Subsea fiber‐optic telecommunication cables can break under fast sediment flows that travel 100s of kilometers through the deep ocean in response to earthquakes and submarine landslides. Similar flows are inferred to form from major river floods whose sediment‐laden waters plunge and travel along the seabed. However, the complex initiation of flood‐related flows and their hazard potential have not been observed until now. Here we use cable fault data from the Gaoping Canyon/Manila Trench off Taiwan to show that a major river flood, formed during Typhoon Morakot (2009), generated two, long run‐out, destructive sediment flows; one during peak flood and the other 3 days later. The latter flow was more damaging with speeds and run‐out similar to that of landslide‐triggered turbidity currents formed in the same catchment. If the second flow was due to remobilized canyon sediment, it occurred during low earthquake (>Mw 2.0) activity, suggesting other triggering mechanisms.

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[1] The increased use of ambient seismic noise for seismic imaging requires better understanding of the ambient seismic noise wavefield and its source locations and mechanisms. Although the source regions and mechanisms of Rayleigh waves have been studied extensively, characterization of Love wave source processes are sparse or absent. We present here the first systematic comparison of ambient seismic noise source directions within the primary (~10-20 s period) and secondary (~5-10 s period) microseism bands for both Rayleigh and Love waves in the Southern Hemisphere using vertical-and horizontalcomponent ambient seismic noise recordings from a dense temporary network of 68 broadband seismometers in New Zealand. Our analysis indicates that Rayleigh and Love waves within the primary microseism band appear to be mostly generated in different areas, whereas in the secondary microseism band they arrive from similar backazimuths. Furthermore, the source areas of surface waves within the secondary microseism band correlate well with modeled deep-water and near-coastal source regions.Citation: Behr Y., J. Townend, M. Bowen, L. Carter, R. Gorman, L. Brooks, and S. Bannister (2013), Source directionality of ambient seismic noise inferred from three-component beamforming,

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The confluence of subtropical and subantarctic boundary currents east of New Zealand creates strong fronts. The fronts have clear signatures in sea surface height (SSH) and sea surface temperature (SST) which make the confluence a good region to investigate the variability of the boundary currents of the South Pacific. Analysis of the 20 year time series of the SSH is used to investigate the location and strength of fronts, measured as the gradient in SSH (rSSH), and the eddy kinetic energy (EKE) and their relationship to local and large-scale wind forcing. The intensity of the rSSH and the EKE have increased at a rate of 0.02 cm km 21 and 32 cm 2 s 22 decade 21 , respectively. There is a significant correlation (r 5 0.7, p < 0.01) between the rSSH and EKE signals, reflecting baroclinic instabilities inherent in the fronts. Differences between northward and southward wind-driven transports across the confluence from the Island Rule are also increasing at 7.5 Sv decade 21 along with an upward trend in the SST differences across the region.Time series of the Southern Annular Mode (SAM) and Southern Oscillation Index (SOI) and local winds were compared to the frontal strength. Although the positive trend in the SOI coincides with increasing subtropical inflows, there is little correspondence of the indices and local winds with short-term variability. While these results indicate a connection between the intensification of the confluence and South Pacific winds, there is little change in frontal location north of Bollons Seamount which suggests bathymetry influences the location of the confluence.