The Fiordland Earthquake and Tsunami, New Zealand, 21 August 2003
The MW7.2 earthquake at 12:12 UT August 21 2003 was the largest shallow earthquake in New Zealand for many years. GPS and seismological data are consistent with the earthquake rupturing the plate interface near the coast of Fiordland, a mountainous and largely unpopulated area in the southwest corner of the South Island. Fortunately, because of the remote location, the earthquake resulted in few injuries and relatively minor damage to property. However the earthquake triggered many landslides on the steep slopes that typify Fiordland. The fall of one landslide into Charles Sound caused a small local tsunami that reached a maximum of 4–5 m above high tide mark on the opposite shore. A small tsunami was also generated on the Tasman Sea coast, which was recorded on tide gauges at Jackson Bay (300 mm peak-to-trough) 190 km northeast of the epicentre, and at Port Kembla (170 mm peak-to-trough) on the east coast of Australia. Spectrogram analyses are used to demonstrate that the observed tide-gauge signals are best explained by the excitation of local resonances by the trans-Tasman tsunami. Modelling of the tsunami indicates that the wave amplitudes are compatible with estimates of offshore coseismic deformation of close to 0.5 m vertically as indicated by preliminary modelling of post-earthquake GPS data, and that the tsunami arrival times are compatible with the timing of the mainshock.
KeywordsTide Gauge Epicentral Area Plate Interface Tide Gauge Record Alpine Fault
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- Beavan, J., Matheson, D., Denys, P., Miller, C. (2003), Fault parameters of Fiordland MW 7.1 earthquake from dislocation modelling of GPS data. Geological Society of New Zealand Miscellaneous Publication 116A, p16.Google Scholar
- Chittleborough, J. (2003). South Island, New Zealand, 21 August 2003. Tsunami Newsletter — International Tsunami Information Center, Volume XXXV, Number 5, p3.Google Scholar
- Cox, S. C., Hancox, G. T., Turnbull, L. M., McGinity, P., O'Neill, T. (2003), Fiordland shaken and stirred — The 22 August 2003 M7.1 Earthquake. Geological Society of New Zealand Miscellaneous Publication 116A, p 37.Google Scholar
- Hancox, G. T., Cox, S. C., Turnbull, L. M., and Crozier, M. J.(2003). Reconnaissance studies of landslides and other ground damage caused by the Mw7.2 Fiordland earthquake of 22 August 2003. Institute of Geological and Nuclear Sciences science report 2003/30.Google Scholar
- Leonard, M. (2004). T phase perception: The August 2003, Mw 7.1, New Zealand earthquake felt in Sydney 1800 km away. Seismological Research Letters, in press.Google Scholar
- Reyners, M., McGinty, P., Cox, S., Turnbull, L., O'Neill, T., Gledhill, K., Hancox, G., Beavan, J., Matheson, D., McVerry, G., Cousins, J., Zhao, J., Cowan, H., Caldwell, G., Bennie S. and the GeoNet team (2003). The Mw 7.2 Fiordland earthquake of August 21, 2003: background and preliminary results. Bulletin of the New Zealand Society for Earthquake Engineering, Vol. 36, No. 4, p233–248, December 2003.Google Scholar
- Reyners, M. and Webb, T. (2002). Large earthquakes in Fiordland, New Zealand. New Zealand Journal of Geology and Geophysics, Vol 45, p.109–120.Google Scholar
- Robinson, R., Webb, T., McGinty, P., Cousins, J. and Eberhart-Philips, D. (2003). The 2000 Thompson Sound earthquake. New Zealand Journal of Geology and Geophysics, Vol 46, (2003), p.331–341.Google Scholar
- Titov, V. V. and Gonzalez, F. L. (1997). Implementation and testing of Method of Splitting Tsunami (MOST) model. NOAA Technical Memorandum ERL PMEL-112.Google Scholar
- Walsh, R. (2003). 'Frightening’ quake biggest in 35 years. The New Zealand Herald, 23 August 2003.Google Scholar