Geoscience Reference
In-Depth Information
foul weather or ship scheduling. Even though tsunamis do not occur frequently, redundancy
in the array is still desirable. The surface buoy has two independent complete communica-
tion systems for full redundancy. In addition, in high-risk source regions, a certain amount of
overlap in spatial coverage is desirable so that instrument failures may be partially compen-
sated by having more than one DART in the region capable of providing a timely, high-quality
signal.
Communication Issues:
•
Bottom roughness. A DART BPR needs to communicate acoustically with its surface unit. For
reliable communications, the BPR must be deployed on a reasonably lat, smooth seabed
that will not produce scattering and interference of the acoustic signals.
Logistical Issues:
•
Although DARTs are typically deployed for two years, and have a design life of four years,
there is considerable expense associated with deploying and maintaining them in remote
regions. For some sites, co-locating DART buoys with other buoy arrays might allow leverag-
ing ship time and maintenance costs if there is no conlict with special DART requirements.
For example, co-location might be considered for other sites maintained by the NDBC, such
as in the equatorial Paciic near the Tropical Atmosphere Ocean Project (TAO) (http://www.
pmel.noaa.gov/tao/) buoy array or near U.S. coastlines where meteorological buoys are
maintained.
Other Issues:
•
Other considerations in choosing buoy sites include the dificulty or ease of obtaining per-
missions to enter other national EEZs (Exclusive Economic Zones), shipping routes, sealoor
infrastructure (e.g., communications cables that could be damaged by the mooring's anchor),
and piracy or a history of damage to unattended buoys that make some areas less desirable
for DART siting.
a
Spillane et al., 2008.
cludes that the numbers, locations, and prioritizations of the DART stations should not be con-
sidered static. These parameters of the DART network clearly deserve frequent re-consideration
in light of constantly changing iscal realities, survivability experience, maintenance cost
experience, model improvements, new technology developments (even new DART designs),
increasing international contributions, and updated information on the entire suite of siting
issues listed in Box 4.1. In addition, simulations of the effectiveness of the DART network, under
