The 1942 Wairarapa, New Zealand, Earthquakes : Analysis of observational and instrumental data

In 1942, two large earthquakes, on June 24 (M w 7.2) and August 1 (UT) (M w 6.8), strongly shook the lower North Island, causing widespread moderate to severe damage. A third earthquake (M s 6.0) occurred in the same area on December 2. These earthquakes have now been studied in detail by re-analysing seismograms from 1942 and by the collection and analysis of contemporary technical information and descriptive accounts from many sources Results include new locations for the three main earthquakes and other moderate magnitude earthquakes in the sequence, summaries of building, lifelines and ground damage, new isoseismal maps and maps showing the distribution of landslides, liquefaction and other ground damage. The study has provided valuable information on the performance of buildings and lifelines in urban and small town environments at high intensities (MM8) and on the distribution of damaged buildings in central Wellington in relation to published ground shaking hazard microzoning maps and foreshore reclamation units. An important result is that scarp-like features described after the June earthquake as surface fault rupture are probably landslide-related rather than tectonically produced. This result and the lack of evidence for any other surface fault rupture, the closeness in time and space of the earthquakes both within the sequence and with the 1934 Pahiatua earthquake, and the similarity of the sequence to the 1990 Weber earthquakes have important implications for seismic hazard assessment of this part of the Hikurangi Margin.