Gurney, J.H. 2023 Isoseismal maps of damaging earthquakes in Taranaki, New Zealand, from historical sources : 1882 to 1942. Lower Hutt, N.Z.: GNS Science. GNS Science report 2023/25. 35 p.; doi: 10.21420/4ZWB-HB54
Abstract
Historical seismicity in the Taranaki region of New Zealand is poorly documented, with only five historical earthquakes known to have caused damage in the region prior to 1942. Of these, only three have origins within the Taranaki region, and only two have had isoseismal maps produced. Utilising a comprehensive collection of historical sources, six further damaging earthquakes that struck the Taranaki region between 1882 and 1942 have been identified. Using macroseismic methods, these six previously undocumented, and one prior-documented, earthquakes had intensities assigned to reported felt locations according to the Modified Mercalli Scale – NZ 2007 (Dowrick et al. 2008). From these intensity datasets, five earthquakes had sufficient data to have isoseismal maps produced for them, allowing magnitude and epicentre estimates to be calculated according to an established attenuation model for isoseismals. This more than doubles the number of historical (pre-1942) earthquakes in the Taranaki region with seismic parameters assessed. The addition of these newly documented damaging earthquakes reveals that the city of New Plymouth has suffered damaging (MM≥6) intensities 11 times since the city’s founding in 1840, with an average return period of 16.6 years. This is more frequent than that in Dowrick and Cousins (2003), who suggested an average return period of 20 years.
