Geoscience Reference
In-Depth Information
closed large gaps in the sea level observation network that had left many U.S. coastal com-
munities subject to uncertain tsunami warnings. Among TWC personnel and tsunami warning
researchers, it is common to ind sentiments echoing the following statement in Whitmore et
al. (2008): “Since 2005, the amount and quality of both tide gage data and DART data [have]
greatly improved. These data are critical to verify the existence of tsunamis and to calibrate
models used to forecast amplitudes throughout the basin. Depending on the source location,
it can take anywhere from 30 minutes to 3 hours to obtain suficient sea level data to provide
forecasts for wave heights outside the source zone, or to verify that no wave has occurred and
cancel the alert. Within the AOR, upgraded sea level networks have dropped the veriication
time to 30 minutes in some regions.”
The implementation of the EarthVu tsunami forecast system and the Short-term Inunda-
tion Forecasting for Tsunamis (SIFT) system into the TWCs (e.g., Weinstein, 2008; see Section
Forecasting of a Tsunami Under Way
) places additional emphasis on the importance of the
proper operation of the sea level stations, especially the open-ocean DART stations whose sea
level observations of the tsunami waves are not distorted by bathymetric irregularities and
local harbor resonances that affect the coastal sea level observations. With these models and
data from the sea level networks, it has become possible to make reasonably accurate predic-
tions of the amplitude of the irst tsunami wave that arrives at a given shoreline, enabling the
issuance of more timely and more spatially reined watches and warnings (e.g., Titov et al.,
2005; Geist et al., 2007; Whitmore et al., 2008).
Furthermore, the array of DART stations, when properly functioning, enables unique
and important capabilities for both tsunami detection and forecasting as described below.
Whether the current DART and coastal sea level networks are suficient for both rapid detec-
tion of tsunamis and accurate tsunami forecasting with respect to all U.S. coastal territories is
addressed below.
Conclusion:
The expansion and upgrades to the DART and coastal sea level network
have closed large gaps in the sea level observation network that had left many U.S.
coastal communities subject to uncertain tsunami warnings. These enhancements to the
detection system have signiicantly improved the TWCs ability to detect and forecast
tsunamis in a timely and more accurate fashion.
Conclusion:
Based on the analysis described below, the coastal and DART sea level gauge
networks have proven their value for the forecasting and warning of far-ield tsunamis,
especially when coupled with numerical propagation and inundation models.
Conclusion:
Despite the improvements in detection and forecasting, some fundamental
issues remain concerning gaps in coverage, the value of individual components of the
network, and the risk to the warning capability due to the gaps and from individual
component failures, or failures of groups of components.
