Mark Stirling, Robert Langridge, Rafael Benites, GNS Science (EQC-funded reconnaissance)
A report on a reconnaissance trip to the area of the magnitude 8.3 June 23 2001 southern Peru earthquake and tsunami.
The earthquake is the best example in nearly 40 years of the maximum-size earthquake that might occur on the Hikurangi subduction zone. Despite the great magnitude of this subduction interface earthquake, it produced only “moderately strong” levels of earthquake shaking (peak ground acceleration of 0.3g on alluvium from the one strong motion accelerograph in the earthquake area, and Modified Mercalli Intensity 8 in the epicentral area), and relatively minor ground damage (liquefaction and landsliding). It did however produce a large and devastating tsunami. Our comparison of the Moquegua accelerograph record and attenuation curves for subduction interface earthquakes shows that the strength of shaking was typical for subduction interface earthquakes. If we apply our observations to New Zealand, they imply that a Hikurangi subduction interface earthquake may be less damaging to built-up areas in the south-eastern part of the North Island (eg, Wellington and Napier/Hastings) than earthquakes on major active faults in the shallow crust. However, the extent of the strongest shaking in a subduction earthquake (300km for the southern Peru event) and the associated tsunami generation will make the earthquake very significant in the regional context.