Tsunamis affecting New Zealand
Tsunamis affecting New Zealand are mainly due to the country being part of the geologically active Pacific Plate and associated with the Pacific Ring of Fire. Tsunamis affect New Zealand's coastline reasonably frequently and tend to be caused by earthquakes on the Pacific Plate both locally and as far away as South America, Japan, and Alaska. Some have been attributed to undersea landslides, volcanoes, and at least one meteor strike. New Zealand is affected by at least one tsunami with the a wave height greater than one metre every ten years on average.[1] The history of tsunamis is limited by the country's written history only dating from the early to mid-1800s with Māori oral traditions and paleotsunami research prior to that time. Studies are also being carried out into possible tsunami's on the larger inland lakes, particularly from landslides.[2]
Frequency
The predicted tsunami return periods for New Zealand based on all available data from 1840 are: 1 metre every 7.7 years, 2.5 metres every 10.6 years, 5 metres every 18.1 years, and 10 metres every 52.5 years.[3]
Significant tsunamis (greater than 1 metre)
Earthquake
1135-1215 southern Hikurangi margin
Research indicates a tsunami of 3.3 metres struck the east coast coast of lower North Island and upper South Island from a megathrust earthquake on the southern Hikurangi margin of the Pacific plate.[4]
1495-1545 southern Hikurangi margin
Research indicates a tsunami from a second mega-thrust earthquake on the southern Hikurangi margin of the Pacific plate struck the east coast coast of lower North Island and upper South Island. It was smaller than the 1135-1215 event.[4]
1820 Southland Tsunami
According to Maori history several hundred Ngati Mamoe Maori were killed by a tsunami while walking along the beach near Orepuki in the 1820s. They had been gathering fish at the Waiau River mouth in autumn as provisions for the winter period. The beach runs between the sea and a line of cliffs meaning that only a moderate tsunami of 2–4 metres high would have been needed to cause so many deaths. The likely source of the tsunami could have been an earthquake on the Fiordland or Puysegur faults. There are questions around the exact date of this event as it is reliant entirely on unverified unnamed sources.[5]
1826 Fiordland Earthquake and Tsunami
In 1826 sealers in Dusky Sound experienced a large earthquake that had aftershocks that went into the following year. The earthquake descriptions are considered consistent with a 7.6 to 8 magnitude quake given the extent of landslides and uplift. A tsunami or seiche caused by the uplift impacted the area where the sealers were. Its size has not been determined but it must have been significant (greater than 1 metre) to concern the sealers. They thought the small island on which they were residing was going to be swamped. There are questions around the accuracy of the year this event occurred.[5] Given that the earthquake responsible for this tsunami was felt as being violent by the sealers, it is unlikely to be the same tsunami as in the previous section, since in the earlier event was not foreshadowed by noticeable ground shaking.
1855 West Wairarapa
The uplift from the earthquake on 23 January 1855 tilted the Wellington Region and with it Wellington Harbour. The eastern side of the harbour moved 80 centimetres higher than the western side displacing the water into the shoreline along Lambton Quay and flooding its houses and shops.[1][6]
In Cook Strait there was a much greater displacement. The Rimutaka Range had risen about 6 metres and with it, the floor of the strait had been uplifted.[1] The exact maximum height of the tsunami was not known but sheds at Te Kopi, South Wairarapa, which were 8 metres above sea level were destroyed.[7] The area impacted by the tsunami was as far north as Otaki and the upper South Island.[8]
About 20 minutes after the earthquake a 3-4 metre high tsunami entered Wellington harbour through its narrow entrance and also across the Lyall Bay to Kilbirnie area.[9] The water was about 1 metre deep across the area. Captain Byron Drury, Commander of the sloop HMS Pandora reported:[10]
For eight hours subsequent to the first and great shock, the tide approached and receded from the shore every 20 minutes, rising from eight to ten feet and receding four feet lower than at spring tides. One ship, I heard, was aground at her anchorage four times.
The action of the earthquake and its tsunami destroyed the bridge across the Hutt River.[11] Coasters entering Wellington harbour after the tsunami reported sailing through a large quantity of dead fish - principally ling.[9]
1868 Chile
The 1868 Arica earthquake occurred on 13 August 1868, near Arica, then part of Peru, now part of Chile, at 21:30 UTC. The tsunami created by the quake reached New Zealand 15 hours later and caused substantial damage on the Chatham Islands and Banks Peninsula.[1] It also affected many areas along New Zealand's eastern coastline from Great Barrier Island to Bluff.[12][13] The tide at Wellington and Port Chalmers was reported as rising and falling by over a metre for a space of about 2 hours.[14]
The first area affected was the Chatham Islands where the tsunami struck at about 1am (New Zealand time) on 15 August. News of the effect on the Chathams did not reach the mainland until 27 August when the schooner Rifleman reached Port Chalmers. The Maori village of Tupuangi was totally destroyed with only sand and seaweed marking its location. Fortunately the first wave was small enough to awaken the sleeping villagers enabling them to make it safety. Subsequent waves carried out the destruction. Captain Anderson, who had a house about four miles from Tupuangi lost his house, but he and his family were able to reach safety. A Maori drowned while trying to save Captain Anderson's boat that had come adrift. Thomas Hay, a local sheep farmer also lost all he had. Buildings at Waitangi were also damaged including Beamish's accommodation house and the Government store.[15]
At about 4am Mr Webb, a railway night watchman noticed barque John Knox was lying on her broadside and nearly touching the jetty she was discharging her cargo on. He woke up Captain Jenkins her Captain and he found that the harbour between the wharf and Officers Point was dry. Minutes later there was a thundering noise from the direction of Officers Point and both her and Mr Webb saw an enormous wave powering its way into the harbour. The power and ferocity of the wave snapped a number of boats warps, snapped the John Knox's mooring chain and drove her into the jetty, dragged the ketch Margaret into the harbour where she fouled the schooner Annie Brown, damaged the schooner Jeanie Duncan and the steamer Novalty. The tide kept rising and falling in the harbour for some hours after the initial wave.[16] The tsunami that entered the harbour has been estimated at 7 metres high but Captain Jenkins had referred to the wave a being 8 feet (2.5 metres) high when he saw it.[1][16]
The bays around Banks Peninsula were also impacted by the tsunami which penetrated far inland along valleys, damaging homes and carrying away bridges and fences.[1] The ketch Georgina was wrecked at Rhodes Bay.[16] At Pigeon Bay a succession of waves reaching up to two metres above the highest high water mark between 3am and 1pm carried away two jetties, 40,000 feet of sawn timber, a boat house, fencing, and the ketch Courier.[17]
On the Waimakariri River a 1.5 metre high wave washed up it at about 3am snapping the stern line on the SS Gazelle which caused her to swing around. The schooner Challenge broke away from her wharf and collided with the Gazelle. The William and Julia were lifted on to the river bank and the Nora and Dart broke free from their wharf.[18]
After the tsunami Ferdinand von Hochstetter undertook a detailed analysis of the tsunami. He charted its progress across the Pacific determining wave speeds and the ocean depth along several paths. It was the first detailed scientific analysis of a major tsunami.[1] Dr Haast, a friend of von Hochstetter and fellow geologist, writing to the Star two days after the tsunami reached New Zealand pointed out that such waves travel at great speed and travel thousands of miles in a day.[19]
In 1912 the Evening Post carried a letter which suggested Westport had been submerged under a 10 metre high wave, with the old township now lying metres under the sea. This story was later modified in the Colonist by its writer to being associated with the Arica earthquake with the sea at Westport receding some 7–8 metres and a returning wave of much less significance.[20][21] The original claims were repeated in a 2015 paper by Professor James Goff, of the University of New South Wales.[22] The Westport Times made no mention of the event in August 1868, other than the impact on other parts of New Zealand.
1868 east of New Zealand
A few days after the Arica tidal wave arrived on 17 August 1868 there was a sharp earthquake, felt at both Nelson and Wellington at 9:57 and 9:56am respectively. Both harbours reported tidal waves with the one at Nelson over-topping the Boulder Bank. The wave was estimated to be just over a metre in height. The paper also reported that the tidal wave had impacted numerous South Island ports. The earthquake was felt at Christchurch at 10:01am.[23] Later reports indicated that the quake was felt almost simultaneously from Napier to Port Chalmers.[24]
1877 Iquique
On 10 May 1877 at 0:59 UTC a magnitude 8.5 earthquake occurred near Iquique Peru (now Chile). The tsunami created by this quake reached New Zealand eastern coastline at between 7 and 8am NZDT on 11 May. The wave had a reported 1-2 metre height in most places and impacted the coast from the Bay of Islands to Bluff. It also reached Westport on the West Coast of New Zealand at 2:30pm.[25] At Akaroa and Gisborne the wave was in the 2-3 metre range. At Port Charles on the Coromandal Peninsula the waves were reported being over 3 metres high.[26]
With the knowledge gained from the 1868 tsunami, newspapers of the day were already speculating that the source of the wave was from a South American earthquake.[27][28] Their hypothesis was confirmed a couple of days later when news of the Iquique earthquake reached New Zealand.[29]
1913 Westport
On 22 February 1913 a 1 metre high tsunami followed a local magnitude 6.8 earthquake.[30] Newspapers at the time seem to indicate a very limited impact to the tidal portion of the Buller River.[31]
1929 Whitecliffs, Karamea
On 17 June 1929 a 2.5 metre high tsunami was generated by the magnitude 7.8 Murchison earthquake.[30]
1931 Napier
The earthquake triggered a landslip at Waikare which in turn caused a localised 15.3 metre tsunami. At Napier there was a tsunami of about 3 metres.[3]
1946 Aleutian Islands
A 1 metre high tsunami was said to have reached Northland from the Aleutian Island earthquake.[30]
1947 Gisborne
- 26 March
On 26 March 1947 at 8:32am NZST Gisborne had what felt like a minor earthquake. Within 30 minutes the coast from Muriwai to Tolaga Bay experienced a tsunami which peaked at 10 metres high at Turihaua. At Tatapouri Point four people at the nearby hotel escaped by getting to high ground. Two waves drove through the hotel ground floor at up to window sill height and a number of small buildings were washed away. Two men in a cottage at Turihaua were swept inland on to the coast road. The cottage was totally destroyed, except for the kitchen they were in. Other damage included the Pouawa River bridge which was swept 600 metres inland, a house at Te Mahanga Beach which was swept off its piles, and six hectares of pumpkins at Murphy's Beach. No one was killed.[1] The quake that caused the tsunami was 7-7.1 magnitude off-shore near Poverty Bay.[32]
- 17 May
On 17 May 1947 another tsunami hit the coast between Gisborne and Tolaga Bay with a maximum height of 6 metres north of Gisborne. Again there were no casualties.[1] Also the impact of this tsunami was less than earlier one because it occurred near low tide. The earthquake responsible for it was a 6.9-7.1 magnitude quake off-shore near Tolaga Bay.[32]
1960 Chile
A tsunami generated by the Mw 9.5 Valdivia earthquake of 23 May 1960, 7:11 pm (NZST) was reported at more than 120 locations in New Zealand during the early morning. As with the other earlier 1868 and 1877 Chilean tsunamis the eastern coast of New Zealand from Cape Reinga to Stewart Island was impacted. More unusually, effects of the tsunami was also observed on the west coast of both islands, including Ahipara, Whanganui, Paremata, Nelson, Motueka, and several West Coast (South Island) towns. At the Chatham Islands and Campbell Island water heights above sea level ranged from 3 metres to over 5 metres. Surprisingly the tsunami did not affect New Plymouth, Foxton, or Himatangi Beach. The largest and most damaged waves were generally within 12 to 15 hours after the first ones although some were within the first 2–4 hours.[33]
The Pacific Tsunami Warning Center alerted New Zealand authorities of the approaching tsunami prompting the first major tsunami evacuation in New Zealand. Port facilities along the east coast of New Zealand were cleared, schools in coastal areas closed and Whitianga, Mercury Bay, Waihi Beach, Whakatane, Ohope, Opotiki and Kaikoura evacuated.[1]
Landslide
Sonar mapping has found the presence of massive submarine landslides near the New Zealand coast that would have triggered large localised tsunamis.[1]
1927-1928 Tolaga Bay
Three large waves greater than 4 metres high over the period 1927 to 1928. Possibly landslip related.[3] No reference to these events were found in the newspapers of the day.
1987 Doubtful Sound
A 3 metre high localised tsunami was caused by a landslide into Deep Cove, Doubtful Sound in May 1987.[5]
2003 Charles Sound
During the magnitude 7 23 August 2003 Fiordland earthquake, a significant landslide swept in to Charles Sound causing a 4 to 5 metres high tsunami that damaged a wharf and helipad in the Sound.[1] This tsunami from this landslide was localised to several hundred metres of coastline.[5] There was also a small tsunami caused by the deformation of the coast recorded 190 km away at Jackson Bay of 0.3 metres and at Port Kembla, New South Wales of 0.17 metres.[34]
Volcano
180 Taupo
Although an inland eruption, the Taupo eruption is considered to have caused an atmospheric pressure wave of sufficient magnitude to cause a tsunami.[1] Radiocarbon dating of prehistoric tsunami in the Cook Strait area indicates a possible correlation with one such event.[3]
1360 Healy
There is evidence of a tsunami in the Bay of Plenty from the Healy volcanic eruption.[1]
1883 Krakatoa
The Krakatoa eruption generated a rissaga of up to 2 metres high on the New Zealand Coast.[3]
Meteor
There is disputed historic evidence that a mega-tsunami with a wave height of greater than 30 metres could have struck Stewart Island in the 15th century.[35] This has been attributed to a meteor impact.[1] This event has been controversially linked by author Gavin Menzies with a disaster which reputedly hit a Chinese exploration fleet in 1422.[36]
Unknown cause
1320-1450 Western Waikato
A tsunami event sometime between 1320 and 1450 is believed to have impacted 150 km of the Western Waikato coastline. It is suspected to have been caused by a submarine slope failure of the Aotea Seamount which is located about 240 km west of Raglan. Evidence of the tsunami came from marine gravel deposits at 32 sites north along the coast from Awakino. However, a study published in 2016 says, "it is very difficult to reconcile the geologic evidence presented by Goff and Chagué-Goff (2015) suggestive of 30 to 60 m tsunami runup heights along the coast of south west Waikato with numerical modelling of potential tsunami source".[37]
A Maori legend called "Coming of the Sand" from the New Plymouth area describes possibly a tsunami inundating the inland area and depositing it with a thick layer of sand.[22]
1470-1510 South Taranaki Bight
The tsunami that occurred between 1470 and 1510 was associated with the South Taranaki Bight possibly extended down to Abel Tasman National Park. Evidence of this tsunami came from D'Urville and Kapiti Islands, and Waitori in South Taranaki[22]
1500s
Maori moved their settlements from low-lying coastal areas inland and onto hill tops. The cause of this change in settlement pattern is believed to have been tsunamis.[1] Archaeological examination of the coastal settlements shows tsunami damage in many places. This may be linked to the previously mentioned Mahuika crater meteor event.
1800s
In what is believed to have been the early 1800s, Moawhitu, a Maori village on D'Urville Island was wiped out by, in Maori oral traditions, a large wave which is now presumed to have been a tsunami. This event is undated.[1]
1924 Chatham Islands
On 19 July 1924 about 7:15 pm (NZMT) the northern and eastern side of Chatham Island and Pitt Island was struck by a series of waves that reach 6 metres above the high water mark. The waves went inland by 100 metres at Kaingaroa destroying a dam and two trawlers. At Wharekauri a bridge was badly damaged and were fences washed away. Te Awanui island was inundated and at Owenga several boats and some shell crushing machinery was damaged. A small hut was also washed away. At Pitt Island the wharf was destroyed and at Mangere Island there was a large landslide. The source of the tsunami is unknown could have been caused by either a landslide or an unidentified earthquake.[38] The Chatham Islands steam ship Tees was struck on its starboard side by the wave at 9:30am. The ship was almost capsized.[39] There was a sudden change in the weather to a southerly storm on the eastern coast of New Zealand on the day of the tsunami that may have masked its effect.[40]
Minor tsunamis (less than 1 metre) from significant earthquakes
There have been numerous minor tsunamis caused by significant large earthquakes. Examples of these are the 1848 Lower Wairau Valley quake, 1922 Vallenar earthquake, 1922 Rangiora quake, 1923 Kanto quake, 1950 Bay of Plenty quake, 1952 Severo-Kurilsk tsunami, 1964 Alaska earthquake, 1976 Kermadecs, 1977 Tongo, 1981 Maquare Ridge, 1982 and 1986 Kermadecs, 1994 Kuril Islands earthquake, 1995 Kobe, 1998 Balleny Island, 1998 Papua New Guinea earthquake, and 2001 southern Peru earthquake.[41]
The effect of the 1923 Kanto earthquake was reported in local newspapers as abnormal tides on 5 September.[42] The 1952 Severo-Kurilsk tsunami reached New Zealand with a wave height of just under 1 metre.[43]
Mitigation measures and early warning systems
There is evidence that Maori abandoned numerous coastal settlements in the 1500s in favour of inland or hilltop sites. It has been suggested that this movement was caused by tsunami's. Initial European settlement was unaware of the tsunami danger until the 1868 and 1877 tsunami's. No warning systems became available until after the 1946 Aleutian earthquake when the National Oceanic and Atmospheric Administration Pacific Tsunami Warning Centre was established in 1949. New Zealand became a member of the Centre and receives warnings of tsunamis caused by distant earthquakes.[1]
The Pacific Tsunami Warning and Mitigation System was established in 1965 due to the 1960 Chile tsunami. New Zealand is one of the 46 member countries.[44]
New Zealand does not have a warning system for tsunamis caused by local events. Tsunamis from these may arrive within a few minutes and this is not enough time for GeoNet to locate the event, determine if it could produce a tsunami, and notify the Ministry of Civil Defence and Emergency Management who issue the warnings.[1] [45] In addition New Zealand, at the time of the 2004 Indian Ocean earthquake and tsunami, did not have sea-based tsunami warning devices.[46] Since then 20 sites have been selected and gauges are now installed at most of them.[47]
Further complicating matters is the Pacific Tsunami Warning Centre's ocean based tsunami warning devices are focused on protecting Alaska, Hawaii, and the United States Pacific coastline. The means that there is a gap in the Southern Ocean.[46] Australia installed a DART buoy in the south-east Tasman Sea which helped cover that area, but installation and maintenance cost has meant they have not been installed as yet by New Zealand.[47]
Blue line project
Wellington was the first place to paint blue lines on its roadways to indicate the limit of potential tsunami hazards. The project won the International Association of Emergency Managers Global and Oceania Public Awareness categories at the Associations annual awards. The project evoked international interest.[48][49]
See also
References
- 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 Willem de Lange and Eileen McSaveney. 'Tsunamis - Tsunamis – New Zealand’s underrated hazard', Te Ara - the Encyclopedia of New Zealand, updated 13-Jul-12
- ↑ https://www.tvnz.co.nz/one-news/new-zealand/lake-tekapo-chosen-probe-risk-tsunamis-new-zealand-lakes Lake Tekapo chosen to probe risk to tsunamis on New Zealand lakes], One News, retrieved 30 March 2016
- 1 2 3 4 5 Table, Tsunami Hazard in New Zealand, Willem de Lange and Rodger Fraser, Tephra, Ministry for Emergency Management, October 1999, page 4
- 1 2 Megaquake could hit central New Zealand, Paul Gorman and Michael Daly, Last updated 08:40, May 19, 2015
- 1 2 3 4 EQC Project 03/490 - Understanding local source tsunami: 1820s Southland tsunami, G Downes et al, Institute of Geological & Nuclear Sciences client report 2005/153 - Project Number: 410W1034 and National Institute for Water and Atmospheric Research Consultancy report HAM2005-135 - Project Number: EQC04201, November 2005
- ↑ Editorial, Taranaki Herald, Volume III, Issue 133, 14 February 1855, Page 2
- ↑ Editorial, Taranaki Herald, Volume III, Issue 134, 21 February 1855, Page 3
- ↑ The late earthquake, Nelson Examiner and New Zealand Chronicle, Volume 712, Issue 712, 21 February 1855, Page 2
- 1 2 Editorial, Daily Southern Cross, Volume XII, Issue 804, 13 March 1855, Page 2
- ↑ Earthquake at Wellington, Nelson Examiner and New Zealand Chronicle, Volume XIII, Issue 705, 27 January 1855, Page 2
- ↑ Wellington, Otago Witness, Volume 06, Issue 182, 17 February 1855, Page 3
- ↑ Earthquake wave in the sea, Lyttelton Times, Volume XXX, Issue 2387, 17 August 1868, Page 2
- ↑ The earthquakes and tidal phenomena, Daily Southern Cross, Volume XXIV, Issue 3467, 26 August 1868, Page 3
- ↑ Editorial, Star, Issue 80, 15 August 1868, Page 2
- ↑ Arrival of the schooner Rifleman from the Chatham Islands, Otago Daily Times , Issue 2048, 28 August 1868, Page 3
- 1 2 3 Extrodinary tidal wave, Star, Issue 80, 15 August 1868, Page 3
- ↑ Earthquake wave in the sea, Star, Issue 81, 17 August 1868, Page 3
- ↑ Kaiapoi, Star , Issue 80, 15 August 1868, Page 3
- ↑ Untitled, Star , Issue 81, 17 August 1868, Page 3
- ↑ - the old days, Nelson Evening Mail, Volume XLVIII, 13 January 1914, Page 3
- ↑ Interesting reminiscences, Evening Post, Volume LXXXIV, Issue 37, 12 August 1912, Page 2
- 1 2 3 West coast is tsunami 'blind spot' - new study, Ian Steward, Last updated 05:00, March 23, 2015
- ↑ Earthquakes abd tidal waves in New Zealand, Colonist, Volume XI, Issue 1142, 4 September 1868, Page 3
- ↑ Remarkalbe tidal waves, Nelson Examiner and New Zealand Chronicle, Volume XXVII, 5 September 1868, Page 2
- ↑ (Per Press Agency), Evening Post, Volume XV, Issue 111, 12 May 1877, Page 2
- ↑ The tidal wave at Port Charles Auckland Star, Volume VIII, Issue 2244, 16 May 1877, Page 2
- ↑ Great tidal wave, Auckland Star, Volume VIII, Issue 2240, 11 May 1877, Page 2
- ↑ Tidal wave on the New Zealand coast, Evening Post, Volume XV, Issue 110, 11 May 1877, Page 2
- ↑ Editorial, Evening Post, Volume XV, Issue 113, 15 May 1877, Page 2
- 1 2 3 New Zealand tsunamis 1840-1982, De Lange and Healy, Table 1, New Zealand Journal of Geology and Geophysics, 1986, vol 29 page 116
- ↑ Earthquake, Nelson Evening Mail, Volume XLVIII, 24 February 1913, Page 5
- 1 2 Gisborne tsunami, 25 March and 17 May 1947
- ↑ Chile tsunami, 23 May 1960
- ↑ Fiordland tsunami, 22 August 2003
- ↑ Goff, James; et al. (2010). "Analysis of the Mahuika comet impact tsunami hypothesis". Marine Geology 271 (3/4): 292–296. doi:10.1016/j.margeo.2010.02.020.
- ↑ Chapter 22 – Tragedy on the high seas: Zheng He’s fleets destroyed by a tsunami, www.gavinmenzies.net, 31 August 2011. Retrieved 11 March 2016.
- ↑ "Numerical modelling of Tsunami Effects at Port Waikato, Raglan and Aotea Waikato West Coast" (PDF). www.waikatoregion.govt.nz. Retrieved 2016-03-10.
- ↑ Chatham Islands tsunami, 19 July 1924
- ↑ A close call, Press, Volume LX, Issue 18141, 2 August 1924, Page 14
- ↑ The weather, Press, Volume LX, Issue 18130, 21 July 1924, Page 10
- ↑ Chapter 4 - Tsunami and storm surge hazard in New Zealand; Goff, Nicol, and Rouse; The New Zealand Coast; Dunmore Press; 2003; page 86; ISBN 978-0-86469-438-6
- ↑ Abnormal low tides, Evening Post, Volume CVI, Issue 57, 5 September 1923, Page 6
- ↑ The 4 November 1952 Kamchatka Earthquake and Tsunami, Commonwealth of Australia 2015, Bureau of Meteorology, ABN 92 637 533 532
- ↑ Pacific Tsunami Warning System 50th Anniversary
- ↑ Does New Zealand have a tsunami warning system? If so, how does it work?
- 1 2 New Zealand tsunami without warning: It could happen here, National Business Review, 11 January 2005
- 1 2 NZ to get more tsunami warning gauges, Last updated 00:00 05/08/2007
- ↑ Tsunami Blue Lines Project adopted in the United States, Friday, 11 March 2016, 10:03 am, Press Release: Wellington City Council, retrieved 30 March 2016
- ↑ Tsunami WalkOut Blue Line Project March 11, 2016, Oregon’s Office of Emergency Management, retrieved 30 March 2016