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Fault displacement accumulation and slip rate variability within the Taupo Rift (New Zealand) based on trench and 3‐D ground‐penetrating radar data
Author(s) -
McClymont Alastair F.,
Villamor Pilar,
Green Alan G.
Publication year - 2009
Publication title -
tectonics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.465
H-Index - 134
eISSN - 1944-9194
pISSN - 0278-7407
DOI - 10.1029/2008tc002334
Subject(s) - geology , trench , seismology , ground penetrating radar , slip (aerodynamics) , fault (geology) , rift , active fault , thrust fault , submarine pipeline , tectonics , radar , geotechnical engineering , telecommunications , chemistry , physics , organic chemistry , layer (electronics) , computer science , thermodynamics
In offshore regions, studies based on densely spaced reflection seismic data tied to stratigraphic logs demonstrate that active faults can have variable displacement rates over relatively short distances and short time intervals. Here, we demonstrate how high‐resolution 3‐D ground‐penetrating (GPR) data tied to trench‐derived stratigraphic logs provide similar information for active faults in onshore regions. To investigate recent (≤24.4 ka) fault activity within the Taupo Rift of New Zealand, we analyze 3‐D GPR data acquired over 10 fault strands within the Maleme fault zone. After correlating three prominent GPR reflection horizons with three faulted chronostratigraphic units observed within a trench, we extrapolate the geometries of the horizons over a ∼150 × 250 m area of the fault zone and determine slip accumulation patterns and rates. Profiles of cumulative fault displacement measured for horizons older than 12.5 ka exhibit characteristic displacement distributions. By calculating average cumulative displacements with time for five practically complete fault strands, we obtain robust slip rate estimates. Slip rates are variable for time intervals ≤12.5 ka long, suggesting that at least four earthquakes are required for these faults to exhibit uniform slip rates characteristic of their long‐term behavior.