The 1947 Gisborne earthquakes and tsunami occurred east of Gisborne and offshore from New Zealand's North Island. Both the two earthquakes are estimated to have measured at most 7.1 on the moment magnitude scale. [1]
The first earthquake, which struck offshore Poverty Bay on 26 March 1947 at 8:32 am NZST, seemed like a minor earthquake in Gisborne, [2] but was 7.0–7.1 Mw . [3] It generated a tsunami with a maximum measured run-up height of 10 metres that struck the coast from Māhia Peninsula to Tokomaru Bay, [3] swamping the coast between Muriwai and Tolaga Bay 30 minutes after the quake. [2] The tsunami was not observed outside of New Zealand. [1] Four people at the Tatapouri Hotel, 13 kilometres by road north of Gisborne, saw the tsunami coming and rushed up a hill. Two waves swept through the ground floor of the hotel up to window sill height, and retreating water then washed small buildings out to sea. A little further north at Turihaua, a 10-metre high wave hit a cottage, sweeping two men who were outside it inland onto the coast road. Three other people were trapped in the kitchen, which filled with water to head height. Retreating water then destroyed the cottage, leaving only the kitchen. The Pouawa River bridge, a little further north, was swept 800 metres inland. [2] Seaweed was later found in telegraph wires 12 metres above sea level at Pouawa Beach. [3] A house at Mahanga Beach, just north of Māhia Peninsula, was moved off its piles. [2]
Seven weeks later, a second earthquake struck offshore Tolaga Bay on 17 May, and was estimated to have been 6.9–7.1 Mw . It also generated a tsunami, which had a maximum measured run-up height of 6 metres. Despite occurring at low tide and being less powerful than the first, the tsunami caused small amounts of damage along the east coast and is noted for washing away construction materials being used to repair damage from the earlier tsunami. [1] No one died in either of the tsunamis, but there could have been a high toll had they struck when beaches were crowded during summer holidays. [2]
New Zealand lies along the boundary between the Indo-Australian and Pacific plates. In the North Island the displacement is mainly taken up along the Hikurangi Subduction Zone, although the remaining dextral strike-slip component of the relative plate motion is accommodated by the North Island Fault System. Both earthquakes are believed to have occurred along the Hikurangi Subduction Zone, in close proximity to each other. Both earthquakes generated tsunami caused by the sudden release of energy from the Earth's crust. Due to the unusually large tsunami that accompanied the earthquake, and the lack of damage due to weak shaking, this event has been identified as a rare "tsunami earthquake". [4]
The 2007 Gisborne earthquake occurred under the Pacific Ocean about 50 kilometres (31 mi) off the eastern coast of New Zealand's North Island at 8:55 pm NZDT on 20 December. With a moment magnitude of 6.7 and maximum Mercalli intensity of VII, the tremor affected the city of Gisborne and was felt widely throughout the country, from Auckland in the north to Dunedin in the south.
Gisborne District or the Gisborne Region is a local government area of northeastern New Zealand. It is governed by Gisborne District Council, a unitary authority. It is named after its largest settlement, the city of Gisborne. The region is also commonly referred to as the East Coast.
The 2009 Dusky Sound earthquake was a Mw 7.8 earthquake that struck a remote region of Fiordland, New Zealand, on 15 July at 21:22 local time. It had an initially–reported depth of 12 km (7.5 mi), and an epicentre near Dusky Sound in Fiordland National Park, which is 160 km (99 mi) north-west of Invercargill. It was the country's largest earthquake magnitude since the 1931 Hawke's Bay earthquake, but caused only minor damage and there were no casualties. A tsunami accompanied the event and had a maximum measured run-up of 230 cm (91 in).
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The 1932 Jalisco earthquakes began on June 3 at 10:36 UTC with a megathrust event that registered 8.1 on the moment magnitude scale. With a maximum perceived intensity of X (Extreme) on the Mercalli intensity scale, at least 400 deaths were caused in Mexico and neighboring Guatemala. It was the first of a series of seismic events that affected parts of western Mexico during the month of June 1932, all reaching magnitude 7 or greater.
The 2014 Eketāhuna earthquake struck at 3:52 pm on 20 January, centred 15 km east of Eketāhuna in the south-east of New Zealand's North Island. It had a maximum perceived intensity of VII on the Mercalli intensity scale. Originally reported as magnitude 6.6 on the Richter Scale, the earthquake was later downgraded to a magnitude of 6.2. A total of 1112 aftershocks were recorded, ranging between magnitudes 2.0 and 4.9 on the Richter Scale.
The 1863 Hawke's Bay earthquake was a devastating magnitude 7.5 Mw earthquake that struck near the town of Waipukurau on 23 February 1863. It remained the single largest earthquake to strike Hawke's Bay until 1931, where a magnitude 7.8 quake levelled much of Napier and Hastings, and killed 256 people.
The Hikurangi Margin is New Zealand's largest subduction zone and fault.
The 1904 Cape Turnagain earthquake struck 10 kilometres (6.2 mi) north of Cape Turnagain on the morning of 9 August with a magnitude estimated at 6.8 Ms and 7.0–7.2 Mw. It was felt throughout the North Island and upper South Island, with many communities within a 500 kilometres (310 mi) radius reporting noticeable ground shaking. Heavy damage occurred to the landscape and personal property and one man died. It was the largest to strike New Zealand since the 7.0 Mw North Canterbury earthquake in 1888.
The 2003 Fiordland earthquake struck the remote region of Fiordland in the South Island of New Zealand on 22 August 2003, at 12:12 am NZST. The epicentre was 12 kilometres (7.5 mi) deep, and was thought to be near Secretary Island at the entrance to Doubtful Sound. At 7.2 Ms magnitude, it was one of the largest quakes in the country for some time, and was the largest shallow quake since the 1968 Inangahua earthquake. There was an aftershock two hours later at 2:12 am, followed over several days by frequent small tremors; two months after the earthquake, there had been 8,000 aftershocks.
Laura Martin Wallace is a geodetic principal scientist who works between the University of Texas at Austin and GNS Science in New Zealand. She was elected Fellow of the Royal Society Te Apārangi in 2018.
The 2018 Fiji earthquakes occurred on August 19, at 00:19:40 UTC and on September 6 15:49 UTC. The epicenters were located close to the Fijian island Lakeba, and around 270 km from the small town of Levuka on Ovalau. The first earthquake registered a magnitude of Mww 8.2, and is the largest earthquake of 2018. It had a focal depth of 600 km, making it the second largest earthquake ever recorded at a depth greater than 300 km; a tie with the 1994 Bolivia earthquake, and behind the 2013 Okhotsk Sea earthquake. The initial earthquake was caused by a normal fault below the South Pacific Ocean. A Mww 7.9 event struck the islands again on September 6 at a depth of 670 km; this earthquake was a mainshock of its own. Both earthquakes may be considered a doublet event.
The 2021 Kermadec Islands earthquakes were a series of earthquakes with magnitudes of 8.1 and 7.4 that occurred at 19:28:31 UTC on 4 March 2021. The epicentres were located southeast of Raoul Island in the Kermadec Islands, part of the New Zealand outlying islands. The main magnitude 8.1 earthquake was preceded by a magnitude 7.4 foreshock and followed by a magnitude 6.1 aftershock. A separate, unrelated magnitude 7.3 earthquake occurred off the coast of the North Island of New Zealand, approximately 900 km to the south, several hours before the main quakes. More than a dozen aftershocks exceeded magnitude 6.
The Nemuro-Oki earthquake in scientific literature, occurred on June 17 at 12:55 local time. It struck with an epicenter just off the Nemuro Peninsula in northern Hokkaidō, Japan. It measured 7.8–7.9 on the moment magnitude scale (Mw ), 8.1 on the tsunami magnitude scale (Mt ) and 7.4 on the Japan Meteorological Agency magnitude scale (MJMA ).
An earthquake occurred on 26 August 2012 at 22:37 local time. The earthquake located off the coast of El Salvador measured 7.3 on the moment magnitude scale and had a focal depth of 16.0 kilometres (10 mi). No deaths were reported, however more than 40 people were injured when they were caught in a tsunami generated by the earthquake. Waves from the tsunami were unusually large for an earthquake of this size. The large waves were attributed to the earthquake's unique rupture characteristic. In addition to the absence of fatalities, damage caused by the earthquake and tsunami was minimal as a result of the sparse population around the affected region and the slow rupture characteristic of the event.
On April 13, 1923 at 15:31 UTC, an earthquake occurred off the northern coast of the Kamchatka Peninsula in the USSR, present-day Russia. The earthquake had a surface-wave magnitude (Ms ) of 6.8–7.3 and an estimated moment magnitude (Mw ) of 7.0–8.2. This event came just two months after a slightly larger earthquake with an epicenter struck south of the April event. Both earthquakes were tsunamigenic although the latter generated wave heights far exceeding that of the one in February. After two foreshocks of "moderate force", the main event caused considerable damage. Most of the 36 casualties were the result of the tsunami inundation rather than the earthquake.
The 1585 Aleutian Islands earthquake is the presumed source of a tsunami along the Sanriku coast of Japan on 11 June 1585, known only from vague historical accounts and oral traditions. The event was initially misdated to 1586, which led to it being associated with the deadly earthquakes in Peru and Japan of that year. A megathrust earthquake on the Aleutian subduction zone in the North Pacific Ocean was hypothesized as the tsunami's source. Paleotsunami evidence from shoreline deposits and coral rocks in Hawaii suggest that the 1585 event was a large megathrust earthquake with a moment magnitude (Mw ) as large as 9.25.
An earthquake occurred off the coast of the Alaska Peninsula on July 28, 2021, at 10:15 p.m. local time. The large megathrust earthquake had a moment magnitude of 8.2 according to the United States Geological Survey (USGS). A tsunami warning was issued by the National Oceanic and Atmospheric Administration (NOAA) but later cancelled. The mainshock was followed by a number of aftershocks, including three that were of magnitude 5.9, 6.1 and 6.9 respectively.
In 1914, two earthquakes shook the upper North Island of New Zealand; on Wednesday 7 October and Wednesday 28 October. They were large and shallow, with their epicentres close together northwest of Ruatoria in the Gisborne District. The earthquakes were felt strongly throughout the East Cape area, most noticeably in areas east of the epicentre such as Waipiro Bay, with a large amount of damage occurring in Tokomaru Bay in particular. One person was killed by a landslide near Cape Runaway.