HR: 08:45h
AN: T11F-04 INVITED    [Abstracts]
TI: Triggered Microearthquakes but no Tremor Accompanying Slow Slip in the Hikurangi Subduction Zone, New Zealand
AU: * Delahaye, E J
EM: delahaye@nrcan.gc.ca
AF: Victoria University of Wellington, Institute of Geophysics, Wellington, 6015, New Zealand
AU: Townend, J
EM: john.townend@vuw.ac.nz
AF: Victoria University of Wellington, Institute of Geophysics, Wellington, 6015, New Zealand
AU: Reyners, M
EM: m.reyners@gns.cri.nz
AF: GNS Science, Avalon, Lower Hutt, 5040, New Zealand
AU: Rogers, G
EM: grogers@nrcan.gc.ca
AF: Natural Resources Canada, Geological Survey of Canada, Pacific Geoscience Centre, Sidney, BC V8L 4B2, Canada
AB: This is the first study to systematically examine continuous broadband seismic data spanning slow slip events in New Zealand. We have reviewed a total of 20 weeks of seismic data spanning three slow slip events: two in the shallow region of the Hikurangi subduction zone near Gisborne (in 2004 and 2006) and one deeper, ~18 month-long event beneath the Manawatu region (early 2004 to mid-2005). We have not detected seismic tremor similar to that seen elsewhere during any of these slow slip events. This observation does not appear to be the result of network limitations: we deployed five additional seismographs during the latter stages of the 2006 Gisborne event to augment the permanent network and still did not detect seismic tremor. However, our analysis has revealed a pronounced increase in M_L 1--2 microseismicity during the 2004 Gisborne event that is spatially,/em> restricted to a region of the subducting plate downdip from the slow slip patch inferred from GPS observations and temporally restricted to the period of slow slip. This increased rate of local seismicity is not evident in the catalog produced by routine analysis and was only detected by a methodical review of the continuous waveform data. These subduction zone microearthquakes have similar spatiotemporal characteristics to the "coshocks" reported by Segall et al. (2006) in an intraplate setting.
DE: 1207 Transient deformation (6924, 7230, 7240)
DE: 7223 Earthquake interaction, forecasting, and prediction (1217, 1242)
DE: 7230 Seismicity and tectonics (1207, 1217, 1240, 1242)
DE: 8118 Dynamics and mechanics of faulting (8004)
DE: 8170 Subduction zone processes (1031, 3060, 3613, 8413)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting