1843 Wanganui earthquake

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1843 Wanganui earthquake
1843 Wanganui earthquake is located in New Zealand
1843 Wanganui earthquake
UTC time 1843-07-09
Local date 8 July 1843 (1843-07-08)
Magnitude Mw  7+
Epicenter near Wanganui, North Island
40°00′S 176°03′E / 40.000°S 176.050°E / -40.000; 176.050Coordinates: 40°00′S 176°03′E / 40.000°S 176.050°E / -40.000; 176.050
Areas affected New Zealand
Casualties 2 deaths

The 1843 Wanganui earthquake occurred on 8 July at 16:45 local time with an estimated magnitude of 7.5 on the Mw scale.[1][2] The maximum perceived intensity was IX (Violent) on the Mercalli intensity scale' possibly reaching X (Extreme).[1] The epicentre is estimated to have been within a zone extending 50 km northeast from Wanganui towards Taihape. GNS Science has this earthquake cataloged and places the epicenter 35 km east of Taihape,[3] near the border of Hawke's Bay. This was the first earthquake in New Zealand over magnitude 7 for which written records exist,[4] and the first for which deaths were recorded.[5]

Tectonic setting[edit]

New Zealand lies along the boundary between the Australian and Pacific Plates. In South Island most of the relative displacement between these plates is taken up along a single dextral (right lateral) strike-slip fault with a major reverse component, the Alpine Fault. In North Island the displacement is mainly taken up along the Kermadec subduction zone, although the remaining dextral strike-slip component of the relative plate motion is accommodated by the North Island Fault System (NIFS).[6] A group of dextral strike-slip structures, known as the Marlborough Fault System, transfer displacement between the mainly transform and convergent type plate boundaries in a complex zone at the northern end of South Island.[7] The presumed epicenter of the 1843 earthquake is not, however, associated with any known fault.

Earthquake characteristics[edit]

The shock was felt over much of North Island and was reported as lasting for three minutes near Mokoia. A magnitude of 7.5 was estimated from the extent of the area that was subject to a shaking level of at least VIII (Severe). At least ten aftershocks were reported on the same day as the mainshock and further shocks were reported until January 1845.[1]

Damage[edit]

Damage in the Wanganui area reached IX-X on the Mercalli intensity scale.[1] Many houses were damaged, and a brick church at Pūtiki was destroyed.[5] There was extensive lateral spreading of the terrace margin to the Whanganui River, and a section of Shakespeare Cliff fell into the river. Two people were killed when their house was swept away by one of the landslides caused by the earthquake.[8]

See also[edit]

References[edit]

  1. ^ a b c d Eiby G.A. (1968). "A descriptive catalogue of New Zealand earthquakes". New Zealand Journal of Geology and Geophysics. 11 (1): 30–32. doi:10.1080/00288306.1968.10423671. 
  2. ^ "Significant earthquake". National Geophysical Data Center. Retrieved 28 August 2014. 
  3. ^ "GeoNet – Quakes". Archived from the original on 15 January 2015. Retrieved 2015-01-12. 
  4. ^ Civil Defence Emergency Management Group Southland. Page on earthquake hazards
  5. ^ a b Eileen McSaveney. "Landslide related fatalities" (PDF). Te Ara The Encyclopedia of New Zealand. Retrieved 28 August 2014. 
  6. ^ Mouslopoulou, V.; Nicol, A.; Little, T.A. & Walsh, J.J. (2007). "Terminations of large strike-slip faults: an alternative model from New Zealand". In Cunningham, W. D. & Mann, P. Tectonics of Strike-Slip Restraining and Releasing Bends. Special Publication. 290. London: Geological Society. pp. 387–415. 
  7. ^ Van Dissen R.; Yeats R.S. (1991). "Hope fault, Jordan thrust, and uplift of the Seaward Kaikoura Range, New Zealand". Geology. 19 (4): 393–396. Bibcode:1991Geo....19..393V. doi:10.1130/0091-7613(1991)019<0393:HFJTAU>2.3.CO;2. 
  8. ^ A tremulous motion, Barry Hawkins