Abstract - The amount of extension accommodated in active rifts by earthquakes that do not
rupture the ground surface (e.g., < Mw 5.5) is often poorly constrained. The Matata
Earthquake Sequence (MES), a high-quality dataset of 2563 relocated microearthquakes
(1 < Mw <4.7) that ruptured the Taupo Rift in New Zealand over a period of 49 months,
has been used to quantify the proportion of extension produced by small to moderate sized
earthquakes. Analysis shows that the extension rate across the rift due to the MES is
2.4 +/- 0.7 mm/yr, an average extension rate for small to moderate
magnitude earthquakes which also prevailed during the preceding 28 years (1977-2004)
and represents up to ca 30% of the total contemporary deformation recorded across the north
Taupo Rift by GPS (15 +/- 5 mm/yr). The bulk of the MES (94%) occurred at depths of 1.5
to 6.5 km and may not be observed in geological datasets (e.g., as displacements of the
ground- or near-surface horizons). Small-scale faulting associated with microseismicity
may record strains not measured by geological datasets and constitute an important
component of the ~3-10 mm/yr disparity between geological and GPS rates of extension
across the Taupo Rift.
Journal of Geophysical Research, 118, 1-13, doi:10.1002/jgrb.50062, 2013.