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170 ° E
35 ° S
Kapiti
5000 BP
3000 BP
1900 BP
1220 AD
1450 AD
1855 AD
North Island
Wairoa
3200 BP
4800 BP
6300 BP
Abel Tasman
National Park
<320 AD
1220 AD
1450 AD
1855 AD
Wellington
Fault
Okarito Lagoon
1450 AD
1826 AD
Palliser Bay
1855 AD
Cook Strait
Alpine Fault
South Island
45 ° S
Figure 5.9. New Zealand palaeotsunami deposit sites and chronologies (after Goff
et al. , 1998 , 2001 , 2004a).
Sand sheets that extend into back-barrier marshes and lagoons are easily
identified as coarser-grained sediment layers within otherwise fine-grained sedi-
ments. Grain size within these sheets typically decreases upwards and landwards
at any one location. These changes in grain size are an important diagnostic tool
foridentifying both multiple separate tsunami events and separate waves within
thesame tsunami event. Each of these scenarios produces a series of upward
fining sediment cycles with the base of each new event marked by the start of
coarser-grained sediments and the top marked by the finest-grained sediments.
The next wave or tsunami event is indicated by the next similar layer. Many
studies have identified multiple events and waves within a single event based
upon the nature of sediment cycles. For example, Goff et al .(1998)identified the
AD 1855 Wellington (New Zealand) tsunami generated by a severe earthquake
resulting in a 9--10 m high tsunami in Cook Strait and a 3--4 m high tsunami
at the entrance to Wellington Harbour (Fig 5.9). Three waves were known to
have inundated the coast during this event; the first wave was the largest. Goff
et al .(1998)found three cycles of upward fining sediment at seven separate
sites examined along the coast near Wellington Harbour (Kapiti, Fig. 5.9). Each
 
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