Chapter 4 – tsunami case studies

Chapter 4 – tsunami case studies Chapter 4 – tsunami case studies Chapter 4 – tsunami case studies Chapter 4 – tsunami case studies Chapter 4 – tsunami case studies Chapter 4 – tsunami case studies Chapter 4 – tsunami case studies Chapter 4 – tsunami case studies Chapter 4 – tsunami case studies

Tsunami Case Studies

Eugene J Farrell1, Jean T Ellis2and Kieran R Hickey1

1

Discipline of Geography, National University Ireland Galway, Galway, Ireland,2Department

of Geography and Marine Science Program, University of South Carolina, Columbia, SC, USA

ABSTRACT

Tsunamis are caused by geological processes, such as earthquakes, landslides, orvolcanic eruptions, that displace large volumes of ocean water Large-magnitude,subduction zone earthquakes, where two plates in the ocean push into each other, arethe most common source of the recent large tsunamis Submarine landslides, sometimestriggered by earthquakes, and coastal or submarine volcanoes also cause tsunamis Thischapter describes 10 modern and historic tsunami events that were significant in terms

of their size, impact, extent, and/or triggering mechanisms Each tsunami event isdescribed using four different categories: (1) tsunami generation; (2) tsunami size, andextent (3) impact of the event at the local, regional and, where applicable, global scales;and (4) lessons learned in the aftermath of the event The case studies are groupedaccording to the tsunamigenic source: earthquake (2004 Indian (SumatraeAndaman)earthquake, 2011 Tohoku earthquake, 1964 Alaska earthquake, 1960 Valdiviaearthquake, 1946 Aleutian Island earthquake, 1908 Messina-Reggio earthquake, 1755Great Lisbon earthquake), landslide (Storegga Slides 30,000 and 7,200e7,000 YBP,Papua New Guinea, 1998), and volcano (Krakatoa 1883)

4.1 INTRODUCTION

Tsunami, or harbor (tsun-) wave (-ami) in Japanese, are caused by geologicalprocesses, such as earthquakes, landslides or volcanic eruptions, which displacelarge volumes of ocean water The displaced sea surface propagates outwardfrom the source as a series of ocean waves with extremely long wavelengthsand periods Wind-generated waves cause water motion to depths of 150 m; atsunami involves water movement to the sea floor bottom The Earth-movingevent is most typically an earthquake, but tsunamis are also generated fromsubmarine or terrestrial landslides and volcanoes (Table 4.1) Other chapters inthis volume review multiple characteristics of tsunamis: Kaˆnoglu and Syno-lakis (generation, modeling, and dynamics), Nott (paleotsunamis), and

Coastal and Marine Hazards, Risks, and Disasters http://dx.doi.org/10.1016/B978-0-12-396483-0.00004-2

© 2015 Elsevier Inc All rights reserved. 93

03/11/2011 Tohoku earthquake or Great East

Japan earthquake and tsunami

230,000 estimated

South and Southeast Asia including, but not limited to, Indonesia, Sri Lanka, Thailand, India, India, Maldives, Bangladesh, and Malaysia Earthquake

( Mw 9.2)

03/27/1964 1964 Great Alaskan earthquake and

Good Friday (Crescent city) tsunami

United States, Hawaii, Japan Earthquake

( Mw 9.5)

05/22/1960 1960 Valdivia earthquake (Great

Chilean earthquake) and tsunami

2,183e6,000 Chile, Hawaii, Japan, Philippines,

New Zealand, and Australia Earthquake

Portugal, Spain, North Africa, Northwest Europe

36,417e120,000 Indonesia, South Africa, New Zealand,

Australia, Japan, Hawaii, Alaska, North and South America, and UK

Hansom (Chapter 11, this volume) Rather, this chapter describes 10 historicand modern tsunami events that were significant in terms of their size, impact,extent, and/or triggering mechanisms Large magnitude subduction-zoneearthquakes, where two plates in the ocean collide, are the most commonsource of large tsunamis in recent years (California Coastal Commission,

2011) For example, the 2004 Indian Ocean (SumatraeAndaman) earthquakeand the 2011 Tohoku earthquake were a subduction-zone type of earthquakethat generated destructive tsunamis Submarine landslides, sometimes triggered

by earthquakes, are another source of tsunami, as witnessed in Papua NewGuinea in 1998 Coastal or submarine volcanoes are a third source of tsunami;Krakatoa is the most famous of this type Geologic evidence also exists thatmeteor strikes have generated large tsunamis, but this is beyond the scope ofthis chapter

In this chapter, we report on earthquake-generated tsunamis in the Indian(SumatraeAndaman Earthquake 2006), Pacific (Tohoku Earthquake 2011;Alaska Earthquake 1964; Valdivia Earthquake 1960; Aleutian Islands 1948,1946), and Atlantic (The Great Lisbon Earthquake 1755) Oceans and theMediterranean Sea (Messina-Reggio Earthquake 1908) Tsunamis triggered bysubmarine landslides (Storegga Slides 30,000 and 7,200e7,000 YBP, PapuaNew Guinea 1998) and volcanic eruptions (Krakatoa 1883) are also presented.Each tsunami event is described using four different categories: (1) tsunamigeneration; (2) tsunami size and extent; (3) impact of the event at the local,regional, and, where applicable, global scales; and (4) lessons learned in theaftermath of the event

The most vivid and popularized depiction of tsunami is likely the gawa Oki Nami-Ura (The Great Wave Off Kanagawa, Figure 4.1(a)) wood-block print (or woodcut) published between between 1830 and 1833 byKatsushika Hokusai This piece is the first print in Hokusai’s FugakuSan1jurokkei (Thirty-six Views of Mount Fuji) series and illustrates an enor-mous wave threatening boats off the coast of Kanagawa in the Kanto region ofHonshu, which is the largest and most populous island of Japan that alsoencompasses the Greater Tokyo area Kanagawa-oki Honmoku no zu (View ofHonmoku off Kanagawa, c.1803,Figure 4.1(b)) and Oshiokuri Hato Tsusen no

Kana-Zu (Fast Cargo Boat Battling the Waves, c.1805,Figure 4.1(c)) by the sameartist are precursors to The Great Wave Off Kanagawa In 1834, Hokusaicreated a second series prints, including Kaijo no Fuji (One hundred views ofMount Fuji,Figure 4.1(d)), which also shows tsunami waves and Mount Fuji,the latter is considered a sacred symbol of Japan’s national identity

The Hokusai illustrations showing the tsunami wave approaching the landwith ships depicts the inherent conflict between nature and humans Tsunamihazards become natural disasters with substantial fatalities and infrastructuredamage (Table 4.1) The latter is exacerbated when nuclear plants, such asFukushima Dai-ichi and Fukushima Dai-ni in Japan, are emplaced alongvulnerable and populated coastlines, for example The extent of a disaster is

mitigated by increased coastal resilience and improved warning systems Forexample, at least 43 percent of Japan’s coastline has some type of engineeredstructure to protect against large typhoon- or tsunami-generated waves How-ever, the 2011 Tohoku, Japan, event made it evident that very few, if any, coastalstructures are able to prevent large tsunamis from laying waste to low lyingcoastal regions Kaˆnoglu and Synolakis (Chapter 2, this volume) document therecent advances to tsunami modeling; however, in addition to improved models,information dissemination warning inhabitants of the impending tsunami inadequate time for evacuation is critical The warning in advance to the 2011Japanese tsunami event saved some lives, but ultimately the tsunami resulted inmany fatalities because the warning was not issued with adequate time.

4.2 EARTHQUAKE-GENERATED TSUNAMIS

4.2.1 The 2011 Tohoku Earthquake (Great East Japan

Earthquake) and Tsunami

4.2.1.1 Generation

The Great East Japan earthquake that generated the tsunami occurred at05:46 UTC (14:46 local time) on 11 March, 2011 Historically, this region hasbeen very seismically active with previous substantial earthquakes and

c 1803; (c) Oshiokuri Hato Tsusen no Zu (Fast Cargo Boat Battling The Waves) c 1805; (d) Kaijo

no Fuji (100 views of Mount Fuji) c 1834.

tsunamis occurring in 1611, 1896, and 1933 Large earthquakes, ones withmoment magnitudes (Mw) of 7.8e8.0, are predicted to occur in this regionwith a 99 percent probability by 2040 (ADRC, 2011) The 11 March, 2011,event had a one in 1,000 year return period and greatly exceeded any pre-disaster expectations The mechanism causing the tsunami consisted of notonly of a slipping movement of the deep plate boundaries that lead to normalocean trench earthquakes in the region, but also a simultaneous slippingmovement at the shallow plate boundaries (GFDRR, 2012) The plate-boundary thrust-faulting earthquake that generated the tsunami had amoment magnitude of 9.0 It is the fourth largest earthquake on record sincemodern records began in 1900 and the largest in Japanese history Numerousstrong aftershocks (>Mw7.0) were recorded and continue to occur (as of June2014) According to the Japanese Meteorological Agency, there have been 776aftershocks greater than Mw5.0 magnitude (as of June 2014).

The March 2011 earthquake epicenter was located 70 km east of theOshika Peninsula in the Tohoku region in the northeast portion of the mainisland of Honshu The earthquake had a relatively shallow depth of 32 km(USGS, 2011) and lasted for 6 min, which, historically, is unusually long Theearthquake was powerful enough to shift parts of Japan’s main island ofHonshu eastward, or 2.5 m closer to the United States mainland The seismicevent also affected the Earth’s axis and orbit (Chang, 2011) The earthquakeresulted in significant plate boundary movement and had a rupture area thatwas approximately 500 km long (north to south) and 200 km wide (east towest), which caused massive displacement of several million tons of water

4.2.1.2 Size and Extent

The maximum tsunami height was approximately 40 m and consisted of anumber of main and subsidiary waves The tsunami struck the Japanesecoastline 36 min after the earthquake Field surveys indicated that the highestrunup height was 38.9 m The tsunami spread over the entire Pacific Ocean;

10 h after the earthquake a 2-m tsunami wave impacted Chile, which isapproximately 17,000 km away from the epicenter The tsunami broke ice-bergs off the Sulzberger Ice Shelf 13,000 km away This was the first time theUnited Sates National Oceanic and Atmospheric Administration (NOAA)reported observational evidence from satellites linking tsunami to ice calving

in Antarctica Reports of impacts in Norwegian fjords also occurred (Brunt

et al., 2011) Two-meter waves were observed on tide gauges in Russia, SouthAmerica, Hawaii, and along the west coast of the United States

4.2.1.3 Impacts

The tsunami impacts were exacerbated by the geologic (magnitude, depth,duration, and displacement) and geographic (proximity to coastline) char-acteristics of the generating earthquake Japan is a leading country regarding

tsunami-disaster prevention and has many structural and nonstructuraltsunami countermeasures along the coast, especially in Sanriku where thecoastline configuration can cause tsunami waves to amplify to heightsexceeding 10 m (Suppasri et al., 2013) An earthquake with a magnitudeequal to the one that occurred in March 2011 was never predicted, norplanned for Emplaced sea defenses were overwhelmed by the tsunami.Despite the issuance of the highest-level tsunami warning (i.e., a “majortsunami” with a tsunami of at least 3 m) by the Japan MeteorologicalAgency, very little chance existed for people to evacuate The actual tsunamiexceeded the warnings and 101 designated tsunami evacuation sites were hit

by the waves resulting in>1,000 deaths (Japan Times, 2011) The relativeineffectiveness of these defenses was a result of the sudden 2-m subsidence

of>400 km of the east coast of Japan and the wave heights that exceeded theseawall heights of 10 m (Chang, 2011) It is now accepted that the pre-disasterpredictions and assumptions greatly underestimated the actual earthquakeand tsunami magnitude and devastation, which initiated a review of Japan’sstrategies of hazard risk and management One suggested approach is toinclude earthquakes, such as the Jogan Sanriku earthquake of 869, theKeicho Sanriku earthquake of 1611, the Enpo Boso earthquake of 1677,and the Meiji Sanriku earthquake in 1896 to tsunami-hazard predictionmodels (GFDRR, 2012)

As of 10 April, 2014, The National Police Academy of Japan confirmed15,885 deaths; 6,148 injures; and 2,623 missing persons resulting from the

2011 tsunami In the latter case, the bodies were likely washed out to sea orburied so deep in sediment and/or debris along the coastline that they areunlikely to be discovered In addition, 340,000 people were displaced because127,290 buildings collapsed, 272,788 buildings were classified as “halfcollapsed,” and 747,989 buildings were partially damaged The tsunami alsocaused one death in Jakarta, Indonesia, and one death in the Klamath River,California, USA

This event was widely covered by international news outlets The mediaportrayed entire coastal towns and villages swept away by one or more majorwaves and showed many people marginally escaping and thousands losingtheir lives The number of fatalities was amplified by the landward penetration

of the tsunami, which in some areas was>10 km The Geospatial InformationAuthority of Japan reported that the tsunami inundated an area of approxi-mately 561 km2in Japan

Extensive damage occurred to almost all parts of NE Japan An estimated4.4 million people were left without electricity because of the damage toelectricity-generating stations and power lines and/or the precautionary shut-down of some nuclear power stations The scale of building devastation wasenormous, and it included the complete destruction of 11 hospitals and damage

to over 300 more Three major commercial ports were destroyed, and>300fishing ports were damaged One oil refinery and a natural gas processing plant

were badly damaged One dam collapsed, causing some fatalities, and otherswere damaged Seven hundred fifty four cultural properties were damaged,which included five properties classified as National Treasures in the affectedregion (Anon, 2011) Major transport disruption occurred, with damage tocritical roads and rail lines that caused large-scale service cancellations andmajor delays Telecommunications were also badly affected An estimated230,000 vehicles were destroyed or damaged, mostly from the tsunami Thetotal cost of damage is estimated at US$250 billion, which makes it the mostexpensive natural disaster in human history This estimate is likely to continue

to rise, particularly because of the nuclear implications of this event Inparticular, two tsunami-related events are going to continue to contribute to thetotal event-related costs, discussed below

The first is the partial meltdown of the Fukushima nuclear power plant thatwas partially inundated by the tsunami This was the worst nuclear disastersince Chernobyl in the Ukraine in 1986 A 20-km exclusion zone wasemplaced for protection against radiation, which affected 80,000 residents.Starting in 2014, a limited number of residents have been allowed to return totheir homes in this zone, but many are too fearful to do so because of theirconcern about the radiation levels In sum, 8 percent of Japan was blanketed byradiation, which results in a huge cleanup effort that will take decades Onecurrent issue is the removal of 23 million tons of contaminated soil that wasscraped from the surface (50-mm layer) from hundreds of thousands ofhectares of farmland (Kamiya, 2011) The cleanup at Fukushima is ongoingand will continue indefinitely (Kingston, 2012) The Fukushima meltdown hasresulted in citizen protest and a reconsideration of Japan’s use of nuclearpower

The second effect is the generation of a mass of between one and twomillion tons of debris, which includes human remains that are being distrib-uted around the Pacific Ocean (Laurent et al., 2013) The first debris to wash

up on the coast of North America occurred in Oregon, USA, on 6 February,

2013 In response, the United States has emplaced protocols through NOAA’sMarine Debris program, for example, to manage this material (Figure 4.2)

4.2.1.4 Relief Efforts

In response to this major disaster, the Japanese government quickly mobilizedthe Self-Defense Forces, including all emergency services and the Army Theimportance of such a rapid response of personal was an important lessonlearned from the Kobe earthquake of 1995 when it took two days to activaterelevant emergency services and the Army Several countries sent search andrescue teams Up to two weeks after the event, many thousands of people wererescued from the rubble and mud Japanese and worldwide aid organizationsresponded, with the Japanese Red Cross reporting USD$1 billion in donations(Nebehay, 2011)

4.2.1.5 Aftermath

Suppasri et al (2013) provided a comprehensive analysis of the performance

of the tsunami countermeasures that were in place in March 2011 and, sequently, the lessons learned and recommendations for future managementstrategies Their findings include the following recommendations: (1) thetsunami countermeasures were not designed to resist an event with themagnitude of the 2011 earthquake event; (2) construction of massive structures

sub-to completely protect against 500- sub-to 100-year return-period tsunamis cannot

be achieved when budget and time are limited; (3) future structures shouldhave stronger foundations and seawall gates should be remotely controlled; (4)control forests should be planted as secondary barriers at higher elevationsbehind the seawalls; (5) wooden structures should be replaced by reinforcedconcrete structures in areas where tsunami inundation is expected; (6) theelevation of railways and roads should be raised to serve as secondary ortertiary tsunami barriers; (7) the design and location of evacuation buildingsshould be reconsidered; (8) increased awareness and training of citizens willreduce the number of fatalities; (9) land-use policies for future developmentshould avoid tsunami-prone areas; and (10) hard (engineered) and soft

FIGURE 4.2 Tsunami debris-watch placard generated by National Oceanic and Atmospheric Administration (NOAA) and placed in communities along the US Pacific coast.

(education; evacuation plans) countermeasures should be used to increasetsunami awareness and community readiness to tsunamis.

4.2.2 The 2004 Indian Ocean (SumatraeAndaman) Earthquake and (Boxing Day) Tsunami

4.2.2.1 Generation

Tsunamis from seismic activity are much more rare in the Indian Oceancompared to the those in the Pacific Ocean (Table 4.1) Nonetheless, the 2004event in the Indian Ocean occurred at 00:58 UTC (08:58 local time) on 26December, 2004 The earthquake-generating tsunami had a moment magni-tude between 9.1 and 9.3 It was the second most powerful event since modernseismic records began in 1900 and was the largest for the preceding 40 years(McKee, 2005) The event affected the orbit of the Earth and triggered otherearthquakes approximately 11,000 km away in Alaska (West et al., 2005).Since 1900, only two earthquakes have been recorded with a similar magni-tude; the 1960 Great Chilean Earthquake (also called the Valdivia Earthquake,

Mw9.5) and the 1964 Great Alaskan Earthquake (also called the Good FridayEarthquake, Mw 9.2) both of which generated significant tsunamis and arereported in this chapter

The epicenter of the SumatraeAndaman megathrust event was 30 kmundersea around 250 km NW of Sumatra along the Indo-Australian plateboundary It is estimated that this section of the plate had not moved for

>200 years, which during that time, accumulated a lot of energy (McKee,

2005) At the time of impact, the earthquake set a new record for the longestduration at between 8 and 10 min (Walton, 2005) The earthquake ruptured theSumatra and Sunda subduction zones over a length of 1,300 km (Sibuet et al.,

2007), which generated a massive tsunami consisting of two or three mainwaves and numerous smaller ones Based upon seabed surveys, it is estimatedthat there was at least 10 and 4e5 m of lateral and vertical movement,respectively, along the fault line (Bagla, 2005)

The main earthquake was followed by a series of aftershocks that wererecorded in the Andaman Islands archipelago in the Bay of Bengal betweenIndia and Myanmar The largest aftershock registered a magnitude of 8.7 offthe coast of Sumatra, which prompted a debate among seismologists onwhether to classify the event as an aftershock or a “triggered earthquake.”Indeed, one of these aftershocks is classified here as separate event (IndianOcean Aftershock 2006, Mw7.7) because it generated a tsunami that resulted

in substantial loss of life

4.2.2.2 Size and Extent

The tsunami took between 15 min (Sumatra) and 7 h (Somalia) to reachvarious locations along the Indian Ocean coastline Locations closest to theepicenter in the northern regions of the Indonesian island of Sumatra were

hit very quickly, whereas Sri Lanka and the east coast of India were hitroughly 2 h later, for example Thailand was also struck about 2 h later,despite being closer to the epicenter, because the tsunami traveled more slowly

in the shallow Andaman Sea The tsunami was recorded by tide gauges onAustralia’s west coast within 5 h of the event The tsunami impacted the PacificOcean where it produced small but measurable waves (<0.50 m) along thewestern coast of North and South America The main tsunami wave wasrecorded on tide gauges along the Chilean and Peruvian coastlines 27 and 28 hlater, respectively Numerical models, such as ones produced by NOAA andbased on quality-controlled source data (e.g., tide gauges), were used toreplicate the generation and propagation of the Indian Ocean tsunami and toillustrate how the waves propagated around the world’s ocean basins

The height of the tsunami varied greatly and depended on its distance anddirection from the epicenter and other factors such as the local bathymetry andcoastal topography The height ranged from 2 to 3 m at the African coast(Kenya) and up to 10e15 m at Sumatra, the region closest to the earthquakeepicenter The maximum height of the main tsunami wave was between 24 and

30 m and the second main wave was between 10 and 15 m high

4.2.2.3 Impacts

This event caused the largest loss of life of any known tsunami with230,00e280,000 estimated fatalities (Diacu, 2009) Based on fatalities, thisevent outranks almost every natural disaster This, and the 2010 Haitiearthquake that killed between 100,000 and 316,000 are the deadliest naturaldisasters of the twenty-first century (Columbian Journalism Review, 2012).The impact of the Boxing Day tsunami, was exacerbated by the scale ofseabed displacement, its proximity to the coastline of Banda Aceh Province

in Indonesia where most fatalities and damage occurred, and the lack of anIndian Ocean Tsunami Detection and Warning System Even with a func-tioning warning system in place, the people of Banda Aceh would have hadless than 15 min to evacuate Ultimately approximately 170,000 of the fa-talities occurred in this area One of the great tragedies of this event is thatwith a warning system in place, it is believed that all 60,000þ lives lost inSri Lanka, Thailand, India, Maldives, Bangladesh, Malaysia, Myanmar, and

in several countries in East Africa could have been avoided (Table 4.2) Thisestimate includes around 9,000 tourists, mainly from Europe, vacationing inThailand; for example, Sweden lost>500 citizens

In addition to the extensive fatalities, approximately 1.69 million peoplewere displaced Indonesia and Sri Lanka were the worst impacted with overhalf million people displaced in each country (Meisl et al., 2006) Manysurvivors lost their livelihoods due to the destruction of their fishing boats andcoastal farms In the case of Thailand, the tourism sector was impacted; evenareas that were not affected by the tsunami experienced a substantial drop inbookings (Jayasuriya and McCawley, 2010)

The scale of destruction and damage was enormous, but in most places, itwas limited to within 1 or 2 km of the coastline Large expanses of the coastalzone were cleared of every building, all vegetation, and soil The total cost ofdamage was estimated at around $15 billion, which is rather low given thescale of the devastation because most of the areas affected were in developingcountries where standards are low compared to the global average Indonesiawas the worst affected with an estimated damage of at least $4.5 billion,followed by Sri Lanka with an estimated $3.5 billion, and India and Thailandwith an estimated damage of>$1.5 billion each.

4.2.2.4 Relief Efforts

No doubt exists that outside of wartime, the relief effort associated with thistsunami was the most extensive the world had ever seen Direct involvementoccurred by almost every nation around the world Significant public donationswere raised, and many governments contributed to the relief effort In sum,governments, aid agencies, and individual donations totaled >US$14 billion(Jayasuriya and McCawley, 2010) Nations that lost their citizens supportedthe relief effort, possibly more than they would had their country not beenaffected Disaster relief teams arrived from all over the world, along with somemilitary assistance The initial purpose of the relief teams was to rescue in-dividuals trapped in buildings and to help treat the injured Unfortunately,many still died unnecessarily due to lack of medical supplies, clean water, andthe essentials required to live The UN designated former US President BillClinton as a United Nations (UN) Special Tsunami Envoy His main objective

TABLE 4.2 Estimated Arrival Time of the First Tsunami Wave

Country

Distance from Epicenter (km)

Elapsed Time to Reach Coast

was to ensure that countries follow through on their commitments for disasterrelief Clinton was also involved in mediating the two preexisting conflicts thatexisted in the region, the Tamil-Sri Lankan issue (separatist activity since1983e65,000þ victims) and the AceheIndonesian issue (separatist activitysince 1976e10,000þ victims) Most residents in the Aceh Province areMuslim and did not want foreign military present, especially those from theUnited States (Barron et al., 2005) The Indian government did not wantassistance on some of the remote Andaman and Nicobar Islands where thereare strategic Indian military bases and indigenous tribes On the Indianmainland thousands of homeless and starving “untouchables” were deniedaccess to clean water and food in relief camps for fear of spiritual contami-nation (Jayasuriya and McCawley, 2010) A substantial concern existed thatlarge portions of the aid were stolen by corrupt individuals and governmentofficials In cases where this was confirmed, harsh sentences were distributed(Asian Development Bank, 2005).

4.2.2.5 Aftermath

In the aftermath of the tsunami, the UN Intergovernmental OceanographicCommission (IOC), comprising UN Educational, Scientific, and Cultural Or-ganization and other partners, began coordinating efforts to create an IndianOcean early warning system and administering evacuation plans At a 2005 UNMeeting in Kobe, Japan, it was agreed to establish a warning system that wouldbecome operational in June, 2006 The warning system consists of 25 seismo-graphic stations reporting to 26 national tsunami information centers and sixDARTÒ(Deep-Ocean Assessment and Reporting of Tsunami) buoys In 2012,Thailand successfully launched their national warning system, which was eightyears after the Andaman coast was destroyed and 5,395 people were killed, many

of whom were tourists The Thai National Disaster Warning Center established

136 warning towers and three tsunami-detection buoys in the Andaman Sea thatare connected to the United States Geological Survey, the World MeteorologicalOrganization, and other authorized disaster-monitoring agencies The efficacy

of Indonesia’s early warning system was tested in April 2012 when an 8.6 Mwearthquake occurred 400 km southwest of Banda Aceh Despite the initial (andlikely justifiable) panic by people in many at-risk coastal locations, according toThorkild Aarup, Head of the Tsunami Unit of the UN IOC, “The three earlywarning systems (and evacuation drills) functioned as they should have acrossthe board The Indonesian early warning was issued at 8.43 UTCdfive minutesafter the quake happened The Australian warning was issued 10 min after, whileIndia’s was issued eight minutes after the earthquake.” The region has certainlybecome much better equipped in the eight years following the devastating 2004Boxing Day tsunami However, it is essential that governments continue to trainpeople to respond to warning systems and prepare the coastal inhabitants fortsunami disasters

4.2.3 Great Alaskan Earthquake and Good Friday

(Crescent City) Tsunami

4.2.3.1 Generation

Alaska is the most seismically active region in the United States; theAlaska Earthquake Information Center locates and reports about22,000 earthquakes each year This tectonically active area comprises theAlaskaeAleutian subduction zone where the oceanic Pacific Plate is beingthrust under the continental North American plate at a rate of 0.06e0.07 mper year, which produces large and destructive earthquakes The shallowercrust of southern Alaska, as a result of the stresses generated by this platecollision, also aids the production of numerous strong earthquakes Three

of the seven largest earthquakes in the twentieth century occurred inAlaska (1957 Aleutian, 1964 Great Alaskan/Prince William Sound, and

1965 Rat Islands) Also noteworthy, the 10 largest earthquakes recorded inthe United States have occurred in Alaska, most of which were megathrustearthquakes along the AlaskaeAleutian subduction zone (USGS, 2014).During the past century, three large and well-documented tsunamis weregenerated by seismic events in the northern Pacific near the Alaskan coast.These include the 1946 (discussed later in this chapter) and 1957 Aleutianevents, and the 1964 Alaskan event (discussed below) Although all threetsunamis were produced by seismic activity, the intensities and areas ofaffected coastline differ

On Good Friday, 27 March, 1964, a Mw 9.2 earthquake struck at02:36 UTC (17:36 local time) The epicenter was 125 km east of Anchorageand 65 km west of Valdez, AK The earthquake lasted approximately 5 min

It was the largest ever recorded in the United States and the second-mostpowerful measured by a seismograph worldwidedthe strongest being the

1960 Chilean earthquake The earthquake seismic activity was reportedworldwide Studies following this earthquake revealed evidence of at leastnine previous similar-type megathrust earthquakes in south central Alaska inthe last 5,500 years Statistically, events of this size have a recurrence in-terval of about 600 years (USGS, 2014) The 1964 earthquake resulted inlarge vertical displacements over an area approximating 260,000-km2, much

of this beneath Prince William Sound The land subsided up to 3 m west ofthe fault system Parts of the Gulf of Alaska, east of the epicenter, wereuplifted 11 m and exposed former tidelands of Montague Island on PrinceWilliam Sound Over 180,000 km2of Alaska, much of which lies along thecoast, subsided over 1 m, thereby making these areas vulnerable to floodingduring high spring tides The large vertical displacement also generated amajor tectonic tsunami that destroyed coastal towns along the southeast coast

of Alaska and caused damage all the along the Pacific coast as far asCalifornia

4.2.3.2 Size and Extent

The earthquake generated a massive trans-oceanic tsunami that propagatedacross the Pacific Ocean to Hawaii and Japan Landslides generated from theshaking generated many local tsunamis in Prince William Sound It is estimatedthat about one third of the fatalities were due to the open ocean tsunami inAlaska, Oregon, and California Locally generated waves in Prince WilliamSound claimed at least 82 lives The tsunami killed 30 people in Port Valdez and

23 of the 68 people living in nearby Chenaga One hundred thirty one fatalitiesoccurred from the earthquake and tsunamis, and US$311 million was spent onrepairing damages (equivalent to US$2.3 billion in 2014) (USGS, 2014)

4.2.3.3 Impacts

The greatest impacts of the tsunami were along the southeastern coast of Alaskawhere many coastal fishing communities along Prince William Sound and KodiakIsland were completely devastated Reports also occurred of tsunami damage inHawaii and Japan The tsunami waves generated by the 1964 earthquake killed

119 people In addition to the primary tectonic tsunami, the violent shaking duringthe earthquake caused many large rockslides and submarine landslides, which inturn, produced destructive local tsunamis 12e21 m high along Prince WilliamSound, such as Port Valdez and Chenaga (Bryant, 2001) Survivor accounts andfield investigations describe a wave that was>8 m high Reports also occurred ofsurvivors who reached higher ground by out-running the wave

All three Pacific west coast states of the United States were impacted by thetsunami In Washington and Oregon, the reported tsunami damage was mainly tocoastal properties and infrastructure (houses, cars, roads, flood defenses, etc.) thatwere impacted by 2- to 5-m waves In some cases, the waves were amplified alongestuary channels causing extensive inland damage The most notable damage was

in Crescent City, CA, where the waves were amplified, causing 10 fatalities and

$15 million damage from a 6.5-m-high tsunami run-up event (relative to MeanLow Water) that flooded most of the town The town is the second-most westernpoint in California and is where the shape of the sea floor amplifies the tsunamienergy and channels it towards the coast Eyewitness accounts describe theinundation as occurring slowly with water levels rising at approximately 0.3 m/min (Dengler and Magoon, 2005) South of Crescent City, wave heights atHumboldt Bay and Eureka exceeded 4 m The tsunami caused an estimatedUS$1 million in damage to San Francisco Bay, where the waves were>1 m high.Wave heights reached>3 m at Half Moon Bay and Santa Cruz, 2.5 m in Mon-terey, and nearly 2 m in San Diego In Long Beach, CA, the tsunami caused onefatality when the wave struck the Cerritos Channel The 1964 tsunami, like thosefrom smaller events in 1946 and 1957, traveled across the Pacific striking theHawaiian Islands, but caused little damage Maximum wave heights reached3.8 m at Hilo, 3.4 m at Kuhului, and 0.3 m a Kana’i When the tsunami reachedJapan, it was<0.25 m high With the aid of the Pacific Tsunami Warning System,

a warning was issued in Honolulu, HI within 46 min of the earthquake At thetime, this warning system had recently been updated following the 1960 Chileanearthquake and tsunami events.

4.2.3.4 Aftermath

A siren-based tsunami warning system was established in Crescent Cityfollowing the 1964 event Evacuation maps were designed and posted alongevacuation routes, which makes Crescent City one of the designated “TsunamiReady” cities in the United States according to the National Weather Service(NWS) This program promotes tsunami-hazard preparedness and is acollaboration among federal, state, and local emergency managementagencies; the public; and the NWS

In 2011, the Tohoku earthquake in Japan resulted in a large trans-oceantsunami that arrived in Crescent City over six and half hours following theearthquake California deployed a pretsunami field team and collected valu-able data during and after the event to help improved tsunami predictionmodels, hazard maps, and guidance for coastal communities (Wilson et al.,

2011) Planners and architects have worked on trying to reduce the tsunamienergy that focuses through the narrow Crescent City harbor entrance andreflects off the steep harbor walls In 2014, a new inner boat basin wascompleted that comprises a 5-m-wide, 2.5-m-deep dock and a hanging un-derwater wall of concrete intended to block the energy of an incomingtsunami The US$33 million inner boat basin is considered the first tsunami-resistant harbor in the United States (Spencer and Grube, 2014)

The 1964 event was a benchmark for the scientific community, as it was thefirst to provide direct evidence that led to a basic understanding of trans-oceantectonic tsunami generation and inundation mapping over large geographicregions At the time of publication, Alaska is conducting the Alaska ShieldExercise, which commemorates the 50-year anniversary earthquake by repli-cating the ground shaking and tsunami impacts associated with the event Thisexercise will assess the State’s progress toward meeting their preparednessobjectives, validate their capabilities, identify shortfalls, and educate thecoastal inhabitants This activity is a centerpiece of FEMA’s (Federal Emer-gency Management Agency) National Exercise Program, which has partici-pants from across the United States and focuses on five mission areas thatenable the country to build, sustain, and deliver core capabilities: prevention,protection, mitigation, response, and recovery (FEMA, 2014) (Table 4.3)

4.2.4 The 1960 Valdivia Earthquake (Great Chilean

Earthquake) and Tsunami

4.2.4.1 Generation

The Valdivia Earthquake occurred at 19:11 UTC (15:11 local time) on 22May, 1960, and is the largest earthquake recorded (M 9.5) It was initially

assessed in 1960 with a magnitude (Mw) of 8.6, but was recalculated as a 9.5

in 2007 (USGS, 2007) A swarm of foreshocks occurred prior to the mainseismic event, measuring as high as Mw 8.0, indicating the severity of thestress at the subduction zone off the coast of Chile The aftershockscontinued until 6 June, 1960

The rupture was a result of the movement of the western margin of theSouth American Plate relative to the subducting Nazca Plate off the coast ofChile The Mw 9.5 event was a megathrust-type earthquake generated fromsudden ruptures of a long segment of a subduction zone (Kanamori and Cipar,

1974) The horizontal movement was estimated at 18.3 m and occurred in anarea measuring approximately 966 km long by 161 km wide, impacting a totalarea of 155,526 km2(Atwater et al., 2005) This massive movement generated

a substantial tsunami consisting of multiple waves propagating across thePacific Ocean

4.2.4.2 Size and Extent

Ten to 15 min after the 9.5 magnitude earthquake, the tsunami wave struckland impacting >800 km of the coast of Chile The maximum height of themain tsunami was approximately 25 m Tsunami waves as high as 10.7 m wererecorded up to 10,000 km away from the epicenter in Hawaii, Japan, and thePhilippines A Hawaiian tide gauge that survived the tsunami recorded eight

TABLE 4.3 Wave RunUp Statistics along the Pacific Ocean Coast from the

Source: From Bryant (2001)

main waves and numerous smaller ones 15 h after the earthquake (Atwater

et al., 2005) (Figure 4.3) The tsunami arrived at Hilo, HI, 15 h after theearthquake event This was the hardest hit city in the Hawaiian Islands (Landerand Lockridge, 1989a) Locations along the Japanese coast measured thearrival of the tsunami 22 h after the earthquake and experienced considerablecoastal flooding and damage The Philippines also recorded the tsunami andexperienced coastal damage In Crescent City, CA, the first wave arrived15.5 h after the earthquake and the wave runup reached 1.7 m (Lander andLockridge, 1989b) The tsunami caused minimal damage to coastal and fishingstructures and some vessels The tsunami was also recorded along the Alaskancoastline and caused minor damage nearly a day after the earthquake (Landerand Lockridge, 1989c)

4.2.4.3 Impacts

It is unclear how many people were killed in the earthquake Reports havevaried from 2,183 to 6,000 At least 3,000 people were injured, and twomillion people were initially displaced because their homes were destroyed(USGS, 2007) In Japan, 142 people were killed by the tsunami (Figure 4.4) InHawaii, 61 people were killed as a result of coastal inundation from thetsunami In Chile, the majority of the fatalities were associated with earth-quake damage Although many of the reported casualties appear to be caused

by the tsunami, it is impossible to quantify the exact cause of deaths

FIGURE 4.3 Water level measurements associated with tsunami waves on the island of Hawaii Low tide ¼ approximately 0 m; tsunami ¼ approximately 4 m; wall of water ¼ 4 m After Atwater

et al (2005)

The biggest earthquake and tsunami impact was at around the city ofValdivia city in southern Chile, which is located closest to where the initialplate movement occurred In Valdivia, it was estimated that 40 percent of thehouses were destroyed causing 20,000 people to become homeless Thedamage and destruction along the Chilean coast was also felt in the agricul-tural sector in southern Chile (Weischet and Von Huene, 1963), which hadlarge economic repercussions for the region The monetary damage from thetsunami varied from $400 to $800 million (USGS, 2007).

The earthquake was responsible for triggering at least one volcaniceruption in the Andes and numerous landslides One of these landslidesgenerated a lake tsunami that killed two people in Argentina 200 km east ofValdivia Danger was also associated with the buildup of water behind riversthat were blocked from tsunami-generated landslides (Weischet and VonHuene, 1963)

This disaster caused a ritual human sacrifice of a 5-year-old orphan boy inthe isolated coastal village of Collileufu by the indigenous Mapuche com-munity The local traditional healer and religious leader demanded the sacri-fice to calm the Earth and the ocean Two men served in jail for murder whenthe judge ruled that those involved had “acted without free will, driven by anirresistible natural force of ancestral tradition” (Tierney, 1990)

4.2.4.4 Relief Efforts

The relief effort was relatively of a small scale given the economic state ofChile at this time Recovery was a relatively slow process Outside aid wasprovided including, but not limited to, a field hospital and a public schooldonated by the United States and Mexico, respectively A national committeewas established in Chile in 1960 to manage the problems generated by theearthquake The committee was still in operation in 1974 when it became theNational Office of Emergency of the Interior Ministry, responsible withnational responsibility for natural disasters

FIGURE 4.4 A view from high ground of one of the first large ( >5 m) waves during the 1960 Chilean tsunami at Onagawa, Japan After Atwater et al (2005)