Seismic wave velocities in the uppermost mantle beneath New Zealand

Haines, A. J.

doi:10.1080/00288306.1979.10424223

Cited by 93 publications

(130 citation statements)

References 35 publications

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“…In the previous paper (Haines 1979) I used differences in arrival times to eliminate errors caused by uncertainty in origin times and focal depths. In doing so, I introduced V aij the velocity in the uppermost mantle from a point offset from station i by 8 i in the direction of the focus to a point offset by 8 j from station j (Haines 1979, fig.…”

Section: Travel Times Between Pairs Of Stationsmentioning

confidence: 99%

“…180 0 E km, and specifying that for each pair of stations there was a high probability before the study began that the difference in the time tenns for S-waves would have the same sign as the difference in time tenns for P-waves (Haines 1976). The constraints took the fonn of a "nonnal" a priori probability distribution for the values of the P-and S-wave time tenns for each station, d(P) and d(s), in which they had expectations…”

Section: °S 175°ementioning

confidence: 99%

“…In doing so, I introduced V aij the velocity in the uppermost mantle from a point offset from station i by 8 i in the direction of the focus to a point offset by 8 j from station j (Haines 1979, fig. 1), and took the same estimate, 40 km, for the offset distances at all stations.…”

Section: Travel Times Between Pairs Of Stationsmentioning

confidence: 99%

“…Because the crustal terms in the original method depend on the wave velocity in the upper mantle it cannot be used in regions such as New Zealand where there are known to be major lateral variations (Haines 1979;Robinson 1976). Haines (1979) overcame this difficulty by introducing a modified version of the method, which he used to calculate velocities in the uppermost mantle beneath New Zealand from the arrival times of Pn and Sn phases from crustal earthquakes of 1971. The arrival times Tj were broken up as follows:…”

Section: Introductionmentioning

confidence: 99%

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Differences in time terms between New Zealand seismograph stations and implications for crustal structure

Haines¹

1980

New Zealand Journal of Geology and Geophysics

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Differences between time terms roughly equal to the crustal contributions to Pn and Sn travel times have been calculated for pairs of stations of the New Zealand seismograph network. The maximum differences found between 2 stations are 2.6 s for P-waves and 6.8 s for S-waves. These differences reflect major differences in crustal structure and, although they cannot be interpreted unambiguously in terms of crustal thickness and/or crustal seismic wave velocities, they provide important constraints on structure not evident from surface geology. The results will ultimately be important in improving the accuracy of local earthquake locations.

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Section: Travel Times Between Pairs Of Stationsmentioning

confidence: 99%

Section: °S 175°ementioning

confidence: 99%

Section: Travel Times Between Pairs Of Stationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Differences in time terms between New Zealand seismograph stations and implications for crustal structure

Haines¹

1980

New Zealand Journal of Geology and Geophysics

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“…Since P readings have been used from a wide range of distances in this solution, with travel times interpolated from the 1940 Jeffreys-Bullen tables, the largest fractional model errors should be in the Sn velocities. Haines (1979) found a 4.65 km/s velocity for Sn in the southern South Island east of Fiordland (his region 8) which is to be compared with the model velocity of 4.60 km/s. It is unlikely that average S velocities between the epicentre and the majority of stations recording S are less than 4.60 km/s.…”

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confidence: 99%

The Puysegur Bank earthquake of 1979 October 12

Webb

Lowry

1982

New Zealand Journal of Geology and Geophysics

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An earthquake of local magnitude 6.4 and surface-wave magnitude of 7.4 (USGS) occurred on 1979 Oct 12 d lOh 25 m U.T. The epicentre was at 46°.67S, 165°.73E and a focal depth of 12 km was adopted. The epicentre was well constrained, but there was poor control of the focal depth in computed solutions. The maximum felt intensity was MM V, the isoseismal pattern being similar to that observed for events in the neighbouring Fiordland region. Damage claims numbered 198 and were mainly for structural damage rather than contents. The strike of one focal plane is 339°with a dip of 78°W. First motions suggest thrust faulting with an unknown strike-slip component. One foreshock and a sequence of 176 aftershocks were studied, a value for b of 1.1 ± 0.2 being determined for the latter. The aftershock area was 9500 km 2 for events within 24 h of the main shock and 13 500 km 2 for all events. The maximum dimension (for 90% of events) was 130 km. The lowfrequency nature of this event, characterised by the type of damage, felt effects, and large excitation of surface waves, is similar to that of tsunamigenerating earthquakes located near the Japan Trench.

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Pn anisotropy beneath the South Island of New Zealand and implications for distributed deformation in continental lithosphere

Collins

Molnár

2014

JGR Solid Earth

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Pn travel times from regional earthquakes recorded both by stations on New Zealand and by ocean bottom seismographs deployed offshore indicate anisotropy in the uppermost mantle beneath the region. The largest anisotropy of~8% (±2%, 1σ) lies beneath the deforming part of the South Island to just off its West Coast, a zone roughly 100-200 km wide. The fastest propagation is aligned N60°E (±3°), essentially parallel to the largely strike-slip relative plate motion since 20 Ma, also~N60°E. The magnitude of anisotropy decreases abruptly northwest and southeast of this zone, and on the southeast side of the island, the orientation of fastest propagation is between N32°W and N-S. The~N60°E orientation of fast propagation is consistent with finite strain within the uppermost part of the mantle lithosphere if the measured 850 km of displacement of the Pacific plate past the Australia plate is spread over a region with a width of 100-200 km. The agreement of this orientation of fast propagation with the orientation or relative plate motion suggests the possibility of but does not require some dynamic recrystallization in rock as cold as 500-800°C, where Peierls creep seems to be the likely deformation mechanism. Such a strain distribution matches deformation of a thin viscous sheet that obeys a constitutive relationship of the form ε e τ n , whereε is the average strain rate and τ is the operative deviatoric stress, with an average value of n ≈ 3-10. Presumably, the NW-SE fast propagation in the region southeast of the island results from strain that precedes the Cenozoic deformation that has shaped the island.

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Seismic wave velocities in the uppermost mantle beneath New Zealand

Cited by 93 publications

References 35 publications

Differences in time terms between New Zealand seismograph stations and implications for crustal structure

Differences in time terms between New Zealand seismograph stations and implications for crustal structure

The Puysegur Bank earthquake of 1979 October 12

Pn anisotropy beneath the South Island of New Zealand and implications for distributed deformation in continental lithosphere

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