1953 Suva earthquake

Fiji lies in a complex tectonic setting along the boundary between the Australian plate and the Pacific plate. Southwards from Fiji the Pacific plate is subducting beneath the Australian plate along the Tonga Trench forming the Tonga Ridge island arc system and the Lau Basin back-arc basin. To the southwest of Fiji the Australian plate is subducting beneath the Pacific plate forming the Vanuatu Ridge island arc system and the North Fiji back-arc basin.{{cite journal|last=Rahiman|first=T.I.H.|author2=Pettinga J.R.|author3=Watts P.|name-list-style=amp|year=2007|title=The source mechanism and numerical modelling of the 1953 Suva tsunami, Fiji|journal=Marine Geology|volume=237|issue=1–2|pages=55–70|doi=10.1016/j.margeo.2006.10.036|bibcode=2007MGeol.237...55R}} Hence, the region has undergone a complex process of plate convergence, subduction, and arc volcanism from the Middle Eocene to the Early Pliocene.{{cite web|url=http://eird.org/deslizamientos/pdf/eng/doc8455/doc8455-2a.pdf|title=Landslide hazards in Fiji|last=Greenbaum|first=D.|author2=Bowker, M. R|author3=Dau, I|author4=Drospy, H|author5=Greally, K. B|author6=McDonald A. J. W|author7=Marsh, S. H|author8=Northmore, K. J|author9=O'Connor, E. A|author10=Prasad, R. S|author11=Tragheim, D. G.|name-list-style=amp|year=1995|work=Technical Report WC/95/28 Rapid methods of landslide hazard mapping : Fiji case study|publisher=British Geological Survey|accessdate=23 March 2011}} Many of the larger islands, such as Viti Levu, are of volcanic origin.{{cite web|url=http://www.sprep.org/att/publication/000713_FIJI_country_papaer_PACC_workshop_samoa_June_July_09.corrected_1.pdf|title=Government of Fiji Country Report on Pacific Adaptation to Climate Change (PACC) Inception Meeting Samoa, from 29th June – 3rd July 2009.|author=Government of Fiji|year=2009|page=2|accessdate=23 March 2011}} Volcanism still exists, and there are Holocene volcanos in Fiji.{{cite web|url=http://www.volcano.si.edu/world/region.cfm?rnum=0405|title=Volcanoes of New Zealand to Fiji: Fiji Islands|publisher=Global Volcanism Program|accessdate=23 March 2011}}

The Fiji Platform lies in a zone bordered with active extension fault lines around which most of the shallow earthquakes were centered. These fault lines are the Fiji fracture zone (FFZ) to the north, the 176° Extension Zone (176°E EZ) to the west, and the Hunter fracture zone (HFZ) to the east.

The earthquake lasted between 25 and 30 seconds and had an estimated magnitude of 6.75 on the surface-wave magnitude scale. The calculated focal mechanism is consistent with slightly oblique dextral (right lateral) strike-slip on a NW-SE trending fault plane, matching the orientation of other fault planes measured in the area and a marked bathymetric lineament. The fault parameters calculated for the earthquake are a length of {{cvt|30|km}}, a width of {{cvt|27|km}} and a slip of {{cvt|1|m}}. The NW trending nodal plane of this earthquake coincides with the strike of the NW trending Naqara Fault on the southeast coast of Viti Levu.{{cite journal |title=Fracture lineaments, fault mesh formation and seismicity: Towards a seismotectonic model for Viti Levu, Fiji |last1=Rahiman |first1=Tariq I.H. |last2=Pettinga |first2=Jarg R. |year=2009 |journal=Bulletin of the New Zealand Society for Earthquake Engineering |volume=42 |issue=1 |pages=63–72 |doi=10.5459/bnzsee.42.1.63-72 |url=http://www.nzsee.org.nz/db/Bulletin/Archive/42(1)0063.pdf |accessdate=3 February 2013}}

The first sign of a tsunami was observed about one minute after the earthquake when a disturbance of the sea surface was noticed by the captain of the cutter Adi Tirisa located about {{cvt|6.4–8.0|km}} southwest of Suva. The boat shook severely before "three great spouts burst out of the sea, carrying mud, stones, and part of a long-wrecked vessel". The location of this disturbance was at the western end of the entrance to the Suva Passage.

The tsunami was triggered by an earthquake-induced partial collapse of a barrier reef at Suva into the Suva Canyon. The current reef edge shows the effects of repeated slope failure. The characteristics of the 1953 landslide scar were investigated using a high resolution multibeam echo sounder. The area immediately offshore from the reef is a composite failure surface, where a young scar measuring {{cvt|800|m}} in width was identified. The slide had an estimated volume of {{cvt|60,000,000|m3}}. Numerical modelling of a landslide successfully reproduced most of the tsunami observations.

The first tsunami wave, measuring {{cvt|0.3|m}}, struck Beqa some thirty seconds after the earthquake. Fifteen minutes later, a {{cvt|1.2-1.5|m}} wave arrived. On Viti Levu, waves estimated at {{cvt|3–15|m}} were observed around the coral reefs off the island's southern coast. As these waves swept onto land, they deposited remnants of the coral reef. A tsunami of {{cvt|20|cm}} amplitude was recorded by the tide gauge in Pago Pago. Just over seven hours after the earthquake, in Honolulu and Port Allen, the tsunami wave measured {{cvt|6|cm}} and {{cvt|10|cm}}.{{cite web |title=Tsunami Event Information |url=https://www.ngdc.noaa.gov/hazel/view/hazards/tsunami/event-more-info/1840 |publisher=National Geophysical Data Center / World Data Service: NCEI/WDS Global Historical Tsunami Database. NOAA National Centers for Environmental Information |access-date=11 September 2024 |doi=10.7289/V5PN93H7 |author1=National Geophysical Data Center }}

This earthquake was the most destructive in Fiji's recorded history; killing three people and seriously injuring twenty others. The most serious damage occurred in the southeastern part of Viti Levu. A wharf, bridges, and buildings were also severely damaged at Suva. The tsunami caused particular damage to coastal areas unprotected by barrier reefs, devastating the villages of Nakasaleka and Makaluva. There were five deaths from the tsunami, three at Suva and two at Nakasaleka. Had the tsunami occurred at high tide, rather than low tide it would have been more damaging.{{cite web|url=http://www.pdc.org/TAK/Fiji/History/Fiji_Significant_Events_1850_to_2004.pdf|title=Summary of Earthquakes and Tsunamis Affecting Fiji 1850–2004|author=Pacific Disaster Center|work=Tsunami Awareness Kit|accessdate=22 March 2011|archive-url=https://web.archive.org/web/20110206064110/http://www.pdc.org/TAK/Fiji/History/Fiji_Significant_Events_1850_to_2004.pdf|archive-date=6 February 2011|url-status=dead}} The landslide that caused the tsunami generated turbidity currents that damaged several underwater cables in the Suva Canyon. The total damage caused by earthquake and tsunami was estimated at $500 thousand.{{cite web|url=http://www.mrd.gov.fj/gfiji/geology/educate/equakes.html |title=Earthquake in Fiji |author=Fiji Mineral Resources Department |accessdate=22 March 2011 |url-status=dead |archiveurl=https://web.archive.org/web/20110928084645/http://www.mrd.gov.fj/gfiji/geology/educate/equakes.html |archivedate=28 September 2011 }}

• List of earthquakes in 1953
• List of earthquakes in Fiji

{{reflist}}

• {{citation|title=The 1953 Suva earthquake and tsunami|url=http://bssa.geoscienceworld.org/content/52/1/1.abstract|first=R. E.|last=Houtz|journal=Bulletin of the Seismological Society of America|volume=52|issue=1|pages=1–12|date=January 1962|doi=10.1785/BSSA0520010001 |bibcode=1962BuSSA..52....1H }}

• {{EQ-isc-link|892001}}

{{Earthquakes in 1953}}

Category:1953 earthquakes

Category:Earthquakes in Fiji

Category:1953 in Fiji

Category:1950s tsunamis

Category:Tsunamis in Fiji

Category:1953 disasters in Fiji