Geoscience Reference
In-Depth Information
The Economic Value of the DART Network
Although the foremost concern for emergency responders is the protection of human
lives in the event of large tsunamis, another signiicant value of the DART stations is to pro-
vide assurance that a large wave has not been generated by a seismic event, permitting an
initial watch or warning to be canceled expeditiously. Thus, the DART stations help to prevent
unnecessary public concern and economic disruption.
Two estimates of economic beneits have been derived for Hawaii. In one, the cost of a
needless evacuation in the state of Hawaii was put at $58.2 million in 1996 dollars (Hawaii
Research and Economic Analysis Division, 1996, cited in Bernard, 2005). A second estimate is
based on nearly identical earthquakes off the Aleutian Islands before and after the existence of
the DART network. On May 7, 1986 (pre-DART), a magnitude 8.0 earthquake near the Aleutian
Islands precipitated a full coastal evacuation in Hawaii at an estimated cost of $30-$40 mil-
lion in lost productivity, emergency provider expenses, and other costs (Hawaii Research
and Economic Analysis Division, 1996; National Science and Technology Council, 2005), yet
tsunami amplitudes did not exceed 0.6 m. On November 17, 2003, a DART station offshore of
the Aleutian Islands clearly showed that a sizable tsunami was not generated by a magnitude
7.8 earthquake in a similar location near the Aleutian Islands, and the watch was canceled (the
subsequent maximum tsunami height reached only 0.33 m in Hawaii). Adjusting the 1986
igure for inlation, the cost to Hawaii's government and businesses in 2003 could have been
$70 million had an evacuation been ordered. These indings are consistent with cost estimates
associated for unnecessary hurricane evacuations along the U.S. coastline between Maine and
Texas (Centrec Consulting Group, LLC, 2007).
Clearly, unwarranted evacuations can cost millions of dollars; and, although the costs
associated with the loss in public conidence are less easy to quantify, the effectiveness of a
warning system is ultimately grounded in credibility. Therefore, a tsunami warning system
should not only provide timely warning of a destructive tsunami, but also should avoid issuing
“false alarms.”
Although the DART stations have their greatest value in discerning tsunami propagation
characteristics in the open ocean, the inundation problem requires, ideally, sea level sensors
along tsunami-prone coastlines because of the spatial variations in tsunami height that are
produced by local bathymetry, coastal geometry, and the resultant system responses (e.g.,
coastal and harbor resonances).
Description of the Coastal Sea Level Gauge Network
Although coastal sea level stations were originally installed for monitoring tides for naviga-
tional purposes, most now serve a broad range of uses (including tsunami detection) that have
contributed to their continued support and upgrades. Stations are commonly located deep
within harbors or bays, where nonlinear hydrodynamic effects and local geographic complex-
ity strongly alter the structure and amplitude of any impinging tsunami waveform. These non-
