Subduction and Back-Arc Activity at the Hikurangi Convergent Margin, New Zealand

Rates of co-seismic strain release over the last 150 years calculated from the moment tensors of large (M 7) historic earthquakes, and strain rates calculated from models of relative plate motions, are generally consistent in the northern South Island, with the rate of seismic activity accommodating about 70% of the relative plate motions. There is some evidence that the distribution of seismicity within the region during the historical period is atypical, because 85% of the co-seismic strain release occurs west of the plate boundary, whereas geological data suggest that 60% of the relative plate movements are accommodated on the Marlborough faults, which are located on or east of the plate boundary.

Section: The Buller Earthquake Of 1929 Jun 16mentioning

confidence: 91%

“…Anderson 1991), instrumentally determined fault-plane solutions are not available in this magnitude range. A similar cutoff magnitude was used by Smith et al (1989) …”

Section: Historical Seismicitymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Rate of co‐seismic strain release in the northern South Island, New Zealand

Pearson

1993

“…More specifically, the reader may consult Grindley (1960) for geology, Cole & Lewis (1981) for tectonics, Smith & Webb (1986) for seismicity, Stem (1985Stem ( ,1987 for heat flow, Darby & Meertens (1995) for geodetics, Bibby et al (1995) for resistivity and hydrothermal properties, and Smith et al (1989) for the plate tectonic significance of the TVZ. The earliest TVZ activity was andesitic and began at c. 2 Ma, followed by at least 31 caldera-forming rhyolitic eruptions since 1.6 Ma in its central part.…”

Section: Introductionmentioning

confidence: 99%

Geodetic measurement of deformation in the Taupo Volcanic Zone, New Zealand: The north Taupo network revisited

Darby

Hodgkinson

Blick

2000

A previous geodetic estimate of 18 mm/yr horizontal extension for the Taupo Volcanic Zone (TVZ) immediately north of Lake Taupo for the period 1949-86 is re-examined for several reasons: this rate has not been confirmed by GPS surveys in the 1990s; newly compiled precise levelling data now allow us to estimate the extent of non-tectonic deformation attributable to the Wairakei geothermal field; and the precise levelling and lake-levelling data reveal a spatial variation in tectonic subsidence that casts doubt on the earlier assumption of homogeneous horizontal strain. We use the vertical and horizontal data to derive a Mogi point source model for the geothermal field, and this model allows us to correct the observed horizontal velocities of survey points. Statistical analysis of the corrected horizontal velocities shows that the strain across the TVZ is not homogeneous. When these factors are accounted for, an extension rate of 8 ± 2 mm/yr (1 SE) can be applicable for both 1949-86 and 1986-97. This is about half the previous estimate, which we now consider to be incorrect. The distribution of deformation differs between these periods, and the seismicity of the region shows temporal variations on a similar time-scale (decades). The extension rate is much greater than can be accounted for by seismic strain release, and the occurrence of historical earthquakes up to M = 6 indicates that a significant part of the measured extension represents seismic strain accumulation. The spatial heterogeneity of the strain partitions the region identically to that derived from geological studies of fault activity. In particular, there is a spatial concentration of extension and tilt about the Whangamata fault system.

“…In the northern South Island, the plateboundary zone passes through continental crust, forming a wide transform fault zone known as the Marlborough Fault System (Lamb & Bibby 1989). To the north of and beneath the Marlborough Fault System, the Pacific plate is subducting obliquely beneath the Australian plate along the Hikurangi margin (Smith et al 1989). The southern end of the Marlborough Fault System meets the main feature of the South Island fault system, the Alpine Fault (Wellman 1953).…”

Section: Tectonicsmentioning

confidence: 99%

The 1990 Lake Tennyson earthquake sequence, Marlborough, New Zealand

McGinty

Robinson

Taber

et al. 1997

Self Cite

Aftershocks from the 1990 Lake Tennyson earthquake (ML 5.8) recorded at nine temporary portable seismographs have been used to invert travel-time data simultaneously for both hypocentre and velocity parameters, resulting in a 1 -D velocity model and station terms for the Lake Tennyson region. The distribution of the best relocated aftershocks outlines a main fault lineation in a ENE direction, and several off-fault clusters. The main fault lineation is 8 km long, with a strike of about 60° and a dip that is nearly vertical. It is located between and subparallel to the Awatere and Fowler Faults, on a previously unknown fault. The mainshock has been relocated in the middle of this lineation zone, which suggests that the fault ruptured bilaterally. The distribution of aftershocks matches that expected from the Coulomb failure criterion, which identifies areas of increased and decreased stress levels due to the occurrence of the mainshock.Focal mechanisms for the mainshock and aftershocks that make up the main fault lineation are consistent with rightlateral strike-slip movement on this fault. Clusters that extend from each end of the main fault lineation predominantly do not have strike-slip focal mechanisms. Aftershocks located in the clusters to the north of the main fault lineation have various thrust mechanisms with no consistent orientation. Most focal mechanisms from this sequence had their P axes closely aligned with the regional axis of compression, and the main fault lineation is consistent with the relative plate motion direction in the Lake Tennyson region.