth and veiocity at shorc 46

PART II Tsunami-formed landscapes 49

3 Signatures of tsunami in the coastal landscape 51Introduction 51Dcpositional signatures of tsunami 53

Buried sand or anomalous sedirnent laycrs 53Foraminifera and diatoms 57Boulder fioaters in sand 59Dump deposits 60Mounds and ridges 63Chevrons and dune bedforms 65Smear deposits 67Large bouldcrs and piles of imbricated boulders 68Turbiditcs 75

Erosional signatures of tsunami 77Small-scale fcaturcs 77Large-scale features 83Flow dynamics 86

4 Coastal landscape erolution 91Introduction 91Caíastrophism vs. uniformitarianism 91Tsunami vs. storms 94

The naturc of tsunami vs. storm deposits 95Movcment of boulders 96

Contents vü

Types of coastal landscapes created by tsunami 98Sandy barrier coasts 98Deltas and alluvial plains 101Rocky coasts 103Atolls 104

Examplcs of tsunami-generated landscapes: Australia 106South coast of New South Walcs 106Caírns Coast, Northeast Queensland 109Northwest West Australia 112

Other cxamplcs of tsunami-generated landscapes 115Grand Cayman 115Bahamas 117Chilean coast 119

PART III Causes of tsunami 125

5 Earthquake-generated tsunami 127Introduction 127

Seismic wavcs 127Magnitudc scalcs for earthquakes and tsunami 129

Earthquakc magnitudc scalcs 129Tsunami earthquakes 130Tsunami magnitude scales 132

Seismic gaps and tsunami occurrence 134Relationships between earthquakes and tsunami 135

How earthquakes genérate tsunami 135Linking tsunami run-up to earthquakc magnitudc 139

Large histórica! tsunamigenic earthquakes 140Lisbon, Novcmber 1, 1755 140Chile, May 22. 1960 143Alaska, March 27, 1964 149

Evcnts of the 1990s 154Slow Nicaraguan tsunami earthquake of September 2, 1992. . . . 156Flores, Decembcr 12. 1992 158The Hokkaido Nansci-Oki tsunami of July 12, 1993 160Papua New Guinea, July 17, 1998 163

The Indian Ocean tsunami, December 26, 2004 167

6 Great landslides 179Introduction 179Causes of submarino landslides 181

viii Conlenis

How submarine landslides genérate tsunami 184Historical tsunami attributable to landslides 186

The Lituya Bay landslide of July 9. 1958 187Grand Banks tsunami, November 18, 1929 189

Geologieal events 193Hawaiian landslides 193The Canary Tslands 196The Storcgga slide of 7950 BP 198

Bristol Channel, U.K., January 30, 1607 205The risk in the world's oceans 213

Other voleanie islands 213Other topography 215

7 V'olcanic eruptions 217Introduction 217Causes of volcano-induced tsunami 217Krakatau, August 26 27, 1883 222Santorini, around 1470 BC 225

8 Comets and asteroids 231Introduction 231Near Earth objects (NEOs) 231

What are they? 231How frequcnt havc comet and asteroid impacts been? 234

How do extraterrcstrial objects genérate tsunami? 236Mechanisms for generating tsunami 236Size of tsunami 238

Geologieal events 245Hypothesizcd frcquency 245Chicxulub, thc Cretaeeous Tertiary (K/T) extinction event 247Other events 251

Deluge Comet impact event 8,200 ±200 years ago 251The Mahuika Comet impact event and eastern Australia 253

Geológica! evidcnce for mega-tsunami 254Maori Icgends supporting a cosmogcnic event 257Aboriginal legcnds supporting a cosmogenic cvcnt 258Timing of Mahuika 260

Events in the Kimbcrlcy, Western Australia 263Legends supporting cosmogcnic tsunami 263Field evidcnce 266

Contente ix

PART IV Modern risk of tsunami 271

9 Risk and avoidanee 273Introduction 273What locations along a coast are at risk from tsunami? 277Warning systcms 280

The Pacific Tsunami Warning Ccntcr 280Flaws in regional warning systems 285Localized tsunami warning systems 286

How long havc you got? 290Where should you go if there is a tsunami warning? 291What if it ís an asteroid or comet? 294Is it all that bad? The case of Sydney 295

10 Epilogue 299Five stories 299

1 An unsuspected earthquake 2992 An unassuming earthquake 3023 A submarine landslide 3034 A volcanic eruption 3045 An asteroid impact with the ocean 305

Concluding comments 306

References 309

Index 325