Figure 6. Spectrogram summary of ambient noise levels on the vertical component of the Hawaii-2 Observatory (H2O) seafloor Guralp seismometer for the duration of Leg 200. Color, as defined in the bar on the right, indicates the relative energy content in decibels relative to m/s^2 squared per hertz (from –190 to -90dB) as a function of frequency from 0.001 to 60Hz. The broad red band at ~0.2–0.3 Hz throughout the week is the microseism peak generated by wave-wave interaction of ocean gravity waves. It appears to be modulated by sediment resonances. The thinner red band at 1.1Hz and the yellow band at 2.0 Hz are resonances in the thin sediment cover at this site. This spectrogram also shows storm cycles. These are the red bands that slope upward to the left from ~1 to 0.2 Hz over 1.5 to 2 days for each storm cycle. The high-energy peak at 8 Hz, on 25 December (Julian day 359), is a passing ship (see Figure 14). The JOIDES Resolution arrived on site at 1500hr on 26 December (Julian day 360). The patches of yellow from 4 to 9 Hz from 26 December to 20 January (Julian days 360/2001 to 20/2002) can be associated with JOIDES Resolution activities (also see Figure 15).

Retun to the 2003 Fall AGU Poster

BROADBAND SEISMIC OBSERVATIONS AT THE HAWAII-2 OBSERVATORY DURING ODP LEG 200