Seismicity, structure and tectonics of the Wellington region, New Zealand

Robinson, Russell

doi:10.1111/j.1365-246x.1986.tb06629.x

Cited by 147 publications

(202 citation statements)

References 55 publications

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“…Figure 12 (snl) shows the receiver function from the Robinson [1986] model with dipping isotropic layers ( Table 2). Some of the features on the radial components are similar to those in the real data.…”

Section: Distinguishing Anisotropy From Dipping Boundariesmentioning

confidence: 99%

Lower crustal anisotropy or dipping boundaries? Effects on receiver functions and a case study in New Zealand

Savage¹

1998

J. Geophys. Res.

283

275

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Abstract. We examine the effects on receiver functions of transverse anisotropy and of dipping isotropic boundaries. Splitting of the Moho Ps phase predicts the anisotropy from a postulated 10-km-thick layer of highly anisotropic crustal material only when other phases can be well isolated and when allowance is made for the rotation of the incident energy out of the plane of energy propagation expected for isotropic models. We examine azimuthal variations of the synthetic radial and transverse receiver functions. For both transversely anisotropic layers and dipping isotropic boundaries, radial receiver functions are symmetric and transverse receiver functions are antisymmetric about a given back azimuth (the horizontal projection of the axis of symmetry or the dip direction). Differences include the following: (1) Transverse energy from dipping boundaries arrives at the time of the initial P phase no matter at what depth the dipping boundaries occur, while transverse energy arrives at the time of the initial P phase for anisotropic material only when the anisotropy is at the surface. (2) Transversely anisotropic systems with horizontal symmetry axes have waveforms with 180 ø periodicity as a function of back azimuth, while dipping symmetry axes or dipping boundaries just have 360 ø periodicity. A consequence of the symmetry is that stacking the initial P and Ps phases from transverse receiver functions for back azimuths that are 180 ø apart tends to decrease the arrivals from shallowly dipping isotropic boundaries and doubles the arrivals from anisotropic layers with horizontal symmetry axes. We examine receiver functions for station SNZO in New Zealand, above a subducting plate dipping at 15 ø beneath the station. Opposite polarities of transverse receiver functions separated by 180 ø in back azimuth suggest that either dipping isotropic layers or dipping axes of symmetry of anisotropic layers are present. The 15 ø dip of the subduction zone is insufficient to explain the energy on the transverse receiver functions by the isotropic structures previously determined from refraction and earthquake travel time inversion. However, modifying the isotropic models for the region by anisotropy determined via shear wave splitting measurements and refraction studies, allows many of the features of both the radial and transverse receiver functions to be explained. A relatively highly anisotropic layer about 7 km thick at the base of the crust with an axis of symmetry dipping at 20 ø -40 ø may be caused by metamorphosed oceanic crust.

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Section: Distinguishing Anisotropy From Dipping Boundariesmentioning

confidence: 99%

Lower crustal anisotropy or dipping boundaries? Effects on receiver functions and a case study in New Zealand

Savage¹

1998

J. Geophys. Res.

283

275

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“…Reyners & Cowan (1993) obtained a value of 6.24 km/s for a similar depth range in the North Canterbury region. Robinson (1986) obtained 6.23 km/s in the northeast of the South Island at depths of 5-15 km. Garrick (1968) …”

Section: Velocity Modelmentioning

confidence: 99%

“…The inversion algorithm has a fixed P/S velocity ratio, but P and S station terms are independent of one another. More details about the program and inversion technique can be found in Robinson (1983Robinson ( , 1986Robinson ( , 1994 and McGinty (1996).…”

Section: Velocity Modelmentioning

confidence: 99%

“…S phases with picking weights 50% were down-weighted to 25%, and S phases of weights <50% were omitted. The S phases were down-weighted because their slower velocities gives them greater weight in the inversion (Robinson 1986). Also, as the S phase is a secondary phase, they are more prone to misidentification.…”

Section: Velocity Modelmentioning

confidence: 99%

“…The high station delay determined in this study for station KHZ is also consistent with a low-velocity zone detected by Eberhart-Phillips & Reyners (1997) in the eastern Marlborough region towards Kaikoura. SE standard error, which is the total estimation error (see Robinson 1986Robinson , 1994. Resolution is the appropriate diagonal element of the resolution matrix.…”

Section: Simultaneous Inversion For Velocity Structure and Station Termsmentioning

confidence: 99%

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The 1990 Lake Tennyson earthquake sequence, Marlborough, New Zealand

McGinty

Robinson

Taber

et al. 1997

New Zealand Journal of Geology and Geophysics

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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.

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Structure and kinematics of the Taupo Rift, New Zealand

et al. 2014

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The structure and kinematics of the continental intra-arc Taupo Rift have been constrained by fault-trace mapping, a large catalogue of focal mechanisms (N = 202) and fault slip striations. The mean extension direction of~137°is approximately orthogonal to the regional trend of the rift and arc front (α = 84°a nd 79°, respectively) and to the strike of the underlying subducting Pacific Plate. Bending and rollback of the subduction hinge strongly influence the location, orientation, and extension direction of intra-arc rifting in the North Island. In detail, orthogonal rifting (α = 85-90°) transitions northward to oblique rifting (α = 69-71°) across a paleovertical-axis rotation boundary where rift faults, extension directions, and basement fabric rotate by~20-25°. Toward the south, extension is orthogonal to normal faults which are parallel to, and reactivate, steeply dipping basement fabric. Basement reactivation facilitates strain partitioning with a portion of margin-parallel motion in the overriding plate mainly accommodated east of the rift by strike-slip faults in the North Island Fault System (NIFS). Toward the north where the rift and NIFS intersect,~4 mm/yr strike slip is transferred into the rift with net oblique extension accommodating a component of margin-parallel motion. The trend and kinematics of the Taupo Rift are comparable to late Miocene-Pliocene intra-arc rifting in the Taranaki Basin, indicating that the northeast strike of the subducting plate and the southeast extension direction have been uniform since at least 4 Ma.

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Seismicity, structure and tectonics of the Wellington region, New Zealand

Cited by 147 publications

References 55 publications

Lower crustal anisotropy or dipping boundaries? Effects on receiver functions and a case study in New Zealand

Lower crustal anisotropy or dipping boundaries? Effects on receiver functions and a case study in New Zealand

The 1990 Lake Tennyson earthquake sequence, Marlborough, New Zealand

Structure and kinematics of the Taupo Rift, New Zealand

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