Dunedin Earthquake

A shallow magnitude 4.7 earthquake shook Otago just after 11 o’clock last night.

Tuesday, 2nd June 2015

A magnitude 4.7 earthquake struck 30 km west of Dunedin city at 11:18 last night. The quake was 7 km deep according to GeoNet.

GeoNet's seismograph network 2 June 2015

GeoNet’s seismograph network 2 June 2015

[click for larger image] The earthquake left a distinct trace on southern parts of GeoNet’s seismograph network, and the public had filed more than 5,000 reports about the quake with GeoNet by midday today. The earthquake was felt in Southland, Otago and South Canterbury, with a few scattered reports from as far north as Wellington.

A magnitude 4.0 earthquake struck the same area at 6:44 p.m. on October 16th last year. This event was also shallow (9 km deep) and attracted nearly 1400 felt reports from the public.

GeoNet has issued a brief report on last night’s event, advising that its modelling suggested that strong shaking was expected to have occurred in spots along State Highway 87. Some of the felt reports filed with GeoNet reported items coming off shelves in various parts of Dunedin city.

Last year’s earthquake was the first quake to have occurred near Dunedin since 1991, and that quake occurred in the same area as a magnitude 4.0 event in 1982. At the time, GeoNet issued a summary of Dunedin earthquakes since 1960.

To date, significant earthquakes which have occurred near Dunedin are:
1 June 2015, magnitude 4.7, centred 30 km west of Dunedin, 7 km deep.
16 October 2014, magnitude 4.0, centred 30 km west of Dunedin, 9 km deep.
21 February 1991, magnitude 4.1, centred 20 km south of Dunedin, 33 km deep
13 July 1989, magnitude 4.3, centred 20 km south-west of Dunedin, 12 km deep
21 October 1986, magnitude 4.1, centred 35 km north-west of Dunedin, 12 km deep
24 June 1984, magnitude 4.1, centred 40 km south-east of Palmerston, 12 km deep
23 December 1982, magnitude 4.0, centred 30 km west of Dunedin, 12 km deep
23 June 1982, magnitude 4.2, centred 25 km south of Dunedin, 12 km deep
9 April 1974, magnitude 4.9, centred 10 km south of Dunedin, 12 km deep

Five of these earthquakes were centred off-shore including the largest event, the magnitude 4.9 earthquake in 1974. Three quakes have occurred close together 30 km west of Dunedin. They struck in 1982, 2014 and last night.

Last year’s report by GeoNet quoted a report on the largest quake near Dunedin compiled by Adams and Kean in 1974. They noted that the magnitude 4.9 quake was the largest to have affected the city of Dunedin since its founding in the middle of the 19th century.

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