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1843 Wanganui earthquake
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| Date | July 8, 1843 |
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| Magnitude | Mw 7+ |
| Epicenter | near Wanganui, North Island |
| Countries or regions | New Zealand |
| Casualties | 2 deaths |
The 1843 Wanganui earthquake occurred on July 8, 1843 with an epicenter near Wanganui, North Island New Zealand. This was the first earthquake in New Zealand over magnitude 7 for which written records exist.[1]
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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).[2] 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.[3] The presumed epicenter of the 1843 earthquake is not, however, associated with any known fault.
Very little is known about the details of this earthquake except that it lasted for a few minutes.[4] There is insufficient information to identify the epicenter or say anything about the type or amount of displacement involved.
Damage in the Wanganui area reached IX-X on the Mercalli intensity scale.[5] Many houses were damaged, and a brick church at Pūtiki was destroyed.[6] 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.[7]