Past earthquake timing and magnitude along the Inglewood fault, Taranaki, New Zealand

  • A. G. Hull GNS Science, Lower Hutt, New Zealand

Abstract

Several active normal faults in the onshore and offshore regions of Taranaki are capable of generating large earthquakes and associated strong ground shaking. Historical earthquakes are concentrated offshore of Cape Egmont, and no significant earthquakes have been detected along the major onshore surface faults. The northeaststriking Inglewood fault is a major onshore, southward-dipping normal fault. It has a known length of c. 20 km and an average scarp height of c. 3 m on landforms less than about 15,000 yrs old. Three subsurface excavations at two sites along the Inglewood fault about 15 km from New Plymouth have revealed three surface fault displacements during the last c. 13,000 years. Earthquakes resulting in about 1.2 m of surface displacement occurred at c. 3,500 radiocarbon yrs BP; between 4,000 and 9,000 radiocarbon yrs BP; and between 10,000 and 13,000 radiocarbon yrs BP, judged by the amount of vertical offset of dated volcanic ash layers. Based on average single-event fault slip values of 1.2-3.0 m and a fault length of 20-30 km, the estimated earthquake magnitudes associated with these past movements range from Mw 6.7 to 7.2.

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Published
1994-06-30
How to Cite
Hull, A. G. (1994). Past earthquake timing and magnitude along the Inglewood fault, Taranaki, New Zealand. Bulletin of the New Zealand Society for Earthquake Engineering, 27(2), 155-162. https://doi.org/10.5459/bnzsee.27.2.155-162
Section
Articles