# Reconstructing the 26 June 1917 Samoa Tsunami Disaster
## 2 Geographical and Historical Context  
Samoa consists of two main islands, Upolu and Savai'i, with several smaller inhabited and uninhabited islands between them (e.g., Manono and Apolima), as well as east and south of Upolu (e.g., Fanuatapu, Namu'a, Nu'utele, Nu'ulua, and Nu'usafe'e) (Figure 1). Comprising part of a larger archipelago encompassing the geologically younger islands of American Samoa to the east, the island chain originated from hotspot volcanic activity and is fringed by coral reefs [15; 16; 17]. The geology of Samoa largely consists of mafic material (e.g., basalt and gabbro), due to its oceanic intraplate volcanic hotspot origins [18]. Savai'i is the bigger island with an area of 1820 km\({}^{2}\), whereas Upolu has an area of 1114 km\({}^{2}\) and accommodates over 67% of the total population of approximately 200,000 people [19]. Apia, the capital of Samoa, is located in the central north of Upolu.  
In 1902, a temporary geophysical observatory was established in Apia on the then-German administered island of Upolu, whereby it was initially set up to obtain baseline earth observations to compare with the British and German south polar expeditions of 1902-1903. Meteorological instruments and seismographs were installed in 1902 and magnetic instruments in 1905. These enabled studies in geomagnetism, seismology, meteorology, tidal variations, and atmospheric electricity and were so productive that in 1908 the observatory was established on a permanent basis.  
In August 1914, troops of the New Zealand Expeditionary Force seized control of German-controlled Samoa and the observatory. Its operations were much curtailed during the World War 1 (WW1) years, but the German Director ([PERSON]) continued observatory operations until it was formerly taken over by the New Zealand government in 1921 [20; 21; 22]. New Zealand administration of the observatory continued until the handover in 1963, shortly after Samoa achieved political independence and control of the observatory.  
Between 1917 to 1919, four tidal waves were recorded by the observatory on continuously recording tidal gauges that correlated with four earthquakes recorded by the seismograph installed at the observatory, with observations reported in [23].  
Situated approximately 100 km north of the Tonga Trench, Samoa is exposed to a range of local geophysical hazards (e.g., earthquakes, volcanoes, landslides, tsunami). For example, the subaerial volcanic eruption from 1905 to 1911 on northeast Savai'i caused displacement/relocation of affected villagers to neighbouring Upolu [24] and generatedseveral small tsunamis during this period, with the most damaging occurring in 1907 [4]. Indeed, the recent 2009 complex earthquake sequence [25] and consequent tsunami that resulted in severe casualties and livelihood destruction in southeast Upolu reinforces this vulnerability [26; 27].  
The lesser known predecessor to the 2009 event, the 26 June 1917 UTC (local time in 1917 = UTC-11) earthquake and tsunami that originated in a proximal source region northwest of the 2009 epicentre (Figure 1), is arguably considered the largest earthquake to have occurred in this region in terms of magnitude (i.e., _Mw_ 8.3 compared with _Mw_ 8.1 for the 2009 earthquake sequence) [11; 28]. However, the scale of impacts from the resulting tsunami appear to have paled in comparison with the devastation observed in the 2009 event (e.g., [12; 29; 30]). Although anecdotal records indicate that the 1917 tsunami inundation had flooded several villages and caused damage to buildings and infrastructure (e.g., Satupaitea in southeast Savai'i and Lotofaga in southeast Upolu) [4; 31; 32], there are virtually no accounts of any casualties. Available modern interpretations assume at least two people lost their lives based on generic descriptions of damage recorded after the event (e.g., [32]). Here, we use our inundation model for the 1917 tsunami along with present-day patterns of inundation exposure as a proxy to discuss and offer alternative views to help elucidate this enigma.