ISSN:
1365-246X
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Geosciences
Notes:
The Leeds Tararua array of nine broad-band, three-component seismometers was deployed in southern North Island, New Zealand, from 1991 January to 1992 September and recorded many local events. We selected 111 events with local magnitude ≥ 2.5 and good station coverage, and attempted to find their source mechanisms by using conventional first motions and by matching of the vertical component waveforms to Rayleigh-mode synthetics. 90 source mechanisms were found: 32 from the method of first motions, 18 by waveform matching, and 40 using both methods. A comparison of mechanisms for events using both methods suggests that waveform matching is reliable even for small events where the coverage on the focal sphere does not allow a first-motion mechanism to be found. The mechanisms are of all types but with a predominance of normal faulting with one of the planes aligned approximately NE–SW. There are many dip-slip events. Deep (60–80 km) events are mostly thrusts, and there is some evidence of a trend from normal faulting in the shallow part of the subducted slab and upper seismic plane to thrusts in the deeper part, although the pattern is not clear cut. A complex stress pattern is to be expected in this region, which is near the southern end of the Tonga–Kermadec–Hikurangi subduction zone. The magnitude–moment relation ML= (0.84 ± 0.23) log M0– (7.53 ± 1.48) is found for the region, where ML is the local magnitude and M0 the seismic moment in N m.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1365-246X.1996.tb06371.x
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