Geoscience Reference
In-Depth Information
Fig. 7.2 Time dependence of sea surface temperature (SST) and of temperature of the near-the-
water atmospheric layer; time and magnitude of seismic events (red triangles) that occurred within
a radius of 300 km from the epicentre of earthquakes of maximum magnitude. The blue line cor-
responds to the SST at the point 7 S, 156 E, which was restored from maps of SST anomalies
(FNMOC), the green and purple curves are data from the TAO Array buoy station with coordinates
5 S, 156 E. Fragments of maps of SST anomalies and the coloured temperature scale in degree
Celsius. The dates indicated along the timescale correspond to 00 h 00 min Greenwich time (see
also Plate 17 in the Colour Plate Section on page 324)
Recurrence of the anomaly on May 12 took place immediately after the earthquake
of May 11. The anomalies persisted for several days.
In the region of Bougainville Island there are several autonomous buoy stations
TAO Array (Tropical Atmosphere Ocean Array, NOAA, http://www.pmel.noaa.gov
/tao/data deliv/). The location of the five stations nearest to the island is shown in
Fig. 7.1. During the time period of interest to us from April 20 to May 31, 1996,
only the following three stations of the ones shown in the figure were functioning:
5S156E, 2S156E, 0N156E (a station is indicated by its coordinates). Note that
not a single station TAO Array was in the immediate vicinity of the temperature
anomaly. The station 5S156E, nearest to the site of the event, was only at the
north-eastern periphery of the anomaly. The stations 2S156E and 0N156E are situ-
ated too far away, and recorded no significant effects.
Figure 7.2 shows the time dependence of the temperature of air at a height of 3 m
(the green curve) and of the water at a depth of 1 m (purple curve), obtained from
the data of station 5S156E. Note, that starting from May 23 this station was out of
operation. On the curve, describing time changes in temperature of the water surface
layer, a process of a 24-h periodicity, representing the daily variation in temperature,
is quite noticeable. Station 5S156E registered a clear violation of this process, which
took place precisely on the day of the earthquake of maximum magnitude (April 29).
On May 2 the daily course, namely, the daily warming, is restored within one cycle;
however, a long period subsequently sets in (up to May 13), when no daily heating
at all is observed, and the temperature variation turns out to be 'smoothed out'.
Moreover, during this period a general tendency toward a decrease in temperature
